SpringBoot案例（数据层、业务层、表现层）

1.创建项目

2.选择坐标

3.添加坐标

说明：为了便于开发，引入了lombak坐标。

        <!--添加mybatis-plus坐标-->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.4.3</version>
        </dependency>
<!--        添加Druid坐标-->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid-spring-boot-starter</artifactId>
            <version>1.2.6</version>
        </dependency>
        <!--      lombok  -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>

4.Lombok

说明：Lombok是java类库，提供了一组注解，简化POJO实体列开发；它有SpringBoot提供，无需指定版本。为当前实体类在编译期设置对应的get/set方法，toString方法，hashCode方法，equals方法等。

5.实体类

package com.forever.domain;

import lombok.Data;


@Data    //Data中封装了getter方法，setter方法，toString封装；没有构造方法

public class User {
    private  Integer id;
    private  String username;
    private  String  password;
    private  String gender;
    private  String addrCity;

}

6.数据层开发

说明：技术实现方案

MyBatisPlus；数据源用Druid；bookDao和bookMapper是同一个意思。

6.1dao层

package com.forever.dao;


import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.forever.domain.User;
import org.apache.ibatis.annotations.Mapper;

@Mapper
public interface UserDao extends BaseMapper<User> {


}

6.2测试类

package com.forever.dao;

import com.forever.domain.User;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

@SpringBootTest
public class daoTest {
    @Autowired
    private UserDao userDao;
    @Test
    void testGetByid() {
        System.out.println(userDao.selectById(1));
    }
    @Test
    void testInsert(){
        User user=new User();
        user.setGender("男");
        user.setUsername("天王");
        user.setPassword("123456");
        user.setAddrCity("成都市");
        userDao.insert(user);
    }

}

6.3注意

问题：

解决：将id-type的值设置为auto

#配置数据库
spring:
  datasource:
    druid:
      driver-class-name: com.mysql.cj.jdbc.Driver
      url: jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC
      username: root
      password: 123456
server:
  port: 80
mybatis-plus:
  global-config:
    db-config:
      table-prefix: tb_
      id-type: auto  #auto是自增策略 assign_id是雪花算法自增id

6.5成功

7.mp日志

说明：mybatis-plus开启日志，配置configuration下的log-impl的值就行了。

#配置数据库
spring:
  datasource:
    druid:
      driver-class-name: com.mysql.cj.jdbc.Driver
      url: jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC
      username: root
      password: 123456
server:
  port: 80
mybatis-plus:
  global-config:
    db-config:
      table-prefix: tb_
      id-type: auto  #auto是自增策略 assign_id是雪花算法自增id
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl  #标准输出日志

8.分页功能实现

说明：需要加入拦截器类

8.1拦截器类

package com.forever.config;


import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class MPConfig {
    @Bean
    //创建了mybatis拦截器的壳
    public MybatisPlusInterceptor mybatisPlusInterceptor(){
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        //拦截分页功能
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor());
        return  interceptor;
    }



}

8.2测试类

说明：加入测试方法。

    @Test
    void testPage(){

        IPage page=new Page(1,5);
        userDao.selectPage(page,null);
    }

8.3成功

8.4知识点

说明：分页操作是在MyBatisPlus的常规操作基础上增强得到，内部是动态的拼写SQL语句，因此需要增强对应的功能，使用MyBatisPlus:拦截器实现。

9.按条件进行查询

9.1QueryWrapper

说明：QueryWrapper手工录入属性名；LambdaQueryWrapper不用手工录入属性名。

    @Test
    void testGetBy(){
        //按条件查询
        QueryWrapper qw = new QueryWrapper<>();
        qw.like("username","李");
        userDao.selectList(qw);
    }

9.2LambadQueryWrapper

    @Test
    void testGetBy2() {
        String name=null;
        //按条件查询
        LambdaQueryWrapper<User> lqw = new LambdaQueryWrapper<User>();
        lqw.like(name!=null, User::getUsername, name);
        userDao.selectList(lqw);
    }

