http/base/src/main/java/org/apache/felix/http/base/internal/registry/ErrorPageRegistry.java - felix - 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.felix.http.base.internal.registry;

 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import java.util.TreeSet;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.regex.Pattern;

 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.annotations.NotNull;

 import org.apache.felix.http.base.internal.handler.ServletHandler;
 import org.apache.felix.http.base.internal.runtime.ServletInfo;
 import org.apache.felix.http.base.internal.runtime.dto.BuilderConstants;
 import org.apache.felix.http.base.internal.runtime.dto.ErrorPageDTOBuilder;
 import org.osgi.service.http.runtime.dto.DTOConstants;
 import org.osgi.service.http.runtime.dto.ErrorPageDTO;
 import org.osgi.service.http.runtime.dto.FailedErrorPageDTO;
 import org.osgi.service.http.runtime.dto.ServletContextDTO;

 /**
  * The error page registry keeps tracks of the active/inactive servlets handling
  * error pages (error code and/or exception).
  * This registry is per servlet context.
  */
 public final class ErrorPageRegistry
 {
     private static final String CLIENT_ERROR = "4xx";
     private static final String SERVER_ERROR = "5xx";
     private static final Pattern ERROR_CODE_PATTERN = Pattern.compile("\\d{3}");

     private static final List<Long> CLIENT_ERROR_CODES = hundredOf(400);
     private static final List<Long> SERVER_ERROR_CODES = hundredOf(500);

     private final Map<String, List<ServletHandler>> errorMapping = new ConcurrentHashMap<String, List<ServletHandler>>();

     private volatile List<ErrorRegistrationStatus> status = Collections.emptyList();

     public static final class ErrorRegistration {
         public final long[] errorCodes;
         public final String[] exceptions;

         public ErrorRegistration(final long[] errorCodes, final String[] exceptions)
         {
             this.errorCodes = errorCodes;
             this.exceptions = exceptions;
         }
     }

     static final class ErrorRegistrationStatus implements Comparable<ErrorRegistrationStatus> {

         private final ServletHandler handler;
         public final Map<Integer, ErrorRegistration> reasonMapping = new HashMap<Integer, ErrorRegistration>();

         public final boolean usesClientErrorCodes;
         public final boolean usesServerErrorCodes;

         public ErrorRegistrationStatus(final ServletHandler handler)
         {
             this.handler = handler;
             this.usesClientErrorCodes = hasErrorCode(handler, CLIENT_ERROR);
             this.usesServerErrorCodes = hasErrorCode(handler, SERVER_ERROR);
         }

         public ServletHandler getHandler()
         {
             return this.handler;
         }

         @Override
         public int compareTo(final ErrorRegistrationStatus o)
         {
             return this.handler.compareTo(o.getHandler());
         }
     }

     private static boolean hasErrorCode(final ServletHandler handler, final String key)
     {
     	for(final String val : handler.getServletInfo().getErrorPage())
     	{
     		if ( key.equals(val) )
     		{
     			return true;
     		}
     	}
     	return false;
     }

     private static List<Long> hundredOf(final int start)
     {
         List<Long> result = new ArrayList<Long>();
         for (long i = start; i < start + 100; i++)
         {
             result.add(i);
         }
         return Collections.unmodifiableList(result);
     }

     private static long[] toLongArray(final Set<Long> set)
     {
         long[] codes = BuilderConstants.EMPTY_LONG_ARRAY;
         if ( !set.isEmpty() )
         {
             codes = new long[set.size()];
             int index = 0;
             for(final Long code : set)
             {
                 codes[index++] = code;
             }
         }
         return codes;
     }

     private static Set<Long> toLongSet(final long[] codes)
     {
         final Set<Long> set = new TreeSet<Long>();
         for(final long c : codes)
         {
             set.add(c);
         }
         return set;
     }

     private static String[] toStringArray(final Set<String> set)
     {
         String[] array = BuilderConstants.EMPTY_STRING_ARRAY;
         if ( !set.isEmpty() )
         {
             array = set.toArray(new String[set.size()]);
         }
         return array;
     }

