How to use Java to develop a persistence framework application based on MyBatis

How to use Java to develop a persistence framework application based on MyBatis

Preface
MyBatis is an excellent persistence framework that can help us simplify database operations code. Whether it is a beginner or an experienced developer, mastering MyBatis is very important. This article will introduce in detail how to use MyBatis for persistence framework application in Java development. We will cover the basic configuration, Mapper and CRUD operations of MyBatis.

1. Basic configuration

1. Add dependencies
   First, we need to add relevant dependencies to the project. Our dependencies can be managed using the Maven or Gradle build tools. The following is an example of Maven:

   <dependencies>
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.5.6</version>
    </dependency>
    <dependency>
        <groupId>org.mybatis</groupId>
        < <artifactId>mybatis-spring</artifactId>
        <version>1.4.2</version>
    </dependency>
    <!-- 其他依赖 -->
   </dependencies>

2. Configuration file
   In the resource folder of the project, create a configuration file named mybatis-config.xml. This file is the core configuration file of MyBatis. We need to configure the database connection information, Mapper, etc. in this file. The following is a simple example:

   <configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost:3306/mydatabase" />
                <property name="username" value="root" />
                <property name="password" value="password" />
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/example/MyMapper.xml"/>
    </mappers>
   </configuration>

   In the above example, we configured the database connection information and specified the Mapper file.

2. Mapper configuration

1. Create Mapper interface
   We first need to create a Mapper interface to define our SQL operations. The method name of the interface should correspond to the SQL statement ID in the Mapper file. For example, if you want to query user information, you can create a UserMapper interface:

   public interface UserMapper {
    User getUserById(int userId);
    List<User> getAllUsers();
    void insertUser(User user);
    void updateUser(User user);
    void deleteUser(int userId);
   }

2. Create a Mapper XML file
   Create a Mapper XML file in the resources directory, the file name is the same as what we have in mybatis -The configuration in config.xml is consistent. For example, we create a file named MyMapper.xml as follows:

   <mapper namespace="com.example.UserMapper">
    <select id="getUserById" parameterType="int" resultType="com.example.User">
        SELECT * FROM user WHERE id = #{userId}
    </select>
    <select id="getAllUsers" resultType="com.example.User">
        SELECT * FROM user
    </select>
    <insert id="insertUser" parameterType="com.example.User">
        INSERT INTO user (id, name, age) VALUES (#{id}, #{name}, #{age})
    </insert>
    <update id="updateUser" parameterType="com.example.User">
        UPDATE user SET name = #{name}, age = #{age} WHERE id = #{id}
    </update>
    <delete id="deleteUser" parameterType="int">
        DELETE FROM user WHERE id = #{userId}
    </delete>
   </mapper>

3. CRUD operation examples
Let’s implement some simple CRUD operation examples.

1. Query user information

   SqlSession sqlSession = sqlSessionFactory.openSession();
   try {
    UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
    User user = userMapper.getUserById(1);
    System.out.println(user);
   } finally {
    sqlSession.close();
   }

2. Add user information

   SqlSession sqlSession = sqlSessionFactory.openSession();
   try {
    UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
    User user = new User();
    user.setId(2);
    user.setName("Tom");
    user.setAge(25);
    userMapper.insertUser(user);
    sqlSession.commit();
   } finally {
    sqlSession.close();
   }

3. Update user information

   SqlSession sqlSession = sqlSessionFactory.openSession();
   try {
    UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
    User user = new User();
    user.setId(2);
    user.setName("John");
    user.setAge(26);
    userMapper.updateUser(user);
    sqlSession.commit();
   } finally {
    sqlSession.close();
   }

4. Delete user information

   SqlSession sqlSession = sqlSessionFactory.openSession();
   try {
    UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
    userMapper.deleteUser(2);
    sqlSession.commit();
   } finally {
    sqlSession.close();
   }

Summary
This article introduces how to use Java to develop a persistence framework application based on MyBatis. Through the configuration file and Mapper interface, we can easily perform CRUD operations on the database. I hope this article can be helpful to beginners and experienced developers when using MyBatis.

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