mybatis_plus简单学习

使用 Spring Initializr 快速初始化一个 Spring Boot 工程

Group：com.atguigu
Artifact：mybatis-plus
版本：2.2.1.RELEASE

1、引入依赖
spring-boot-starter、spring-boot-starter-test
添加：mybatis-plus-boot-starter、MySQL、lombok、
在项目中使用Lombok可以减少很多重复代码的书写。比如说getter/setter/toString等方法的编写

<?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>2.3.0.RELEASE</version>        <relativePath/> <!-- lookup parent from repository -->    </parent>    <groupId>com.mybatisplus</groupId>    <artifactId>myplus</artifactId>    <version>0.0.1-SNAPSHOT</version>    <name>myplus</name>    <description>Demo project for Spring Boot</description>    <properties>        <java.version>1.8</java.version>    </properties>    <dependencies>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter</artifactId>        </dependency>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-thymeleaf</artifactId>        </dependency>        <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>        <!--mybatis-plus-->        <dependency>            <groupId>com.baomidou</groupId>            <artifactId>mybatis-plus-boot-starter</artifactId>            <version>3.0.5</version>        </dependency>        <!--mysql-->        <dependency>            <groupId>mysql</groupId>            <artifactId>mysql-connector-java</artifactId>        </dependency>        <!-- https://mvnrepository.com/artifact/io.springfox/springfox-swagger2 -->        <dependency>            <groupId>io.springfox</groupId>            <artifactId>springfox-swagger2</artifactId>            <version>2.9.2</version>        </dependency>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-test</artifactId>            <scope>test</scope>            <exclusions>                <exclusion>                    <groupId>org.junit.vintage</groupId>                    <artifactId>junit-vintage-engine</artifactId>                </exclusion>            </exclusions>        </dependency>    </dependencies>    <build>        <plugins>            <plugin>                <groupId>org.springframework.boot</groupId>                <artifactId>spring-boot-maven-plugin</artifactId>            </plugin>        </plugins>    </build></project>

在 application.properties 配置文件中添加 MySQL 数据库的相关配置：
mysql5

spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driverspring.datasource.url=jdbc:mysql://localhost:3306/loadtest?serverTimezone=GMT%2B8spring.datasource.username=rootspring.datasource.password=123456#thymelea模板配置spring.thymeleaf.prefix=classpath:/templates/spring.thymeleaf.suffix=.htmlspring.thymeleaf.mode=HTML5spring.thymeleaf.encoding=UTF-8spring.thymeleaf.servlet.content-type=text/html#热部署文件，页面不产生缓存，及时更新# 开发阶段务必关闭缓存 (=false)spring.thymeleaf.cache=falsespring.resources.chain.strategy.content.enabled=truespring.resources.chain.strategy.content.paths=/**#logging.level.com.dy.springboot.server.mapper=debugspring.jackson.date-format=yyyy-MM-dd HH:mm:ssspring.jackson.time-zone=GMT+8spring.servlet.multipart.max-file-size=100MBspring.servlet.multipart.max-request-size=1000MBserver.port=8081#mybatis日志mybatis-plus.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl

注意：

1、这里的 url 使用了 ?serverTimezone=GMT%2B8 后缀，因为Spring Boot 2.1 集成了 8.0版本的jdbc驱动，这个版本的 jdbc 驱动需要添加这个后缀，否则运行测试用例报告如下错误：

java.sql.SQLException: The server time zone value 'Öйú±ê׼ʱ¼ä' is unrecognized or represents more

2、这里的 driver-class-name 使用了 com.mysql.cj.jdbc.Driver ，在 jdbc 8 中 建议使用这个驱动，之前的 com.mysql.jdbc.Driver 已经被废弃，否则运行测试用例的时候会有 WARN 信息

1、主类
在 Spring Boot 启动类中添加 @MapperScan 注解，扫描 Mapper 文件夹
注意：扫描的包名根据实际情况修改

import org.mybatis.spring.annotation.MapperScan;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;/** * * @author liwen406 * @date 2020-05-27 11:22 */@MapperScan("com.mybatisplus.mapper")@SpringBootApplicationpublic class MyplusApplication {    public static void main(String[] args) {        SpringApplication.run(MyplusApplication.class, args);    }}

2、实体
创建包 entity 编写实体类 ProjectInterface.java（此处使用了 Lombok 简化代码）

import com.baomidou.mybatisplus.annotation.IdType;import com.baomidou.mybatisplus.annotation.TableId;import io.swagger.annotations.ApiModel;import io.swagger.annotations.ApiModelProperty;import lombok.Data;import lombok.EqualsAndHashCode;import lombok.experimental.Accessors;import java.io.Serializable;import java.util.Date;/** * <p> * 工程接口 * </p> * * @author liwen * @since 2020-05-25 */@Data@EqualsAndHashCode(callSuper = false)@Accessors(chain = true)@ApiModel(value = "ProjectInterface对象", description = "工程接口")public class ProjectInterface implements Serializable {    private static final long serialVersionUID = 1L;    @ApiModelProperty(value = "主键ID")    @TableId(value = "id", type = IdType.AUTO)    private Long id;    @ApiModelProperty(value = "工程id")    private Long projectId;    private String interName;    @ApiModelProperty(value = "接口url")

Lombok使用参考：
https://blog.csdn.net/motui/article/details/79012846

3、mapper
创建包 mapper 编写Mapper 接口： ProjectInterfaceMapper.java

import com.baomidou.mybatisplus.core.mapper.BaseMapper;import com.mybatisplus.pojo.ProjectInterface;import org.springframework.stereotype.Repository;/** * @author liwen * @Title: ProjectInterfaceMapper * @Description: * @date 2020/5/27 / 11:33 * IDEA在 userMapper 处报错，因为找不到注入的对象，因为类是动态创建的，但是程序可以正确的执行。 * <p> * 为了避免报错，可以在 dao 层 的接口上添加 @Repository 注 */@Repositorypublic interface ProjectInterfaceMapper extends BaseMapper<ProjectInterface> {}

添加测试类，进行功能测试：

import com.mybatisplus.mapper.ProjectInterfaceMapper;import com.mybatisplus.pojo.ProjectInterface;import org.junit.jupiter.api.Test;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.boot.test.context.SpringBootTest;import java.util.List;@SpringBootTestclass MyplusApplicationTests {    @Autowired    ProjectInterfaceMapper projectInterfaceMapper;    @Test    void contextLoads() {        System.out.println(("----- selectAll method test ------"));        List<ProjectInterface> projectInterfaces = projectInterfaceMapper.selectList(null);        projectInterfaces.forEach(System.out::println);    }}