Additional operations on single tables

Earlier we saw how to build mybatis framework and query operations, here we talk about how to use mybatis to increase user operations. First, insert method is added to user.xml file. The code is as follows

       <!-- Add user -->
	<insertid="insertUser"parameterType="cn.itcast.mybatis.po.User">
	  insert into user(username,birthday,sex,address) 
          <!--There#The value in {} must be the same as the attribute name in the user class. It is recommended to paste it directly - >.
	  values(#{username},#{birthday},#{sex},#{address})
	</insert>

 

Then write a test method, code as follows:

// Adding user information
	@Test
	publicvoid testInsert() {
		// Database session instance
		SqlSession sqlSession = null;
		try {
			// Create database session instance sqlSession
			sqlSession = sqlSessionFactory.openSession();
			// Adding user information
			User user = new User();
			user.setUsername("Zhang Xiaoming");
			user.setAddress("Zhengzhou, Henan");
			user.setSex("1");
			
			sqlSession.insert("test.insertUser", user);
			//Submit a transaction,Manual submission is required here. 
			sqlSession.commit();
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			if (sqlSession != null) {
				sqlSession.close();
			}
		}
	}

Note: It's important to emphasize that mybatis automatically opens things because it uses jdbc defaults, but it doesn't know when to submit them, so it's necessary to submit things manually.
A more careful classmate may have noticed that we did not write the value of id in our insert statement. This requires that our database grow by itself, but there is still a problem: the users we add in are inconsistent with the user information in our memory because our users in our memory do not have primary keys. How to solve this problem? We need to concentrate on these configurations in user.xml:

	<insert id="insertUser" parameterType="cn.itcast.pojo.User">
		<!-- 
		select LAST_INSERT_ID() mybatis Function is the primary key for querying the last added data id
		
		keyProperty:Put the data queried by this database function into the input parameter User Object id Save in attributes
		order: current mysql Function relative to insert Execution order of statements, stay insert Pre execution is before, stay insert Post execution is after
		resultType: keyProperty Return specified in id Types of attributes
		 -->
		<selectKey keyProperty="id" order="AFTER" resultType="java.lang.Integer">
			select LAST_INSERT_ID()
		</selectKey>
		insert into user (username, birthday, sex, address) values(#{username}, #{birthday}, #{sex}, #{address})
	</insert>

In this case, selectKey can return the primary key automatically generated by the database, and then assign our primary key to our user object automatically, so that the data in the database and system memory will be consistent.
Some students may say that if I don't use primary keys to grow by myself, what should I do with uuid? Here's how mybatis generates primary keys through uuid. In fact, it is very simple, that is, to put our.

select LAST_INSERT_ID()

change into

select uuid()

Then change after to before. The code is as follows:

<insert id="insertUser" parameterType="cn.itcast.mybatis.po.User">
<selectKey resultType="java.lang.String" order="BEFORE"
keyProperty="id">
select uuid()
</selectKey>
insert into user(id,username,birthday,sex,address) 
		 values(#{id},#{username},#{birthday},#{sex},#{address})
</insert>

//Note: The order used here is "BEFORE"

Delete operation of single table

It's easier to delete users, so I just paste my code here.

1.user.xml file

<!-- delete user -->
<deleteid="deleteUserById"parameterType="int">
	delete from user where id=#{id}
</delete>

2. Test code

	@Test
	publicvoidtestDelete() {
		// Database session instance
		SqlSession sqlSession = null;
		try {
			// Create database session instance sqlSession
			sqlSession = sqlSessionFactory.openSession();
			// delete user
			sqlSession.delete("test.deleteUserById",18);
			// Submission of affairs
			sqlSession.commit();
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			if (sqlSession != null) {
				sqlSession.close();
			}
		}
	}

Modification of a single table

Modifying the code is relatively simple, paste the source code directly:

1.user.xml file

	<updateid="updateUser"parameterType="cn.itcast.mybatis.po.User">
		update user set username=#{username},birthday=#{birthday},sex=#{sex},address=#{address}
		where id=#{id}
	</update>

2. Testing procedures

	@Test
	publicvoidtestUpdate() {
		// Database session instance
		SqlSession sqlSession = null;
		try {
			// Create database session instance sqlSession
			sqlSession = sqlSessionFactory.openSession();
			// Adding user information
			User user = new User();
			user.setId(16);
			user.setUsername("Zhang Xiaoming");
			user.setAddress("Zhengzhou, Henan");
			user.setSex("1");
			user.setPrice(1999.9f);
			sqlSession.update("test.updateUser", user);
			// Submission of affairs
			sqlSession.commit();
 
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			if (sqlSession != null) {
				sqlSession.close();
			}
		}
	}