How to Use MyBatis in Java to Implement Database Operations
MyBatis is a lightweight Java persistence layer framework that provides database manipulation methods through the Mapper interface and implements configuration and mapping relationships using XML or annotations. MyBatis is capable of mapping Java objects to database tables, allowing developers to complete database operations by writing simple SQL statements.
The advantages of MyBatis include:
1. Easy to use: MyBatis has a simple configuration, low learning cost, and provides rich documentation and sample code.
2. High flexibility: MyBatis allows developers to use annotations or XML to configure SQL statements to adapt to different project and team requirements.
3. Provide high performance: MyBatis uses a caching mechanism at the bottom, which can improve query performance and manually control and configure caching policies.
4. Easy integration: MyBatis can seamlessly integrate with various Java frameworks and support multiple databases.
The drawbacks of MyBatis include:
1. XML configuration is complex: When using XML to configure SQL statements, it is necessary to manually write SQL statements, and the configuration is relatively cumbersome.
2. Not suitable for complex business: For scenarios with complex business logic, MyBatis' flexibility may bring certain development and maintenance costs.
The following is a Java sample code that uses MyBatis to add, delete, modify, and query:
1. Define the data table:
sql
CREATE TABLE user (
id INT PRIMARY KEY AUTO_INCREMENT,
name VARCHAR(50),
age INT
);
2. Define the entity class User. java:
public class User {
private int id;
private String name;
private int age;
//Omitting getter and setter methods
}
3. Define the Mapper interface UserMapper.java:
public interface UserMapper {
void insertUser(User user);
void deleteUser(int id);
void updateUser(User user);
User getUser(int id);
}
4. Define the Mapper configuration file UserMapper.xml:
<?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">
<insert id="insertUser" parameterType="com.example.entity.User">
INSERT INTO user(name, age) VALUES(#{name}, #{age})
</insert>
<delete id="deleteUser" parameterType="int">
DELETE FROM user WHERE id = #{id}
</delete>
<update id="updateUser" parameterType="com.example.entity.User">
UPDATE user SET name = #{name}, age = #{age} WHERE id = #{id}
</update>
<select id="getUser" resultType="com.example.entity.User">
SELECT * FROM user WHERE id = #{id}
</select>
</mapper>
5. Configure the MyBatis configuration file mybatis config.xml:
<?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/mybatis_test"/>
<property name="username" value="root"/>
<property name="password" value="password"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="com/example/mapper/UserMapper.xml"/>
</mappers>
</configuration>
6. Use MyBatis for database operations:
public class MyBatisExample {
public static void main(String[] args) {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession session = sessionFactory.openSession();
try {
UserMapper userMapper = session.getMapper(UserMapper.class);
//Insert Data
User user = new User();
user.setName("John");
user.setAge(25);
userMapper.insertUser(user);
//Query data
User fetchedUser = userMapper.getUser(user.getId());
System.out.println(fetchedUser.getName() + " " + fetchedUser.getAge());
//Update data
fetchedUser.setAge(30);
userMapper.updateUser(fetchedUser);
fetchedUser = userMapper.getUser(fetchedUser.getId());
System.out.println(fetchedUser.getName() + " " + fetchedUser.getAge());
//Delete data
userMapper.deleteUser(fetchedUser.getId());
fetchedUser = userMapper.getUser(fetchedUser.getId());
System.out.println(fetchedUser);
} finally {
session.close();
}
}
}
Note: The above code uses the core dependencies of MyBatis and needs to be added to the pom.xml file:
<dependencies>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.6</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.26</version>
</dependency>
</dependencies>
Framework official website link: [MyBatis official website]（ https://mybatis.org/mybatis-3/zh/index.html ）
