gateway-server/src/main/java/org/apache/knox/gateway/GatewayFilter.java - knox - Git at Google

 /*
  * Licensed to the Apache Software Foundation (ASF) under one
  * or more contributor license agreements.  See the NOTICE file
  * distributed with this work for additional information
  * regarding copyright ownership.  The ASF licenses this file
  * to you under the Apache License, Version 2.0 (the
  * "License"); you may not use this file except in compliance
  * with the License.  You may obtain a copy of the License at
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 package org.apache.knox.gateway;

 import org.apache.knox.gateway.audit.api.Action;
 import org.apache.knox.gateway.audit.api.ActionOutcome;
 import org.apache.knox.gateway.audit.api.AuditContext;
 import org.apache.knox.gateway.audit.api.AuditService;
 import org.apache.knox.gateway.audit.api.AuditServiceFactory;
 import org.apache.knox.gateway.audit.api.Auditor;
 import org.apache.knox.gateway.audit.api.CorrelationContext;
 import org.apache.knox.gateway.audit.api.CorrelationServiceFactory;
 import org.apache.knox.gateway.audit.api.ResourceType;
 import org.apache.knox.gateway.audit.log4j.audit.AuditConstants;
 import org.apache.knox.gateway.config.GatewayConfig;
 import org.apache.knox.gateway.filter.AbstractGatewayFilter;
 import org.apache.knox.gateway.i18n.messages.MessagesFactory;
 import org.apache.knox.gateway.i18n.resources.ResourcesFactory;
 import org.apache.knox.gateway.topology.Topology;
 import org.apache.knox.gateway.util.ServletRequestUtils;
 import org.apache.knox.gateway.util.urltemplate.Matcher;
 import org.apache.knox.gateway.util.urltemplate.Parser;
 import org.apache.knox.gateway.util.urltemplate.Template;

 import javax.servlet.Filter;
 import javax.servlet.FilterChain;
 import javax.servlet.FilterConfig;
 import javax.servlet.ServletContext;
 import javax.servlet.ServletException;
 import javax.servlet.ServletRequest;
 import javax.servlet.ServletResponse;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletRequestWrapper;
 import javax.servlet.http.HttpServletResponse;

 import java.io.IOException;
 import java.net.URISyntaxException;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Enumeration;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import java.util.UUID;

 public class GatewayFilter implements Filter {

   private static final FilterChain EMPTY_CHAIN = new FilterChain() {
     @Override
     public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse ) throws IOException, ServletException {
     }
   };

   private static final GatewayMessages LOG = MessagesFactory.get( GatewayMessages.class );
   private static final GatewayResources RES = ResourcesFactory.get( GatewayResources.class );
   private static AuditService auditService = AuditServiceFactory.getAuditService();
   private static Auditor auditor = auditService.getAuditor(
       AuditConstants.DEFAULT_AUDITOR_NAME, AuditConstants.KNOX_SERVICE_NAME,
       AuditConstants.KNOX_COMPONENT_NAME );

   private Set<Holder> holders;
   private Matcher<Chain> chains;
   private FilterConfig config;

   public GatewayFilter() {
     holders = new HashSet<>();
     chains = new Matcher<>();
   }

   @Override
   public void init( FilterConfig filterConfig ) throws ServletException {
     this.config = filterConfig;
   }

   @Override
   public void doFilter( ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain ) throws IOException, ServletException {
     doFilter( servletRequest, servletResponse );
     if( filterChain != null ) {
       filterChain.doFilter( servletRequest, servletResponse );
     }
   }

   @SuppressWarnings("unchecked")
   public void doFilter( ServletRequest servletRequest, ServletResponse servletResponse ) throws IOException, ServletException {
     HttpServletRequest httpRequest = (HttpServletRequest)servletRequest;
     HttpServletResponse httpResponse = (HttpServletResponse)servletResponse;

     //TODO: The resulting pathInfo + query needs to be added to the servlet context somehow so that filters don't need to rebuild it.  This is done in HttpClientDispatch right now for example.
     String path = httpRequest.getPathInfo();
     String requestPath = ServletRequestUtils.getRequestPath(httpRequest);
     String requestPathWithQuery = ServletRequestUtils.getRequestPathWithQuery(httpRequest);

