在 Servlet 中解析传入的 multipart/form-data 参数的便捷方法 [英] Convenient way to parse incoming multipart/form-data parameters in a Servlet
问题描述
有没有什么方便的方法可以从传入的请求中读取和解析数据.
Is there any convenient way to read and parse data from incoming request.
例如客户端发起发布请求
E.g client initiate post request
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);
我无法使用 request.getParameter("paramName") 获取参数.以下代码
I’m not able to get param using request.getParameter("paramName"). The following code
BufferedReader reader = new BufferedReader(new InputStreamReader(
request.getInputStream()));
StringBuilder sb = new StringBuilder();
for (String line; (line = reader.readLine()) != null;) {
System.out.println(line);
}
但是为我显示内容
-----------------------------29772313742745
Content-Disposition: form-data; name="name"
J.Doe
-----------------------------29772313742745
Content-Disposition: form-data; name="email"
abuse@spamcop.com
-----------------------------29772313742745
解析传入请求的最佳方法是什么?不想自己写解析器，大概有现成的方案.
What is the best way to parse incoming request? I don’t want to write my own parser, probably there is a ready solution.
推荐答案
multipart/form-data 编码的请求确实在 3.0 版本之前的 Servlet API 中默认不支持.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() 调用将全部返回 null.如果您已经使用 Servlet 3.0 (Glassfish 3，Tomcat 7 等)，然后您可以使用 HttpServletRequest#getParts().另请参阅此博客以获取扩展示例.
multipart/form-data encoded 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-urlencoded encoding. 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 blog for extended examples.
在 Servlet 3.0 之前，一个 事实上的 标准来解析 multipart/form-data 请求将使用 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.我在这里之前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).
Prior to Servlet 3.0, a de facto standard to parse multipart/form-data requests would be using Apache Commons FileUpload. Just carefully read its User Guide and Frequently Asked Questions sections 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).
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