     private static Set<String> toStringSet(final String[] array)
     {
         final Set<String> set = new TreeSet<String>();
         for(final String s : array)
         {
             set.add(s);
         }
         return set;
     }

     private static String parseErrorCodes(final Set<Long> codes, final String string)
     {
         if (CLIENT_ERROR.equalsIgnoreCase(string))
         {
             codes.addAll(CLIENT_ERROR_CODES);
         }
         else if (SERVER_ERROR.equalsIgnoreCase(string))
         {
             codes.addAll(SERVER_ERROR_CODES);
         }
         else if (ERROR_CODE_PATTERN.matcher(string).matches())
         {
             codes.add(Long.parseLong(string));
         }
         else
         {
             return string;
         }
         return null;
     }

     /**
      * Parse the registration properties of the servlet for error handling
      * @param info The servlet info
      * @return An error registration object if the servlet handles errors
      */
     public static @Nullable ErrorRegistration getErrorRegistration(@NotNull final ServletInfo info)
     {
         if ( info.getErrorPage() != null )
         {
             final Set<Long> errorCodes = new TreeSet<Long>();
             final Set<String> exceptions = new TreeSet<String>();

             for(final String val : info.getErrorPage())
             {
                 final String exception = parseErrorCodes(errorCodes, val);
                 if ( exception != null )
                 {
                     exceptions.add(exception);
                 }
             }
             final long[] codes = toLongArray(errorCodes);
             final String[] exceptionsArray = toStringArray(exceptions);

             return new ErrorRegistration(codes, exceptionsArray);
         }
         return null;
     }

     /**
      * Add the servlet for error handling
      * @param handler The servlet handler.
      */
     public synchronized void addServlet(@NotNull final ServletHandler handler)
     {
         final ErrorRegistration reg = getErrorRegistration(handler.getServletInfo());
         if ( reg != null )
         {
             final ErrorRegistrationStatus status = new ErrorRegistrationStatus(handler);
             for(final long code : reg.errorCodes)
             {
                 addErrorHandling(handler, status, code, null);
             }
             for(final String exception : reg.exceptions)
             {
                 addErrorHandling(handler, status, 0, exception);
             }
             final List<ErrorRegistrationStatus> newList = new ArrayList<ErrorPageRegistry.ErrorRegistrationStatus>(this.status);
             newList.add(status);
             Collections.sort(newList);
             this.status = newList;
         }
     }

     /**
      * Remove the servlet from error handling
      * @param info The servlet info.
      */
     public synchronized void removeServlet(@NotNull final ServletInfo info, final boolean destroy)
     {
         final ErrorRegistration reg = getErrorRegistration(info);
         if ( reg != null )
         {
             final List<ErrorRegistrationStatus> newList = new ArrayList<ErrorPageRegistry.ErrorRegistrationStatus>(this.status);
             final Iterator<ErrorRegistrationStatus> i = newList.iterator();
             while ( i.hasNext() )
             {
                 final ErrorRegistrationStatus status = i.next();
                 if ( status.handler.getServletInfo().equals(info) )
                 {
                     i.remove();
                     break;
                 }
             }
             this.status = newList;

             for(final long code : reg.errorCodes)
             {
                 removeErrorHandling(info, code, null);
             }
             for(final String exception : reg.exceptions)
             {
                 removeErrorHandling(info, 0, exception);
             }
         }
     }

     public synchronized void cleanup()
     {
         this.errorMapping.clear();
         this.status = Collections.emptyList();
     }

     private void addErrorHandling(final ServletHandler handler, final ErrorRegistrationStatus status, final long code, final String exception)
     {
         final String key = (exception != null ? exception : String.valueOf(code));