     Template pathWithQueryTemplate;
     try {
       pathWithQueryTemplate = Parser.parseLiteral( requestPathWithQuery );
     } catch( URISyntaxException e ) {
       throw new ServletException( e );
     }
     String contextWithPathAndQuery = ServletRequestUtils.getContextPathWithQuery(httpRequest);
     LOG.receivedRequest( httpRequest.getMethod(), requestPath );

     servletRequest.setAttribute(
         AbstractGatewayFilter.SOURCE_REQUEST_URL_ATTRIBUTE_NAME, pathWithQueryTemplate );
     servletRequest.setAttribute(
         AbstractGatewayFilter.SOURCE_REQUEST_CONTEXT_URL_ATTRIBUTE_NAME, contextWithPathAndQuery );

     Matcher<Chain>.Match match = chains.match( pathWithQueryTemplate );

     // if there was no match then look for a default service for the topology
     if (match == null) {
       Topology topology = (Topology) servletRequest.getServletContext().getAttribute("org.apache.knox.gateway.topology");
       if (topology != null) {
         String defaultServicePath = topology.getDefaultServicePath();
         if (defaultServicePath != null) {
           try {
             String newPathWithQuery = defaultServicePath + "/" + pathWithQueryTemplate;
             match = chains.match(Parser.parseLiteral(newPathWithQuery));
             String origUrl = ((HttpServletRequest) servletRequest).getRequestURL().toString();
             String url = origUrl;
             if (path == null || "/".equals(path)) {
               url += defaultServicePath;
             } else {
               int index = origUrl.indexOf(path);
               url = origUrl.substring(0, index) + "/" + defaultServicePath + path;
             }
             servletRequest = new ForwardedRequest((HttpServletRequest) servletRequest,
                 defaultServicePath,
                 url);
           } catch (URISyntaxException e) {
             throw new ServletException( e );
           }
         }
       }
     }

     assignCorrelationRequestId();
     // Populate Audit/correlation parameters
     AuditContext auditContext = auditService.getContext();
     auditContext.setTargetServiceName( match == null ? null : match.getValue().getResourceRole() );
     auditContext.setRemoteIp( getRemoteAddress(servletRequest) );
     auditContext.setRemoteHostname( servletRequest.getRemoteHost() );
     auditor.audit(
         Action.ACCESS, contextWithPathAndQuery, ResourceType.URI,
         ActionOutcome.UNAVAILABLE, RES.requestMethod(((HttpServletRequest)servletRequest).getMethod()));

     if( match != null ) {
       Chain chain = match.getValue();
       servletRequest.setAttribute( AbstractGatewayFilter.TARGET_SERVICE_ROLE, chain.getResourceRole() );
       try {
         chain.doFilter( servletRequest, servletResponse );
       } catch( IOException | RuntimeException | ThreadDeath | ServletException e ) {
         LOG.failedToExecuteFilter( e );
         auditor.audit( Action.ACCESS, contextWithPathAndQuery, ResourceType.URI, ActionOutcome.FAILURE );
         throw e;
       } catch( Throwable e ) {
         LOG.failedToExecuteFilter( e );
         auditor.audit( Action.ACCESS, contextWithPathAndQuery, ResourceType.URI, ActionOutcome.FAILURE );
         throw new ServletException( e );
       } finally {
         // Make sure to destroy the correlationContext to prevent threading issues
         CorrelationServiceFactory.getCorrelationService().detachContext();
       }
     } else {
       LOG.failedToMatchPath( requestPath );
       httpResponse.setStatus( HttpServletResponse.SC_NOT_FOUND );

       // Make sure to destroy the correlationContext to prevent threading issues
       CorrelationServiceFactory.getCorrelationService().detachContext();
     }

     //KAM[ Don't do this or the Jetty default servlet will overwrite any response setup by the filter.
     // filterChain.doFilter( servletRequest, servletResponse );
     //]
   }

   private String getRemoteAddress(ServletRequest servletRequest) {
     GatewayConfig gatewayConfig =
         (GatewayConfig) servletRequest.getServletContext().
         getAttribute(GatewayConfig.GATEWAY_CONFIG_ATTRIBUTE);

