SpringBoot——Mybatis - Mybatis——CRUD - 《Java》

动态代理Mapper

public class User {
    private Integer id;
    private String userName;
    private String password;
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getUserName() {
        return userName;
    }
    public void setUserName(String userName) {
        this.userName = userName;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", userName='" + userName + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

import com.example.mybatis.domain.User;
import com.example.mybatis.service.impl.UserServiceImpl;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import java.io.InputStream;
/**
 * @Description:
 * @Author: baxiang
 * @Date: 2021/8/31.
 */
public class UserServiceTest {
    private InputStream is;
    private UserService userService;
    private SqlSession sqlSession;
    @Before
    public void setUp() throws Exception {
        String resource = "mybatis-config.xml";
        // 读取配置文件
        is = Resources.getResourceAsStream(resource);
        // 构建SqlSessionFactory
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
        // 获取sqlSession
        sqlSession = sqlSessionFactory.openSession();
        this.userService = new UserServiceImpl(sqlSession);
    }
    @After
    public void tearDown() throws Exception {
        sqlSession.commit();
        sqlSession.close();
        is.close();
    }
    @Test
    public void queryUserById() {
        System.out.println(this.userService.queryUserById(1));
    }
    @Test
    public void insertUser() {
        User user = new User();
        user.setUserName("test");
        user.setPassword("123456");
        this.userService.insertUser(user);
        this.sqlSession.commit();
    }
    @Test
    public void updateUser() {
        User user = new User();
        user.setId(1);
        user.setUserName("Test1");
        user.setPassword("654321");
        this.userService.updateUser(user);
        this.sqlSession.commit();
    }
    @Test
    public void deleteUserById() {
        this.userService.deleteUserById(1);
        this.sqlSession.commit();
    }
}

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">
<!-- 根标签 -->
<configuration>
    <!-- 属性 -->
    <properties>
        <property name="driver" value="com.mysql.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://127.0.0.1:3306/test?useSSL=false&amp;characterEncoding=utf-8&amp;allowMultiQueries=true"/>
        <property name="username" value="root"/>
        <property name="password" value="123456"/>
    </properties>
    <!-- 全局设置 -->
    <settings>
        <!-- 使用jdbc的getGeneratedKeys 获取数据库自增主键值 -->
        <setting name="useGeneratedKeys" value="true"/>
        <!-- 开启驼峰命名转换 -->
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>
    <!-- 环境，可以配置多个，default：指定采用哪个环境 -->
    <environments default="dev">
        <!-- id：唯一标识 -->
        <environment id="dev">
            <!-- 事务管理器，JDBC类型的事务管理器 -->
            <transactionManager type="JDBC" />
            <!-- 数据源，池类型的数据源 -->
            <dataSource type="POOLED">
                <property name="driver" value="${driver}" /> <!-- 配置了properties，所以可以直接引用 -->
                <property name="url" value="${url}" />
                <property name="username" value="${username}" />
                <property name="password" value="${password}" />
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="mappers/UserMapper.xml" />
    </mappers>
</configuration>

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:根标签，namespace：命名空间，保证命名空间唯一 -->
<mapper namespace="UserMapper">

    <!--获取用户-->
    <select id="selectUser" resultType="com.example.mybatis.domain.User">
        SELECT
            id ,
            user_name ,
            password
        FROM
            user
        WHERE id = #{id};
    </select>

    <!--插入数据-->
    <insert id="insertUser" parameterType="com.example.mybatis.domain.User">
        INSERT INTO user (
            user_name,
            password
        )
        VALUES
            (
                #{userName},
                #{password}
            );
    </insert>

    <update id="updateUser" parameterType="com.example.mybatis.domain.User">
        UPDATE user
        <trim prefix="set" suffixOverrides=",">
            <if test="userName!=null">user_name = #{userName},</if>
            <if test="password!=null">password = #{password},</if>
        </trim>
        WHERE
        (id = #{id});
    </update>

    <delete id="deleteUser">
        DELETE FROM user WHERE id=#{id}
    </delete>
</mapper>

接口类

public interface UserService {
    /**
     * 根据id查询用户信息
     *
     * @param id
     * @return
     */
    User selectUser(Integer id);



    /**
     * 新增用户
     *
     * @param user
     */
    void insertUser(User user);

    /**
     * 更新用户信息
     *
     * @param user
     */
    void updateUser(User user);

    /**
     * 根据id删除用户信息
     *
     * @param id
     */
    void deleteUser(Integer id);
}

UserServiceImpl
�

import com.example.mybatis.domain.User;
import com.example.mybatis.service.UserService;
import org.apache.ibatis.session.SqlSession;



public class UserServiceImpl implements UserService {

    private SqlSession sqlSession;

    public UserServiceImpl(SqlSession sqlSession) {
        this.sqlSession = sqlSession;
    }

    @Override
    public User selectUser(Integer id) {
        return this.sqlSession.selectOne("UserMapper.selectUser", id);
    }

    @Override
    public void insertUser(User user) {
        this.sqlSession.insert("UserMapper.insertUser", user);
    }

    @Override
    public void updateUser(User user) {
        this.sqlSession.update("UserMapper.updateUser", user);
    }

    @Override
    public void deleteUser(Integer id) {
        this.sqlSession.delete("UserMapper.deleteUser", id);
    }
}

动态代理Mapper

接口->实现类->mapper.xml
2、实现类中，使用mybatis的方式非常类似
3、xml中的sql statement 硬编码到java代码中。

思考：能否只写接口，不写实现类。只编写接口和Mapper.xml即可？
因为在dao（mapper）的实现类中对sqlsession的使用方式很类似。因此mybatis提供了接口的动态代理。

import com.example.mybatis.domain.User;



public interface UserMapper {
    /**
     * 根据id查询用户信息
     *
     * @param id
     * @return
     */
    User selectUser(Integer id);


    /**
     * 新增用户
     *
     * @param user
     */
    void insertUser(User user);

    /**
     * 更新用户信息
     *
     * @param user
     */
    void updateUser(User user);

    /**
     * 根据id删除用户信息
     *
     * @param id
     */
    void deleteUser(Integer id);
}

，在UserMapper.xml中配置接口的全路径
mapper.xml namespace
如果希望使用mybatis通过的动态代理的接口，就需要namespace中的值，和需要对应的Mapper(dao)接口的全路径一致。Mapper中Namespace的定义本身是没有限制的，只要不重复即可，但如果使用Mybatis的DAO接口动态代理，则namespace必须为DAO接口的全路径，例如：com.example.mybatis.mapper.UserMapper
� 图片.png
// 1. 映射文件的命名空间（namespace）必须是mapper接口的全路径
// 2. 映射文件的statement的id必须和mapper接口的方法名保持一致
// 3. Statement的resultType必须和mapper接口方法的返回类型一致
// 4. statement的parameterType必须和mapper接口方法的参数类型一致（不一定）