mybatis-simple-usage-guide.md

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The Overview of MyBatis Simple Usage Guide

Here's a simple usage guide for MyBatis:

1. Define your database schema: Before you can use MyBatis, you need to have a database schema defined. This includes tables, columns, and relationships.

2. Create your data model: Next, you need to create your data model in Java. This data model should correspond to the database schema. You can use annotations to map the data model to the database schema. For example, if you have a table called users with columns id, name, and email, you could create a Java class like this:

   public class User {
     private int id;
     private String name;
     private String email;
   
     // Getters and setters
   }

   You can use annotations like @Table and @Column to specify the database table and column names:

   @Table(name = "users")
   public class User {
     @Column(name = "id")
     private int id;
     
     @Column(name = "name")
     private String name;
     
     @Column(name = "email")
     private String email;
   
     // Getters and setters
   }

3. Create your MyBatis configuration file: You need to create a MyBatis configuration file that specifies the database connection details and mappings between SQL queries and Java methods. Here's an example of a simple MyBatis configuration file:

   <?xml version="1.0" encoding="UTF-8" ?>
   <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
       "http://mybatis.org/dtd/mybatis-3-config.dtd">
   <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="myuser"/>
           <property name="password" value="mypassword"/>
         </dataSource>
       </environment>
     </environments>
     <mappers>
       <mapper resource="com/example/mapper/UserMapper.xml"/>
     </mappers>
   </configuration>

   In this example, the configuration file specifies the JDBC driver, database URL, username, and password. It also includes a mapper file that contains SQL statements.

4. Create your MyBatis mapper file: The MyBatis mapper file contains SQL queries and maps them to Java methods. Here's an example of a simple mapper 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.mapper.UserMapper">
       <select id="getUserById" parameterType="int" resultType="com.example.model.User">
           SELECT * FROM users WHERE id = #{id}
       </select>
   </mapper>

   In this example, the mapper file specifies a select statement that retrieves a user by ID.

5. Use MyBatis APIs to execute queries: Finally, you can use MyBatis APIs to execute SQL queries. Here's an example of how to use MyBatis to retrieve a user by ID:

   String resource = "mybatis-config.xml";
   InputStream inputStream = Resources.getResourceAsStream(resource);
   SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
   
   SqlSession session = sqlSessionFactory.openSession();
   try {
     UserMapper mapper = session.getMapper(UserMapper.class);
     User user = mapper.getUserById(1);
   } finally {
     session.close();
   }