mybatis mapper xml

MyBatis Mapper XML is a configuration file used in MyBatis, a Java-based persistence framework, to define SQL mappings between Java objects and database tables. The Mapper XML file contains SQL statements and mapping rules that are used to interact with the database.

In the Mapper XML file, you define the SQL statements such as SELECT, INSERT, UPDATE, DELETE, etc., using the MyBatis XML syntax. You also define the mapping rules to map the result of the SQL queries to Java objects or vice versa.

Here is an example of a simple Mapper XML file:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.example.UserMapper">
    <select id="getUserById" resultType="com.example.User">
        SELECT * FROM users WHERE id = #{id}
    </select>
    <insert id="insertUser" parameterType="com.example.User">
        INSERT INTO users (id, name, email) VALUES (#{id}, #{name}, #{email})
    </insert>
    <update id="updateUser" parameterType="com.example.User">
        UPDATE users SET name = #{name}, email = #{email} WHERE id = #{id}
    </update>
    <delete id="deleteUser" parameterType="int">
        DELETE FROM users WHERE id = #{id}
    </delete>
</mapper>

In this example, the Mapper XML file defines four SQL statements: `getUserById`, `insertUser`, `updateUser`, and `deleteUser`. Each statement has an ID, parameterType (input parameter), resultType (output result mapping), and the actual SQL query.

You can then use the defined SQL statements in your Java code by referencing the Mapper XML file and the statement ID using MyBatis API.

Note that the actual mapping between Java objects and database tables is usually done through Java annotations or XML configuration files in addition to the Mapper XML file. The Mapper XML file primarily focuses on defining the SQL statements and their mappings.

I hope this gives you a basic understanding of MyBatis Mapper XML. Let me know if you have any further questions!