How to write a servlet which can transfer data written in ISO8859-1 into GB2312 or another kind of character encoding?

You can use this method to transfer your data from one standard encoding to another one. I have written it out and tested it under JSDK 2.0, and it runs well. The following is the java code I have written.

import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class commonServlet extends HttpServlet 
{
/*the method of Convert transfer data in typeof String (String Input) from one format(StandardFrom)  to
 another format(StandardTo)*/
	public static String convert (String Input, String  StandardFrom, String StandardTo)
	{
		byte[]  bytes;
		String conResult = new String();
		try
		{
			bytes = Input.getBytes(StandardFrom);
			conResult = new String (bytes, StandardTo);
		}   		

		catch(Exception e)
		{
			//debugging begins here
			System.out.println(e);
			//debugging ends here
			return("null");
		}
		return conResult;
	}//method convert ends here
   	
	//Do nothing within methods doGet & doPost
	public void doGet(HttpServletRequest req, HttpServletResponse res)
	{  }	
	public void doPost(HttpServletRequest req, HttpServletResponse res)
	{  }    
}

swarraj kulkarni also contributed to this answer and adds:

You should always check and verify character encoding and Supported Encodings. In addition, the international version of the JDK/JRE is required to have all the encodings available.