servlet请求参数字符编码 [英] servlet request parameter character encoding

问题描述

我有一个Java Servlet，它通过HTTP GET请求从上游系统接收数据。该请求包括一个名为文本的参数。如果上游系统将此参数设置为：

I have a Java servlet that receives data from an upstream system via a HTTP GET request. This request includes a parameter named "text". If the upstream system sets this parameter to:

TEST3 please ignore:

它在上游系统的日志中显示为：

It appears in the logs of the upstream system as:

00 54 00 45 00 53 00 54 00 33 00 20 00 70 00 6c   //TEST3 pl
00 65 00 61 00 73 00 65 00 20 00 69 00 67 00 6e   //ease ign
00 6f 00 72 00 65 00 3a                           //ore:   

（//注释实际上没有出现在日志）

(The // comments do not actually appear in the logs)

在我的servlet中，我读取了以下参数：

In my servlet I read this parameter with:

String text = request.getParameter("text");

如果我将 text 的值打印到在控制台上，它显示为：

If I print the value of text to the console, it appears as:

T E S T 3  p l e a s e  i g n o r e :

如果我在调试器中检查 text 的值，则显示为：

If I inspect the value of text in the debugger, it appears as:

\u000T\u000E\u000S\u000T\u0003\u0000 \u000p\u000l\u000e\u000a\u000s\u000e\u0000 
\u000i\u000g\u000n\u000o\u000r\u000e\u000:

所以字符编码似乎有问题。上游系统应该使用UTF-16。我的猜测是，该servlet假定使用UTF-8，因此读取的字符数应该是它的两倍。对于消息 TEST3，请忽略：，每个字符的第一个字节为 00 。当servlet读取消息时，这被解释为一个空格，它解释了servlet记录消息时出现在每个字符之前的空格。

So it seems that there's a problem with the character encoding. The upstream system is supposed to use UTF-16. My guess is that the servlet is assuming UTF-8 and therefore is reading twice the number of characters it should be. For the message "TEST3 please ignore:" the first byte of each character is 00. This is being interpreted as a space when read by the servlet, which explains the space that appears before each character when the message is logged by the servlet.

显然，我的目标是当我阅读 text 请求参数时，只是得到消息 TEST3请忽略：。我的猜测是，可以通过指定请求参数的字符编码来实现此目的，但是我不知道该怎么做。

Obviously my goal is simply to get the message "TEST3 please ignore:" when I read the text request param. My guess is that I could achieve this by specifying the character encoding of the request parameter, but I don't know how to do this.

推荐答案

像这样使用

new String(req.getParameter("<my request value>").getBytes("ISO-8859-1"),"UTF-8")

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