SpringBoot 整合MyBatis-Plus

一、什麼是MyBatis-Plus

Mybatis是作爲一個半自動的持久層ORM框架一直以其可以直接在XML中通過SQL語句操作數據庫的靈活可控穩居持久層框架前列。但正其操作都要通過SQL語句進行，就必須寫大量的xml文件，很是麻煩。而我們今天要介紹的Mybatis-Plus就是爲了解決這些問題的。

Mybatis-Plus是一個 Mybatis 的增強工具，在 Mybatis 的基礎上只做增強不做改變，爲簡化開發、提高效率而生（官方定義）。它已經封裝好了一些crud方法，單表的增刪改查可以不用在xml中寫 sql 語句了，直接調用這些方法就行，就類似於JPA，使用 MyBatis-Plus 可以減少大量的開發時間。

二、使用Mybatis-Plus

2.1 添加依賴

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.6.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.oycbest</groupId>
    <artifactId>springboot-ssm</artifactId>
    <version>1.0.1</version>
    <name>springboot-ssm</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <druid.version>1.1.9</druid.version>
        <mybatis-plus.version>3.1.2</mybatis-plus.version>
        <mybatisplus-spring-boot-starter.version>1.0.5</mybatisplus-spring-boot-starter.version>
    </properties>

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

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

        <!-- druid -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>${druid.version}</version>
        </dependency>
        <!-- Mybatis-plus -->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatisplus-spring-boot-starter</artifactId>
            <version>${mybatisplus-spring-boot-starter.version}</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/com.baomidou/mybatis-plus -->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>${mybatis-plus.version}</version>
        </dependency>
        <!-- 這是mybatis-plus的代碼自動生成器 -->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-generator</artifactId>
            <version>${mybatis-plus.version}</version>
        </dependency>
       <!-- lombok 可以爲我們生產getter、setter、構造方法、toString方法等-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

2.2 編寫MyBatis-plus配置

/**
 * @Description: Mybatis-Plus配置類
 * @Author oyc
 * @Date 2020/4/29 7:46 下午
 */
@EnableTransactionManagement
@Configuration
//掃描的mapper文件路徑
@MapperScan(value = "com.oycbest.ssmblog.mapper")
public class MybatisPlusConfig {
    /**
     * 分頁插件
     */
    @Bean
    public PaginationInterceptor paginationInterceptor() {
        return new PaginationInterceptor();
    }
}

2.3 編寫代碼

讓service、mapper分別繼承Mybatis-Plus定義好的基礎實現

（1） mapper

/**
 * (SsmUser)表數據庫訪問層
 *
 * @author oyc
 * @since 2020-04-28 23:21:52
 */
public interface SsmUserMapper extends BaseMapper<SsmUser> {
}

（2）service接口

/**
 * (SsmUser)表服務接口
 *
 * @author oyc
 * @since 2020-04-28 23:21:53
 */
public interface SsmUserService extends IService<SsmUser> {
}

（3）service實現類

/**
 * (SsmUser)表服務實現類
 *
 * @author oyc
 * @since 2020-04-28 23:21:54
 */
@Service("ssmUserService")
public class SsmUserServiceImpl extends ServiceImpl<SsmUserMapper, SsmUser> implements SsmUserService {
}

（4）controller 調用service中的基礎方法完成數據的crud

package com.oycbest.ssmblog.controller;
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.oycbest.ssmblog.domain.SsmUser;
import com.oycbest.ssmblog.service.SsmUserService;
import org.apache.ibatis.annotations.Delete;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import javax.annotation.Resource;
/**
 * (SsmUser)表控制層
 *
 * @author oyc
 * @since 2020-04-28 23:24:43
 */
@RestController
@RequestMapping("ssmUser")
public class SsmUserController {
    /**
     * 服務對象
     */
    @Resource
    private SsmUserService ssmUserService;
    /**
     * 通過主鍵查詢單條數據
     *
     * @param id 主鍵
     * @return 單條數據
     */
    @GetMapping("{id}")
    public ResponseEntity selectOne(@PathVariable("id") Integer id) {
        return ResponseEntity.ok().body(ssmUserService.getById(id));
    }
    /**
     * 列表數據
     *
     * @return 列表數據
     */
    @GetMapping
    public ResponseEntity list(SsmUser user,
                               @RequestParam(name = "pageNo", defaultValue = "1") Integer pageNo,
                               @RequestParam(name = "pageSize", defaultValue = "10") Integer pageSize) {
        Page<SsmUser> page = new Page<>(pageNo, pageSize);
        QueryWrapper<SsmUser> wrapper = new QueryWrapper<>();
        wrapper.setEntity(user);
        IPage<SsmUser> pageList = ssmUserService.page(page, wrapper);
        return ResponseEntity.ok().body(pageList);
    }
    /**
     * 列表數據
     *
     * @return 列表數據
     */
    @GetMapping("list")
    public ResponseEntity list() {
        return ResponseEntity.ok().body(ssmUserService.list());
    }
    /**
     * 修改數據
     *
     * @param ssmUser 實例對象
     * @return 實例對象
     */
    @PostMapping
    public ResponseEntity save(SsmUser ssmUser) {
        return ResponseEntity.ok().body(ssmUserService.save(ssmUser));
    }
    /**
     * 新增或修改數據
     *
     * @param ssmUser 實例對象
     * @return 實例對象
     */
    @PutMapping
    public ResponseEntity saveOrUpdate(SsmUser ssmUser) {
        return ResponseEntity.ok().body(ssmUserService.saveOrUpdate(ssmUser));
    }
    /**
     * 通過主鍵刪除數據
     *
     * @param id 主鍵
     * @return 是否成功
     */
    @Delete("{id}")
    public ResponseEntity delete(@PathVariable("id") Integer id) {
        return ResponseEntity.ok().body(ssmUserService.removeById(id));
    }
}

源碼參考：https://github.com/oycyqr/springboot-learning-demo/tree/master/springboot-ssm