QueryRunner 结果处理器

package cn.itcast.dbutil;import java.sql.SQLException;import java.util.List;import java.util.Map;import org.apache.commons.dbutils.QueryRunner;import org.apache.commons.dbutils.handlers.ArrayHandler;import org.apache.commons.dbutils.handlers.ArrayListHandler;import org.apache.commons.dbutils.handlers.BeanHandler;import org.apache.commons.dbutils.handlers.BeanListHandler;import org.apache.commons.dbutils.handlers.ColumnListHandler;import org.apache.commons.dbutils.handlers.KeyedHandler;import org.apache.commons.dbutils.handlers.MapHandler;import org.apache.commons.dbutils.handlers.MapListHandler;import org.apache.commons.dbutils.handlers.ScalarHandler;import org.junit.Test;import cn.itcast.domain.Account;import cn.itcast.util.DBCPUtil;//查询练习public class DbUtilDemo2 {    private QueryRunner qr = new QueryRunner(DBCPUtil.getDataSource());    @Test//BeanHandler    public void test1() throws SQLException{        Account a = qr.query("select * from account where id=?", new BeanHandler<Account>(Account.class), 1);        System.out.println(a);    }    @Test//BeanListHandler    public void test2() throws SQLException{        List<Account> list = qr.query("select * from account", new BeanListHandler<Account>(Account.class));        for(Account a:list)            System.out.println(a);    }        @Test//ArrayHandler：把结果集中的第一行数据转成对象数组。只适合结果集有一条记录的情况    public void test3() throws SQLException{        //该数组中每个元素就是记录的每列的值        Object objs[] = qr.query("select * from account where id=?", new ArrayHandler(),1);        for(Object o:objs)            System.out.println(o);    }    @Test//ArrayListHandler：把结果集中的每一行数据都转成一个数组，再存放到List中。    public void test4() throws SQLException{        //该数组中每个元素就是记录的每列的值        List<Object[]> list = qr.query("select * from account", new ArrayListHandler());        for(Object[] objs:list){            System.out.println("-----------------");            for(Object o:objs)                System.out.println(o);        }    }    @Test//ColumnListHandler：将结果集中某一列的数据存放到List中    public void test5() throws SQLException{        List<Object> list = qr.query("select * from account", new ColumnListHandler("id"));        for(Object o:list)            System.out.println(o);    }    @Test//KeyedHandler(name)：将结果集中的每一行数据都封装到一个Map<列名,列值>里，再把这些map再存到一个map里，其key为指定的key。    public void test6() throws SQLException{        Map<Object, Map<String,Object>> bmap= qr.query("select * from account", new KeyedHandler("id"));        for(Map.Entry<Object, Map<String,Object>> bme:bmap.entrySet()){            System.out.println("-----------------");            Map<String,Object> lmap = bme.getValue();            for(Map.Entry<String,Object> lme:lmap.entrySet()){                System.out.println(lme.getKey()+"="+lme.getValue());            }        }    }    @Test//MapHandler：将结果集中的第一行数据封装到一个Map里，key是列名，value就是对应的值。    public void test7() throws SQLException{        Map<String,Object> map= qr.query("select * from account where id=?", new MapHandler(),1);        for(Map.Entry<String, Object> me:map.entrySet()){            System.out.println(me.getKey()+"="+me.getValue());        }    }    @Test//MapListHandler：将结果集中的每一行数据都封装到一个Map里，然后再存放到List    public void test8() throws SQLException{        List<Map<String,Object>> list= qr.query("select * from account", new MapListHandler());        for(Map<String,Object> map:list){            System.out.println("-----------------");            for(Map.Entry<String, Object> me:map.entrySet()){                System.out.println(me.getKey()+"="+me.getValue());            }        }    }    @Test//ScalarHandler 适合取一条一列的记录。比如记录总数    public void test9() throws SQLException{        Object obj = qr.query("select count(*) from account", new ScalarHandler(1));        System.out.println(obj.getClass().getName());        int num = ((Long)obj).intValue();        System.out.println(num);    }}