         final List<ServletHandler> newList;
         final List<ServletHandler> list = errorMapping.get(key);
         if ( list == null )
         {
             newList = Collections.singletonList(handler);
         }
         else
         {
             newList = new ArrayList<ServletHandler>(list);
             newList.add(handler);
             Collections.sort(newList);
         }
         if ( newList.get(0) == handler )
         {
             // try to activate (and deactivate old handler)
             final int result = handler.init();
             addReason(status, code, exception, result);
             if ( result == -1 )
             {
                 if ( list != null )
                 {
                     final ServletHandler old = list.get(0);
                     old.destroy();
                     errorMapping.put(key, newList);
                     ErrorRegistrationStatus oldStatus = null;
                     final Iterator<ErrorRegistrationStatus> i = this.status.iterator();
                     while ( oldStatus == null && i.hasNext() )
                     {
                         final ErrorRegistrationStatus current = i.next();
                         if ( current.handler.getServletInfo().equals(old.getServletInfo()) )
                         {
                             oldStatus = current;
                         }
                     }
                     if ( oldStatus != null )
                     {
                         removeReason(oldStatus, code, exception, -1);
                     	boolean addReason = true;
                     	if ( exception == null )
                     	{
                     		if ( code >= 400 && code < 500 && oldStatus.usesClientErrorCodes && !status.usesClientErrorCodes )
                     		{
                     			addReason = false;
                     		}
                     		else if ( code >= 500 && code < 600 && oldStatus.usesServerErrorCodes && !status.usesServerErrorCodes )
                     		{
                     			addReason = false;
                     		}
                     	}
                     	if ( addReason )
                     	{
                     		addReason(oldStatus, code, exception, DTOConstants.FAILURE_REASON_SHADOWED_BY_OTHER_SERVICE);
                     	}
                     }
                 }
                 else
                 {
                     errorMapping.put(key, newList);
                 }
             }
         }
         else
         {
             // failure
         	boolean addReason = true;
         	if ( exception == null )
         	{
         		if ( code >= 400 && code < 500 && status.usesClientErrorCodes && !hasErrorCode(newList.get(0), CLIENT_ERROR) )
         		{
         			addReason = false;
         		}
         		else if ( code >= 500 && code < 600 && status.usesServerErrorCodes && !hasErrorCode(newList.get(0), SERVER_ERROR) )
         		{
         			addReason = false;
         		}
         	}
         	if ( addReason )
         	{
         		addReason(status, code, exception, DTOConstants.FAILURE_REASON_SHADOWED_BY_OTHER_SERVICE);
         	}
             errorMapping.put(key, newList);
         }
     }

     /**
      * Make an entry in the status object (which are used to create the DTOs)
      * @param status The status object
      * @param code Either the code
      * @param exception or the exception
      * @param reason The code for the failure reason or {@code -1} for success.
      */
     private void addReason(final ErrorRegistrationStatus status,
     		final long code,
     		final String exception,
     		final int reason)
     {
         ErrorRegistration reg = status.reasonMapping.get(reason);
         if ( reg == null )
         {
             if ( exception != null )
             {
                 reg = new ErrorRegistration(BuilderConstants.EMPTY_LONG_ARRAY, new String[] {exception});
             }
             else
             {
                 reg = new ErrorRegistration(new long[] {code}, BuilderConstants.EMPTY_STRING_ARRAY);
             }
         }
         else
         {
             long[] codes = reg.errorCodes;
             String[] exceptions = reg.exceptions;
             if ( exception != null )
             {
                 final Set<String> set = toStringSet(exceptions);
                 set.add(exception);
                 exceptions = toStringArray(set);
             }
             else
             {
                 final Set<Long> set = toLongSet(codes);
                 set.add(code);
                 codes = toLongArray(set);
             }

             reg = new ErrorRegistration(codes, exceptions);
         }
         status.reasonMapping.put(reason, reg);
     }

     private void removeReason(final ErrorRegistrationStatus status, final long code, final String exception, final int reason)
     {
         ErrorRegistration reg = status.reasonMapping.get(reason);
         if ( reg != null )
         {
             long[] codes = reg.errorCodes;
             String[] exceptions = reg.exceptions;
             if ( exception != null )
             {
                 final Set<String> set = toStringSet(exceptions);
                 set.remove(exception);
                 exceptions = toStringArray(set);
             }
             else
             {
                 final Set<Long> set = toLongSet(codes);
                 set.remove(code);
                 codes = toLongArray(set);
             }
             if ( codes.length == 0 && exceptions.length == 0 )
             {
                 status.reasonMapping.remove(reason);
             }
             else
             {
                 status.reasonMapping.put(reason, new ErrorRegistration(codes, exceptions));
             }
         }
     }

