spring boot实现图片上传和下载功能

下面我将针对“spring boot实现图片上传和下载功能”的完整操作过程进行详细讲解，并提供两个示例以供参考。

准备工作

在开始实现图片上传和下载功能之前，我们需要先准备好开发环境和所需要的依赖。具体流程如下：

环境搭建

JDK 1.8及以上版本
Maven 3.2及以上版本
IDE开发工具（如Eclipse、IntelliJ IDEA等）

需要依赖

在Maven项目的pom.xml文件中添加以下依赖：

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
    <version>2.3.9.RELEASE</version>
</dependency>

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
    <version>2.3.9.RELEASE</version>
</dependency>

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-thymeleaf</artifactId>
    <version>2.3.9.RELEASE</version>
</dependency>

同时，为了让程序能够上传和下载文件，还需要引入以下依赖：

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-websocket</artifactId>
    <version>2.3.9.RELEASE</version>
</dependency>

<dependency>
    <groupId>commons-fileupload</groupId>
    <artifactId>commons-fileupload</artifactId>
    <version>1.2.2</version>
</dependency>

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>1.4</version>
</dependency>

实现图片上传和下载功能

实现图片上传

创建上传文件的Controller类，并添加上传文件页面。

@Controller
public class FileUploadController {

    @GetMapping("/")
    public String index() {
        return "upload";
    }

    @PostMapping("/upload")
    public String upload(@RequestParam("file") MultipartFile file, Model model) throws IOException {
        FileUtils.writeByteArrayToFile(new File("D://" + file.getOriginalFilename()), file.getBytes());
        model.addAttribute("msg", "File uploaded successfully");
        return "upload_status";
    }
}

其中，/是上传文件的页面路径，upload是上传文件的页面名称，/upload是上传文件的处理路径，upload_status是处理上传结果的页面名称。

创建上传页面upload.html。

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <title>File Upload</title>
</head>
<body>
<div>
    <form method="POST" enctype="multipart/form-data" th:action="@{/upload}">
        <input type="file" name="file" />
        <button type="submit">Submit</button>
    </form>
</div>
</body>
</html>

创建上传结果页面upload_status.html。

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <title>File Upload Status</title>
</head>
<body>
<h1 th:text="${msg}"></h1>
</body>
</html>

实现图片下载

创建实体类File。

@Entity
public class File {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String name;

    private String path;

    private String type;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPath() {
        return path;
    }

    public void setPath(String path) {
        this.path = path;
    }

    public String getType() {
        return type;
    }

    public void setType(String type) {
        this.type = type;
    }
}

创建文件上传和下载服务类FileService。

@Service
public class FileService {

    @Autowired
    private FileRepository fileRepository;

    public void upload(MultipartFile file) throws Exception {
        String path = "D://";
        String name = file.getOriginalFilename();
        File f = new File();
        f.setName(name);
        f.setPath(path);
        f.setType(file.getContentType());
        FileUtils.writeByteArrayToFile(new File(path + name), file.getBytes());
        fileRepository.save(f);
    }

    public ResponseEntity<Resource> download(Long id) throws Exception {
        Optional<File> optional = fileRepository.findById(id);
        if (optional.isPresent()) {
            File f = optional.get();
            InputStreamResource resource = new InputStreamResource(new FileInputStream(new File(f.getPath() + f.getName())));
            return ResponseEntity.ok()
                    .header(HttpHeaders.CONTENT_TYPE, f.getType())
                    .header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"" + f.getName() + "\"")
                    .body(resource);
        }
        throw new Exception("File not found.");
    }
}

其中，FileRepository是用于声明和操作实体类File的数据库操作类。

创建上传文件处理器和下载文件处理器。

@Controller
public class FileController {

    @Autowired
    private FileService fileService;

    @GetMapping("/download/{id}")
    public ResponseEntity<Resource> download(@PathVariable Long id) throws Exception {
        return fileService.download(id);
    }

    @PostMapping("/upload")
    public String upload(@RequestParam("file") MultipartFile file, Model model) throws Exception {
        fileService.upload(file);
        model.addAttribute("msg", "File uploaded successfully");
        return "upload_status";
    }
}

其中，/download/{id}是下载文件的处理路径，/upload是上传文件的处理路径。

创建下载文件页面download.html。

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <title>File Download</title>
</head>
<body>
<div>
    <h1>File Download</h1>
    <table>
        <tr>
            <th>ID</th>
            <th>Name</th>
            <th>Action</th>
        </tr>
        <tr th:each="file : ${files}">
            <td th:text="${file.id}"></td>
            <td th:text="${file.name}"></td>
            <td><a th:href="@{/download/{id}(id=${file.id})}">Download</a></td>
        </tr>
    </table>
</div>
</body>
</html>