filter应用
web.xml
?
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
?xmlns="http://java.sun.com/xml/ns/j2ee"
?xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
?xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
?http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
? <filter>
???? <filter-name>CharsetEncodingFilter</filter-name>
???? <filter-class>com.util.filter.CharsetEncodingFilter</filter-class>
???? <init-param>
???????????
??????????? <param-name>encoding</param-name>
??????????? <param-value>GB18030</param-value>
???? </init-param>
???? <init-param>
???<param-name>cityCode</param-name>
??????????? <param-value>091</param-value>
???? </init-param>
?</filter>
?<filter-mapping>
???? <filter-name>CharsetEncodingFilter</filter-name>
???? <url-pattern>/TestServlet</url-pattern>
</filter-mapping>
? <servlet>
??? <servlet-name>TestServlet</servlet-name>
??? <servlet-class>org.mvo.servlet.TestServlet</servlet-class>
? </servlet>
? <servlet-mapping>
??? <servlet-name>TestServlet</servlet-name>
??? <url-pattern>/TestServlet</url-pattern>
? </servlet-mapping>
?
? <welcome-file-list>
??? <welcome-file>index.jsp</welcome-file>
? </welcome-file-list>
</web-app>
?
filter
?
package com.util.filter;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import org.mvo.common.StringUtils;
import java.util.*; // For Date class
/**
?* Simple filter that prints a report on the standard output each time an
?* associated servlet or JSP page is accessed.
?*/
// 定义一个成员变量用于在init（）方法里得到配置文件里<init-param>中对应 <paramname>encoding</param-name> 的
// <param-value>GB18030</param-value>值；其中GB18030值可以更改比如gbk等；
public class CharsetEncodingFilter implements javax.servlet.Filter {
?FilterConfig fc;
?public void doFilter(ServletRequest request, ServletResponse response,
???FilterChain chain) throws ServletException, IOException {
??// 1,doFilter方法的第一个参数为ServletRequest对象。此对象给过滤器提供了对进入的信息（包括表单数据、cookie和HTTP请求头）的完全访问。第二个参数为ServletResponse，通常在简单的过滤器中忽略此参数。最后一个参数为FilterChain，此参数用来调用servlet或JSP页。
??HttpServletRequest req = (HttpServletRequest) request;// 如果处理HTTP请求，并且需要访问诸如getHeader或getCookies等在ServletRequest中无法得到的方法，就要把此request对象构造成HttpServletRequest。
??// request1.setCharacterEncodeing("");
??// System.out.println("进来");
??
??String provCode = fc.getInitParameter("cityCode");
??
??boolean flg = false;
??
??HttpSession session = req.getSession();
??String cityCode = (String) session.getAttribute("CityCode");
??cityCode = StringUtils.StrNullDeal(cityCode);
??
??System.out.println(cityCode);
??if (cityCode.equals(provCode)) {
???if ("有手机号".equals("有手机号")) {
????session.setAttribute("CityCode", "910");
????flg = true;
???}
??}
??chain.doFilter(request, response);
??if (flg) {
???session.setAttribute("CityCode", provCode);
??}
??System.out.println(session.getAttribute("CityCode").toString());
??// System.out.println("出去");
??// 2.调用FilterChain对象的doFilter方法。Filter接口的doFilter方法取一个FilterChain对象作为它的一个参数。在调用此对象的doFilter方法时，激活下一个相关的过滤器。如果没有另一个过滤器与servlet或JSP页面关联，则servlet或JSP页面被激活。
?}
?public void init(FilterConfig config) throws ServletException {
??this.fc = config;
//??String provCode = config.getInitParameter("cityCode");
//??System.out.println(provCode);
??// encoding =
??// FilterConfig.getInitParameter("encoding");//FilterConfig对象具有一个getInitParameter方法，它能够访问部署描述符件
??// //（web.xml）中分配的过滤器初始化参数
?}
?public void destroy() {
??fc.getInitParameter("cityCode");
?}
}
?
