Explain Mybatis in simple terms (2)

Next, let's do another test to query the user's record based on the user name.

Similarly, now add a sql statement to userMapper.xml

<select id="selectUserByName" parameterType="java.lang.String" resultType="com.beyond.mybatis.po.User">
        select * from user WHERE username like '%${value}%'
    </select>

Since the results of the query may return multiple items, we use selectList to query here.

/**
     *   @author：kevin
     * @Description: Fuzzy query based on username
     *   @Date：12:08 2018/3/24
     */
    @Test
    public void findUserByName() throws IOException {
        String resource = "SqlMapConfig.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        //create session factory
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(inputStream);
        //create session
        SqlSession sqlSession = factory.openSession();
        //Operate the database through sqlsession
        List user = sqlSession.selectList("test.selectUserByName","李");
        System.out.println(user);
        sqlSession.close();
    }

output:

summary:

parameterType：

Specify the types of input parameters in the mapping file

resultType：

Specify the type of the returned result in the mapping file.

The difference between #{} and ${}

#{} represents a placeholder. When #{} receives a simple type, it can contain any parameters #{value}, #{id}, etc., receive the value of the pojo object, and read the attribute value in the formation through OGNL.

${} represents a splicing symbol, which will cause SQL injection, so it is not recommended to use it. When ${} receives a simple type, it can only contain value, ${value}.

selectOne queries a single record.

selectList queries multiple records.

Add user information.

<!-- add user
     parameterType: Specifies that the input parameter type is pojo
     -->
    <insert id="insertUser" parameterType="com.beyond.mybatis.po.User">
        insert into user(id,username,birthday,sex,addr) VALUES (#{id},#{username},#{birthday},#{sex},#{addr})
    </insert>

/**
     *   @author：kevin
     * @Description: add user
     *   @Date：12:08 2018/3/24
     */
    @Test
    public void insertUser() throws IOException {
        String resource = "SqlMapConfig.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        //create session factory
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(inputStream);
        //create session
        SqlSession sqlSession = factory.openSession();
        //Operate the database through sqlsession
        //List user = sqlSession.selectList("test.selectUserByName","李");
        User user = new User();
        user.setUsername("Wang Xiaochuan");
        user.setBirthday(new Date());
        user.setSex("1");
        user.setAddr("Chengdu, Sichuan");
        sqlSession.insert("test.insertUser",user);
        // commit the transaction
        sqlSession.commit();   
        sqlSession.close();
    }

View database after successful insertion

Auto-increment primary key return

    MySQL auto-incrementing primary key, execute insert commit to automatically generate an auto-incrementing primary key. Get the auto-incrementing primary key of the record just inserted through the mysql function:

LAST_INSERT_ID(), called after insert.

The definition of insertUser needs to be modified as follows:

<insert id="insertUser" parameterType="com.beyond.mybatis.po.User">
        <!--
        Return the primary key of the inserted data to the user object
         SELECT LAST_INSERT_ID(): Get the primary key value of the record just inserted, only applicable to self-incrementing primary key
         keyProperty: which property of the object specified by parameterType is set to the primary key value of the query
         order: SELECT LAST_INSERT_ID() execution order, its execution order relative to insert
         -->
        <selectKey keyProperty="id" order="AFTER">
            SELECT LAST_INSERT_ID()
        </selectKey>
        insert into user(id,username,birthday,sex,addr) VALUES (#{id},#{username},#{birthday},#{sex},#{addr})
    </insert>

Execute the insert again:

This time the console prints out an id of 39.

Return of non-auto-incrementing primary key:

Such as the return of the uuid primary key

Need to modify the id type to varchar, and then get the uuid before insert

<selectKey keyProperty="id" order="BEFORE" resultType="java.lang.String">
            SELECT uuid()
</selectKey>

delete users:

<!-- delete by id-->
    <delete id="deleteUserById" parameterType="int">
        DELETE FROM USER WHERE id=#{id}
    </delete>

/**
     *   @author：kevin
     * @Description: delete user information based on id
     *   @Date：12:08 2018/3/24
     */
    @Test
    public void deleteUser() throws IOException {
        String resource = "SqlMapConfig.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        //create session factory
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(inputStream);
        //create session
        SqlSession sqlSession = factory.openSession();
        //Operate the database through sqlsession
        sqlSession.delete("test.deleteUserById",39);
        // commit the transaction
        sqlSession.commit();
        sqlSession.close();
    }

Update user:

<!-- update user -->
    <update id="updateUser" parameterType="com.beyond.mybatis.po.User">
        UPDATE USER SET username=#{username},birthday=#{birthday},sex=#{sex} WHERE id=#{id}
    </update>

/**
     *   @author：kevin
     * @Description: update user
     *   @Date：12:08 2018/3/24
     */
    @Test
    public void updateUser() throws IOException {
        String resource = "SqlMapConfig.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        //create session factory
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(inputStream);
        //create session
        SqlSession sqlSession = factory.openSession();
        //Operate the database through sqlsession
        //List user = sqlSession.selectList("test.selectUserByName","李");
        User user = new User();
        user.setId(38);
        user.setUsername("Luo Feng");
        user.setBirthday(new Date());
        user.setSex("1");
        user.setAddr("Chengdu, Sichuan");
        sqlSession.update("test.updateUser",user);
        // commit the transaction
        sqlSession.commit();
        sqlSession.close();
    }

At this point, the introductory procedure of Mybatis is almost over.