[框架那点事儿-快速开发季]编写自己的数据持久层（4）分页查询

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上一章节讲述的查询，都是不带分页的查询，但是在实际应用中，有相当一部分的需求是针对于分页查询的，比如页面的分页功能等。所以，作为底层的API，势必不能缺失针对于分页的查询接口封装。这一章节，我们提供以下几个分页查询，分别针对于：对象查询、部分字段查询两大类。

class</a>="java">/** * 分页查询对象 * * 根据指定参数分页查询对象列表 * 用法示例： * ---------------------------------------------------------- * //设置查询参数 * Map<String,Object> params = new HashMap(); * params.put("city","hangzhou"); * * Paginal p = queryObjectListForPaging(Person.<a class="tags" href="/tags/CLASS.html" title=class>class</a>,params,1,10); * ... * * @param <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class 对象类型 * @param params 查询参数 * @param pageNomber 页号 * @param pageSize 分页大小 * @return 分页封装 */ @SuppressWarnings({ "rawtypes"}) public Paginal queryObjectListForPaging(final Class <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class,Map<String,Object> params,int pageNomber,int pageSize){ return queryObjectListForPagingOrderRow(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class,params,pageNomber,pageSize); } /** * 分页-排序查询对象 * * 分页查询，结果按照指定的条件排序 * 使用示例 * ---------------------------------------------------------- * //设置查询参数 * Map<String,Object> params = new HashMap(); * params.put("city","hangzhou"); * * Map<String,String> orderByAge = new HashMap<String,String>(); * orderByName.put("age","desc"); * * Map<String,String> orderByType = new HashMap<String,String>(); * orderByName.put("type","asc"); * * Paginal p = queryObjectListForPagingOrderRow(Person.<a class="tags" href="/tags/CLASS.html" title=class>class</a>,params,1,10,orderByAge,orderByType); * ... * * @param <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class 字段所在类 * @param params 查询参数 * @param pageNomber 页号 * @param pageSize 分页大小 * @param orders 排序字段 * @return 查询结果 */ @SuppressWarnings({ "rawtypes", "unchecked" }) public Paginal queryObjectListForPagingOrderRow(final Class <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class,Map<String,Object> params,int pageNomber,int pageSize,Map<String,String>... orders){ //~~~ return value Paginal<? extends Object> paginal = new Paginal<Object>(); // 初始化分页器 paginal.setPageNomber(pageNomber); paginal.setPageSize(pageSize); //获取表名 tableName = getTableConfigName(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class); //组装查询<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>语句 String <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> = buildQuerySql(null, params, paginal.getOffset(),paginal.getPageSize(),false,orders); //查询总记录数 int totalCount = queryCount(params,<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class); paginal.setTotalCount(totalCount);//总记录数 paginal.setPageNum(totalCount,pageSize);//总页码 //执行查询 List resultList = queryForList(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>,params,<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class); paginal.setResultList(resultList); return paginal; } /** * 分页查询部分字段 * * 使用示例 * ----------------------------------------------------------------- * //设置查询参数 * Map<String,Object> params = new HashMap(); * params.put("city","hangzhou"); * * //设置需要查询的字段名称，名称使用DO中的即可 * List<String> fields = new ArrayList<String>(); * fields.add("id"); * fields.add(name); * fields.add("address"); * * Paginal p = queryFieldsListForPaging(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class,params,fields,1,10); * ... * * @param <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class 字段所在的类 * @param params 查询参数 * @param returnFields 需要查询的字段列表 * @param pageNomber 页号 * @param pageSize 分页大小 * @return 查询结果 */ @SuppressWarnings({ "rawtypes"}) public Paginal queryFieldsListForPaging(final Class <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class,Map<String,Object> params,List<String> returnFields,int pageNomber,int pageSize){ return queryFieldsListForPagingOrderRow(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class,params,returnFields,pageNomber,pageSize); } /** * 分页-排序查询部分字段 * * 使用示例 * ----------------------------------------------------------------- * //设置查询参数 * Map<String,Object> params = new HashMap(); * params.put("city","hangzhou"); * * //设置需要查询的字段名称，名称使用DO中的即可 * List<String> fields = new ArrayList<String>(); * fields.add("id"); * fields.add(name); * fields.add("address"); * * Map<String,String> orderByAge = new HashMap<String,String>(); * orderByName.put("age","desc"); * * Map<String,String> orderByType = new HashMap<String,String>(); * orderByName.put("type","asc"); * * Paginal p = queryFieldsListForPaging(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class,params,fields,1,10,orderByAge,orderByType); * ... * * @param <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class 字段所在的类 * @param params 查询参数 * @param returnFields 需要查询的字段列表 * @param pageNomber 页号 * @param pageSize 分页大小 * @param orders 排序字段 * @return 查询结果 */ @SuppressWarnings({ "rawtypes", "unchecked" }) public Paginal queryFieldsListForPagingOrderRow(final Class <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class,Map<String,Object> params,List<String> returnFields,int pageNomber,int pageSize,Map<String,String>... orders){ //~~~ return value Paginal<? extends Object> paginal = new Paginal<Object>(); // 初始化分页器 paginal.setPageNomber(pageNomber); paginal.setPageSize(pageSize); //获取表名 tableName = getTableConfigName(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class); //组装查询<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>语句 String <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> = buildQuerySql(returnFields, params, paginal.getOffset(),paginal.getPageSize(),false,orders); //查询总记录数 int totalCount = queryCount(params,<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class); paginal.setTotalCount(totalCount);//总记录数 paginal.setPageNum(totalCount,pageSize);//总页码 //查询得到 List<Map<String,Object>> List resultList = queryForMapList(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>,params,<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class); paginal.setResultList(resultList); return paginal; } /** * 查询总记录数 * * 根据指定查询条件查询记录总数，一般用于分页中等 * * @param params 查询条件参数 * @param <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class 对象类型 * @return 记录数 */ @SuppressWarnings({ "rawtypes"}) public int queryCount(Map<String,Object> params,Class <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class){ //获取表名 tableName = getTableConfigName(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class); //组装查询总记录数<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>语句 String count<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> = buildQueryConteSql(params); //查询对象,存储查询条件数组 Object[] queryObject = getQueryObject(params); //查询总记录数 int totalCount = getJdbcTemplate().queryForInt(count<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>, queryObject); return totalCount; }