     String addrHeaderName = gatewayConfig.getHeaderNameForRemoteAddress();
     String addr = ((HttpServletRequest)servletRequest).getHeader(addrHeaderName);
     if (addr == null || addr.trim().isEmpty()) {
       addr = servletRequest.getRemoteAddr();
     }
     return addr;
   }

   @Override
   public void destroy() {
     for( Holder holder : holders ) {
       holder.destroy();
     }
   }

   private void addHolder( Holder holder ) {
     holders.add( holder );
     Chain chain = chains.get( holder.template );
     if( chain == null ) {
       chain = new Chain();
       chain.setResourceRole( holder.getResourceRole() );
       chains.add( holder.template, chain );
     }
     chain.chainList.add( holder );
   }

   public void addFilter( String path, String name, Filter filter, Map<String,String> params, String resourceRole ) throws URISyntaxException {
     Holder holder = new Holder( path, name, filter, params, resourceRole );
     addHolder( holder );
   }

   public void addFilter( String path, String name, String clazz, Map<String,String> params, String resourceRole ) throws URISyntaxException {
     Holder holder = new Holder( path, name, clazz, params, resourceRole );
     addHolder( holder );
   }

   // Now creating the correlation context only if required since it may be created upstream in the CorrelationHandler.
   private void assignCorrelationRequestId() {
     CorrelationContext correlationContext = CorrelationServiceFactory.getCorrelationService().getContext();
     if( correlationContext == null ) {
       correlationContext = CorrelationServiceFactory.getCorrelationService().createContext();
     }
     String requestId = correlationContext.getRequestId();
     if( requestId == null ) {
       correlationContext.setRequestId( UUID.randomUUID().toString() );
     }
   }

   private class Chain implements FilterChain {
     private List<Holder> chainList;
     private String resourceRole;

     Chain() {
       this.chainList = new ArrayList<>();
     }

     Chain( List<Holder> chainList) {
       this.chainList = chainList;
     }

     @Override
     public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse ) throws IOException, ServletException {
       if( chainList != null && !chainList.isEmpty() ) {
         final Filter filter = chainList.get( 0 );
         final FilterChain chain = subChain();
         filter.doFilter( servletRequest, servletResponse, chain );
       }
     }

     private FilterChain subChain() {
       if( chainList != null && chainList.size() > 1 ) {
         return new Chain( chainList.subList( 1, chainList.size() ) );
       } else {
         return EMPTY_CHAIN;
       }
     }

     private String getResourceRole() {
       return resourceRole;
     }

     private void setResourceRole( String resourceRole ) {
       this.resourceRole = resourceRole;
     }
   }

   private class Holder implements Filter, FilterConfig {
     private Template template;
     private String name;
     private Map<String,String> params;
     private Filter instance;
     private Class<? extends Filter> clazz;
     private String type;
     private String resourceRole;

     Holder( String path, String name, Filter filter, Map<String,String> params, String resourceRole ) throws URISyntaxException {
       this.template = Parser.parseTemplate( path );
       this.name = name;
       this.params = params;
       this.instance = filter;
       this.clazz = filter.getClass();
       this.type = clazz.getCanonicalName();
       this.resourceRole = resourceRole;
     }

     Holder( String path, String name, String clazz, Map<String,String> params, String resourceRole ) throws URISyntaxException {
       this.template = Parser.parseTemplate( path );
       this.name = name;
       this.params = params;
       this.instance = null;
       this.clazz = null;
       this.type = clazz;
       this.resourceRole = resourceRole;
     }

     @Override
     public String getFilterName() {
       return name;
     }

     @Override
     public ServletContext getServletContext() {
       return GatewayFilter.this.config.getServletContext();
     }

     @Override
     public String getInitParameter( String name ) {
       String value = null;
       if( params != null ) {
         value = params.get( name );
       }
       return value;
     }

     @Override
     public Enumeration<String> getInitParameterNames() {
       Enumeration<String> names = null;
       if( params != null ) {
         names = Collections.enumeration( params.keySet() );
       }
       return names;
     }

