java过滤器的使用

package yangfan.filter; 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; public class EncodingFilter implements Filter { private FilterConfig config; String encoding="ISO8859_1"; public void destroy() { config=null; } public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { request.setCharacterEncoding(encoding); chain.doFilter(request,response); } public void init(FilterConfig config) throws ServletException { this.config=config; String s=config.getInitParameter("encoding"); if(s!=null){ encoding=s; } } }