【初心者】Springで画像やファイルをアップロード【自己満】

.
└── _src
    └── _main
        ├── _java
        |   ├── _com.example.demo
        |       ├── FileUpdateController
        |       └── DemoApplication 
        └── _resources
            ├── _static
            |   ├── bootstrap.css
            |   ├── bootstrap.min.css
            |   └── training.css
            ├── _templates
            |   ├── uploadView.html
            |   └── uploadStatusView.html
            └── application.properties

<?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 http://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>2.1.5.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>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-thymeleaf</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.assertj</groupId>
            <artifactId>assertj-core</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

spring.thymeleaf.mode=HTML
spring.datasource.url=jdbc:mysql://localhost:3306/DB名?autoReconnect=true&
useSSL=false&serverTimezone=JST
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

spring.servlet.multipart.max-file-size=15MB
spring.servlet.multipart.max-request-size=15MB

package com.example.demo;

import com.example.demo.controller.FileUploadController;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;

import java.io.File;

@SpringBootApplication
@ComponentScan({"com.example.demo", "controller"})
public class DemoApplication {

    public static void main(String[] args) {
        new File(FileUploadController.uploadDirectory).mkdir();
        SpringApplication.run(DemoApplication.class, args);
    }

}

package com.example.demo.controller;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.MultipartFile;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

@Controller
public class FileUploadController {
    public static String uploadDirectory = System.getProperty("user.dir")+"uploads";

    @RequestMapping("/")
    public String UploadPage(Model model){
        return "uploadView";

    }

    @RequestMapping("/upload")
    public String upload(Model model, @RequestParam("files") MultipartFile[] files){
        StringBuilder fileNames = new StringBuilder();
        for(MultipartFile file : files){
            Path fileNameAndPath = Paths.get(uploadDirectory, file.getOriginalFilename());
            fileNames.append(file.getOriginalFilename());
            try {
                Files.write(fileNameAndPath, file.getBytes());
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        model.addAttribute("msg", "Successfully uploaded files "+ fileNames.toString());
        return "uploadStatusView";
    }
}

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
    <head>  
        <meta charset="UTF-8">
        <title>Title</title>
    </head>
    <body>
    <form action="/upload" method="post" enctype="multipart/form-data">
        <input type="file" name="files" multiple>
        <input type="submit" value="Upload Files">
    </form>
    </body>
</html>

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <div th:if="${msg}">
        <span th:text="${msg}"></span>
    </div>
    <div>
        <span><a href="/">Upload More</a></span>
    </div>
</body>
</html>