     @Override
     public void init( FilterConfig filterConfig ) throws ServletException {
       getInstance().init( filterConfig );
     }

     @Override
     public void doFilter( ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain ) throws IOException, ServletException {
       final Filter filter = getInstance();
       filter.doFilter( servletRequest, servletResponse, filterChain );
     }

     @Override
     public void destroy() {
       if( instance != null ) {
         instance.destroy();
         instance = null;
       }
     }

     @SuppressWarnings("unchecked")
     private Class<? extends Filter> getClazz() throws ClassNotFoundException {
       if( clazz == null ) {
         ClassLoader loader = Thread.currentThread().getContextClassLoader();
         if( loader == null ) {
           loader = this.getClass().getClassLoader();
         }
         clazz = (Class)loader.loadClass( type );
       }
       return clazz;
     }

     private Filter getInstance() throws ServletException {
       if( instance == null ) {
         try {
           if( clazz == null ) {
             clazz = getClazz();
           }
           Filter f = clazz.newInstance();
           f.init(this);
           instance = f;
         } catch( Exception e ) {
           throw new ServletException( e );
         }
       }
       return instance;
     }

     private String getResourceRole() {
       return resourceRole;
     }

   }

   /**
    * A request wrapper class that wraps a request and adds the context path if
    * needed.
    */
   static class ForwardedRequest extends HttpServletRequestWrapper {

     private String newURL;
     private String contextpath;

     ForwardedRequest(final HttpServletRequest request,
         final String contextpath, final String newURL) {
       super(request);
       this.newURL = newURL;
       this.contextpath = contextpath;
     }

     @Override
     public StringBuffer getRequestURL() {
       return new StringBuffer(newURL);
     }

     @Override
     public String getRequestURI() {
       return newURL;
     }

     @Override
     public String getContextPath() {
       return super.getContextPath() + "/" + this.contextpath;
     }

   }
 }
	/*
	* Licensed to the Apache Software Foundation (ASF) under one
	* or more contributor license agreements. See the NOTICE file
	* distributed with this work for additional information
	* regarding copyright ownership. The ASF licenses this file
	* to you under the Apache License, Version 2.0 (the
	* "License"); you may not use this file except in compliance
	* with the License. You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/
	package org.apache.knox.gateway;

	import org.apache.knox.gateway.audit.api.Action;
	import org.apache.knox.gateway.audit.api.ActionOutcome;
	import org.apache.knox.gateway.audit.api.AuditContext;
	import org.apache.knox.gateway.audit.api.AuditService;
	import org.apache.knox.gateway.audit.api.AuditServiceFactory;
	import org.apache.knox.gateway.audit.api.Auditor;
	import org.apache.knox.gateway.audit.api.CorrelationContext;
	import org.apache.knox.gateway.audit.api.CorrelationServiceFactory;
	import org.apache.knox.gateway.audit.api.ResourceType;
	import org.apache.knox.gateway.audit.log4j.audit.AuditConstants;
	import org.apache.knox.gateway.config.GatewayConfig;
	import org.apache.knox.gateway.filter.AbstractGatewayFilter;
	import org.apache.knox.gateway.i18n.messages.MessagesFactory;
	import org.apache.knox.gateway.i18n.resources.ResourcesFactory;
	import org.apache.knox.gateway.topology.Topology;
	import org.apache.knox.gateway.util.ServletRequestUtils;
	import org.apache.knox.gateway.util.urltemplate.Matcher;
	import org.apache.knox.gateway.util.urltemplate.Parser;
	import org.apache.knox.gateway.util.urltemplate.Template;

	import javax.servlet.Filter;
	import javax.servlet.FilterChain;
	import javax.servlet.FilterConfig;
	import javax.servlet.ServletContext;
	import javax.servlet.ServletException;
	import javax.servlet.ServletRequest;
	import javax.servlet.ServletResponse;
	import javax.servlet.http.HttpServletRequest;
	import javax.servlet.http.HttpServletRequestWrapper;
	import javax.servlet.http.HttpServletResponse;