     private void removeErrorHandling(final ServletInfo info, final long code, final String exception)
     {
         final String key = (exception != null ? exception : String.valueOf(code));

         final List<ServletHandler> list = errorMapping.get(key);
         if ( list != null )
         {
             int index = 0;
             final Iterator<ServletHandler> i = list.iterator();
             while ( i.hasNext() )
             {
                 final ServletHandler handler = i.next();
                 if ( handler.getServletInfo().equals(info) )
                 {
                     final List<ServletHandler> newList = new ArrayList<ServletHandler>(list);
                     newList.remove(handler);

                     if ( index == 0 )
                     {
                         handler.destroy();

                         index++;
                         while ( index < list.size() )
                         {
                             final ServletHandler next = list.get(index);
                             ErrorRegistrationStatus nextStatus = null;
                             for(final ErrorRegistrationStatus s : this.status)
                             {
                                 if ( s.handler.getServletInfo().equals(next.getServletInfo()) )
                                 {
                                     nextStatus = s;
                                     break;
                                 }
                             }
                             this.removeReason(nextStatus, code, exception, DTOConstants.FAILURE_REASON_SHADOWED_BY_OTHER_SERVICE);
                             final int reason = next.init();
                             this.addReason(nextStatus, code, exception, reason);
                             if ( reason == -1 )
                             {
                                 break;
                             }
                             else
                             {
                                 newList.remove(next);
                             }
                         }
                     }
                     if ( newList.isEmpty() )
                     {
                         errorMapping.remove(key);
                     }
                     else
                     {
                         errorMapping.put(key, newList);
                     }

                     break;
                 }
                 index++;
             }
         }
     }

     /**
      * Get the servlet handling the error (error code or exception).
      * If an exception is provided, a handler for the exception is searched first.
      * If no handler is found (or no exception provided) a handler for the error
      * code is searched.
      * @param exception Optional exception
      * @param errorCode Error code
      * @return The servlet handling the error or {@code null}
      */
     public ServletHandler get(final Throwable exception, final int errorCode)
     {
         ServletHandler errorHandler = this.get(exception);
         if (errorHandler != null)
         {
             return errorHandler;
         }

         return get(errorCode);
     }

     /**
      * Get the servlet handling the error code
      * @param errorCode Error code
      * @return The servlet handling the error or {@code null}
      */
     private ServletHandler get(final long errorCode)
     {
         final List<ServletHandler> list = this.errorMapping.get(String.valueOf(errorCode));
         if ( list != null )
         {
             return list.get(0);
         }
         return null;
     }

     /**
      * Get the servlet handling the exception
      * @param exception Error exception
      * @return The servlet handling the error or {@code null}
      */
     private ServletHandler get(final Throwable exception)
     {
         if (exception == null)
         {
             return null;
         }

         ServletHandler servletHandler = null;
         Class<?> throwableClass = exception.getClass();
         while ( servletHandler == null && throwableClass != null )
         {
             final List<ServletHandler> list = this.errorMapping.get(throwableClass.getName());
             if ( list != null )
             {
                 servletHandler = list.get(0);
             }
             if ( servletHandler == null )
             {
                 throwableClass = throwableClass.getSuperclass();
                 if ( !Throwable.class.isAssignableFrom(throwableClass) )
                 {
                     throwableClass = null;
                 }
             }

