QueryRunner 结果处理器

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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);
}
}

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