Java 在 Servlet 中解析传入的 multipart/form-data 参数的便捷方法

Convenient way to parse incoming multipart/form-data parameters in a Servlet

提问by atuser

Is there any convenient way to read and parse data from incoming request.

有什么方便的方法可以从传入的请求中读取和解析数据。

E.g client initiate post request

例如客户端发起发布请求

URLConnection connection = new URL(url).openConnection();
connection.setDoOutput(true);
connection.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary);
PrintWriter writer = null;
try {
    OutputStream output = connection.getOutputStream();
    writer = new PrintWriter(new OutputStreamWriter(output, charset), true); // true = autoFlush, important!
    // Send normal param.
    writer.println("--" + boundary);
    writer.println("Content-Disposition: form-data; name=\"param\"");
    writer.println("Content-Type: text/plain; charset=" + charset);
    writer.println();
    writer.println(param);

I'm not able to get param using request.getParameter("paramName"). The following code

我无法使用request.getParameter("paramName"). 以下代码

BufferedReader reader = new BufferedReader(new InputStreamReader(
    request.getInputStream()));
  StringBuilder sb = new StringBuilder();
  for (String line; (line = reader.readLine()) != null;) {
   System.out.println(line);

  }

however displays the content for me

但是为我显示内容

-----------------------------29772313742745
Content-Disposition: form-data; name="name"
J.Doe
-----------------------------29772313742745
Content-Disposition: form-data; name="email"
[email protected]
-----------------------------29772313742745

What is the best way to parse incoming request? I don't want to write my own parser, probably there is a ready solution.

解析传入请求的最佳方法是什么？我不想编写自己的解析器，可能有现成的解决方案。

采纳答案by BalusC

multipart/form-dataencoded requests are indeed not by default supported by the Servlet API prior to version 3.0. The Servlet API parses the parameters by default using application/x-www-form-urlencodedencoding. When using a different encoding, the request.getParameter()calls will all return null. When you're already on Servlet 3.0 (Glassfish 3, Tomcat 7, etc), then you can use HttpServletRequest#getParts()instead. Also see this blogfor extended examples.

multipart/form-data3.0 之前的 Servlet API 默认不支持编码请求。Servlet API 默认使用application/x-www-form-urlencoded编码解析参数。当使用不同的编码时，request.getParameter()调用都会返回null. 如果您已经使用 Servlet 3.0（Glassfish 3、Tomcat 7等），则可以HttpServletRequest#getParts()改用。另请参阅此博客以获取扩展示例。

Prior to Servlet 3.0, a de factostandard to parse multipart/form-datarequests would be using Apache Commons FileUpload. Just carefully read its User Guideand Frequently Asked Questionssections to learn how to use it. I've posted an answer with a code example before here(it also contains an example targeting Servlet 3.0).

在 Servlet 3.0 之前，解析请求的事实上的标准multipart/form-data是使用Apache Commons FileUpload。只需仔细阅读其用户指南和常见问题部分，即可了解如何使用它。我之前在这里发布了一个带有代码示例的答案（它还包含一个针对 Servlet 3.0 的示例）。

回答by renura

Solutions:

解决方案：

Solution A:

解决方案一：

1. Download http://www.servlets.com/cos/index.html
2. Invoke getParameters() on com.oreilly.servlet.MultipartRequest

1. 下载http://www.servlets.com/cos/index.html
2. 调用 getParameters() com.oreilly.servlet.MultipartRequest

Solution B:

解决方案B：

1. Download http://jakarta.Apache.org/commons/fileupload/
2. Invoke readHeaders() in org.apache.commons.fileupload.MultipartStream

1. 下载http://jakarta.Apache.org/commons/fileupload/
2. 在中调用 readHeaders() org.apache.commons.fileupload.MultipartStream

Solution C:

解决方案 C：

1. Download http://users.boone.net/wbrameld/multipartformdata/
2. Invoke getParameter on com.bigfoot.bugar.servlet.http.MultipartFormData

1. 下载http://users.boone.net/wbrameld/multipartformdata/
2. 在 com.bigfoot.bugar.servlet.http.MultipartFormData 上调用 getParameter

Solution D:

解决方案 D：

Use Struts. Struts 1.1 handles this automatically.

使用支柱。Struts 1.1 会自动处理这个问题。

Reference: http://www.jguru.com/faq/view.jsp?EID=1045507

参考：http: //www.jguru.com/faq/view.jsp?EID= 1045507

回答by Luca Rasconi

Not always there's a servlet before of an upload (I could use a filter for example). Or could be that the same controller ( again a filter or also a servelt ) can serve many actions, so I think that rely on that servlet configuration to use the getPart method (only for Servlet API >= 3.0), I don't know, I don't like.

在上传之前并不总是有一个 servlet（例如，我可以使用过滤器）。或者可能是同一个控制器（又是一个过滤器或一个 servelt ）可以提供许多操作，所以我认为依靠那个 servlet 配置来使用 getPart 方法（仅适用于 Servlet API >= 3.0），我不知道，不喜欢。

In general, I prefer independent solutions, able to live alone, and in this case http://commons.apache.org/proper/commons-fileupload/is one of that.

一般来说，我更喜欢独立的解决方案，能够独自生活，在这种情况下 http://commons.apache.org/proper/commons-fileupload/就是其中之一。

List<FileItem> multiparts = new ServletFileUpload(new DiskFileItemFactory()).parseRequest(request);
    for (FileItem item : multiparts) {
        if (!item.isFormField()) {
            //your operations on file
        } else {
            String name = item.getFieldName();
            String value = item.getString();
            //you operations on paramters
        }
}