[Java][服务器][MyBatis-Plus] 建立工程步骤预览

一、步骤预览

二、初始化工程

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

Group：com.mybatisplus

Artifact：demo;

版本：2.2.1.RELEASE

 

三、添加依赖

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

 

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

        <!--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>

        <!--lombok用来简化实体类-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
    </dependencies>

2、idea中安装lombok插件

 

四、配置

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.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/mybatis_plus?serverTimezone=GMT%2B8
spring.datasource.username=root
spring.datasource.password=123456

 

mysql8以上（spring boot 2.1）

spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

spring.datasource.url=jdbc:mysql://localhost:3306/mybatis_plus?serverTimezone=GMT%2B8

spring.datasource.username=root

spring.datasource.password=123456

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

五、编写代码

1、主类

在 Spring Boot 启动类中添加 @MapperScan 注解，扫描 Mapper 包名

package com.mybatisplus.demo;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@MapperScan("com.mybatisplus.demo.mapper")
public class DemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}

2、实体

package com.mybatisplus.demo.entity;
import lombok.Data;

@Data
public class User {

    private Long id;
    private String name;
    private Integer age;
    private String email;
}

3、mapper

创建包 mapper 编写Mapper 接口： UserMapper.java

package com.mybatisplus.demo.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.mybatisplus.demo.entity.User;
import org.springframework.stereotype.Repository;

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

六、开始使用

使用测试类，进行功能测试：

package com.mybatisplus.demo;

import com.mybatisplus.demo.entity.User;
import com.mybatisplus.demo.mapper.UserMapper;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.List;

@SpringBootTest
class DemoApplicationTests {

    @Autowired
    private UserMapper userMapper;

    //查询user表所有数据
    @Test
    public void findAll() {
        List<User> users = userMapper.selectList(null);
        System.out.println(users);
    }
}

直接点击运行findAll()方法可以测试

输出结果如下

[User(id = 1, name = Jone, age = 18, email = test1 @baomidou.com), 
 User(id = 2, name = Jack, age = 20, email = test2 @baomidou.com), 
 User(id = 3, name = Tom, age = 28, email = test3 @baomidou.com), 
 User(id = 4, name = Sandy, age = 21, email = test4 @baomidou.com), 
 User(id = 5, name = Billie, age = 24, email = test5 @baomidou.com)]

七、配置日志

在配置文件中application.properties添加

mybatis-plus.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl

可以在控制台查看sql输出日志

Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@67110f71] was not registered for synchronization because synchronization is not active
JDBC Connection [HikariProxyConnection@1713129148 wrapping com.mysql.cj.jdbc.ConnectionImpl@37864b77] will not be managed by Spring
==>  Preparing: SELECT id,name,age,email FROM user 
==> Parameters: 
<==    Columns: id, name, age, email
<==        Row: 1, Jone, 18, [email protected]
<==        Row: 2, Jack, 20, [email protected]
<==        Row: 3, Tom, 28, [email protected]
<==        Row: 4, Sandy, 21, [email protected]
<==        Row: 5, Billie, 24, [email protected]
<==      Total: 5
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@67110f71]