Referring to the source code, many students fear, in fact, this is very normal from the point of view of human nature, because people of the unknown things, are very afraid, secondly, your heart may always feel, as if not principle can still work ah, there is no strong desire in your subconscious. From the experience of reading source code,Java three framework SSM,Mybatis source is the most suitable for entry.

Simple to use

This is a simple example of Mybatis saving objects

@Test
public void testSave(a) throws Exception {
    // Create a sessionFactory object
    SqlSessionFactory sf = new SqlSessionFactoryBuilder().
            build(Resources.getResourceAsStream("mybatis-config.xml"));
    // Get the session object
    SqlSession session = sf.openSession();
    // Create entity objects
    User user = new User();
    user.setUsername("toby");
    user.setPassword("123");
    user.setAge(23);
    // Save data to database
    session.insert("com.toby.mybatis.domain.UserMapper.add", user);
    // Commit transaction, this is a must, otherwise even if the SQL is not saved in the database
    session.commit();
    // Close the resource
    session.close();
}
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<mapper namespace="com.toby.mybatis.domain.UserMapper">
    <! --#{} find the corresponding attribute value in the object passed in -->
    <! ParameterType What type of argument is passed in -->
    <insert id="add" parameterType="com.toby.mybatis.domain.User">
        INSERT INTO USER (username,password,age) VALUES (#{username},#{password},#{age})
    </insert>
</mapper>
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Which leads to the theme

But in reality, we don’t do that, we do CRUD operations through Mapper interfaces, calling interface methods, so the key is, what does this interface do, that’s what we care about.

Just look at what’s going on in this code and see what the Mapper interface is doing.

public void testGetObject(a) throws Exception {
    SqlSession session = MybatisUtil.openSession();

    UserMapper mapper = session.getMapper(UserMapper.class);
    User user = mapper.get(5L);

    System.out.println(user);
    session.close();
}
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public interface UserMapper {

    public void add(User user);
    public User get(Long id);
}
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The flow chart

But I think a flow chart and a sequence diagram will tell you what happened in between

Write in the last

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