10.业务层

说明：创建了业务层接口，和实现类。

10.1业务接口

package com.forever.service;

import com.baomidou.mybatisplus.core.metadata.IPage;
import com.forever.domain.User;

import java.awt.print.Book;
import java.util.List;

public interface UserService {
   Boolean save(User user);
   Boolean update(User user);
   Boolean delete(Integer id);
   User getByID(Integer id);
   List<User> getAll();
   //分页实现用int类型
   IPage<User> getPage(int currentPage,int pageSize);

}

10.2业务实现类

package com.forever.service.impl;

import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.forever.dao.UserDao;
import com.forever.domain.User;
import com.forever.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.awt.print.Book;
import java.util.List;

@Service
public class UserServiceImpl implements UserService {

    @Autowired
    private UserDao userDao;

    @Override
    public Boolean save(User user) {
        //对于数据层的操作都是影响行数
        return userDao.insert(user) > 0;
    }

    @Override
    public Boolean update(User user) {
        return userDao.updateById(user) > 0;
    }

    @Override
    public Boolean delete(Integer id) {
        return userDao.deleteById(id) > 0;
    }

    @Override
    public User getByID(Integer id) {
        return userDao.selectById(id);
    }

    @Override
    public List<User> getAll() {
        return userDao.selectList(null);
    }

    @Override
    public IPage<User> getPage(int currentPage, int pageSize) {
        IPage page = new Page(currentPage, pageSize);
         userDao.selectPage(page, null);
         return  page;
    }
}

10.3测试类

package com.forever.service;

import com.baomidou.mybatisplus.core.metadata.IPage;
import com.forever.domain.User;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

@SpringBootTest
public class UserServiceTestCase {
    @Autowired
    private  UserService userService;
    @Test
    void testGetById(){
        //关注的是数据能否正常的显示
        System.out.println( userService.getByID(1));;
    }
    @Test
    void  testGetAll(){
        User user=new User();
        user.setGender("男");
        user.setUsername("李四");
        user.setPassword("123456");
        user.setAddrCity("成都市");
        userService.save(user);
    }
    @Test
    void testGetPage(){
       IPage page=userService.getPage(1,5);
        System.out.println(page.getTotal());
    }


}

10.4简化业务层

说明：业务接口

package com.forever.service;

import com.baomidou.mybatisplus.extension.service.IService;
import com.forever.domain.User;

//业务层接口

public interface IUserService extends IService<User> {

}

业务接口实现类

package com.forever.service.impl;

import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.forever.dao.UserDao;
import com.forever.domain.User;
import com.forever.service.IUserService;
import org.springframework.stereotype.Service;

//泛型第一个是实现类，第二个模型类
@Service
public class UserServiceImpl extends ServiceImpl<UserDao, User> implements IUserService {
}

测试类

package com.forever.service;


import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.forever.domain.User;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

@SpringBootTest
public class UserServiceTestCase {
    @Autowired
    private  IUserService userService;
    @Test
    void testGetById(){
        //关注的是数据能否正常的显示
        System.out.println( userService.getById(1));;
    }
    @Test
    void  testGetAll(){
        User user=new User();
        user.setGender("男");
        user.setUsername("李四");
        user.setPassword("123456");
        user.setAddrCity("成都市");
        userService.save(user);
    }
    @Test
    void testGetPage(){
        IPage<User> page=new Page<User>(1,5);
        userService.page(page);
        System.out.println(page.getTotal());
    }


}

11.表现层

说明：基于Restful进行表现层接口开发；使用Postman测试表现层接口功能。

package com.forever.controller;

import com.baomidou.mybatisplus.core.metadata.IPage;
import com.forever.domain.User;
import com.forever.service.IUserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/users")
public class UserController {
    @Autowired
    private IUserService userService;
    @GetMapping
    public List<User> getAll(){
        return userService.list();
    }

    @PostMapping
    public  Boolean save(@RequestBody User user){
        return  userService.save(user);
    }

    @GetMapping("{id}")
    public User getByid(@PathVariable Integer id){
        return  userService.getById(id);
    }
    //占位符
    @GetMapping("{currentPage}/{pageSize}")
    public IPage<User> getPage(@PathVariable int currentPage,@PathVariable int pageSize){
        return userService.getPage(currentPage,pageSize);
    }

}