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From Michael Greco <mike.james.gr...@gmail.com>
Subject Rewriting entire request /body in Servlet Filter not working as expected
Date Sun, 04 Oct 2015 18:03:57 GMT
First time post here.

Using :
Tomcat 8.0.26
JDK1.8.0 update 51
Apache MyFaces 2.2.8.
Maven build of webapp war file
Chrome  45.0.2454.101 m 64 bit
Windows 7 64 bit

Trying to rewrite the entire request body in a filter using a http request
wrapper.  Not entirely sure if this is the right approach or even possible
but researching similar examples it seems this approach should work.
Created a simple test case with a one page test app, expecting the
index.xhtml page's text value of  "Welcome" to be replaced with the text
"NEW TEXT HERE" found in the filter code, but I only get "Welcome" back
when the page is rendered in the browser.

Below is what I have in the index page, the filter and the web.xml and the
pom.xml.  The reason I can see is that the getInputStream() or getReader()
calls are never called by the FacesServlet in the extended
HttpServletRequestWrapper.  I did override the getParameter function to put
some simple debug output in there to ensure the wrapped request was
actually used, so I know it's definitely getting into this class but not
calling the methods that would return it the new body content.

I even tried to re-read the entire request in the getParametersMap() from
examples I found on the web, but this didn't seen to do the job either.  It
seems that the request body is somehow cached somewhere / somehow and not
changable?

Thanks in advance for any insight on this.

index page code (index.xhtml) :
---------------------------------------------------------------------------------
<!DOCTYPE html>
<html lang="en"
  xmlns="http://www.w3.org/1999/xhtml"
  xmlns:jsf="http://xmlns.jcp.org/jsf"
  xmlns:h="http://xmlns.jcp.org/jsf/html">
<head jsf:id="head">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
<title>Test Webapp</title>
</head>
<body jsf:id="body">
    <div><h1>Welcome</h1></div>
</body>
</html>

Filter code :
--------------------------------------------------------------------------
package com.testwebapp.reqrewrite.filter;

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStreamReader;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ReadListener;
import javax.servlet.ServletException;
import javax.servlet.ServletInputStream;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

public class RewriteBodyTestFilter implements Filter {

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

public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain)
throws IOException, ServletException {
String newReqBody = new String("<div><h1>NEW TEXT HERE</h1></div>");
HttpServletRequest req = (HttpServletRequest)request;
RewriteBodyRequestWrapper rewriteBodyRequestWrapper = new
RewriteBodyRequestWrapper(req, newReqBody);
chain.doFilter(rewriteBodyRequestWrapper, response);
}

public void destroy() {
return;
}
class RewriteBodyRequestWrapper extends HttpServletRequestWrapper {

private byte[] buffer;

public RewriteBodyRequestWrapper(HttpServletRequest req, String reqBody)
throws IOException {
super(req);
System.out.println("entering RewriteBodyRequestWrapper() constructor");
this.buffer = reqBody.getBytes();
}

@Override
public ServletInputStream getInputStream() {
System.out.println("entering RewriteBodyRequestWrapper().getInputStream()");
try {
ByteArrayInputStream bais = new ByteArrayInputStream(buffer);
BufferedServletInputStream bsis = new BufferedServletInputStream(bais);
return bsis;
} catch (Exception ex) {
ex.printStackTrace();
throw new RuntimeException(ex);
}
}

@Override
public BufferedReader getReader() {
System.out.println("entering RewriteBodyRequestWrapper().getReader()");
InputStreamReader isr = new InputStreamReader(getInputStream());
return new BufferedReader(isr);
}

}
class BufferedServletInputStream extends ServletInputStream  {

ByteArrayInputStream bais;

public BufferedServletInputStream(ByteArrayInputStream bais) {
this.bais = bais;
}

@Override
public int available() {
return bais.available();
}

@Override
public boolean isFinished() {
return bais.available() == 0;
}

@Override
public boolean isReady() {
return true;
}

@Override
public void setReadListener(ReadListener readListener) {
return;
}

@Override
public int read() {
return bais.read();
}

@Override
public int read(byte[] buf) {
return this.read(buf, 0, buf.length);
}

@Override
public int read(byte[] buf, int off, int len) {
return bais.read(buf, off, len);
}

}
}

web.xml code:
--------------------------------------------------------------------------------------------------
<?xml version="1.0" encoding="ISO-8859-1"?>
<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/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
metadata-complete="true" version="3.0">

<display-name>Test Webapp Req Rewrite</display-name>

<!-- Change to "Production" when you are ready to deploy -->
<context-param>
<param-name>javax.faces.PROJECT_STAGE</param-name>
<param-value>Development</param-value>
</context-param>

<!-- JSF mapping -->
<servlet>
<servlet-name>FacesServlet</servlet-name>
<servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>

<!-- Map these files with JSF -->
<servlet-mapping>
<servlet-name>FacesServlet</servlet-name>
<url-pattern>/faces/*</url-pattern>
</servlet-mapping>

<!-- Session timeout -->
<session-config>
<session-timeout>30</session-timeout>
</session-config>

<!-- Welcome page -->
<welcome-file-list>
<welcome-file>faces/index.xhtml</welcome-file>
</welcome-file-list>

<!-- Filters -->
<filter>
<filter-name>RewriteBodyTestFilter</filter-name>
<filter-class>com.testwebapp.reqrewrite.filter.RewriteBodyTestFilter
</filter-class>
</filter>

<!-- Filter mappings / chain ordering -->
<filter-mapping>
<filter-name>RewriteBodyTestFilter</filter-name>
<servlet-name>FacesServlet</servlet-name>
<dispatcher>REQUEST</dispatcher>
<dispatcher>FORWARD</dispatcher>
</filter-mapping>

</web-app>

pom.xml :
-------------------------------------------------------------------------------------
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="
http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.testwebapp.reqrewrite</groupId>
  <artifactId>reqrewrite</artifactId>
  <packaging>war</packaging>
  <version>1.0-SNAPSHOT</version>
  <name>reqrewrite Maven Webapp</name>
  <url>http://maven.apache.org</url>
<dependencies>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.1.0</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.apache.myfaces.core</groupId>
<artifactId>myfaces-api</artifactId>
<version>2.2.8</version>
</dependency>
<dependency>
<groupId>org.apache.myfaces.core</groupId>
<artifactId>myfaces-impl</artifactId>
<version>2.2.8</version>
</dependency>
</dependencies>
  <build>
    <finalName>reqrewrite</finalName>
  </build>
</project>

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