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java set encoding file_系统变量file.encoding对Java的运行影响有多大?(转)good

news 来源：原创 2024/5/8 16:32:18

这个话题来自: Nutz的issue 361

在考虑这个issue时, 我一直倾向于使用系统变量file.encoding来改变JVM的默认编码.

今天,我想到, 这个系统变量,对JVM的影响到底有多大呢? 我使用最简单的方法看看这个变量的影响--在JDK 1.6.0_20的src.zip文件中,查找包含file.encoding字眼的文件. 共找到4个, 分别是: 先上重头戏 java.nio.Charset类:

publicstaticCharsetdefaultCharset(){if(defaultCharset ==null){synchronized(Charset.class){java.security.PrivilegedActionpa =newGetPropertyAction("file.encoding");Stringcsn =(String)AccessController.doPrivileged(pa);Charsetcs =lookup(csn);if(cs !=null)defaultCharset =cs;elsedefaultCharset =forName("UTF-8");}}returndefaultCharset;}

java.net.URLEncoder的静态构造方法,影响到的方法 java.net.URLEncoder.encode(String)

static{dontNeedEncoding =newBitSet(256);inti;for(i ='a';i <='z';i++){dontNeedEncoding.set(i);}for(i ='A';i <='Z';i++){dontNeedEncoding.set(i);}for(i ='0';i <='9';i++){dontNeedEncoding.set(i);}dontNeedEncoding.set(' ');/* encoding a space to a + is done

* in the encode() method */dontNeedEncoding.set('-');dontNeedEncoding.set('_');dontNeedEncoding.set('.');dontNeedEncoding.set('*');dfltEncName =(String)AccessController.doPrivileged (newGetPropertyAction("file.encoding"));}

com.sun.org.apache.xml.internal.serializer.Encoding的getMimeEncoding方法(209行起)

staticStringgetMimeEncoding(Stringencoding){if(null==encoding){try{// Get the default system character encoding. This may be// incorrect if they passed in a writer, but right now there// seems to be no way to get the encoding from a writer.encoding =System.getProperty("file.encoding","UTF8");if(null!=encoding){/*

* See if the mime type is equal to UTF8. If you don't

* do that, then convertJava2MimeEncoding will convert

* 8859_1 to "ISO-8859-1", which is not what we want,

* I think, and I don't think I want to alter the tables

* to convert everything to UTF-8.

*/Stringjencoding =(encoding.equalsIgnoreCase("Cp1252")||encoding.equalsIgnoreCase("ISO8859_1")||encoding.equalsIgnoreCase("8859_1")||encoding.equalsIgnoreCase("UTF8"))?DEFAULT_MIME_ENCODING

:convertJava2MimeEncoding(encoding);encoding =(null!=jencoding)?jencoding :DEFAULT_MIME_ENCODING;}else{encoding =DEFAULT_MIME_ENCODING;}}catch(SecurityExceptionse){encoding =DEFAULT_MIME_ENCODING;}}

最后一个javax.print.DocFlavor类的静态构造方法:

static{hostEncoding =(String)java.security.AccessController.doPrivileged(newsun.security.action.GetPropertyAction("file.encoding"));}

可以看到,系统变量file.encoding影响到

1. Charset.defaultCharset() Java环境中最关键的编码设置

2. URLEncoder.encode(String) Web环境中最常遇到的编码使用

3. com.sun.org.apache.xml.internal.serializer.Encoding 影响对无编码设置的xml文件的读取

4. javax.print.DocFlavor 影响打印的编码

故,影响还是很大的哦, 可以说是Java中编码的一个关键钥匙!

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