mybatis实现最简单的增删改查

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1.数据库设计

2.项目结构（针对User不用管Blogger）

User.java

package com.yunqing.mybatis.bean;

public class User {
    private Integer id;
    private String name;
    private String gender;
    private String email;

    //构造函数
    public User() {
    }
    //带参构造函数
    public User(Integer id, String name, String gender, String email) {
        this.id = id;
        this.name = name;
        this.gender = gender;
        this.email = email;
    }

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

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

UserMapper.java接口类

package com.yunqing.mybatis.dao;

import com.yunqing.mybatis.bean.User;
import org.apache.ibatis.annotations.Select;

import java.util.List;

public interface UserMapper {

　　//这种写法可以用于简单的sql操作，复杂的请写在sql的xml映射文件中
    @Select("select * from t_user")
    List<User> getAllUser();

    User getUserById(Integer id);

　　//mybatis的增删改可以定义Integer|Long|boolean三种返回值类型
    void insertUser(User user);

    void updateUser(User user);

    void deleteUserById(Integer id);

}

UserMapper.xml(需要与接口类同名，批量注册到mybatis-config.xml中的时候与接口类放在同一个包下)

<?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">
<!--
namespace:命名空间,指定为接口的全类名
selectUserById：唯一标识
resultType：返回值类型
-->
<mapper namespace="com.yunqing.mybatis.dao.UserMapper">
    <select id="getUserById" resultType="com.yunqing.mybatis.bean.User">
        select * from t_user where id = #{id}
    </select>
    <insert id="insertUser" parameterType="com.yunqing.mybatis.bean.User" useGeneratedKeys="true">
        INSERT INTO t_user(name,gender,email) VALUES (#{name},#{gender},#{email})
    </insert>
    <update id="updateUser" parameterType="com.yunqing.mybatis.bean.User">
        UPDATE t_user SET name=#{name},gender=#{gender},email=#{email} where id=#{id}
    </update>
    <delete id="deleteUserById">
        DELETE from t_user where id=#{id}
    </delete>
</mapper>

UserMapperAnnotation.java介绍注解的方式（不用写sql的xml映射文件 ）

package com.yunqing.mybatis.dao;

import com.yunqing.mybatis.bean.User;
import org.apache.ibatis.annotations.Select;

public interface UserMapperAnnotation {

    @Select("SELECT * FROM t_user where id = #{id}")
    User getUserById(Integer id);
}

mybatis-config.xml全局配置

<?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="conf/dbconfig.properties"></properties>
    <environments default="development">
        <environment id="test">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql:///db_blog"/>
                <property name="username" value="root"/>
                <property name="password" value="5678"/>
            </dataSource>
        </environment>
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>
    <!--将写好的sql映射文件注册到全局配置文件中，类路径下直接写 UserMapper.xml就行，要是在包中则写com/yunqing/.../UserMapper.xml-->
    <mappers>
        <!--<mapper resource="conf/UserMapper.xml"/>-->
        <!--<mapper class="com.yunqing.mybatis.dao.UserMapperAnnotation"/>-->
        <package name="com.yunqing.mybatis.dao"/>
    </mappers>
</configuration>

dbconfig.properties

jdbc.driver = com.mysql.jdbc.Driver
jdbc.url = jdbc:mysql:///mybatis
jdbc.username = root
jdbc.password = 5678

测试文件MybatisTest.java

package com.yunqing.mybatis.test;

import com.yunqing.mybatis.bean.Blogger;
import com.yunqing.mybatis.bean.User;
import com.yunqing.mybatis.dao.BloggerMapper;
import com.yunqing.mybatis.dao.UserMapper;
import com.yunqing.mybatis.dao.UserMapperAnnotation;
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.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class MybatisTest {

    @Test
    public void getAllUser() throws IOException {
        //从xml中获取sqlSessionFactory
        String resource = "conf/mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        //获取sqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();

        //之前的mybatis的写法
        /*User user = sqlSession.selectOne("com.yunqing.mybatis.UserMapper.selectUserById",1);
        System.out.println(user);*/

        //现在的mybatis接口式编程写法
        //相当于接口的实现类
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        List<User> list = userMapper.getAllUser();//查询第一条记录
        System.out.println(list);
        sqlSession.close();
    }

    @Test
    public void getUserById() throws IOException {
        //从xml中获取sqlSessionFactory
        String resource = "conf/mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        //获取sqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();

        /*//之前的mybatis的写法
        User user = sqlSession.selectOne("com.yunqing.mybatis.UserMapper.selectUserById",1);
        System.out.println(user);*/

        //现在的mybatis接口式编程写法
        //相当于接口的实现类
        UserMapperAnnotation userMapperAnnotation = sqlSession.getMapper(UserMapperAnnotation.class);
        User user = userMapperAnnotation.getUserById(1);//查询第一条记录
        System.out.println(user);
        sqlSession.close();
    }
    @Test
    public void insertUser() throws IOException {
        String resource = "conf/mybatis-config.xml";
        InputStream is = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);

        //使用自动提交，如果不使用则需要sqlSession.commit();手动提交
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        //SqlSession sqlSession = sqlSessionFactory.openSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        //需要写有参和无参构造函数
        User user = new User(null,"Letme","1","letme@qq.com");
        userMapper.insertUser(user);
        //sqlSession.commit();
    }
    @Test
    public void updateUser() throws IOException {
        String res = "conf/mybatis-config.xml";
        InputStream is = Resources.getResourceAsStream(res);
        SqlSessionFactory  sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User user = new User(9,"uzi","1","uzi@qq.com");
        userMapper.updateUser(user);

    }
    @Test
    public void deleteUserById() throws IOException {
        String res = "conf/mybatis-config.xml";
        InputStream is = Resources.getResourceAsStream(res);
        SqlSessionFactory  sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        userMapper.deleteUserById(9);
    }
    /*@Test
    public void test2() throws IOException {
        String resource = "conf/mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        BloggerMapper bloggerMapper = sqlSession.getMapper(BloggerMapper.class);
        List<Blogger> list= bloggerMapper.getAllBloger();
        System.out.println(list);
        sqlSession.close();
    }*/
}

如果想获取自增主键的值需要在sql的映射xml文件中加上这两个参数