1. Mybatis快速入门

Untitled

  1. 创建数据表

    CREATE DATABASE mybatis ;

USE mybatis ;

CREATE TABLE USER(
  id INT NOT NULL PRIMARY KEY,
  NAME VARCHAR (30) DEFAULT NULL,
  pwd VARCHAR (30) DEFAULT NULL
) ENGINE = INNODB DEFAULT CHARSET = utf8 ;

INSERT INTO USER(id, NAME, pwd) 
VALUES
  (1, '李四', '123'),
  (2, '王五', '456'),
  (3, '李明', '789')

  2. 创建User表，添加数据

  3. 创建模块，导入坐标

    <dependencies>
    <!--mysql驱动-->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.22</version>
    </dependency>
    <!--mybatis驱动-->
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.4.6</version>
    </dependency>
    <!--junit-->
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
    </dependency>
</dependencies>

<build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>2.22.1</version>
                <configuration>
                    <skipTests>true</skipTests>
                </configuration>
            </plugin>
        </plugins>

        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
        </resources>
    </build>

  4. 编写Mybatis核心配置文件： mybatis-config.xml

    编写Mybatis核心配置文件，在resources下创建mybatis-config.xml文件，配置自己的数据库地址、名字、密码以及mysql驱动

    <?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>
    
    <!--配置Mybatis运行环境-->
    <environments default="development">
        <environment id="development">
            <!--配置JDBC事务管理-->
            <transactionManager type="JDBC"/>
            <!--POOLED配置JDBC数据源连接池-->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useUnicode=true&amp;characterEncoding=utf8&amp;serverTimezone=UTC"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
		<mappers>
			<mapper resource="com/itheima/mapper/UserMapper.xml"/>
		</mappers>

</configuration>

  5. 编写SQL映射文件: 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="test">
    <select id="findAll" resultType="com.mybatis.entity.User">
        select * from tb_user
    </select>
</mapper>

  6. 编码

    1. 定义POJO类

      //实体类
public class User {
    private  int id;
    private String name;
    private String pwd;

    public User(int id, String name, String pwd) {
        this.id = id;
        this.name = name;
        this.pwd = pwd;
    }

    public User() {
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\\'' +
                ", pwd='" + pwd + '\\'' +
                '}';
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }
}

    2. 加载核心配置文件，获取SQLSessionFactory对象

    3. 获取SQLSession对象，执行SQL语句

    4. 释放资源

      //SqlSessionFactory --> sqlSession
public class MybatisUtils {

	public static void main(String[] args) throws IOException {
		String resource="mybatis-config.xml";
		InputStream inputStream = Resources.getResourceAsStream(resource);
		sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

		SqlSession sqlSession = sqlSessionFactory.openSession();

		List<User> users = sqlSession.selectList("test.findAll");
		System.out.println(users);

		sqlsession.close();
	}
}

2. Mapper代理开发

  1. 定义与SQL映射文件同名的Mapper接口，并且将Mapper 和SQL映射文件放置在同一目录下

    public interface UserDao {
     List<User> findAll();
}

  2. 设置SQL映射文静的namespace属性为Mapper接口全限定名

  3. 在Mapper接口中定义方法，方法名就是SQL映射文件中的SQL语句的id，并保持参类型的返回值类型一致

    <?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.mybatis.dao.UserDao">
    <select id="findAll" resultType="com.mybatis.entity.User">
        select * from user
    </select>
</mapper>

  4. 编码

    //SqlSessionFactory --> sqlSession
public class MybatisUtils {

	public static void main(String[] args) throws IOException {
		String resource="mybatis-config.xml";
		InputStream inputStream = Resources.getResourceAsStream(resource);
		sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

		SqlSession sqlSession = sqlSessionFactory.openSession();

		UserMapper userMapper = sqlsession.getMapper(userMapper.class);
		List<User> users = userMapper.findAll();
		System.out.println(users);

		sqlsession.close();
	}
}

<aside> 🌷 如果Mapper接口吗名称和SQL映射文件文件名称相同，并在同一目录下，则可以使用包扫描的方式简化SQL映射文件的加载

<mappers>
		<package name="com.itheima.mapper"/>
</mappers>

</aside>