spring boot入门(二)-Mybatis-Plus CRUD

本文是spring boot的新手入门教程，目标是使用Mybatis Plus 实现简单的Mysql单表增删改查，不考虑事务等。

参考资料：

前置条件

安装Mysql服务端，或已有Mysql服务端
Mysql已经有初始化库 test 表 User

数据库初始化表和数据

数据库 test 中，已经初始化有一张 User 表，其表结构如下：

id	name	age	email
1	Jone	18	test1@baomidou.com
2	Jack	20	test2@baomidou.com
3	Tom	28	test3@baomidou.com
4	Sandy	21	test4@baomidou.com
5	Billie	24	test5@baomidou.com

其对应的数据库 Schema 脚本如下：

CREATE TABLE user
(
	id BIGINT(20) NOT NULL COMMENT '主键ID',
	name VARCHAR(30) NULL DEFAULT NULL COMMENT '姓名',
	age INT(11) NULL DEFAULT NULL COMMENT '年龄',
	email VARCHAR(50) NULL DEFAULT NULL COMMENT '邮箱',
	PRIMARY KEY (id)
);

其对应的数据库 Data 脚本如下：

INSERT INTO user (id, name, age, email) VALUES
(1, 'Jone', 18, 'test1@baomidou.com'),
(2, 'Jack', 20, 'test2@baomidou.com'),
(3, 'Tom', 28, 'test3@baomidou.com'),
(4, 'Sandy', 21, 'test4@baomidou.com'),
(5, 'Billie', 24, 'test5@baomidou.com');

添加依赖

引入 mybatis-plus-boot-starter、mysql-connector-java、junit依赖：

<dependencies>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>com.baomidou</groupId>
        <artifactId>mybatis-plus-boot-starter</artifactId>
        <version>3.4.1</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.49</version>
        <scope>runtime</scope>
    </dependency>
</dependencies>

配置

为了方便，我们将 application.properties 重命名为 application.yml，yaml格式的配置更易读写，也属于Spring Boot识别的属性文件
然后在 application.yml 配置文件中添加 Mysql 数据库的相关配置：

# DataSource Config
spring:
  datasource:
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=gbk&autoReconnect=true&failOverReadOnly=false
    username: root
    password: 123456

在 Spring Boot 启动类中添加 @MapperScan 注解，扫描 Mapper 文件夹：

@SpringBootApplication
@MapperScan("com.example.demo.mapper")
public class DemoApplication {

	public static void main(String[] args) {
		SpringApplication.run(DemoApplication.class, args);
	}

}

编码

在包 com.example.demo.model 下新增实体类 User.java

package com.example.demo.model;

public class User {
    private Long id;
    private String name;
    private Integer age;
    private String email;
    
    public Long getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getEmail() {
        return email;
    }

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

在包 com.example.demo.mapper 下新增Mapper类 UserMapper.java

package com.example.demo.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.example.demo.model.User;

public interface UserMapper extends BaseMapper<User> {

}

开始使用

在项目的 src/test/java 测试目录，新增测试类 UserMapperTest , 放在包 com.example.demo.mapper 下，尽量和源码对应，进行功能测试：

package com.example.demo.mapper;

import com.example.demo.model.User;
import org.junit.Assert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

import java.util.List;

@RunWith(SpringRunner.class)
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class UserMapperTest {

    @Autowired
    private UserMapper userMapper;

    @Test
    public void testSelect() {
        System.out.println(("----- selectAll method test ------"));
        List<User> userList = userMapper.selectList(null);
        Assert.assertEquals(5, userList.size());
        userList.forEach(System.out::println);
    }
}

在方法 testSelect 上右键，进行单元测试代码调试：
执行单元测试
::: tip
UserMapper 中的 selectList() 方法的参数为 MP 内置的条件封装器 Wrapper，所以不填写就是无任何条件
:::
控制台输出(可以重载User这个Java Bean对象的toString()方法，输出对象内容，例如Mybatis-Plus快速开始中的lombok的@Data注解，就做了重载)：

com.example.demo.model.User@227a933d
com.example.demo.model.User@25de8898
com.example.demo.model.User@bfb93cf
com.example.demo.model.User@dd737ea
com.example.demo.model.User@7bc2ae16

实现简单增删改查RESTFUL接口

新增Controller类 UserController ，用于对外提供增删改查接口，当然实际一般不会用mapper类进行dao操作，还会封装一层Service，Dao，事务管理等

package com.example.demo.controller;

import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.example.demo.mapper.UserMapper;
import com.example.demo.model.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/user")
public class UserController {

    @Autowired
    private UserMapper userMapper;

    @RequestMapping(method = RequestMethod.POST)
    public User create(@RequestBody User user) {
        userMapper.insert(user);
        return userMapper.selectById(user.getId());
    }

    @RequestMapping(value = "/{id}", method = RequestMethod.DELETE)
    public Integer delete(@PathVariable("id") Long id) {
        return userMapper.deleteById(id);
    }

    @RequestMapping(value = "/{id}", method = RequestMethod.PATCH)
    public Integer update(@PathVariable("id") Long id,@RequestBody User user) {
        user.setId(id);
        return userMapper.updateById(user);
    }

    @RequestMapping(value = "/{id}", method = RequestMethod.GET)
    public User update(@PathVariable("id") Long id) {
        LambdaQueryWrapper<User> queryWrapper = new LambdaQueryWrapper<>();
        queryWrapper.eq(User::getId,id);
         return userMapper.selectOne(queryWrapper);
    }

    @RequestMapping(value = "/actions/list-all", method = RequestMethod.GET)
    public List<User> update() {
        return userMapper.selectList(null);
    }
}

使用MockMvc测试新写的接口

在测试目录下，新增 UserController 对应的测试类 UserControllerTest，该单元测试用例，创建了一个用户，然后为了数据干净，直接调用mapper，将创建的数据，进行了删除：

package com.example.demo.controller;

import com.example.demo.mapper.UserMapper;
import com.example.demo.model.User;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.http.MediaType;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.test.web.servlet.MockMvc;

import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;

@RunWith(SpringRunner.class)
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
@AutoConfigureMockMvc
public class UserControllerTest {

    @Autowired
    MockMvc mockMvc;

    @Autowired
    private UserMapper userMapper;

    @Test
    public void create() throws Exception {
        // 分页查询用户信息
        String result = mockMvc.perform(   //执行一个RequestBuilder请求，会自动执行SpringMVC的流程并映射到相应的控制器执行处理；
                post("/user")  //模拟请求的url,及请求的方法是post
                        .contentType(MediaType.APPLICATION_JSON)  //数据的格式
                        .content("{\"name\":\"mockmvc-test\",\"age\":20,\"email\":\"mockmvc-test@test.com\"}"))   //请求的参数体
                .andExpect(
                        status().isOk()    //预期返回的状态码是200
                )
                .andReturn().getResponse().getContentAsString();  //将相应的数据转换为字符串
        System.out.println("新增User请求，返回："+result);
        ObjectMapper mapper = new ObjectMapper();
        User user = mapper.readValue(result,User.class);
        userMapper.deleteById(user.getId().toString());
    }
}