Java上传文件API实现： |21xrx.com

Java上传文件API实现：

2023-06-13 02:51:32 深夜i -- --

Java 文件上传 API

Java作为目前主流的后端开发语言，其支持自带的文件上传API可以方便地实现上传文件的功能。下面将详细介绍Java如何接收文件上传的API实现方法。

1.创建表单

表单是提交文件的必要途径，可以通过HTML创建文件上传的表单：

2.编写Java代码

在Java中可以通过Servlet或者SpringMVC来实现文件上传的功能。

Servlet：


@WebServlet("/upload.java")
@MultipartConfig
public class FileUploadServlet extends HttpServlet {
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    response.setContentType("text/html");
    
    PrintWriter out = response.getWriter();
    try {
      String contentType = request.getContentType();
      if ((contentType != null) && (contentType.indexOf("multipart/form-data") >= 0)) {
        DataInputStream in = new DataInputStream(request.getInputStream());
        int formDataLength = request.getContentLength();
        byte dataBytes[] = new byte[formDataLength];
        int byteRead = 0;
        int totalBytesRead = 0;
        while (totalBytesRead < formDataLength) {
          byteRead = in.read(dataBytes, totalBytesRead, formDataLength);
          totalBytesRead += byteRead;
        }
        String file = new String(dataBytes);
        String saveFile = file.substring(file.indexOf("filename=\"") + 10);
        saveFile = saveFile.substring(0, saveFile.indexOf("\n"));
        saveFile = saveFile.substring(saveFile.lastIndexOf("\\") + 1, saveFile.indexOf("\""));
        int lastIndex = contentType.lastIndexOf("=");
        String boundary = contentType.substring(lastIndex + 1, contentType.length());
        int pos;
        pos = file.indexOf("filename=\"");
        pos = file.indexOf("\n", pos) + 1;
        pos = file.indexOf("\n", pos) + 1;
        pos = file.indexOf("\n", pos) + 1;
        int boundaryLocation = file.indexOf(boundary, pos) - 4;
        int startPos = ((file.substring(0, pos)).getBytes()).length;
        int endPos = ((file.substring(0, boundaryLocation)).getBytes()).length;
        File newFile = new File(saveFile);
        FileOutputStream fos = new FileOutputStream(newFile);
        fos.write(dataBytes, startPos, (endPos - startPos));
        fos.flush();
        fos.close();
        out.println("File saved as " + saveFile);
      }
    } catch (Exception e) {
      out.println("Exception in uploading file.");
    }
  }
}

SpringMVC：


@PostMapping("/upload")
@ResponseBody
public String handleFileUpload(@RequestParam("file") MultipartFile file,
              RedirectAttributes redirectAttributes) {
  try {
    byte[] bytes = file.getBytes();
    Path path = Paths.get(file.getOriginalFilename());
    Files.write(path, bytes);
    return "File uploaded successfully!";
  } catch (IOException e) {
    e.printStackTrace();
    return "File upload failed!";
  }
}

3.运行代码

通过以上代码实现文件上传功能，启动Tomcat服务器或Spring Boot项目后，在表单中选择上传的文件并点击上传，终端或网页中会显示上传成功或失败的信息。

以上就是Java接收文件上传的API实现方法，它可以为后端开发工程师提供便利，实现文件上传功能。 3个

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