数据库-jdbc

Posted 2021-02-18 FlyingDreams

1、核心代码块

@Test
	public void testConn() throws Exception {
		// 1. 加载数据库的连接驱动
		// Driver=com.mysql.jdbc.Driver
		Class.forName("com.mysql.jdbc.Driver");

		// 2. 造桥，建立连接
		// url = jdbc:mysql://localhost:3306/数据名称
		String url = "jdbc:mysql://localhost:3306/xc";
		String user = "root";
		String password = "root";
		Connection conn = DriverManager.getConnection(url, user, password);

		// 3.获取传送指令(SQL)的接口对象
		Statement stmt = conn.createStatement();
		// stmt.executeQuery(sql); // 当你要做查询的时候，用query
		// stmt.executeUpdate(sql); // insert update delete 使用update
		String sql = " SELECT * FROM user  ";
		// 4. 得到结果集，然后处理结果集
		ResultSet rs = stmt.executeQuery(sql);
		// rs.next() 返回true表示rs结果有数据 false表示没有数据了
		while (rs.next()) {
			// 获取单个的数据，一个一个的列
			int studentNo = rs.getInt("id");//
			String loginPwd = rs.getString(2);
			String studentName = rs.getString("name");
			//String sex = rs.getString("sex");

			System.out.println(
					"studentNo=" + studentNo + " loginPwd=" + loginPwd + " studentName=" +studentName);
		}
		
		// 5.拆桥 ,释放资源
		rs.close();
		stmt.close();
		conn.close();
	}
	

　　

2、crud

// 1. 新增
	@Test
	public void testInsert() throws Exception {
		String sql = " INSERT INTO DOG VALUES(NULL,‘拉布拉多‘, 80, 100, ‘大型犬‘) ";
		try {
			this.insertOrUpdateOrDelete(sql );
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	
	// 2. 修改
	@Test
	public void testUpdate() throws Exception {
		String sql = " UPDATE DOG SET health = 90 WHERE id = 4 ";
		try {
			this.insertOrUpdateOrDelete(sql );
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	
	// 3. 删除
	@Test
	public void testDelete() {
		String sql = " DELETE FROM DOG WHERE ID = 4 ";
		try {
			this.insertOrUpdateOrDelete(sql );
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	
	// 4. 查询
	@Test
	public void testSelectDog() throws Exception {
		String sql = " SELECT * FROM DOG ";
		ResultSet rs = stmt.executeQuery(sql);
		List<Dog> list = new ArrayList<Dog>();
		while(rs.next()) {
			Dog dog = new Dog();
			dog.setId(rs.getInt("id"));
			dog.setName(rs.getString("name"));
			
			list.add(dog);
		}

　　

3、防止注入

 

@Test
	public void testPpStmt() {
		Connection conn= null;
		PreparedStatement pstm = null;
		ResultSet rs = null;
		try {
			Class.forName("com.mysql.jdbc.Driver");
			conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/xdsc", "root", "root");
			String sql = " SELECT * FROM MASTER WHERE NAME=? AND PASSWORD=? ";
			pstm = conn.prepareStatement(sql);
			// 将占位符赋值
			// SELECT * FROM MASTER WHERE NAME=‘123123‘ AND PASSWORD=‘YEAHSIR‘
			pstm.setString(1, "YEAHSIR");
			pstm.setString(2, "123123");
			// 执行SQL
			rs = pstm.executeQuery();
			while(rs.next()) {
				Master master = new Master(rs.getInt("id"), rs.getString("name"), rs.getString("password"), rs.getInt("money"));
				System.out.println(master);
			}
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (SQLException e) {
			e.printStackTrace();
		} finally {
			try {
				rs.close();
			} catch (SQLException e) {
				e.printStackTrace();
				System.out.println("关闭结果集出了问题");
			}
			try {
				pstm.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
			try {
				conn.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
		
		
	}