javaweb|使用spring boot完成增删改查--（一）查询 javaweb|java技术

下一节传送门：使用spring boot完成增删改查--（二）增删改、拦截器
使用工具：IDEA2018,Mysql8.0(用的是PHP study自带的mysql8.0，安装方便)，Tomcat9.0
首先新建一个springboot项目

文章图片

点next

文章图片

next

文章图片

就建成项目了
【javaweb|使用spring boot完成增删改查--（一）查询】修改配置文件
然后新建application.yml和application-dev.yml(原来的application.properties可以删除，spring boot会把application.yml解析成application.properties)
application.yml

spring: profiles: active: dev

application-dev.yml

server: port: 8080spring: datasource: username: root password: root url: jdbc:mysql://localhost:3306/springboot?useUnicode=true&characterEncoding=utf-8&userSSL=true&serverTimezone=UTC driver-class-name: com.mysql.cj.jdbc.Drivermybatis: mapper-locations: classpath:mapping/*Mapping.xml type-aliases-package: com.example.entity#showSql logging: level: com: example: mapper: debug

两个文件的意思是：

在项目中配置多套环境的配置方法。因为现在一个项目有好多环境，开发环境，测试环境，准生产环境，生产环境，每个环境的参数不同，所以我们就可以把每个环境的参数配置到yml文件中，这样在想用哪个环境的时候只需要在主配置文件中将用的配置文件写上就行如application.yml笔记：在Spring Boot中多环境配置文件名需要满足application-{profile}.yml的格式，其中{profile}对应你的环境标识，比如：application-dev.yml：开发环境 application-test.yml：测试环境 application-prod.yml：生产环境至于哪个具体的配置文件会被加载，需要在application.yml文件中通过spring.profiles.active属性来设置，其值对应{profile}值。

还有在配置文件中不要添加中文注释，会报错
接下来把启动文件（DemoApplication）移到com.example下，而且springboot的启动类不能放在java目录下！！！必须要个包将它包进去
否则会报错误：

Your ApplicationContext is unlikely to start due to a @ComponentScan of the default package.

然后开始新建实体类实现业务流程，创建包controller、entity、mapper、service。resources下创建mapping文件夹，用于写sql语句，也可以用注解的方式直接写在mapper文件里。下面直接贴代码
CREATE TABLE `user` ( `id` int(32) NOT NULL AUTO_INCREMENT, `userName` varchar(32) NOT NULL, `passWord` varchar(50) NOT NULL, `realName` varchar(32) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;

文章图片
entity.java
package com.example.entity; /** * Created with IntelliJ IDEA. * User: LYP_PC * Date: 2020/2/8 * Time: 17:31 * Description: No Description */ public class User { private Integer id; private String userName; private String passWord; private String realName; public Integer getId() { return id; }public void setId(Integer id) { this.id = id; }public String getUserName() { return userName; }public void setUserName(String userName) { this.userName = userName; }public String getPassWord() { return passWord; }public void setPassWord(String passWord) { this.passWord = passWord; }public String getRealName() { return realName; }public void setRealName(String realName) { this.realName = realName; }@Override public String toString() { return "User{" + "id=" + id + ", userName='" + userName + '\'' + ", passWord='" + passWord + '\'' + ", realName='" + realName + '\'' + '}'; } }
UserConteoller.java
package com.example.controller; import com.example.service.UserService; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; /** * Created with IntelliJ IDEA. * User: LYP_PC * Date: 2020/2/8 * Time: 17:46 * Description: No Description */ @RestController @RequestMapping("/testBoot") public class UserController {@Autowired private UserService userService; @RequestMapping("getUser/{id}") public String GetUser(@PathVariable int id){ return userService.Sel(id).toString(); } }

UserService.java
package com.example.service; import com.example.entity.User; import com.example.mapper.UserMapper; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service; /** * Created with IntelliJ IDEA. * User: LYP_PC * Date: 2020/2/8 * Time: 17:55 * Description: No Description */ @Service public class UserService {@Autowired UserMapper userMapper; public User Sel(int id){ return userMapper.Sel(id); } }

UserMapper.java
package com.example.mapper; import com.example.entity.User; import org.springframework.stereotype.Repository; /** * Created with IntelliJ IDEA. * User: LYP_PC * Date: 2020/2/8 * Time: 17:57 * Description: No Description */ @Repository public interface UserMapper {User Sel(int id); }

Usermapping.xml
select * from user where id = #{id}

最终框架结构

文章图片

完成以上，下面在启动类里加上注解用于给出需要扫描的mapper文件路径@MapperScan("com.example.mapper")

package com.example; import org.mybatis.spring.annotation.MapperScan; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; @MapperScan("com.example.mapper") //扫描的mapper @SpringBootApplication public class DemoApplication {public static void main(String[] args) { SpringApplication.run(DemoApplication.class, args); }}

最后启动，浏览器输入地址看看吧：http://localhost:8080/testBoot/getUser/1