青岛姜戈庄码头:chain.doFilter(request,response)

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chain.doFilter(request,response)

(2009-02-28 14:15:22)

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分类： Java,Jsp 这句话的真正意思，我到现在才体会出来。他的作用是将请求转发给过滤器链上下一个对象。这里的“下”指的是哪里？值得是下一个filter，如果没有filter那就是你请求的资源。一般filter都是一个链,web.xml 里面配置了几个就有几个。一个一个的连在一起 request -> filter1 -> filter2 ->filter3 -> .... -> request resource.
下面举一个例子：input.jsp是用来提交输入的，当提交后，过滤器检测姓名和年龄，如果整常的话会提交给output.jsp,如果不正常提交给erroroutput.jsp.在此同时也有一个过滤器，它是用来检测一个页面是否设置了字符编码，如果没有则进行设置。（防止乱码问题存在）。myfilter.java======================package servletbean;import javax.swing.JOptionPane;public class myfilter implements Filter {public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {response.setContentType("text/html");response.setCharacterEncoding("GB2312");PrintWriter out=response.getWriter();String name="";String age="";int age1;name=request.getParameter("name");age=request.getParameter("age");RequestDispatcher dispatch=request.getRequestDispatcher("erroroutput.jsp"); if(name==null||name==""||name==" "||age==null){JOptionPane.showMessageDialog(null,"用户名和年龄输入错误！");dispatch.forward(request, response);return;}else{try{age1=Integer.parseInt(age);}catch(Exception e){//JOptionPane.showMessageDialog(null,"年龄必须为数字！");dispatch.forward(request,response);return;//如果是错误页面就到erroroutput.jsp中}}chain.doFilter(request, response);//这里表示是正确的，也就是说，他回去找下一个链，但是旗下面已经没有了，所以就会去跳转页面了，此时要跳转的页面就是action="output.jsp"了。}}==================encodefilter.java===================package servletbean;public class encodefilter implements Filter {public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {if(request.getCharacterEncoding()==null){System.out.println(encoding);request.setCharacterEncoding(encoding);}chain.doFilter(request, response);//到下一个链}public void init(FilterConfig fConfig) throws ServletException {this.config=fConfig;encoding=fConfig.getInitParameter("encoding");}
}==============input.jsp==============
================web.xml===============注意：filter是有顺序的

encodefilter

servletbean.encodefilter

encoding

GB2312

encodefilter

myfilter

servletbean.myfilter

myfilter

/output.jsp

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name
age