系统变量file.encoding对Java的运行影响有多大?
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:
public static Charset defaultCharset() {
if (defaultCharset == null) {
synchronized (Charset.class) {
java.security.PrivilegedAction pa =
new GetPropertyAction("file.encoding");
String csn = (String)AccessController.doPrivileged(pa);
Charset cs = lookup(csn);
if (cs != null)
defaultCharset = cs;
else
defaultCharset = forName("UTF-8");
}
}
return defaultCharset;
}
java.net.URLEncoder的静态构造方法,影响到的方法 java.net.URLEncoder.encode(String)
static {
dontNeedEncoding = new BitSet(256);
int i;
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 (
new GetPropertyAction("file.encoding")
);
}
com.sun.org.apache.xml.internal.serializer.Encoding的getMimeEncoding方法(209行起)
static String getMimeEncoding(String encoding)
{
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.
*/
String jencoding =
(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 (SecurityException se)
{
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(
new sun.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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