	import java.io.IOException;
	import java.net.URISyntaxException;
	import java.util.ArrayList;
	import java.util.Collections;
	import java.util.Enumeration;
	import java.util.HashSet;
	import java.util.List;
	import java.util.Map;
	import java.util.Set;
	import java.util.UUID;

	public class GatewayFilter implements Filter {

	private static final FilterChain EMPTY_CHAIN = new FilterChain() {
	@Override
	public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse ) throws IOException, ServletException {
	}
	};

	private static final GatewayMessages LOG = MessagesFactory.get( GatewayMessages.class );
	private static final GatewayResources RES = ResourcesFactory.get( GatewayResources.class );
	private static AuditService auditService = AuditServiceFactory.getAuditService();
	private static Auditor auditor = auditService.getAuditor(
	AuditConstants.DEFAULT_AUDITOR_NAME, AuditConstants.KNOX_SERVICE_NAME,
	AuditConstants.KNOX_COMPONENT_NAME );

	private Set<Holder> holders;
	private Matcher<Chain> chains;
	private FilterConfig config;

	public GatewayFilter() {
	holders = new HashSet<>();
	chains = new Matcher<>();
	}

	@Override
	public void init( FilterConfig filterConfig ) throws ServletException {
	this.config = filterConfig;
	}

	@Override
	public void doFilter( ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain ) throws IOException, ServletException {
	doFilter( servletRequest, servletResponse );
	if( filterChain != null ) {
	filterChain.doFilter( servletRequest, servletResponse );
	}
	}

	@SuppressWarnings("unchecked")
	public void doFilter( ServletRequest servletRequest, ServletResponse servletResponse ) throws IOException, ServletException {
	HttpServletRequest httpRequest = (HttpServletRequest)servletRequest;
	HttpServletResponse httpResponse = (HttpServletResponse)servletResponse;

	//TODO: The resulting pathInfo + query needs to be added to the servlet context somehow so that filters don't need to rebuild it. This is done in HttpClientDispatch right now for example.
	String path = httpRequest.getPathInfo();
	String requestPath = ServletRequestUtils.getRequestPath(httpRequest);
	String requestPathWithQuery = ServletRequestUtils.getRequestPathWithQuery(httpRequest);

	Template pathWithQueryTemplate;
	try {
	pathWithQueryTemplate = Parser.parseLiteral( requestPathWithQuery );
	} catch( URISyntaxException e ) {
	throw new ServletException( e );
	}
	String contextWithPathAndQuery = ServletRequestUtils.getContextPathWithQuery(httpRequest);
	LOG.receivedRequest( httpRequest.getMethod(), requestPath );

	servletRequest.setAttribute(
	AbstractGatewayFilter.SOURCE_REQUEST_URL_ATTRIBUTE_NAME, pathWithQueryTemplate );
	servletRequest.setAttribute(
	AbstractGatewayFilter.SOURCE_REQUEST_CONTEXT_URL_ATTRIBUTE_NAME, contextWithPathAndQuery );

	Matcher<Chain>.Match match = chains.match( pathWithQueryTemplate );

	// if there was no match then look for a default service for the topology
	if (match == null) {
	Topology topology = (Topology) servletRequest.getServletContext().getAttribute("org.apache.knox.gateway.topology");
	if (topology != null) {
	String defaultServicePath = topology.getDefaultServicePath();
	if (defaultServicePath != null) {
	try {
	String newPathWithQuery = defaultServicePath + "/" + pathWithQueryTemplate;
	match = chains.match(Parser.parseLiteral(newPathWithQuery));
	String origUrl = ((HttpServletRequest) servletRequest).getRequestURL().toString();
	String url = origUrl;
	if (path == null \|\| "/".equals(path)) {
	url += defaultServicePath;
	} else {
	int index = origUrl.indexOf(path);
	url = origUrl.substring(0, index) + "/" + defaultServicePath + path;
	}
	servletRequest = new ForwardedRequest((HttpServletRequest) servletRequest,
	defaultServicePath,
	url);
	} catch (URISyntaxException e) {
	throw new ServletException( e );
	}
	}
	}
	}

