利用Filter检查Request参数

　2007-12-23 12:35:44　来源：WEB开发网　闂傚倷绶氬ḿ褍螞閹绢喖绠柨鐕傛嫹

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核心提示：import java.io.IOException;import java.util.Enumeration;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import ja

import java.io.IOException;
import java.util.Enumeration;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class CheckFilter implements Filter {

　PRivate FilterConfig config;

　public CheckFilter() {
　}

　public void init(FilterConfig filterConfig) throws ServletException {

　　this.config = filterConfig;

　}

　public void doFilter(ServletRequest request, ServletResponse response,
　　　FilterChain chain) throws IOException, ServletException {

　　Enumeration params = request.getParameterNames();
　　boolean rejected = false;

　　while (params.hasMoreElements()) {

　　　if (isEmpty(request.getParameter((String) params.nextElement()))) {
　　　　reject(request, response);
　　　　rejected = true;
　　　}

　　}

　　if (!rejected)
　　　chain.doFilter(request, response);

　}// doFilter

　private boolean isEmpty(String param) {

　　if (param == null param.length() < 1) {
　　　return true;
　　}

　　return false;

　}

　private void reject(ServletRequest request, ServletResponse response)
　　　throws IOException, ServletException {

　　request.setAttribute("errorMsg",
　　　　　　"Please make sure to provide a valid value for all of the text fields.");

　　Enumeration params = request.getParameterNames();
　　String paramN = null;

　　while (params.hasMoreElements()) {

　　　paramN = (String) params.nextElement();

　　　request.setAttribute(paramN, request.getParameter(paramN));

　　}

　　RequestDispatcher dispatcher = request
　　　　.getRequestDispatcher("/form.jsp");
　　dispatcher.forward(request, response);

　}

　public void destroy() {
　　/*
　　 * called before the Filter instance is removed from service by the web
　　 * container
　　 */
　}

}

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