springboot头像上传回显

在Spring Boot中，实现头像上传并回显的步骤如下：

1. 添加文件上传依赖

在`pom.xml`中添加以下依赖：

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

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

<dependency>
   <groupId>commons-io</groupId>
   <artifactId>commons-io</artifactId>
   <version>2.6</version>
</dependency>

2. 编写上传页面

在HTML页面中添加上传表单：

<form method="post" action="/upload" enctype="multipart/form-data">
    <input type="file" name="file"/>
    <input type="submit" value="Upload"/>
</form>

3. 编写上传接口

在控制器中添加上传接口：

@PostMapping("/upload")
public String uploadFile(@RequestParam("file") MultipartFile file, Model model) {
    String fileName = StringUtils.cleanPath(file.getOriginalFilename());
    try {
        FileUploadUtil.saveFile(uploadDir, fileName, file);
    } catch (IOException e) {
        e.printStackTrace();
    }
    model.addAttribute("message", "File uploaded successfully!");
    model.addAttribute("fileName", fileName);
    return "upload-result";
}

其中，`FileUploadUtil`是一个工具类，用于保存文件：

public class FileUploadUtil {
    public static void saveFile(String uploadDir, String fileName, MultipartFile multipartFile) throws IOException {
        Path uploadPath = Paths.get(uploadDir);

        if (!Files.exists(uploadPath)) {
            Files.createDirectories(uploadPath);
        }

        try (InputStream inputStream = multipartFile.getInputStream()) {
            Path filePath = uploadPath.resolve(fileName);
            Files.copy(inputStream, filePath, StandardCopyOption.REPLACE_EXISTING);
        } catch (IOException ioe) {
            throw new IOException("Could not save image file: " + fileName, ioe);
        }
    }
}

4. 显示上传结果

在上传成功后，跳转到上传结果页面，显示上传的文件名和头像：

<h1>Upload Result</h1>
<p th:text="'File uploaded successfully: ' + ${fileName}"></p>
<img th:src="@{${'/uploads/' + fileName}}" width="200" height="200"/>

其中，`/uploads/`是上传文件保存的目录。需要在`application.properties`中添加以下配置：

spring.servlet.multipart.enabled=true
spring.servlet.multipart.file-size-threshold=2KB
spring.servlet.multipart.max-file-size=200MB
spring.servlet.multipart.max-request-size=215MB

# Upload directory for files
file.upload-dir=uploads

在控制器中添加注入`uploadDir`的代码：

@Value("${file.upload-dir}")
private String uploadDir;

5. 运行应用程序

现在，启动Spring Boot应用程序并访问上传页面。选择要上传的文件并单击“上传”按钮。上传成功后，将显示上传结果页面，并显示上传的文件名和头像。