QueryRunner 結果處理器

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;

//查詢練習
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：把結果集中的第一行數據轉成對象數組。只適合結果集有一條記錄的情況
    public void test3() throws SQLException{
        //該數組中每個元素就是記錄的每列的值
        Object objs[] = qr.query("select * from account where id=?", new ArrayHandler(),1);
        for(Object o:objs)
            System.out.println(o);
    }
    @Test//ArrayListHandler：把結果集中的每一行數據都轉成一個數組，再存放到List中。
    public void test4() throws SQLException{
        //該數組中每個元素就是記錄的每列的值
        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：將結果集中某一列的數據存放到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)：將結果集中的每一行數據都封裝到一個Map<列名,列值>里，再把這些map再存到一個map里，其key為指定的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：將結果集中的第一行數據封裝到一個Map里，key是列名，value就是對應的值。
    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：將結果集中的每一行數據都封裝到一個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 適合取一條一列的記錄。比如記錄總數
    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);
    }
}