	assignCorrelationRequestId();
	// Populate Audit/correlation parameters
	AuditContext auditContext = auditService.getContext();
	auditContext.setTargetServiceName( match == null ? null : match.getValue().getResourceRole() );
	auditContext.setRemoteIp( getRemoteAddress(servletRequest) );
	auditContext.setRemoteHostname( servletRequest.getRemoteHost() );
	auditor.audit(
	Action.ACCESS, contextWithPathAndQuery, ResourceType.URI,
	ActionOutcome.UNAVAILABLE, RES.requestMethod(((HttpServletRequest)servletRequest).getMethod()));

	if( match != null ) {
	Chain chain = match.getValue();
	servletRequest.setAttribute( AbstractGatewayFilter.TARGET_SERVICE_ROLE, chain.getResourceRole() );
	try {
	chain.doFilter( servletRequest, servletResponse );
	} catch( IOException \| RuntimeException \| ThreadDeath \| ServletException e ) {
	LOG.failedToExecuteFilter( e );
	auditor.audit( Action.ACCESS, contextWithPathAndQuery, ResourceType.URI, ActionOutcome.FAILURE );
	throw e;
	} catch( Throwable e ) {
	LOG.failedToExecuteFilter( e );
	auditor.audit( Action.ACCESS, contextWithPathAndQuery, ResourceType.URI, ActionOutcome.FAILURE );
	throw new ServletException( e );
	} finally {
	// Make sure to destroy the correlationContext to prevent threading issues
	CorrelationServiceFactory.getCorrelationService().detachContext();
	}
	} else {
	LOG.failedToMatchPath( requestPath );
	httpResponse.setStatus( HttpServletResponse.SC_NOT_FOUND );

	// Make sure to destroy the correlationContext to prevent threading issues
	CorrelationServiceFactory.getCorrelationService().detachContext();
	}

	//KAM[ Don't do this or the Jetty default servlet will overwrite any response setup by the filter.
	// filterChain.doFilter( servletRequest, servletResponse );
	//]
	}

	private String getRemoteAddress(ServletRequest servletRequest) {
	GatewayConfig gatewayConfig =
	(GatewayConfig) servletRequest.getServletContext().
	getAttribute(GatewayConfig.GATEWAY_CONFIG_ATTRIBUTE);

	String addrHeaderName = gatewayConfig.getHeaderNameForRemoteAddress();
	String addr = ((HttpServletRequest)servletRequest).getHeader(addrHeaderName);
	if (addr == null \|\| addr.trim().isEmpty()) {
	addr = servletRequest.getRemoteAddr();
	}
	return addr;
	}

	@Override
	public void destroy() {
	for( Holder holder : holders ) {
	holder.destroy();
	}
	}

	private void addHolder( Holder holder ) {
	holders.add( holder );
	Chain chain = chains.get( holder.template );
	if( chain == null ) {
	chain = new Chain();
	chain.setResourceRole( holder.getResourceRole() );
	chains.add( holder.template, chain );
	}
	chain.chainList.add( holder );
	}

	public void addFilter( String path, String name, Filter filter, Map<String,String> params, String resourceRole ) throws URISyntaxException {
	Holder holder = new Holder( path, name, filter, params, resourceRole );
	addHolder( holder );
	}

	public void addFilter( String path, String name, String clazz, Map<String,String> params, String resourceRole ) throws URISyntaxException {
	Holder holder = new Holder( path, name, clazz, params, resourceRole );
	addHolder( holder );
	}

	// Now creating the correlation context only if required since it may be created upstream in the CorrelationHandler.
	private void assignCorrelationRequestId() {
	CorrelationContext correlationContext = CorrelationServiceFactory.getCorrelationService().getContext();
	if( correlationContext == null ) {
	correlationContext = CorrelationServiceFactory.getCorrelationService().createContext();
	}
	String requestId = correlationContext.getRequestId();
	if( requestId == null ) {
	correlationContext.setRequestId( UUID.randomUUID().toString() );
	}
	}

	private class Chain implements FilterChain {
	private List<Holder> chainList;
	private String resourceRole;

