SpringBoot整合MyBatis并实现简单的查询功能

学了SpringBoot整合MyBatis才知道什么叫做省事，想当初用SSM的时候，那配置是真的多，SpringBoot真的是太友好了，到底有多好，接下来演示一个对数据库的查询功能，然初学者的我们大开眼界。首先创建一个springboot项目，说起整合，第一次听还是spring整合mybatis呢，那个时候需要导入mybatis-spring的依赖，现在是整合springboot了，当然也难免导入依赖，mybatis-spring-boot-starter（他是媒人）

<!-- https://mvnrepository.com/artifact/org.mybatis.spring.boot/mybatis-spring-boot-starter -->
<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>2.1.1</version>
</dependency>

既然要与数据库打交道，那就需要数据库驱动的支持

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <scope>runtime</scope>
</dependency>

首先我们写一个实体类，对应数据库中的字段

package com.hzy.pojo;

public class User {
    private int id;
    private String username;
    private String password;

    public User() {
    }

    public User(int id, String username, String password) {
        this.id = id;
        this.username = username;
        this.password = password;
    }

    public int getId() {
        return id;
    }

    public void setId(int 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 + '\'' +
                '}';
    }
}

然后就是我们的mapper接口

package com.hzy.mapper;

import com.hzy.pojo.User;
import org.apache.ibatis.annotations.Mapper;
import org.springframework.stereotype.Repository;

import java.util.List;

// 表示这是mybatis的一个mapper类
@Mapper
@Repository //相当于@Component
public interface UserMapper {
    List<User> queryAllUser();
    User queryUserById(int id);
    int addUser(User user);
    int updateUser(User user);
    int deleteUser(int id);
}

写完mapper接口，我们需要去写对应的UserMapper.xml完成相应的功能

<?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.hzy.mapper.UserMapper">
    <select id="queryAllUser" resultType="User">
            select * from user
    </select>
</mapper>

接下来就是连接数据库和整合了，写到application.properties，如果喜欢yaml也一样，

spring.datasource.username=root
spring.datasource.password=root
spring.datasource.url=jdbc:mysql://localhost:3306/mybatis?userSSL=true&useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
# 整合mybatis
mybatis.type-aliases-package=com.hzy.pojo
mybatis.mapper-locations=classpath:mybatis/mapper/*.xml

 

接下来就是测试了

package com.hzy;

import com.hzy.mapper.UserMapper;
import com.hzy.pojo.User;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import javax.sql.DataSource;
import java.sql.SQLException;
import java.util.List;

@SpringBootTest
class Springboot08MybatisApplicationTests {

    @Autowired
    UserMapper userMapper;
    @Test
    void contextLoads() throws SQLException {
        List<User> users = userMapper.queryAllUser();
        for (User user : users) {
            System.out.println(user);
        }
    }

}