1、简介：

• commons-dbutils是Apache组织提供的一个开源JDBC工具类库，是对JDBC的简单封装

2、前提

• 需要导入commons-dbutils-x.x.jar架包

3、主要API

1. QueryRunner：主要处理——增删改

// 测试添加
@Test
public void testInsert() throws Exception {
    
    
	QueryRunner runner = new QueryRunner(); //创建一个实例
	Connection conn = JDBCUtils.getConnection3(); //获取连接
	String sql = "insert into customers(name,email,birth)values(?,?,?)";
	int count = runner.update(conn, sql, "何成飞", "[email protected]", "1992-09-08");

	System.out.println("添加了" + count + "条记录");
		
	JDBCUtils.closeResource(conn, null);//这是已经提前准备好的资源处理工具类库

}

2. ResultSetHandler：主要处理——查
   

/*
 * 测试查询:查询一条记录
 * 
 * 使用ResultSetHandler的实现类：BeanHandler
 */
@Test
public void testQueryInstance() throws Exception{
    
    
	QueryRunner runner = new QueryRunner();

	Connection conn = JDBCUtils.getConnection3();
		
	String sql = "select id,name,email,birth from customers where id = ?";
		
	//
	BeanHandler<Customer> handler = new BeanHandler<>(Customer.class);
	Customer customer = runner.query(conn, sql, handler, 23);
	System.out.println(customer);	
	JDBCUtils.closeResource(conn, null);
}

/*
 * 测试查询:查询多条记录构成的集合
 * 
 * 使用ResultSetHandler的实现类：BeanListHandler
 */
@Test
public void testQueryList() throws Exception{
    
    
	QueryRunner runner = new QueryRunner();

	Connection conn = JDBCUtils.getConnection3();
		
	String sql = "select id,name,email,birth from customers where id < ?";
		
	//
	BeanListHandler<Customer> handler = new BeanListHandler<>(Customer.class);
	List<Customer> list = runner.query(conn, sql, handler, 23);
	list.forEach(System.out::println);
		
	JDBCUtils.closeResource(conn, null);
}


/*
 * 自定义ResultSetHandler的实现类
 */
@Test
public void testQueryInstance1() throws Exception{
    
    
	QueryRunner runner = new QueryRunner();

	Connection conn = JDBCUtils.getConnection3();
		
	String sql = "select id,name,email,birth from customers where id = ?";
		
	ResultSetHandler<Customer> handler = new ResultSetHandler<Customer>() {
    
    

		@Override
		public Customer handle(ResultSet rs) throws SQLException {
    
    
			System.out.println("handle");
//			return new Customer(1,"Tom","[email protected]",new Date(123323432L));
				
			if(rs.next()){
    
    
				int id = rs.getInt("id");
				String name = rs.getString("name");
				String email = rs.getString("email");
				Date birth = rs.getDate("birth");
					
				return new Customer(id, name, email, birth);
			}
			return null;
				
		}
	};
		
	Customer customer = runner.query(conn, sql, handler, 23);
		
	System.out.println(customer);
		
	JDBCUtils.closeResource(conn, null);
}


/*
 * 如何查询类似于最大的，最小的，平均的，总和，个数相关的数据，
 * 使用ScalarHandler
 * 
 */
@Test
public void testQueryValue() throws Exception{
    
    
	QueryRunner runner = new QueryRunner();

	Connection conn = JDBCUtils.getConnection3();
		
	//测试一：
//	String sql = "select count(*) from customers where id < ?";
//	ScalarHandler handler = new ScalarHandler();
//	long count = (long) runner.query(conn, sql, handler, 20);
//	System.out.println(count);
		
	//测试二：
	String sql = "select max(birth) from customers";
	ScalarHandler handler = new ScalarHandler();
	Date birth = (Date) runner.query(conn, sql, handler);
	System.out.println(birth);
		
	JDBCUtils.closeResource(conn, null);
}

3. DbUtils：工具类，资源的处理，如关闭连接