映射Filter的细节一

Posted 2020-10-31

在默认情况下，Filter只过滤Request的请求，即web资源之间的转包和包含不过滤

MappingFilter::doFilter():A
FromServlet::doGet()
ToServlet::doGet()
MappingFilter::doFilter():B

FromServlet

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class FromServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        System.out.println("FromServlet::doGet()");
        request.getRequestDispatcher("/ToServlet").forward(request,response);
        //request.getRequestDispatcher("/ToServlet").include(request,response);
    }
}

ToServlet

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ToServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
        System.out.println("ToServlet::doGet()");
        //int i = 10 / 0;
    }
}

MappingFilter

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 MappingFilter implements Filter {
    public void destroy() {
    }
    public void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {
        System.out.println("MappingFilter::doFilter():A");
        chain.doFilter(request,response);
        System.out.println("MappingFilter::doFilter():B");

    }
    public void init(FilterConfig filterConfig) throws ServletException {
    }
}

web.xml

<filter>
    <filter-name>MappingFilter</filter-name>
    <filter-class>cn.web.filter.MappingFilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>MappingFilter</filter-name>
    <url-pattern>/FromServlet</url-pattern>
  </filter-mapping>
  <filter-mapping>
    <filter-name>MappingFilter</filter-name>
    <url-pattern>/ToServlet</url-pattern>
  </filter-mapping>