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);

     }

 }