Using Filters and Wrappers
I have been trying to use a Filter to add code to my html after a servlet is run. I decided to wrap the response and then use a filter to add stuff before and after it. The problem is I'm having problems getting the content of the actual page to display. The filter works its just the it bypasses the writing of the content of the page itself.
I'm running on a tomcat server 6.0 with no warnings or errors
Here is my code:
ApplicationResponseWrapper.java
package com.safetab.wrapper;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.PrintWriter;
publicclass ApplicationResponseWrapperextends HttpServletResponseWrapper{
private ByteArrayOutputStream output;
privateint contentLength;
private String contentType;
public ApplicationResponseWrapper(HttpServletResponse response){
super(response);
output =new ByteArrayOutputStream();
}
public ServletOutputStream getOutputStream()throws IOException{
returnnew FilterServletOutputStream(output);
}
public PrintWriter getWriter()throws IOException{
returnnew PrintWriter(getOutputStream(),true);
}
publicbyte[] getData(){
return output.toByteArray();
}
publicint getContentLenght(){
return this.contentLength;
}
publicvoid setContentLength(int len){
this.contentLength = len;
super.setContentLength(len);
}
public String getContentType(){
return this.contentType;
}
publicvoid setContentType(String type){
this.contentType=type;
super.setContentType(type);
}
}
FilterServletOutputStream.java
package com.safetab.wrapper;
import javax.servlet.ServletOutputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.OutputStream;
publicclass FilterServletOutputStreamextends ServletOutputStream{
private DataOutputStream stream;
public FilterServletOutputStream(OutputStream output){
stream =new DataOutputStream(output);
}
publicvoid write(int b)throws IOException{
stream.write(b);
}
publicvoid write(byte[] b,int off,int len)throws IOException{
stream.write(b, off, len);
}
publicvoid write(byte[] b)throws IOException{
stream.write(b);
}
}
GenericFilter.java
package com.safetab.wrapper;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
publicclass GenericFilterimplements javax.servlet.Filter{
private FilterConfig filterConfig;
publicvoid doFilter(final ServletRequest request,
final ServletResponse response, FilterChain chain)
throws java.io.IOException, javax.servlet.ServletException{
chain.doFilter(request, response);
}
public FilterConfig getFilterConfig(){
return filterConfig;
}
publicvoid init(FilterConfig config){
this.filterConfig = config;
}
publicvoid destroy(){
this.filterConfig =null;
}
}
TestFilter.java
package com.safetab.wrapper;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.OutputStream;
publicclass TestFilterextends GenericFilter{
publicvoid doFilter(final ServletRequest request,final ServletResponse
response, FilterChain chain)
throws IOException, ServletException
{
OutputStream out = response.getOutputStream();
out.write("<HR>PRE<HR>".getBytes());
ApplicationResponseWrapper wrapper =new ApplicationResponseWrapper((HttpServletResponse) response);
chain.doFilter(request, wrapper);
out.write(wrapper.getData());
out.write("<HR>POST<HR>".getBytes());
out.close();
}
}
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app 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"
version="2.4">
<description>
Sample web.xmlfor MyFaces 1.1.5, taken from MyFaces site, but
with .jsf extension changed back to standard .faces.
http://www.coreservlets.com/JSF-Tutorial/
</description>
<filter>
<filter-name>TestFilter</filter-name>
<filter-class>com.safetab.wrapper.TestFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>TestFilter</filter-name>
<url-pattern>*.jsp</url-pattern>
</filter-mapping>
</web-app>
test.jsp
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC"-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd">
<HTML>
<HEAD>
<TITLE>Lesson 3</TITLE>
</HEAD>
<BODY>
<P>This is a pure testpage</P>
</BODY>
</HTML>
outcome
PRE
POST
-
