java中byte, iso-8859-1, UTF-8，乱码的根源

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Post@https://ryan-miao.github.io

背景

还是多语言, 在项目中遇到本地环境和服务端环境不一致乱码的情形。因此需要搞清楚乱码产生的过程，来分析原因。

获取多语言代码如下：

private Map<String, String> getLocalizationContent(Locale locale) {ResourceBundle bundle = ResourceBundle.getBundle(this.resourceBundleName, Locale.US);ResourceBundle bundleLocale = ResourceBundle.getBundle(this.resourceBundleName, locale);Set<String> keys = bundle.keySet();Map<String, String> map = new HashMap();String key;String translation;for(Iterator var6 = keys.iterator(); var6.hasNext(); map.put(key, translation)) {key = (String)var6.next();try {translation = bundleLocale.getString(key);translation = new String(translation.getBytes("ISO-8859-1"), "UTF-8");translation = this.escapeStringForJavaScript(translation);} catch (UnsupportedEncodingException | MissingResourceException var10) {translation = bundle.getString(key);}}return map;
}

其中，因为ResourceBundle通过PropertyResourceBundle读取properties文件。这就要看以哪种方式load Properties了。提供了两种构造函数：

public PropertyResourceBundle (InputStream stream) throws IOException {Properties properties = new Properties();properties.load(stream);lookup = new HashMap(properties);
}
public PropertyResourceBundle (Reader reader) throws IOException {Properties properties = new Properties();properties.load(reader);lookup = new HashMap(properties);
}

通过跟踪ResourceBundle.getBundle(this.resourceBundleName, locale);源码发现创建bundle的方法为：

public ResourceBundle newBundle(String baseName, Locale locale, String format,ClassLoader loader, boolean reload)throws IllegalAccessException, InstantiationException, IOException {String bundleName = toBundleName(baseName, locale);ResourceBundle bundle = null;if (format.equals("java.class")) {try {@SuppressWarnings("unchecked")Class<? extends ResourceBundle> bundleClass= (Class<? extends ResourceBundle>)loader.loadClass(bundleName);// If the class isn't a ResourceBundle subclass, throw a// ClassCastException.if (ResourceBundle.class.isAssignableFrom(bundleClass)) {bundle = bundleClass.newInstance();} else {throw new ClassCastException(bundleClass.getName()+ " cannot be cast to ResourceBundle");}} catch (ClassNotFoundException e) {}} else if (format.equals("java.properties")) {final String resourceName = toResourceName0(bundleName, "properties");if (resourceName == null) {return bundle;}final ClassLoader classLoader = loader;final boolean reloadFlag = reload;InputStream stream = null;try {stream = AccessController.doPrivileged(new PrivilegedExceptionAction<InputStream>() {public InputStream run() throws IOException {InputStream is = null;if (reloadFlag) {URL url = classLoader.getResource(resourceName);if (url != null) {URLConnection connection = url.openConnection();if (connection != null) {// Disable caches to get fresh data for// reloading.connection.setUseCaches(false);is = connection.getInputStream();}}} else {is = classLoader.getResourceAsStream(resourceName);}return is;}});} catch (PrivilegedActionException e) {throw (IOException) e.getException();}if (stream != null) {try {bundle = new PropertyResourceBundle(stream);} finally {stream.close();}}} else {throw new IllegalArgumentException("unknown format: " + format);}return bundle;
}