JDBC之通过DBUtils提供的jar包实现CRUD操作

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已于 2022-03-25 18:00:38 修改

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分类专栏： JDBC 文章标签： mysql 数据库

于 2022-03-25 17:53:17 首次发布

本文链接：https://blog.youkuaiyun.com/Z2658172512/article/details/123741217

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当当当当~~~~欢迎大家阅读，今天我们学习通过DBUtils提供的jar包实现CRUD操作

步骤一：导入jar包

步骤二：测试

使用现成的jar中的QueryRunner测试增、删、改的操作

//测试插入
	@Test
	public void testInsert() {
		Connection conn = null;
		try {
			QueryRunner runner = new QueryRunner();
			conn = JDBCUtils.getConnection3();
			String sql = "insert into customers(name,email,birth)values(?,?,?)";
			int insertCount = runner.update(conn, sql, "蔡徐坤","caixukun@126.com","1997-09-08");
			System.out.println("添加了" + insertCount + "条记录");
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			
			JDBCUtils.closeResource(conn, null);
		}
		
	}

使用现成的jar中的QueryRunner测试查询的操作

BeanHander:是ResultSetHandler接口的实现类，用于封装表中的一条记录。
将结果集中的第一行数据封装到一个对应的JavaBean实例中

@Test
	public void testQuery1(){
		Connection conn = null;
		try {
			QueryRunner runner = new QueryRunner();
			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);
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally{
			JDBCUtils.closeResource(conn, null);
			
		}
		
	}

BeanListHandler:是ResultSetHandler接口的实现类，用于封装表中的多条记录构成的集合。
将结果集中的每一行数据都封装到一个对应的JavaBean实例中，存放到List里

@Test
	public void testQuery2() {
		Connection conn = null;
		try {
			QueryRunner runner = new QueryRunner();
			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);
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			
			JDBCUtils.closeResource(conn, null);
		}
		
	}

MapHander:是ResultSetHandler接口的实现类，对应表中的一条记录。
将字段及相应字段的值作为map中的key和value

@Test
	public void testQuery3(){
		Connection conn = null;
		try {
			QueryRunner runner = new QueryRunner();
			conn = JDBCUtils.getConnection3();
			String sql = "select id,name,email,birth from customers where id = ?";
			MapHandler handler = new MapHandler();
			Map<String, Object> map = runner.query(conn, sql, handler, 23);
			System.out.println(map);
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			JDBCUtils.closeResource(conn, null);
			
		}
		
	}

MapListHander:是ResultSetHandler接口的实现类，对应表中的多条记录。
将字段及相应字段的值作为map中的key和value。将这些map添加到List中

@Test
	public void testQuery4(){
		Connection conn = null;
		try {
			QueryRunner runner = new QueryRunner();
			conn = JDBCUtils.getConnection3();
			String sql = "select id,name,email,birth from customers where id < ?";
		
			MapListHandler handler = new MapListHandler();
			List<Map<String, Object>> list = runner.query(conn, sql, handler, 23);
			list.forEach(System.out::println);
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			JDBCUtils.closeResource(conn, null);
			
		}
		
	}

ScalarHandler:用于查询特殊值

@Test
	public void testQuery5(){
		Connection conn = null;
		try {
			QueryRunner runner = new QueryRunner();
			conn = JDBCUtils.getConnection3();
			
			String sql = "select count(*) from customers";
			
			ScalarHandler handler = new ScalarHandler();
			
			Long count = (Long) runner.query(conn, sql, handler);
			System.out.println(count);
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			JDBCUtils.closeResource(conn, null);
			
		}
		
	}

@Test
	public void testQuery6(){
		Connection conn = null;
		try {
			QueryRunner runner = new QueryRunner();
			conn = JDBCUtils.getConnection3();
			
			String sql = "select max(birth) from customers";
			
			ScalarHandler handler = new ScalarHandler();
			Date maxBirth = (Date) runner.query(conn, sql, handler);
			System.out.println(maxBirth);
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			JDBCUtils.closeResource(conn, null);
		}
	}

自定义ResultSetHandler的实现类

@Test
	public void testQuery7(){
		Connection conn = null;
		try {
			QueryRunner runner = new QueryRunner();
			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 {
					
					if(rs.next()){
						int id = rs.getInt("id");
						String name = rs.getString("name");
						String email = rs.getString("email");
						Date birth = rs.getDate("birth");
						Customer customer = new Customer(id, name, email, birth);
						return customer;
					}
					return null;
					
				}
				
			};
			Customer customer = runner.query(conn, sql, handler,23);
			System.out.println(customer);
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			JDBCUtils.closeResource(conn, null);
			
		}
		
	}

使用dbutils.jar包中的DbUtils工具类实现连接等资源的关闭：

public static void closeResource1(Connection conn,Statement ps,ResultSet rs){
//		try {
//			DbUtils.close(conn);
//		} catch (SQLException e) {
//			e.printStackTrace();
//		}
//		try {
//			DbUtils.close(ps);
//		} catch (SQLException e) {
//			e.printStackTrace();
//		}
//		try {
//			DbUtils.close(rs);
//		} catch (SQLException e) {
//			e.printStackTrace();
//		}
		
		DbUtils.closeQuietly(conn);
		DbUtils.closeQuietly(ps);
		DbUtils.closeQuietly(rs);
	}

以上就是DBUtils提供的jar包实现CRUD操作啦，希望我的文章对你有所帮助，如果有错误的地方还望大家批评指正，谢谢大家阅读!