springboot整合MyBatis-Plus

一、添加依赖

pom.xml中添加：

<!-- mybatis-plus -->
<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.5.1</version>
</dependency>

二、配置MyBatis-Plus使用分页插件

新建MybatisPlusConfig类，并在MybatisPlusConfig.java文件中进行配置：

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

/**
 * MybatisPlus配置
 */
@Configuration
@MapperScan("com.qiancheng.springboot.mapper")//配置扫描mapper包
public class MybatisPlusConfig {

    /**
     * 新的分页插件,一缓和二缓遵循mybatis的规则,需要设置 MybatisConfiguration#useDeprecatedExecutor = false 避免缓存出现问题(该属性会在旧插件移除后一同移除)
     */
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.H2));
        return interceptor;
    }

}

新建一个 xxxMapper 接口继承 BaseMapper<实体类>，例如：

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.qiancheng.springboot.entity.User;
import org.apache.ibatis.annotations.*;

import java.util.List;

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

    @Select("SELECT * FROM sys_user")
    List<User> findAll();

}

新建xxxService类继承ServiceImpl，例如：

import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.qiancheng.springboot.entity.User;
import com.qiancheng.springboot.mapper.UserMapper;
import org.springframework.stereotype.Service;

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

    public boolean saveUser(User user) {
//        if (user.getId() == null){
//           return save(user);//mybatis-plus提供的方法
//        }else {//user有id则表示修改
//            return updateById(user);//mybatis-plus提供的方法
//        }
        return saveOrUpdate(user);//mybatis-plus提供的方法
    }
}

使用MyBatis-Plus提供的简单单表操作方法，例如：

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.qiancheng.springboot.entity.User;
import com.qiancheng.springboot.mapper.UserMapper;
import com.qiancheng.springboot.service.UserService;
import org.apache.logging.log4j.util.Strings;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
import java.util.List;

@RestController
//@CrossOrigin //临时解决跨域
@RequestMapping("/user")
public class UserController {

    @Autowired
    private UserService userService;

    @GetMapping
    public List<User> findAll(){
//        使用原始MyBatis方法查询
//        List<User> all = userMapper.findAll();
//        return all;

//        使用mybatis-plus方法查询
        return userService.list();//list方法为mybatis-plus提供
    }

    @PostMapping("/save")
    public boolean save(@RequestBody User user){
        //新增或者更新
        return userService.saveUser(user);
    }

    //传统手写分页查询
    //接口路径： /user/page?pageNum=1&pageSize=10
    //@RequestParam注解接收： ?pageNum=1&pageSize=10
    //limit第一个参数：(pageNum-1)*pageSize
    //limit第二个参数：pageSize
//    @GetMapping("/page")
//    public Map<String,Object> findPage(@RequestParam Integer pageNum,
//                                       @RequestParam Integer pageSize,
//                                       @RequestParam String username){
//        Integer pageIndex = (pageNum - 1) * pageSize;
//        List<User> data = userMapper.selectPage(pageIndex,pageSize,username);
//        Integer total = userMapper.selectTotal(username);
//        Map<String,Object> res = new HashMap<>();
//        res.put("data",data);
//        res.put("total",total);
//        return res;
//    }

    //使用MyBatis-Plus分页查询
    @GetMapping("/page")
    public IPage<User> findPage(@RequestParam(required = true) Integer pageNum,
                                @RequestParam(required = true) Integer pageSize,
                                @RequestParam(required = false) String username,
                                @RequestParam(defaultValue = "") String nickname,
                                @RequestParam(defaultValue = "") String address){
        IPage<User> page = new Page<>(pageNum,pageSize);
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();//分页条件
        queryWrapper.like(!Strings.isEmpty(username),"username",username);//!Strings.isEmpty(username)表示username不为null时候才加入这个模糊查询条件
        queryWrapper.like(!Strings.isEmpty(nickname),"nickname",nickname);
        queryWrapper.like(!Strings.isEmpty(address),"address",address);
        IPage<User> userPage = userService.page(page,queryWrapper);
        return userPage;
    }
}