搭建 spring boot + mybatis plus 项目框架并进行调试

本文为博主原创，未经允许不得转载：

　　1.创建一个spring boot的工程应用：

　　 File ---- > New ----->Project ----> 然后选中Spring Initializr 继续创建：

2.添加spring boot ，mybatis plus 以及 mysql 相关的依赖：

 <dependencies>
        <!-- spring boot web启动 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <!-- mysql 数据库连接 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <!-- mybatis plus 代码生成器 -->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.2.0</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.47</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/javax.persistence/persistence-api -->
        <dependency>
            <groupId>javax.persistence</groupId>
            <artifactId>persistence-api</artifactId>
            <version>1.0</version>
        </dependency>
    </dependencies>

3. spring boot 的配置文件中配置项目启动名称，端口号，数据库连接等：

此处需要注意的是：spring boot 项目的配置文件是application.properties ,不是bootstrap.yml，bootstrap.yml是spring cloud 中定义解析配置文件的格式

server.port=8002

spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://127.0.0.1:3306/test?autoReconnect=true&useUnicode=true&characterEncoding=utf8&useSSL=false&serverTimezone=UTC
spring.datasource.username=root
spring.datasource.password=root

# mybatis plus 调用打印 sql
mybatis-plus.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl

并启动项目，查看启动日志，会打印spring 以及 mybatis plus 的banner 图案

4.创建用户表，定义表结构如下：

CREATE TABLE `user` (
  `id` bigint(20) NOT NULL COMMENT '主键ID',
  `name` varchar(30) DEFAULT NULL COMMENT '姓名',
  `age` int(11) DEFAULT NULL COMMENT '年龄',
  `email` varchar(50) DEFAULT NULL COMMENT '邮箱',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf-8;

5. 业务代码：

　　5.1 创建实体类：

package com.example.demo.entity;

import lombok.Data;
import javax.persistence.Table;

@Data
@Table(name = "user")
public class User {

    private Long id;

    private String name;

    private int age;

    private String email;
}

　　5.2 创建 mapper，需要继承BaseMapper

　　　　mapper接口需要在项目启动时进行加载扫描，可以使用两种方式进行配置：

　　　　　　第一种可以使用 @Mapper注解，在每个mapper接口进行注解，第二种可以在启动类上使用 @MapperScan 注解，其中的值为mapper的包路径

　　　　其中@Repository 表示持久层

package com.example.demo.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.example.demo.entity.User;
import org.apache.ibatis.annotations.Mapper;
import org.springframework.stereotype.Repository;

@Repository
//@Mapper
public interface UserMapper extends BaseMapper<User> {
}

　　5.3 创建service 接口,需要继承IService

package com.example.demo.service;

import com.baomidou.mybatisplus.extension.service.IService;
import com.example.demo.entity.User;

import java.util.List;

public interface UserService extends IService<User> {
    /**
     * query all
     * @return
     */
    List<User> queryAllUser();
}

　　5.4 实现service接口，需要继承 ServiceImpl

package com.example.demo.service.impl;

import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.example.demo.entity.User;
import com.example.demo.mapper.UserMapper;
import com.example.demo.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.List;

@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {

    @Autowired
    private UserMapper userMapper;
    @Override
    public List<User> queryAllUser() {
        return userMapper.selectList(null);
    }
}

　　5.5 创建controller

package com.example.demo.controller;

import com.example.demo.entity.User;
import com.example.demo.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

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

    @Autowired
    private UserService userService;

    @RequestMapping("/queryAllUser")
    public List<User> queryAllUser(){
        List<User> userList = userService.queryAllUser();
        return userList;
    }

}

6.测试类

　　测试类需要添加spring boot 的test依赖，其中已经依赖过了junit test 的依赖，不需要再进行单独添加。

package com.example.demo;

import com.alibaba.fastjson.JSON;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.example.demo.controller.UserInfoController;
import com.example.demo.entity.User;
import com.example.demo.mapper.UserMapper;
import com.example.demo.service.UserService;
import lombok.extern.slf4j.Slf4j;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.List;

@Slf4j
@SpringBootTest
class DemoApplicationTests {

    @Autowired
    private UserMapper userMapper;

    @Autowired
    private UserService userService;

    @Autowired
    private UserInfoController userInfoController;

    @Test
    void test() {
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper.eq("name", "2");
        User user = userMapper.selectOne(wrapper);
        log.info("userMapper.selectOne result is {}", JSON.toJSONString(user));

        int count = userService.count();
        System.out.println(count);
        log.info("userService.count() result is {}", count);
        List<User> userList = userInfoController.queryAllUser();
        log.info("userInfoController.queryAllUser() result is {}", JSON.toJSONString(userList));
    }
}

如果使用以上测试时，出现测试类中注入的bean一直为空时，可使用下面的方式：

@RunWith(SpringRunner.class)
@SpringBootTest(classes = GeneratorApp.class, webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class UserTest {

 　　@Autowired
    private UserService userService;

执行以上测试类截图：

7. 配置 mybatis plus 的分页

package com.example.demo.config;

import com.baomidou.mybatisplus.extension.plugins.PaginationInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class MybatisPlusConfig {
    // 分页插件
    @Bean
    public PaginationInterceptor paginationInterceptor() {
        return new PaginationInterceptor();
    }

}

通过 junit 进行调试

 @Test
    void testPage() {
        Page<User> page = new Page<>(1, 5);
        IPage<User> paVo = userMapper.selectPage(page, null);
        log.info("------------------{}", JSON.toJSONString(paVo));
    }

mybatis plus 分页之后的格式如下：

{
    "current": 1,
    "orders": [],
    "pages": 1,
    "records": [{
        "age": 3,
        "email": "4",
        "id": 1,
        "name": "2"
    }, {
        "age": 23,
        "email": "344",
        "id": 1352980081638248450,
        "name": "test"
    }, {
        "age": 23,
        "email": "344",
        "id": 1352980446211342337,
        "name": "test"
    }, {
        "age": 23,
        "email": "344",
        "id": 1352980660057944066,
        "name": "test"
    }],
    "searchCount": true,
    "size": 5,
    "total": 4
}

搭建框架过程中遇到的坑：

　　1. spring boot start启动的依赖是 spring-boot-starter-web ，不是 spring-boot-starter

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

　　2. spring boot 默认解析的配置文件是 application.properties 文件，不是bootstrap.yaml ， bootstrap.yaml 是spring cloud 中加载解析的配置文件格式