	Chain() {
	this.chainList = new ArrayList<>();
	}

	Chain( List<Holder> chainList) {
	this.chainList = chainList;
	}

	@Override
	public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse ) throws IOException, ServletException {
	if( chainList != null && !chainList.isEmpty() ) {
	final Filter filter = chainList.get( 0 );
	final FilterChain chain = subChain();
	filter.doFilter( servletRequest, servletResponse, chain );
	}
	}

	private FilterChain subChain() {
	if( chainList != null && chainList.size() > 1 ) {
	return new Chain( chainList.subList( 1, chainList.size() ) );
	} else {
	return EMPTY_CHAIN;
	}
	}

	private String getResourceRole() {
	return resourceRole;
	}

	private void setResourceRole( String resourceRole ) {
	this.resourceRole = resourceRole;
	}
	}

	private class Holder implements Filter, FilterConfig {
	private Template template;
	private String name;
	private Map<String,String> params;
	private Filter instance;
	private Class<? extends Filter> clazz;
	private String type;
	private String resourceRole;

	Holder( String path, String name, Filter filter, Map<String,String> params, String resourceRole ) throws URISyntaxException {
	this.template = Parser.parseTemplate( path );
	this.name = name;
	this.params = params;
	this.instance = filter;
	this.clazz = filter.getClass();
	this.type = clazz.getCanonicalName();
	this.resourceRole = resourceRole;
	}

	Holder( String path, String name, String clazz, Map<String,String> params, String resourceRole ) throws URISyntaxException {
	this.template = Parser.parseTemplate( path );
	this.name = name;
	this.params = params;
	this.instance = null;
	this.clazz = null;
	this.type = clazz;
	this.resourceRole = resourceRole;
	}

	@Override
	public String getFilterName() {
	return name;
	}

	@Override
	public ServletContext getServletContext() {
	return GatewayFilter.this.config.getServletContext();
	}

	@Override
	public String getInitParameter( String name ) {
	String value = null;
	if( params != null ) {
	value = params.get( name );
	}
	return value;
	}

	@Override
	public Enumeration<String> getInitParameterNames() {
	Enumeration<String> names = null;
	if( params != null ) {
	names = Collections.enumeration( params.keySet() );
	}
	return names;
	}

	@Override
	public void init( FilterConfig filterConfig ) throws ServletException {
	getInstance().init( filterConfig );
	}

	@Override
	public void doFilter( ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain ) throws IOException, ServletException {
	final Filter filter = getInstance();
	filter.doFilter( servletRequest, servletResponse, filterChain );
	}

	@Override
	public void destroy() {
	if( instance != null ) {
	instance.destroy();
	instance = null;
	}
	}

	@SuppressWarnings("unchecked")
	private Class<? extends Filter> getClazz() throws ClassNotFoundException {
	if( clazz == null ) {
	ClassLoader loader = Thread.currentThread().getContextClassLoader();
	if( loader == null ) {
	loader = this.getClass().getClassLoader();
	}
	clazz = (Class)loader.loadClass( type );
	}
	return clazz;
	}

	private Filter getInstance() throws ServletException {
	if( instance == null ) {
	try {
	if( clazz == null ) {
	clazz = getClazz();
	}
	Filter f = clazz.newInstance();
	f.init(this);
	instance = f;
	} catch( Exception e ) {
	throw new ServletException( e );
	}
	}
	return instance;
	}

	private String getResourceRole() {
	return resourceRole;
	}

	}

	/**
	* A request wrapper class that wraps a request and adds the context path if
	* needed.
	*/
	static class ForwardedRequest extends HttpServletRequestWrapper {

	private String newURL;
	private String contextpath;

	ForwardedRequest(final HttpServletRequest request,
	final String contextpath, final String newURL) {
	super(request);
	this.newURL = newURL;
	this.contextpath = contextpath;
	}

	@Override
	public StringBuffer getRequestURL() {
	return new StringBuffer(newURL);
	}

	@Override
	public String getRequestURI() {
	return newURL;
	}

	@Override
	public String getContextPath() {
	return super.getContextPath() + "/" + this.contextpath;
	}

	}
	}