以上提供了几个分页查询api，封装的思路大致是：

分页查询 -> 带排序的分页查询

其实各种查询归根结底就是查询使用的class="tags" href="/tags/SQL.html" title=sql>sql的不同，由于之前我们封装的class="tags" href="/tags/SQL.html" title=sql>sql的生成方法和采用可编程度参数指定查询排序字段的方式，使得后续的工作变得很顺利。

分页器：

class</a>="java">package com.netease.space.dao.base; import java.io.Serializable; import java.util.List; /** * 分页器 * * my<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>的分页机制：limit offset,pagesize [] 从0开始计数偏移offset位的pagesize条数据 * 比如： * pagesize = 10; * ------------------------------------------------- * | 页号 | 起始地址 | 结束地址 | 包含记录ID |offset| * ------------------------------------------------- * | 1 | 0 | 9 |0,1,2...9 | 0 | * | 2 | 10 | 19 |10,11,12...19 | 10 | * | 3 | 20 | 29 |20,22,23...29 | 20 | * -------------------------------------------------- * * 用法示例： * limit getOffset(),pagesize; * * @author quzishen * @param <T> 查询结果的具体类型 */ public <a class="tags" href="/tags/CLASS.html" title=class>class</a> Paginal<T extends Object> implements Serializable{ private static final long serialVersionUID = -5159256681785242925L; // 分页大小 private int pageSize; // 页号，从1开始 private int pageNomber; // 总记录数 private int totalCount; // 总页数 private int pageNum; // 查询对象列表 private List<T> resultList; /** * 获取当前页的起始地址 * @return 起始地址 */ protected int getBeginIndex(){ return (pageNomber - 1)*pageSize; } /** * 获取当前页的结束地址 * @return 结束地址 */ protected int getEndIndex(){ return pageNomber*pageSize - 1; } /** * 获取当前页的偏移量 * @return 偏移量 */ protected int getOffset(){ if(pageNomber == 1){ return 0; } else { return (pageNomber-1)*pageSize; } } /** * 根据总记录数和分页大小设置总页数 * @param totalCount 总记录数 * @param pagesize 分页大小 */ public void setPageNum(int totalCount,int pagesize){ int num = totalCount / pagesize; if(0 != totalCount % pagesize){ num += 1; } pageNum = num; } public int getPageSize() { return pageSize; } public void setPageSize(int pageSize) { this.pageSize = pageSize; } public int getPageNomber() { return pageNomber; } public void setPageNomber(int pageNomber) { this.pageNomber = pageNomber; } public int getTotalCount() { return totalCount; } public void setTotalCount(int totalCount) { this.totalCount = totalCount; } public int getPageNum() { return pageNum; } public void setPageNum(int pageNum) { this.pageNum = pageNum; } public List<T> getResultList() { return resultList; } public void setResultList(List<T> resultList) { this.resultList = resultList; } }

