第四篇 - Spring Boot写一个登录功能1

SpringBoot + Mysql + jdk8

一、新建Spring Boot项目

 创建成功后的目录为

 创建多个package，结构如下：

 先尝试build一下项目

 报错java: 警告: 源发行版 17 需要目标发行版 17

 Rebuild一下项目

 报错类文件具有错误的版本 61.0, 应为 52.0

 重启IDEA，Rebuild项目，成功。

接下来尝试Run一下项目

 报错Unable to instantiate org.mybatis.spring.boot.autoconfigure.MybatisDependsOnDatabaseInitializationDetector

 二、配置MySQL环境

参考链接：https://zhuanlan.zhihu.com/p/348166709

pom.xml添加依赖

<dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.38</version>
</dependency>

application.properties添加配置

spring.datasource.url=jdbc:mysql://localhost:3307/test?useUnicode=true&characterEncoding=utf8
spring.datasource.username=root
spring.datasource.password=123456
spring.datasource.driver-class-name=com.mysql.jdbc.Driver

spring.jpa.properties.hibernate.hbm2ddl.auto=update
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL5InnoDBDialect
spring.jpa.show-sql= true

在controller文件夹下新建一个UserController类

package com.example.demo.controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class UserController {
    @RequestMapping("/getuserlist")
    public String getUserList()
    {
        return "获取成功！";
    }
}

新建一个entity文件夹并再此文件夹下新建一个User类

package com.example.demo.entity;

public class User {
    public String user_account;
    public String user_password;

    public String getUsername() {
        return user_account;
    }

    public void setUsername(String User_account) {
        this.user_account = User_account;
    }

    public String getUserpassword() {
        return user_password;
    }

    public void setUserpassword(String User_password) {
        this.user_password = User_password;
    }

}

在mapper文件夹下新建一个UserMapper类

package com.example.demo.mapper;

import com.example.demo.entity.User;
import org.apache.ibatis.annotations.Select;
import org.springframework.stereotype.Component;

import java.util.List;

@Component
public interface UserMapper {
    //然后做一些数据库的对应操作，这次是查询操作
    @Select("select * from user")
    List<User> getUserList();
}

文件目录

UserService.java

package com.example.demo.service;

import com.example.demo.entity.User;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public interface UserService {
    //和mapper相呼应，有一个对应的方法
    List<User> getUserList();
}

UserServiceImpl.java

package com.example.demo.service.impl;

import com.example.demo.entity.User;
import com.example.demo.mapper.UserMapper;
import com.example.demo.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;

import java.util.List;

@Repository
public class UserServiceImpl implements UserService {
    @Autowired
    private UserMapper userMapper;

    @Override
    public List<User> getUserList() {
        try{
            List<User> users= userMapper.getUserList();
            return users;

        }catch (Exception e){
            //好像是 如果不throw的话，会报错。。。
            e.printStackTrace();
            throw e;
        }
    }
}

修改UserController.java

package com.example.demo.controller;

import com.example.demo.entity.User;
import com.example.demo.service.impl.UserServiceImpl;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@RestController
public class UserController {
    @Autowired
    private UserServiceImpl userServer;

    @RequestMapping("/getuserlist")
    public List<User> getUserList()
    {
        return userServer.getUserList();
    }
}

最后在Demo1Application.java中添加注解

package com.example.demo;

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

@SpringBootApplication
@MapperScan("com.example.demo")
public class Demo1Application {

    public static void main(String[] args) {
        SpringApplication.run(Demo1Application.class, args);
    }

}

报错类文件具有错误的版本 61.0, 应为 52.0

 重启IDEA，运行项目，成功。

访问http://localhost:8080/getuserlist