Mybatis--->固定套路

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
<!--    父工程-->
    <groupId>org.example</groupId>
    <artifactId>Maven04</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>
    <modules>
        <module>Maven4</module>
    </modules>
    <!--依赖-->
    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.18</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.9</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.5</version>
        </dependency>
    </dependencies>

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

</project>

最后这个<build>很重要 ，不然读不到配置文件

2、配置mybatis-config.xml（每一个Mapper都需要注册）

<?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>
    <properties resource="db.properties">
    </properties>
    <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="${name}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>
<mappers>
//class定位类的属性
<mapper class="com.xian.pojo.Student"/>
<mapper resource="com/xian/dao/TeacherMapper"/> 
</mappers> 
</configuration>

3、配置db.properties

driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/testdb?serverTimezone=UTC&useUnicode=ture&characterEncoding=UTF-8
name=root
password=123456

4、编写MybatisUtils类

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 {
            String resource = "mybatis-config.xml";
//            InputStream inputStream  = Resources.getResourceAsStream(resource);
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public static SqlSession getSqlsession(){
        return sqlSessionFactory.openSession();
    }
}

5、UserMapper接口和UserMapper.xml

1. 接口只需写明返回值类型和方法名（每一个接口对应一个Mapper，接口和Mapper的名字要一致）

   import com.xian.pojo.User;
   import com.xian.pojo.User2;
   
   import java.util.List;
   import java.util.Map;
   
   public interface UserMapper {
       //查询所有
       List<User> getUserList();
       //查询用户BYid
       User getUserById(int id);
       //添加用户
       int add(User user);
       //修改
       int upData(User user);
       int upData2(Map<String,Object> map);
       //删除
       int delete(int id);
       //修改User2密码，根据id改密码
       int updata3(Map<String,Object> map);
       List<User2> selectAll();
       //User2 模糊查询
       List<User> selectLittle(String name);
       //Limit 分页
       List<User> Limit(Map<String,Integer> map);
   }

2. 接口对应的Mapper.xml（注意nameSpace、返回值类型参数类型）

   <?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.xian.dao.UserMapper">
       <resultMap id="UserMap" type="com.xian.pojo.User">
   
       </resultMap>
       <select id="getUserList" resultType="user">
       select * from testdb.test001
     </select>
       <select id="getUserById" resultType="com.xian.pojo.User">
       select * from testdb.test001 where id=#{id}
       </select>
   
       <insert id="add" parameterType="com.xian.pojo.User">
           insert into testdb.test001 (id,name) values (#{id},#{name})
       </insert>
       <delete id="delete" parameterType="int">
           delete from testdb.test001 where id=#{id}
       </delete>
       <update id="upData" parameterType="com.xian.pojo.User">
           update  testdb.test001 set name=#{name} where id=#{id}
       </update>
       <update id="upData2" parameterType="map">
           update  testdb.test001 set name=#{username} where id=#{userid}
       </update>
   
       <update id="updata3" parameterType="map">
           update testdb.test002 set pwd=#{userPwd} where id=#{userId}
       </update>
   
       <select id="selectAll" resultType="com.xian.pojo.User2">
           select * from testdb.test002
       </select>
       <select id="selectLittle" resultType="com.xian.pojo.User">
           select * from testdb.test001 where name LIKE #{name}
       </select>
   <!--    <select id="Limit" resultMap="com.xian.pojo.User" parameterType="map">-->
       <!--        select * from testdb.test001 limit #{index},#{end}-->
       <!--    </select>-->
       <select id="Limit" resultType="user" parameterType="map">
           select * from testdb.test001 limit #{index},#{end }
       </select>
   
   </mapper>

6、测试

  @Test
    public void test001(){
        SqlSession sqlsession = MybatisUtils.getSqlsession();
        UserMapper mapper = sqlsession.getMapper(UserMapper.class);
        List<User> userList = mapper.getUserList();
        for (User user : userList) {
            System.out.println(user);
        }
        sqlsession.close();
    }