请看详细代码：

class</a>="java:collapse">package com.netease.space.dao.base; import java.lang.reflect.Field; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>.ResultSet; import java.<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>.ResultSetMetaData; import java.<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>.SQLException; import java.util.ArrayList; import java.util.HashMap; import java.util.Iterator; import java.util.List; import java.util.Map; import org.apache.commons.beanutils.ConvertUtils; import org.apache.commons.lang.StringUtils; import org.springframework.beans.factory.InitializingBean; import org.springframework.jdbc.core.RowMapper; import org.springframework.jdbc.core.simple.SimpleJdbcInsert; import org.springframework.jdbc.core.support.JdbcDaoSupport; /** * DAO抽象父类，提供针对于数据库的基本操作 * 工程名称：NormandyPosition * 类型名称：AbstractBaseDAO * 概要： * * 提供针对于DAO基础操作服务 * 注意使用该类提供的API，必须保证DO类的属性名称，与对应数据库表的名称相同，不区分大小写 * * 创建时间：2010-7-27 上午12:58:42 * 创建人：quzishen * 最后修改时间：2010-7-27 上午12:58:42 * 最后修改内容： * @version 1.0 */ public abstract <a class="tags" href="/tags/CLASS.html" title=class>class</a> AbstractBaseDAO extends JdbcDaoSupport implements InitializingBean{ //~~~ instance fields // table name private String tableName; //used for insert SimpleJdbcInsert inserActor; //default getter method prefix public String GET_METHOD_PRE = "get"; //default setter method prefix public String SET_METHOD_PRE = "set"; //default key name public String DEFAULT_ID_NAME = "id"; //default serialVersionUID name public String DEFAULT_SERIALVERSIONUID_NAME = "serialVersionUID"; //~~~ static final fields start ****************// private final static String SQL_SELECT = " select "; private final static String SQL_FROM = " from "; private final static String SQL_WHERE = " where "; private final static String SQL_AND = " and "; private final static String SQL_UPDATE = " update "; private final static String SQL_SET = " set "; private final static String SQL_ORDER_BY = " order by "; private final static String SQL_LIMIT = " limit "; private final static String SQL_COUNT = " count(*) "; private final static String SQL_EQUAL = " = "; private final static String SQL_SPLIT = " , "; private final static String SQL_PLACE_HOLDER = " ? "; //~~~ static final fields end ****************// /**************************************///public method begin /*******************************/ /** * 新增一条记录 * * 要求DO：遵循spring风格的getter和setter方法 * 属性的名称和数据库的名称要对应，大小写不区分 * 示例: * ----------------------------------------------------- * TABLE Person{ * ID BIGINT NOT NULL, * NAME VARCHAR(16) .... * }//数据库中字段为大写 * ----------------------------------------------------- * <a class="tags" href="/tags/CLASS.html" title=class>class</a> Person{ * private long id; * private String name; * }//DO类中的字段为小写 * ----------------------------------------------------- * Person person = new Person(); * person.setName("quzishen"); * long id = insertObject(person); * * * @param 插入对象 * @return 主键ID * @throws RuntimeException */ public int insertObject(Object <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>) throws RuntimeException{ // 获取类型 @SuppressWarnings("rawtypes") Class <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class = <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>.getClass(); //获取表名 tableName = getTableConfigName(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class); // 使用SimpleJdbcInsert完成插入的动作 inserActor = new SimpleJdbcInsert(getJdbcTemplate()).withTableName(tableName); // 获取该对象的所有的private protected publick的属性 Field[] fields = getFieldsFromClass(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class); // 将属性名字保存下来 List<String> fieldNameSet = getFiledNameList(fields); // 设置需要更新的字段以及主键 setUsingListFromNameSet(fieldNameSet); // 获取插入数据库<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>需要的参数Map Map<String, Object> paramMap = getParamMap(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>, fields); //简便起见，可以使用SqlParameterSource parameters = new BeanPropertySqlParameterSource(Actor); // 获取到的参数为空 if(null == paramMap){ throw new RuntimeException("can not insert a null value!"); } //执行插入并返回主键 return inserActor.executeAndReturnKey(paramMap).intValue(); } /** * 查询单一对象 * * 要求：遵循spring风格的getter和setter方法 * 属性的名称和数据库的名称要对应，大小写不区分 * 这里一定要注意，如果属性的大小写有点个性非常强的个人色彩， * 那么相应的setter方法要保证'set'后的属性首字母大写，其他字母大小写保持不变 * 如：pArAm ----> getPArAm & setPArAm * 示例： * ------------------------------------------------------------- * <a class="tags" href="/tags/CLASS.html" title=class>class</a> Person{ * private long id; * } * ------------------------------------------------------------- * Map<String,Object> params = new HashMap<String,Object>(); * params.put("id","10000"); * Person person = (Person) queryForObject(params,Person.<a class="tags" href="/tags/CLASS.html" title=class>class</a>); * * * @param params 查询条件map,key 属性名字大小写无所谓 * @param returnClass 对象类型 * @return 查询结果 */ public Object queryForObject(Map<String,Object> params,@SuppressWarnings("rawtypes") final Class returnClass) throws RuntimeException{ // 组装查询<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>，参数使用占位符 String <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> = buildQuerySql(null,params,-1,-1,false); //获取表名 tableName = getTableConfigName(returnClass); // 查询对象,存储查询条件数组 Object[] queryObject = getQueryObject(params); //调用queryForObject并且重新RowMapper回调方法 return getJdbcTemplate().queryForObject(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>, queryObject,new RowMapper() { public Object mapRow(ResultSet resultSet, int rowNum) throws SQLException { if(1 < rowNum){ throw new RuntimeException("query result is more than one!"); } //~~~ return value 组装返回对象 Object <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a> = getObjectFromResultSet(resultSet,returnClass); return <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>; } }); } /** * 查询对象列表结果 * * 要求：遵循spring风格的getter和setter方法 * 属性的名称和数据库的名称要对应，大小写不区分 * 这里一定要注意，如果属性的大小写有点个性非常强的个人色彩， * 那么相应的setter方法要保证'set'后的属性首字母大写，其他字母大小写保持不变 * 如：pArAm ----> getPArAm & setPArAm * 示例： * ------------------------------------------------------------- * <a class="tags" href="/tags/CLASS.html" title=class>class</a> Person{ * private String desc; * } * ------------------------------------------------------------- * Map<String,Object> params = new HashMap<String,Object>(); * params.put("desc","10000"); * List<Person> persons = (List<Person>) queryForList(params,Person.