【项目】第一个spring boot 登录项目(java1.8)

技术栈：spring boot + spring data jpa + thymeleaf + spring mvc + mysql

新建项目

可以使用官网的starter或者IDEA新建项目
Flie->New Project->Spring Initializr.
(出现过连接超时问题，等会重试，设置代理方法解决？)


spring连接失败处理方法.png

新建项目New Project 名字任意，直接下一步，引入相关依赖见下图：


depend.png
项目结构，新建项目之后新建如下所示的目录结构和java、html文件
项目结构.png

pom.xml中的依赖

首先在pom.xml中引入如下依赖（之前在新建项目的时候引入过相关依赖可以忽略）：

<?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.example</groupId>
    <artifactId>login_demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>login_demo</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-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</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-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>

application.properties

在这里进行相关配置，端口号，数据库等配置

server.port=8080
spring.application.admin.enabled=false

spring.thymeleaf.cache=false
spring.thymeleaf.prefix=classpath:/templates/
spring.thymeleaf.check-template-location=true
spring.thymeleaf.suffix=.html
spring.thymeleaf.encoding=UTF-8
spring.thymeleaf.mode=HTML5

#服务器端
#数据库基本配置
spring.datasource.url=jdbc:mysql://127.0.0.1:3306/user?serverTimezone=GMT%2B8&useUnicode=true&characterEncoding=utf-8
spring.datasource.username=root
spring.datasource.password=1234
spring.datasource.driver-class-name=com.mysql.jdbc.Driver

#用来在控制台输出JPA自动生成的sql语句。
spring.jpa.show-sql=true
spring.jpa.database=mysql
spring.jpa.hibernate.ddl-auto=update

LoginController.java

登录功能的控制类

package com.example.login_demo.controller;

import com.example.login_demo.entity.User;
import com.example.login_demo.repository.UserRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;

/**
 * @auther Devin
 * 2020/6/9 13:35
 * @description 登录
 */
@RestController
@RequestMapping("/")
public class LoginController {

    @Autowired
    UserRepository userRepository;

    @GetMapping("/login")
    public ModelAndView login(ModelAndView modelAndView) {
        modelAndView.setViewName("login");
        return modelAndView;
    }

    @PostMapping("/toLogin")
    public ModelAndView login(HttpServletRequest request, ModelAndView modelAndView) {

        String username = request.getParameter("username");
        String pwd = request.getParameter("pwd");

        User user = userRepository.findUserByUsernameAndAndPwd(username, pwd);
        if (username != "" && pwd != "") {
            if (user!= null) {
                modelAndView.setViewName("hello");
                return modelAndView;

            } else {
                modelAndView.setViewName("login");
                modelAndView.addObject("msg","账号密码错误");
                return modelAndView;
            }

        } else {
            modelAndView.setViewName("error");
            return modelAndView;
        }
    }
}

User.java

用户实体类

package com.example.login_demo.entity;


import javax.persistence.*;

/**
 * @auther Devin
 * 2020/6/9 13:29
 * @description 用户实体类
 */
@Entity
@Table(name="tb_user")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    @Column(name = "username")
    private String username;
    @Column(name = "pwd")
    private String pwd;

    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 getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }
}

UserRepository.java

package com.example.login_demo.repository;

import com.example.login_demo.entity.User;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;
import org.springframework.stereotype.Repository;

/**
 * @auther Devin
 * 2020/6/9 13:48
 * @description
 */
@Repository
public interface UserRepository extends JpaRepository<User,Integer> {
    User findUserByUsernameAndAndPwd(String username ,String pwd);
}

login.html

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <meta http-equiv="Content-Type" content="text/html;charset=UTF-8" />
    <title>登录</title>
</head>
<body>
<form th:action="@{/toLogin}" method="post">
    <p style="color: red" th:text="${msg}" th:if="${not #strings.isEmpty(msg) }"></p>
    <div>
        <input id="username" name="username" type="text" placeholder="用户名" />
    </div>
    <br />
    <div>
        <input id="pwd" name="pwd" type="password" placeholder="密码" />
    </div>
    <br />
    <button type="submit" >登 录</button>
</form>
</body>
</html>

error.html 和 hello.html

两个文件的<title>和<h1>标签的内容不同

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>登录成功</title>
</head>
<body>
<h1>登录成功</h1>
</body>
</html>

完成！A

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