有没有办法为Java的Charset名称添加别名 [英] Is there a way to add aliases for Java's Charset names
问题描述
我得到一个异常,埋没在第三方库中,有这样的消息:
I'm getting an exception, buried way inside a 3rd party library, with a message like this:
java.io。 UnsupportedEncodingException:BIG-5
java.io.UnsupportedEncodingException: BIG-5
我认为这是因为Java没有为 java.nio定义此名称.charset.Charset
。 Charset.forName(big5)
没问题,但是 Charset.forName(big-5)
会抛出例外。 (所有这些名称似乎都不区分大小写。)
I think this happening because Java doesn't define this name for java.nio.charset.Charset
. Charset.forName("big5")
is fine, but Charset.forName("big-5")
throws the exception. (All these names appear to be case insensitive.)
这与utf-8不同,后者有一些别名可以更宽容。例如, Charset.forName(utf8
)和 Charset.forName(utf-8)
工作很好。
This is different from "utf-8", which has some aliases to be more forgiving. For example, both Charset.forName("utf8"
) and Charset.forName("utf-8")
work fine.
问题:有没有办法添加别名,以便big-5映射到big5?
Question: is there a way to add the alias so that "big-5" maps to "big5"?
推荐答案
您可以尝试 mail.mime.contenttypehandler 系统属性:
在某些情况下,JavaMail无法使用无效的Content-Type标头处理消息。标头可能具有不正确的语法或其他问题。此属性指定在JavaMail使用它之前将用于清除Content-Type标头值的类的名称。该类必须具有带有此签名的方法:public static String cleanContentType(MimePart mp,String contentType)每当JavaMail访问消息的Content-Type标头时,它都会将值传递给此方法并使用返回的值。
In some cases JavaMail is unable to process messages with an invalid Content-Type header. The header may have incorrect syntax or other problems. This property specifies the name of a class that will be used to clean up the Content-Type header value before JavaMail uses it. The class must have a method with this signature: public static String cleanContentType(MimePart mp, String contentType) Whenever JavaMail accesses the Content-Type header of a message, it will pass the value to this method and use the returned value instead.
这方面的一个例子是:
import java.util.Arrays;
import javax.mail.Session;
import javax.mail.internet.ContentType;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimePart;
public class FixEncodingName {
public static void main(String[] args) throws Exception {
MimeMessage msg = new MimeMessage((Session) null);
msg.setText("test", "big-5");
msg.saveChanges();
System.out.println(msg.getContentType());
System.out.println(Arrays.toString(msg.getHeader("Content-Type")));
}
public static String cleanContentType(MimePart p, String mimeType) {
if (mimeType != null) {
String newContentType = mimeType;
try {
ContentType ct = new ContentType(mimeType);
String cs = ct.getParameter("charset");
if ("big-5".equalsIgnoreCase(cs)) {
ct.setParameter("charset", "big5");
newContentType = ct.toString();
}
} catch (Exception ignore) {
newContentType = newContentType.replace("big-5", "big5");
}
/*try { //Fix the header in the message.
p.setContent(p.getContent(), newContentType);
if (p instanceof Message) {
((Message) p).saveChanges();
}
} catch (Exception ignore) {
}*/
return newContentType;
}
return mimeType;
}
}
使用 -Dmail运行时.mime.contenttypehandler = FixEncodingName
将输出:
text/plain; charset=big5
[text/plain; charset=big-5]
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