<a class="tags" href="/tags/CLASS.html" title=class>class</a>); * * * @param params 参数Map * @param returnClass 返回列表中的对象类型 * @return */ @SuppressWarnings("rawtypes") public List queryForObjectList(Map<String,Object> params,final Class returnClass){ return queryForObjectListOrderRow(params,returnClass); } /** * 查询对象列表结果，查询按照指定列排序 * * 关于排序列（可变长度参数部分）： * 根据排序的列的次序依次排列，每个Map中存放一个键值对，允许指定的排序为 asc || desc * * 示例： * Map<String,String> orderByName = new HashMap<String,String>(); * orderByName.put("name","asc"); * * Map<String,String> orderByAge = new HashMap<String,String>(); * orderByName.put("age","desc"); * * Map<String,String> orderByType = new HashMap<String,String>(); * orderByName.put("type","asc"); * * queryForListOrderRow(params,returnClass,orderByName,orderByAge,orderByType) * * @param params * @param returnClass * @param orders * @return */ @SuppressWarnings("rawtypes") public List queryForObjectListOrderRow(Map<String,Object> params, final Class returnClass, Map<String,String>... orders){ // 组装查询<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>，参数使用占位符替代 String <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> = buildQuerySql(null,params,-1,-1,false,orders); if(logger.isDebugEnabled()){ logger.debug("RUN SQL:"+<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>); } //执行查询 return queryForList(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>,params,returnClass); } /** * 查询部分字段 * * 根据指定的属性名称查询特定字段，返回一个List<Map<属性名称，属性值>> * * 使用示例： * --------------------------------------------------------------- * //设置查询参数 * Map<String,Object> params = new HashMap(); * params.put("city","hangzhou"); * * //设置需要查询的字段名称，名称使用DO中的即可 * List<String> fields = new ArrayList<String>(); * fields.add("id"); * fields.add(name); * fields.add("address"); * * List<Map<String,Object>> resultList = queryFieldsList(Person.<a class="tags" href="/tags/CLASS.html" title=class>class</a>,params,fields); * ... * * * @param <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class 返回属性所在的类 * @param <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class * @param params 查询参数map * @param returnFields 返回字段列表 * @return 返回值，用map保存每一列的结果 */ public List<Map<String,Object>> queryFieldsList(@SuppressWarnings("rawtypes")final Class <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class,Map<String,Object> params,List<String> returnFields){ return queryFieldsListOrderRow(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class,params,returnFields); } /** * 查询部分字段,查询结果根据指定列排序 * * 根据指定的属性名称查询特定字段，并且根据指定的列排序，返回一个List<Map<属性名称，属性值>> * 使用示例： * --------------------------------------------------------------- * //设置查询参数 * Map<String,Object> params = new HashMap(); * params.put("city","hangzhou"); * * //设置需要查询的字段名称，名称使用DO中的即可 * List<String> fields = new ArrayList<String>(); * fields.add("id"); * fields.add(name); * fields.add("address"); * * Map<String,String> orderByAge = new HashMap<String,String>(); * orderByName.put("age","desc"); * * Map<String,String> orderByType = new HashMap<String,String>(); * orderByName.put("type","asc"); * * List<Map<String,Object>> resultList = queryFieldsList(Person.<a class="tags" href="/tags/CLASS.html" title=class>class</a>,params,fields,orderByAge,orderByType); * ... * * * @param <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class 返回属性所在的类 * @param params 查询参数map * @param returnFields 返回字段列表 * @param orders 查询语句排序指定字段 * @return 返回值，用map保存每一列的结果 */ @SuppressWarnings("unchecked") public List<Map<String,Object>> queryFieldsListOrderRow(@SuppressWarnings("rawtypes")final Class <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class, Map<String,Object> params,List<String> returnFields,Map<String,String>... orders){ // 组装查询<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>，参数使用占位符替代 String <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> = buildQuerySql(returnFields,params,-1,-1,false,orders); //获取表名 tableName = getTableConfigName(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class); return queryForMapList(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>,params,<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class); } /** * 分页查询对象 * * 根据指定参数分页查询对象列表 * 用法示例： * ---------------------------------------------------------- * //设置查询参数 * Map<String,Object> params = new HashMap(); * params.put("city","hangzhou"); * * Paginal p = queryObjectListForPaging(Person.<a class="tags" href="/tags/CLASS.html" title=class>class</a>,params,1,10); * ... * * @param <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class 对象类型 * @param params 查询参数 * @param pageNomber 页号 * @param pageSize 分页大小 * @return 分页封装 */ @SuppressWarnings({ "rawtypes"}) public Paginal queryObjectListForPaging(final Class <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class,Map<String,Object> params,int pageNomber,int pageSize){ return queryObjectListForPagingOrderRow(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class,params,pageNomber,pageSize); } /** * 分页-排序查询对象 * * 分页查询，结果按照指定的条件排序 * 使用示例 * ---------------------------------------------------------- * //设置查询参数 * Map<String,Object> params = new HashMap(); * params.put("city","hangzhou"); * * Map<String,String> orderByAge = new HashMap<String,String>(); * orderByName.put("age","desc"); * * Map<String,String> orderByType = new HashMap<String,String>(); * orderByName.put("type","asc"); * * Paginal p = queryObjectListForPagingOrderRow(Person.