在 Java 中实现图片上传可以通过多种方式进行，常见的有基于原生 Servlet、Spring 框架、以及第三方库（如 Apache Commons FileUpload）等。以下是这些方式的详细介绍以及示例代码。
步骤流程：
Part 对象，从中提取上传的文件数据。示例代码：
@WebServlet("/upload")
@MultipartConfig
public class FileUploadServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
Part filePart = request.getPart("file"); // 表单中文件域的名称
String fileName = Paths.get(filePart.getSubmittedFileName()).getFileName().toString();
// 指定上传目录
String uploadDir = "/path/to/upload/directory/";
File file = new File(uploadDir + fileName);
try (InputStream fileContent = filePart.getInputStream()) {
Files.copy(fileContent, file.toPath(), StandardCopyOption.REPLACE_EXISTING);
}
response.getWriter().println("File uploaded successfully");
}
}
步骤流程：
MultipartFile 来处理上传的文件数据。Maven 依赖：
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
Gradle 依赖：
implementation 'org.springframework.boot:spring-boot-starter-web'
示例代码：
@RestController
public class FileUploadController {
@PostMapping("/upload")
public String uploadFile(@RequestParam("file") MultipartFile file) throws IOException {
String fileName = file.getOriginalFilename();
// 指定上传目录
String uploadDir = "/path/to/upload/directory/";
File targetFile = new File(uploadDir + fileName);
file.transferTo(targetFile);
return "File uploaded successfully";
}
}
步骤流程：
ServletFileUpload 来解析请求并获取文件数据。Maven 依赖：
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.4</version>
</dependency>
Gradle 依赖：
implementation 'commons-fileupload:commons-fileupload:1.4'
示例代码：
@WebServlet("/upload")
public class FileUploadServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
DiskFileItemFactory factory = new DiskFileItemFactory();
ServletFileUpload upload = new ServletFileUpload(factory);
try {
List<FileItem> items = upload.parseRequest(request);
for (FileItem item : items) {
if (!item.isFormField()) {
String fileName = new File(item.getName()).getName();
// 指定上传目录
String uploadDir = "/path/to/upload/directory/";
File file = new File(uploadDir + fileName);
item.write(file);
}
}
response.getWriter().println("File uploaded successfully");
} catch (Exception e) {
response.getWriter().println("File upload failed");
}
}
}
无论选择哪种方式，都需要根据具体的业务需求和项目框架来决定使用哪种方法来实现图片上传功能。以上只是基本示例，实际应用中还需要添加适当的错误处理和安全机制。
