Java多语言编码问题解析

package org.kyle.web.sample;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.UnavailableException;
public class SetCharacterEncodingFilter implements Filter 
{
/**
* The default character encoding to set for requests that pass through
* this filter.
*/
protected String encoding = null; 
/**
* The filter configuration object we are associated with.  If this value
* is null, this filter instance is not currently configured.
*/
protected FilterConfig filterConfig = null; 
/**
* Should a character encoding specified by the client be ignored?
*/
protected boolean ignore = true;
/**
* Take this filter out of service.
*/
public void destroy() 
{
this.encoding = null;
this.filterConfig = null;
}
/**
* Select and set (if specified) the character encoding to be used to
* interpret request parameters for this request.
*
* @param request The servlet request we are processing
* @param result The servlet response we are creating
* @param chain The filter chain we are processing
*
* @exception IOException if an input/output error occurs
* @exception ServletException if a servlet error occurs
*/
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain)
throws IOException, ServletException 
{
// Conditionally select and set the character encoding to be used
if (ignore || (request.getCharacterEncoding() == null)) 
{
String encoding = selectEncoding(request);
if (encoding != null)
request.setCharacterEncoding(encoding);
}
// Pass control on to the next filter
chain.doFilter(request, response);
}
/**
* Place this filter into service.
*
* @param filterConfig The filter configuration object
*                    
*encoding
* UTF-8
*
*/
public void init(FilterConfig filterConfig) throws ServletException
{
this.filterConfig = filterConfig;
this.encoding = filterConfig.getInitParameter("encoding");
String value = filterConfig.getInitParameter("ignore");
if (value == null)
this.ignore = true;
else if (value.equalsIgnoreCase("true"))
this.ignore = true;
else if (value.equalsIgnoreCase("yes"))
this.ignore = true;
else
this.ignore = false;
}
/**
* Select an appropriate character encoding to be used, based on the
* characteristics of the current request and/or filter initialization
* parameters.  If no character encoding should be set, return
* null.
* 
* The default implementation unconditionally returns the value configured
* by the encoding initialization parameter for this
* filter.
*
* @param request The servlet request we are processing
*/
protected String selectEncoding(ServletRequest request) 
{
return (this.encoding);
}
}