<a class="tags" href="/tags/CLASS.html" title=class>class</a>,params,1,10,orderByAge,orderByType); * ... * * @param <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class 字段所在类 * @param params 查询参数 * @param pageNomber 页号 * @param pageSize 分页大小 * @param orders 排序字段 * @return 查询结果 */ @SuppressWarnings({ "rawtypes", "unchecked" }) public Paginal queryObjectListForPagingOrderRow(final Class <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class,Map<String,Object> params,int pageNomber,int pageSize,Map<String,String>... orders){ //~~~ return value Paginal<? extends Object> paginal = new Paginal<Object>(); // 初始化分页器 paginal.setPageNomber(pageNomber); paginal.setPageSize(pageSize); //获取表名 tableName = getTableConfigName(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class); //组装查询<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>语句 String <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> = buildQuerySql(null, params, paginal.getOffset(),paginal.getPageSize(),false,orders); //查询总记录数 int totalCount = queryCount(params,<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class); paginal.setTotalCount(totalCount);//总记录数 paginal.setPageNum(totalCount,pageSize);//总页码 //执行查询 List resultList = queryForList(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>,params,<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class); paginal.setResultList(resultList); return paginal; } /** * 分页查询部分字段 * * 使用示例 * ----------------------------------------------------------------- * //设置查询参数 * Map<String,Object> params = new HashMap(); * params.put("city","hangzhou"); * * //设置需要查询的字段名称，名称使用DO中的即可 * List<String> fields = new ArrayList<String>(); * fields.add("id"); * fields.add(name); * fields.add("address"); * * Paginal p = queryFieldsListForPaging(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class,params,fields,1,10); * ... * * @param <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class 字段所在的类 * @param params 查询参数 * @param returnFields 需要查询的字段列表 * @param pageNomber 页号 * @param pageSize 分页大小 * @return 查询结果 */ @SuppressWarnings({ "rawtypes"}) public Paginal queryFieldsListForPaging(final Class <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class,Map<String,Object> params,List<String> returnFields,int pageNomber,int pageSize){ return queryFieldsListForPagingOrderRow(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class,params,returnFields,pageNomber,pageSize); } /** * 分页-排序查询部分字段 * * 使用示例 * ----------------------------------------------------------------- * //设置查询参数 * Map<String,Object> params = new HashMap(); * params.put("city","hangzhou"); * * //设置需要查询的字段名称，名称使用DO中的即可 * List<String> fields = new ArrayList<String>(); * fields.add("id"); * fields.add(name); * fields.add("address"); * * Map<String,String> orderByAge = new HashMap<String,String>(); * orderByName.put("age","desc"); * * Map<String,String> orderByType = new HashMap<String,String>(); * orderByName.put("type","asc"); * * Paginal p = queryFieldsListForPaging(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class,params,fields,1,10,orderByAge,orderByType); * ... * * @param <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class 字段所在的类 * @param params 查询参数 * @param returnFields 需要查询的字段列表 * @param pageNomber 页号 * @param pageSize 分页大小 * @param orders 排序字段 * @return 查询结果 */ @SuppressWarnings({ "rawtypes", "unchecked" }) public Paginal queryFieldsListForPagingOrderRow(final Class <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class,Map<String,Object> params,List<String> returnFields,int pageNomber,int pageSize,Map<String,String>... orders){ //~~~ return value Paginal<? extends Object> paginal = new Paginal<Object>(); // 初始化分页器 paginal.setPageNomber(pageNomber); paginal.setPageSize(pageSize); //获取表名 tableName = getTableConfigName(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class); //组装查询<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>语句 String <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> = buildQuerySql(returnFields, params, paginal.getOffset(),paginal.getPageSize(),false,orders); //查询总记录数 int totalCount = queryCount(params,<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class); paginal.setTotalCount(totalCount);//总记录数 paginal.setPageNum(totalCount,pageSize);//总页码 //查询得到 List<Map<String,Object>> List resultList = queryForMapList(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>,params,<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class); paginal.setResultList(resultList); return paginal; } /** * 查询总记录数 * * 根据指定查询条件查询记录总数，一般用于分页中等 * * @param params 查询条件参数 * @param <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class 对象类型 * @return 记录数 */ @SuppressWarnings({ "rawtypes"}) public int queryCount(Map<String,Object> params,Class <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class){ //获取表名 tableName = getTableConfigName(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class); //组装查询总记录数<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>语句 String count<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> = buildQueryConteSql(params); //查询对象,存储查询条件数组 Object[] queryObject = getQueryObject(params); //查询总记录数 int totalCount = getJdbcTemplate().queryForInt(count<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>, queryObject); return totalCount; } /*****************************///private methods begin .../*****************************/ /** * 查询列表 * @param <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> 查询<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>，其中参数部分使用占位符？代替具体的值 * @param params 查询条件值的map * @param returnClass 返回值类型 * @return 查询列表 */ @SuppressWarnings("rawtypes") private List queryForList(String <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>,Map<String,Object> params,final Class returnClass){ //获取表名 tableName = getTableConfigName(returnClass); // 查询对象,存储查询条件数组 Object[] queryObject = getQueryObject(params); //执行查询，设置rowMapper进行结果从List<Map> --> List<Object>的转换 return getJdbcTemplate().query(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>, queryObject,new RowMapper(){ public Object mapRow(ResultSet resultSet, int rowNum) throws SQLException { //~~~ return value 组装返回对象 Object <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a> = getObjectFromResultSet(resultSet,returnClass); return <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>; } }); } @SuppressWarnings({ "rawtypes","unchecked" }) private List queryForMapList(String <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>,Map<String,Object> params,final Class <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class){ //获取查询参数 Object[] queryObject = getQueryObject(params); //获取对象声明的属性 final Field[] fields = getFieldsFromClass(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class); return (List<Map<String,Object>>)getJdbcTemplate().query(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>, queryObject, new RowMapper(){ public Object mapRow(ResultSet resultSet, int count) throws SQLException { try{ Map<String,? extends Object> resultMap = getResultMapFromResultSet(resultSet,fields); return resultMap; }catch(Exception e){ throw new RuntimeException("can not get result from resultSet!"); } } }); } /** * 获取注解中配置的表名称 * @param Class 注解所添加位置的类 * @return String 注解中配置的tablename */ protected String getTableConfigName(@SuppressWarnings("rawtypes") Class <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class){ @SuppressWarnings("unchecked") Table tableAnnotation = (Table)<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>Class.getAnnotation(Table.<a class="tags" href="/tags/CLASS.html" title=class>class</a>); String tableName = tableAnnotation.tableName(); return tableName; } /** * 根据<a class="tags" href="/tags/CLASS.html" title=class>class</a>和resultSet填充对象 * 通过反射，调用setter方法设置DO * @param resultSet 查询返回值 * @param returnClass 返回值类型 */ private Object getObjectFromResultSet(ResultSet resultSet,@SuppressWarnings("rawtypes") Class returnClass) throws RuntimeException{ // ~~~ return value Object <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a> = getInstanceByClass(returnClass); if(null != <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>){ if(null == resultSet){ return null; } // 根据返回类型获取fields Field[] fields = getFieldsFromClass(returnClass); try{ //获取结果map<属性名,属性值>,用于方便的获取属性对应的值 Map<String,? extends Object> resultMap = getResultMapFromResultSet(resultSet,fields); //遍历列表设置值,通过反射调用setter方法设置 for(Field field : fields){ if(checkIsSerivalVersioinUID(field.getName())){ //如果是序列ID，掠过 continue; } // 获取方法名 String methodName = getSetMethod(field.getName()); // 获取方法 Method method = <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>.getClass().getMethod(methodName, field.getType()); // 获取参数 Object param = resultMap.get(field.getName());//不能直接从resultSet中取值，因为其中的name是数据库的列名 // 执行setter方法 method.invoke(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>, param); } }catch(Exception e){ logger.error("queryForObject exception!",e); throw new RuntimeException(e); } }else { //获取实例失败，这里抛出异常 throw new RuntimeException("build result <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a> failed!"); } return <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>; } /** * 根据传入Map获取查询参数数组对象 * @param params 参数Map * @return Object[] */ private Object[] getQueryObject(Map<String,Object> params){ // 查询对象,存储查询条件数组 Object[] queryObject = new Object[params.size()]; // 获取查询参数 int index = 0; // 初始化查询对象 for(String param : params.keySet()){ queryObject[index++] = params.get(param); } return queryObject; } /** * 组装查询语句 * * 目前只支持了全部列查询 * 关于排序列（可变长度参数部分）： * @see queryForListOrderRow * * @param rows 需要查找的列，如果null，则全字段 * @param params 参数map * @param offset 偏移量，-1标示不分页 * @param pagesize 分页大小，-1标示不分页 * @param useValue 是否使用参数值作为搜索条件的值，若false，则使用？代替 * @return <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/STRING.html" title=string>string</a> 查询<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> */ private String buildQuerySql(List<String> rows,Map<String,Object> params,int offset,int pagesize, boolean useValue,Map<String,String>... orders){ // 获取需要查找的列 String listStr = getSelecteKeyFromList(rows); // 组装<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> String <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> = SQL_SELECT+listStr+ SQL_FROM + tableName; //如果后面不含有查询条件，则直接返回 if(null!=params && 0 < params.size()){ <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> = getSqlCondition(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>,params, useValue); } if(-1 != offset || -1 != pagesize){ // limit offset,pagesize <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> += (SQL_LIMIT+offset+SQL_SPLIT+pagesize+" "); } return getSqlOrder(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>,orders); } /** * 组装根据条件查询总记录数的<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> * @param params 条件 * @return <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>语句 */ private String buildQueryConteSql(Map<String,Object> params){ // 获取需要查找的列 String <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> = SQL_SELECT+SQL_COUNT+SQL_FROM+ tableName; //如果后面不含有查询条件，则直接返回 if(null!=params && 0 < params.size()){ <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> = getSqlCondition(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>,params, false); } return <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>; } /** * 从查询列的列表中取出列名，并按照<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>的要求逗号隔开，如 a,b,c,d * 如果传入查询列的列表为空，或者长度为0，怎返回 * ，代表全部字段都查询 * @param rows * @return */ private static String getSelecteKeyFromList(List<String> rows){ if(null == rows || 0 == rows.size()){ return "*"; } String listStr = rows.toString(); listStr = getSubString(listStr, 1, 1); return listStr; } /** * 组装更新语句 * 除了主键外的全字段更新，限制条件可以自由设定 * @param <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a> * @param useValue * @param conditions * @return */ private String buildUpdateObjectSql(Object <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>,boolean useValue,Map<String,Object> conditions){ //组装更新<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> String <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> = SQL_UPDATE + tableName + SQL_SET; //获取域数组 Field[] fields = getFieldFromObject(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>); //获取属性和值的map，不包括主键和序列ID Map<String, Object> params = getParamMap(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>, fields); //更新<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>必须含有需要修改的字段的内容，否则抛出异常 if(null == params || 0 >= params.size()){ throw new RuntimeException("can not update without values!"); } //添加修改字段的<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>片段 for(String key : params.keySet()){ <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> += (key + SQL_EQUAL +(useValue? params.get(key):SQL_PLACE_HOLDER)); <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> += SQL_SPLIT; } <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> = getSubString(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>,0,1);//去掉最后的一个逗号 return getSqlCondition(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>,conditions, useValue); } /** * 获取<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>语句的后半部分，从where开始的条件设定部分 * @param <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>前半部分，可以是select或者update或者delte，不限 * @param conditions 条件map * @param useValue 是否使用具体值替代占位符？ * @return */ private static String getSqlCondition(String <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>,Map<String,Object> conditions,boolean useValue){ //开始组装条件 <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> += SQL_WHERE; for(String key : conditions.keySet()){ <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> += (key+SQL_EQUAL); <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> += useValue? conditions.get(key):SQL_PLACE_HOLDER; <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> += SQL_AND; } return getSubString(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>,0, 5);//取消最后的" and "; } /** * 获取<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>的后半order by的部分，如果没有指定排序，那么直接返回<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> * @param <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>前半部分，通常截止于where语句 * @param orders 排序列的map，按照排序的次序依次排列 * @return 转换后的<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> */ private static String getSqlOrder(String <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>,Map<String,String>... orders){ if(null == orders || 0 == orders.length){ return <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>; }else { <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> += SQL_ORDER_BY; } //遍历order组，添加附加的排序条件 for(int i = 0; i < orders.length; i++){ //获取其中的每一组，并获取其中的key和value Map<String,String> orderItem = orders[i]; if(!orderItem.keySet().isEmpty()){ //使用迭代器取出map中的第一个键值对，通常也是当前map中的唯一一对 Iterator<String> index = orderItem.keySet().iterator(); if(index.hasNext()){ String key = index.next(); <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> += (" " + key + " "+orderItem.get(key));//like name desc <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> += SQL_SPLIT;//like name desc, } } } int splitPoint = <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>.lastIndexOf(','); <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a> = getSubString(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>,0, <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>.length()-splitPoint);//去掉最后一个逗号 return <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>; } /** * 获取部分字符串 * @param str * @param begin 起始位数，从首位开始计数，0开始 * @param end 从末尾开始计数的，截止位 * @return */ private static String getSubString(String str,int begin,int end){ return str.sub<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/STRING.html" title=string>string</a>(begin, str.length()-end); } /** * 从对象中获取Field数组 * @param <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a> * @return */ private Field[] getFieldFromObject(Object <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>){ @SuppressWarnings("rawtypes") Class <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a><a class="tags" href="/tags/CLASS.html" title=class>class</a> = <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>.getClass(); Field[] fields = getFieldsFromClass(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a><a class="tags" href="/tags/CLASS.html" title=class>class</a>); return fields; } /** * 获取结果的map<fieldName,fieldValue> * * 从数据库中获取而来的ResultSet，类型为 <数据库字段相同大小写的字符串，数据库字段类型> * 我们需要转换成：<对象中的属性名称大小写的字符串，对象中的属性的类型> * * @param resultSet 结果set * @param fields 属性数组 * @throws Exception */ private Map<String,? extends Object> getResultMapFromResultSet(ResultSet resultSet,Field[] fields) throws Exception{ //~~~ return value Map<String,Object> map = new HashMap<String,Object>(); //获取元数据 ResultSetMetaData setMetaData = resultSet.getMetaData(); //遍历各列，获取各列的值和在DO类中对应的属性的名称 for(int i=1;i<=setMetaData.getColumnCount();i++){ //获得列名称 String columnName = setMetaData.getColumnName(i);//特别注意，这里的下标从1开始 if(logger.isDebugEnabled()){ logger.debug("get column:"+columnName); } //获得当前列的值 Object rowObject = resultSet.getObject(columnName) == null ? "":resultSet.getObject(columnName); //获取当前列对应的属性在属性组中的下标 int index = getFieldIndexOfObject(fields,columnName); if(-1 == index){ throw new Exception("can not find index of column :"+columnName+" in fields."); } //将当前字段从数据库类型转换成DO中的类型 rowObject = ConvertUtils.convert(rowObject.toString(), fields[index].getType()); //获得当前列在对象中对应的属性名 String realName = getFieldRealNameOfObject(fields,columnName); if(null == realName || "".equals(realName)){ logger.error("no field match the name:"+columnName); throw new Exception(); } map.put(realName, rowObject); } return map; } /** * 用于获取fields中当前数据库列对应的名字 * @param fields 属性域数组 * @param rowNameInResultSet * @return */ private String getFieldRealNameOfObject(Field[] fields,String rowNameInResultSet){ List<String> fieldNameSet = getFiledNameList(fields); //一次遍历，不分大小写，用于解决DO和数据库字段的属性名字大小写不一致的问题 for(String s:fieldNameSet){ if(StringUtils.equalsIgnoreCase(s, rowNameInResultSet)){ return s; } } return null; } /** * 返回当前列对应的属性在field数组中的下标 * @param fields * @param rowNameInResultSet * @return */ private int getFieldIndexOfObject(Field[] fields,String rowNameInResultSet){ List<String> fieldNameSet = getFiledNameList(fields); //一次遍历，不分大小写，用于解决DO和数据库字段的属性名字大小写不一致的问题 int index = 0; for(String s:fieldNameSet){ if(StringUtils.equalsIgnoreCase(s, rowNameInResultSet)){ return index; } index++; } return -1; } /** * 根据<a class="tags" href="/tags/CLASS.html" title=class>class</a>获取一个实例对象 * @param <a class="tags" href="/tags/CLASS.html" title=class>class</a> * @return null 或者对象实例 */ private Object getInstanceByClass(@SuppressWarnings("rawtypes") Class <a class="tags" href="/tags/CLASS.html" title=class>class</a>Name){ Object <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a> = null; try { <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a> = <a class="tags" href="/tags/CLASS.html" title=class>class</a>Name.newInstance();//new 一个对象 //把产生的异常都吃掉，这里返回null可以触发上层抛出异常 } catch (InstantiationException e) { logger.error("new instance exception!",e); } catch (IllegalAccessException e) { logger.error("can not access the instance method!",e); } //return null or a <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a> return <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>; } /** * 根据类名获取所有声明的属性列表 * 注意其中也包含了不属于数据库对应字段的属性，比如序列号ID * @param <a class="tags" href="/tags/CLASS.html" title=class>class</a>Name 类名称 * @return field数组 */ private Field[] getFieldsFromClass(@SuppressWarnings("rawtypes") Class <a class="tags" href="/tags/CLASS.html" title=class>class</a>Name){ Field[] fields = <a class="tags" href="/tags/CLASS.html" title=class>class</a>Name.getDeclaredFields(); return fields; } /** * 根据属性数组获取属性名称的set * 这里必须使用list，以保持次序 * @param fields * @return */ private List<String> getFiledNameList(Field[] fields) { //~~~ return value List<String> fieldNameSet = new ArrayList<String>(); // get the name of each for (int i = 0; i < fields.length; i++) { fieldNameSet.add(fields[i].getName()); } return fieldNameSet; } /** * 设置需要增加的属性以及主键 * 针对于insert方法，提供需要插入的字段名称，其中不包括主键ID和序列号SerivalVserionId * @param fieldNameSet */ private void setUsingListFromNameSet(List<String> fieldNameSet) { //~~~ return value List<String> usingColums = new ArrayList<String>(); // 使用所有的除了主键和序列号的字段名称 for (String field : fieldNameSet) { if (StringUtils.equalsIgnoreCase(field, DEFAULT_SERIALVERSIONUID_NAME)) { //序列号掠过 continue; } if (!StringUtils.equalsIgnoreCase(field, DEFAULT_ID_NAME)) { //不是主键，放入字段列表 usingColums.add(field); } else { //主键作为返回字段 inserActor = inserActor.usingGeneratedKeyColumns(field); } } inserActor.setColumnNames(usingColums); } /** * 检查是否是序列号ID * @param field * @return */ private boolean checkIsSerivalVersioinUID(String field){ return StringUtils.equalsIgnoreCase(field,DEFAULT_SERIALVERSIONUID_NAME); } /** * 获取插入数据库中的<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/SQL.html" title=sql>sql</a>需要的参数Map * 其中不包括主键和序列号 * @param <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a> 实例化后的对象 * @param fields 对象类包含的<a class="tags" href="/tags/CLASS.html" title=class>class</a> * @return <属性名称，属性值> * @throws SecurityException */ private Map<String, Object> getParamMap(Object <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>, Field[] fields) throws SecurityException{ //~~~ return value Map<String, Object> paramMap = new HashMap<String, Object>(); //依次遍历对象的get方法，获取对象的属性值，放入map中 for (int i = 0; i < fields.length; i++) { if (!checkIsNeedField(fields[i].getName())) { continue; } else { String methodName = getGetMethod(fields[i].getName()); if(logger.isDebugEnabled()){ logger.debug("run method:" + methodName); } try { // 通过代理执行访问器 Method method = <a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>.getClass().getMethod(methodName); // get方法没有参数，不需要获取参数类型，fields[i].getGenericType().getClass() Object result = method.invoke(<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>, new Object[] {});//调用get方法获取属性值 String value = null==result? "":result.toString(); paramMap.put(fields[i].getName(), value); } catch (SecurityException e) { // 由安全管理器抛出的异常，指示存在安全侵犯 throw e; } catch (NoSuchMethodException e) { // 没有该方法 logger.error("There is no method '"+methodName+"' in Class "+<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>.getClass()+"! Check your getter method name!",e); return null; }catch (IllegalArgumentException e) { // 参数不正确 logger.error("IllegalArgumentException happend because the method '"+methodName+"'"+"' in Class "+<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>.getClass()+ "has some parameters!",e); return null; } catch (IllegalAccessException e) { // 访问的方法不能被访问，一般是由于private等权限问题 logger.error("The method '"+methodName+"' in Class "+<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>.getClass()+"can not be accessed!Check your getter method whether it is private of protected!",e); return null; } catch (InvocationTargetException e) { // 映射目标异常 logger.error("The invoke method '"+methodName+"' in Class "+<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/OBJECT.html" title=object>object</a>.getClass()+"is not right!Check your getter method name!",e); return null; } } } return paramMap; } /** * 获取默认的get方法的名字,根据spring的默认规则 * @param fieldName * @return */ private String getGetMethod(String fieldName){ //生成诸如getParam1的方法名称 String methodName = GET_METHOD_PRE + changeFirstChar2upper(fieldName); return methodName; } private String getSetMethod(String fieldName){ //生成诸如setParam1的方法名称 String methodName = SET_METHOD_PRE + changeFirstChar2upper(fieldName); return methodName; } /** * 将字符串的首字母大写 * @param fieldName * @return */ private static String changeFirstChar2upper(String fieldName){ return fieldName.toUpperCase().charAt(0) + fieldName.sub<a <a class="tags" href="/tags/CLASS.html" title=class>class</a>="tags" href="/tags/STRING.html" title=string>string</a>(1, fieldName.length()); } /** * 检查是否是必要的需要修改的字段 * @param fieldName * @return */ private boolean checkIsNeedField(String fieldName){ if (StringUtils.equalsIgnoreCase(fieldName, DEFAULT_SERIALVERSIONUID_NAME) || StringUtils.equalsIgnoreCase(fieldName, DEFAULT_ID_NAME)) { return false; } return true; } /***************************************///getter & setter //*********************************************** public String getTableName() { return tableName; } public void setTableName(String tableName) { this.tableName = tableName; } }

可以看到，正如我之前所讲，这几种不同的查询全部依赖于底层的几个基础方法：

封装查询class="tags" href="/tags/SQL.html" title=sql>sql的方法：buildQuerySql

查询对象列表方法：queryForList

查询map列表方法：queryForMapList 即部分属性查询方法

通过这几个方法的组合以及可变长度参数的使用，可以灵活封装不同的api。

----------------------------------------------

从下一章节，我们开始讲述修改相关的操作。

[框架那点事儿-快速开发季]编写自己的数据持久层（4）分页查询

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