09_MyBatis基于注解的CRUD

近些年来使用注解开发越来越流行，MyBatis顺应潮流，也可以使用注解开发。使用注解开发就可以不用写持久层映射配置文件了。这篇文章我们就来学习一下在MyBatis中如何使用注解进行CRUD。

一、MyBatis的常用注解说明

@Insert：实现新增
@Update：实现更新
@Delete：实现删除
@Select：实现查询
@Result：实现结果集封装
@Results：可以与@Result一起使用，封装多个结果集
@ResultMap：实现引用@Results定义的封装
@One：实现一对一结果集封装
@Many：实现一对多结果集封装

二、使用MyBatis注解实现单表CRUD

2.1、编写实体类User

注意：User类的属性名和数据库user表的列名不对应

package org.codeaction.domain;

import java.io.Serializable;
import java.util.Date;
import java.util.List;

public class User implements Serializable {
    private Integer userId;
    private String userName;
    private Date userBirthday;
    private String userSex;
    private String userAddress;

    public Integer getUserId() {
        return userId;
    }

    public void setUserId(Integer userId) {
        this.userId = userId;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public Date getUserBirthday() {
        return userBirthday;
    }

    public void setUserBirthday(Date userBirthday) {
        this.userBirthday = userBirthday;
    }

    public String getUserSex() {
        return userSex;
    }

    public void setUserSex(String userSex) {
        this.userSex = userSex;
    }

    public String getUserAddress() {
        return userAddress;
    }

    public void setUserAddress(String userAddress) {
        this.userAddress = userAddress;
    }

    @Override
    public String toString() {
        return "User{" +
                "userId=" + userId +
                ", userName='" + userName + '\'' +
                ", userBirthday=" + userBirthday +
                ", userSex='" + userSex + '\'' +
                ", userAddress='" + userAddress + '\'' +
                '}';
    }
}

2.2、使用注解方式开发持久层接口IUserDao

package org.codeaction.dao;

import org.apache.ibatis.annotations.*;
import org.codeaction.domain.User;

import java.util.List;

public interface IUserDao {
    @Select("select * from user")
    @Results(
        id = "userMap",
        value = {
                @Result(id = true, column = "id", property = "userId"),
                @Result(column = "username", property = "userName"),
                @Result(column = "birthday", property = "userBirthday"),
                @Result(column = "sex", property = "userSex"),
                @Result(column = "address", property = "userAddress")
        }
    )
    List<User> findAll();
    @Select("select * from user where id=#{id}")
    @ResultMap("userMap")
    User findById(Integer id);
    @Select("select * from user where username like #{name}")
    @ResultMap("userMap")
    List<User> findByName(String name);
    @Select("select count(id) from user")
    Integer findTotal();
    @Insert("insert into user(username, birthday, sex, address) " +
            "values(#{userName}, #{userBirthday}, #{userSex}, #{userAddress})")
    @SelectKey(keyColumn = "id",
            keyProperty = "userId",
            resultType = Integer.class,
            before = false,
            statement = {"select last_insert_id()"})
    Integer add(User user);
    @Delete("delete from user where id=#{id}")
    Integer del(Integer id);
    @Update("update user set username=#{userName}, birthday=#{userBirthday}, " +
            "sex=#{userSex}, address=#{userAddress} where id=#{userId}")
    Integer update(User user);
}

2.3、编写主配置文件SqlMapConfig.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">
<!-- mybatis的主配置文件 -->
<configuration>
    <properties resource="jdbcConfig.properties"></properties>
    <!-- 配置环境 -->
    <environments default="mysql">
        <!-- 配置mysql的环境 -->
        <environment id="mysql">
            <!-- 配置事务的类型 -->
            <transactionManager type="JDBC"></transactionManager>
            <!-- 配置数据源连接池-->
            <dataSource type="POOLED">
                <!-- 配置连接数据库的4个基本信息 -->
                <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>

    <!-- 指定映射配置文件的位置，映射配置文件指的是每个dao独立的配置文件 -->
    <mappers>
        <!-- 也可以使用mapper标签的class属性 -->
        <package name="org.codeaction.dao"/>
    </mappers>
</configuration>

2.4、编写测试方法

package org.codeaction.test;

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.codeaction.dao.IUserDao;
import org.codeaction.domain.User;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.List;

public class MyBatisTest {
    private InputStream in;
    private SqlSession session;

    @Before
    public void init() throws IOException {
        //读取配置文件
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        //创建SqlSessionFactory工厂
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        SqlSessionFactory factory = builder.build(in);
        //使用工厂生产SqlSession对象
        session = factory.openSession();
    }

    @After
    public void destroy() throws IOException {
        //提交事务
        session.commit();
        //释放资源
        session.close();
        in.close();
    }

    @Test
    public void testFindAll() throws IOException {
        //使用SqlSession创建Dao接口的代理对象
        IUserDao userDao = session.getMapper(IUserDao.class);
        //使用代理对象执行方法
        List<User> list = userDao.findAll();
        list.forEach(user -> {
            System.out.println(user);
        });
    }

    @Test
    public void testFindById() {
        IUserDao userDao = session.getMapper(IUserDao.class);
        User user = userDao.findById(41);

        System.out.println(user);
    }

    @Test
    public void testAdd() {
        User user = new User();
        user.setUserName("小李");
        user.setUserSex("男");
        user.setUserAddress("CHN");
        user.setUserBirthday(new Date());

        IUserDao userDao = session.getMapper(IUserDao.class);
        Integer result = userDao.add(user);
        System.out.println(result);
    }

    @Test
    public void testDel() {
        IUserDao userDao = session.getMapper(IUserDao.class);
        Integer result = userDao.del(60);
        System.out.println(result);
    }

    @Test
    public void testUpdate() {
        User user = new User();
        user.setUserId(59);
        user.setUserName("小李");
        user.setUserSex("女");
        user.setUserAddress("CHN");
        user.setUserBirthday(new Date());

        IUserDao userDao = session.getMapper(IUserDao.class);
        Integer result = userDao.update(user);
        System.out.println(result);
    }

    @Test
    public void testFindByName() {
        IUserDao userDao = session.getMapper(IUserDao.class);
        List<User> list = userDao.findByName("%王%");
        list.forEach(System.out::println);
    }

    @Test
    public void testFindTotal() {
        IUserDao userDao = session.getMapper(IUserDao.class);
        Integer total = userDao.findTotal();
        System.out.println(total);
    }
}