Mybatis流程

一、准备工作

1、pom.xml

1)导入Maven依赖

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.21</version>
</dependency>
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.7</version>
</dependency>       
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.18.20</version>
</dependency>
<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.12</version>
    <scope>test</scope>
</dependency>

2)让配置文件与项目共同编译

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

2、db.properties (数据库连接文件

driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=UTF-8&serverTimezone=GMT
username=root
password=123456

3、IdUtils (uuid自动生成类

import java.util.UUID;

public class IdUtils {
    public static String getId(){
        return UUID.randomUUID().toString().replaceAll("-","");
    }

}

4、MybatisUtils (获取SqlSession对象

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 java.io.IOException;
import java.io.InputStream;

public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        try {
            //获取SqlSessionFactory对象
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    //从 SqlSessionFactory 中获取 SqlSession
    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession(true);
    }

}

二、编写实体类 Blog

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.Date;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Blog {
    private String id;
    private String title;
    private String author;
    private Date createTime;
    private int views;
}

三、编写核心配置文件 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>
    <!--外部文件-->
    <properties resource="db.properties"/>

    <settings>
        <!--日志-->
        <setting name="logImpl" value="STDOUT_LOGGING"/>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>
    <!--别名-->
    <typeAliases>
        <package name="com.konlsvg.pojo"/>
    </typeAliases>
    <!--环境配置-->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>
    <!--映射地址-->

    <mappers>
        <mapper class="com.konlsvg.mapper.BlogMapper"/>
    </mappers>
</configuration>

四、编写接口 BlogMapper

import com.konlsvg.pojo.Blog;

import java.util.List;
import java.util.Map;

public interface BlogMapper {

    int addBlog(Blog blog);

    List<Blog> queryBlogIF(Map map);

    List<Blog> queryBlogChoose(Map map);

    int updateBlog(Map map);
}

五、编写Mapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.konlsvg.mapper.BlogMapper">
    <insert id="addBlog" parameterType="Blog">
        insert into blog (id,title,author,create_time,views)
        values (#{id},#{title},#{author},#{createTime},#{views});
    </insert>
    
    <select id="queryBlogIF" parameterType="map" resultType="Blog">
        select * from blog
        <where>
            <if test="title!=null">
                and title = #{title}
            </if>
            <if test="author!=null">
                and author = #{author}
            </if>
        </where>

    </select>

    <select id="queryBlogChoose" parameterType="map" resultType="Blog">
        select * from blog
        <where>
            <choose>
                <when test="title!=null">
                    title = #{title}
                </when>
                <when test="author!=null">
                    author = #{author}
                </when>
                <otherwise>
                    views = #{views}
                </otherwise>
            </choose>
        </where>
    </select>
    
    <update id="updateBlog" parameterType="map">
        update blog
        <set>
            <if test="title != null">
                title = #{title},
            </if>
            <if test="author != null">
                author = #{author}
            </if>
        </set>
        where id = #{id}
    </update>
</mapper>

六、测试

import com.konlsvg.mapper.BlogMapper;
import com.konlsvg.pojo.Blog;
import com.konlsvg.utils.IdUtils;
import com.konlsvg.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class MyTest {

    @Test
    public void testAddBlog(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        BlogMapper mapper = sqlSession.getMapper(BlogMapper.class);
        Blog blog = new Blog();

        blog.setId(IdUtils.getId());
        blog.setTitle("Mybatis");
        blog.setAuthor("狂神说");
        blog.setCreateTime(new Date());
        blog.setViews(9999);

        mapper.addBlog(blog);

        blog.setId(IdUtils.getId());
        blog.setTitle("Java");
        mapper.addBlog(blog);

        blog.setId(IdUtils.getId());
        blog.setTitle("Spring");
        mapper.addBlog(blog);

        blog.setId(IdUtils.getId());
        blog.setTitle("微服务");
        mapper.addBlog(blog);

        sqlSession.close();
    }

    @Test
    public void testQueryBlogIF(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        BlogMapper mapper = sqlSession.getMapper(BlogMapper.class);

        Map map = new HashMap();
        map.put("author","狂神说");

        List<Blog> blogs = mapper.queryBlogIF(map);

        for (Blog blog : blogs) {
            System.out.println(blog);
        }

        sqlSession.close();
    }

    @Test
    public void testQueryBlogChoose(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        BlogMapper mapper = sqlSession.getMapper(BlogMapper.class);

        Map map = new HashMap();
        map.put("author","狂神说");
        map.put("views",1000);

        List<Blog> blogs = mapper.queryBlogChoose(map);

        for (Blog blog : blogs) {
            System.out.println(blog);
        }

        sqlSession.close();
    }

    @Test
    public void updateBlog(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        BlogMapper mapper = sqlSession.getMapper(BlogMapper.class);

        Map map = new HashMap();
        map.put("title","Spring");
        map.put("author","狂神说");
        map.put("id","875747b2ec8847918fa572667963b3d7");

        mapper.updateBlog(map);

        sqlSession.close();
    }
}