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);
     }
 }