         }
         return servletHandler;
     }

     /**
      * Get DTOs for error pages.
      * @param dto The servlet context DTO
      * @param failedErrorPageDTOs The failed error page DTOs
      */
     public void getRuntimeInfo(final ServletContextDTO dto,
             final Collection<FailedErrorPageDTO> failedErrorPageDTOs)
     {
         final List<ErrorPageDTO> errorPageDTOs = new ArrayList<ErrorPageDTO>();
         final List<ErrorRegistrationStatus> statusList = this.status;
         for(final ErrorRegistrationStatus status : statusList)
         {
             for(final Map.Entry<Integer, ErrorRegistration> entry : status.reasonMapping.entrySet())
             {
                 final ErrorPageDTO state = ErrorPageDTOBuilder.build(status.getHandler(), entry.getKey());
                 state.errorCodes = Arrays.copyOf(entry.getValue().errorCodes, entry.getValue().errorCodes.length);
                 state.exceptions = Arrays.copyOf(entry.getValue().exceptions, entry.getValue().exceptions.length);

                 if ( entry.getKey() == -1 )
                 {
                     errorPageDTOs.add(state);
                 }
                 else
                 {
                     failedErrorPageDTOs.add((FailedErrorPageDTO)state);
                 }
             }
         }
         if ( !errorPageDTOs.isEmpty() )
         {
             dto.errorPageDTOs = errorPageDTOs.toArray(new ErrorPageDTO[errorPageDTOs.size()]);
         }
     }
 }
	/*
	* 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.felix.http.base.internal.registry;

	import java.util.ArrayList;
	import java.util.Arrays;
	import java.util.Collection;
	import java.util.Collections;
	import java.util.HashMap;
	import java.util.Iterator;
	import java.util.List;
	import java.util.Map;
	import java.util.Set;
	import java.util.TreeSet;
	import java.util.concurrent.ConcurrentHashMap;
	import java.util.regex.Pattern;

	import org.jetbrains.annotations.Nullable;
	import org.jetbrains.annotations.NotNull;

	import org.apache.felix.http.base.internal.handler.ServletHandler;
	import org.apache.felix.http.base.internal.runtime.ServletInfo;
	import org.apache.felix.http.base.internal.runtime.dto.BuilderConstants;
	import org.apache.felix.http.base.internal.runtime.dto.ErrorPageDTOBuilder;
	import org.osgi.service.http.runtime.dto.DTOConstants;
	import org.osgi.service.http.runtime.dto.ErrorPageDTO;
	import org.osgi.service.http.runtime.dto.FailedErrorPageDTO;
	import org.osgi.service.http.runtime.dto.ServletContextDTO;

	/**
	* The error page registry keeps tracks of the active/inactive servlets handling
	* error pages (error code and/or exception).
	* This registry is per servlet context.
	*/
	public final class ErrorPageRegistry
	{
	private static final String CLIENT_ERROR = "4xx";
	private static final String SERVER_ERROR = "5xx";
	private static final Pattern ERROR_CODE_PATTERN = Pattern.compile("\\d{3}");

	private static final List<Long> CLIENT_ERROR_CODES = hundredOf(400);
	private static final List<Long> SERVER_ERROR_CODES = hundredOf(500);

	private final Map<String, List<ServletHandler>> errorMapping = new ConcurrentHashMap<String, List<ServletHandler>>();

	private volatile List<ErrorRegistrationStatus> status = Collections.emptyList();

	public static final class ErrorRegistration {
	public final long[] errorCodes;
	public final String[] exceptions;

	public ErrorRegistration(final long[] errorCodes, final String[] exceptions)
	{
	this.errorCodes = errorCodes;
	this.exceptions = exceptions;
	}
	}

	static final class ErrorRegistrationStatus implements Comparable<ErrorRegistrationStatus> {

	private final ServletHandler handler;
	public final Map<Integer, ErrorRegistration> reasonMapping = new HashMap<Integer, ErrorRegistration>();

	public final boolean usesClientErrorCodes;
	public final boolean usesServerErrorCodes;

	public ErrorRegistrationStatus(final ServletHandler handler)
	{
	this.handler = handler;
	this.usesClientErrorCodes = hasErrorCode(handler, CLIENT_ERROR);
	this.usesServerErrorCodes = hasErrorCode(handler, SERVER_ERROR);
	}

	public ServletHandler getHandler()
	{
	return this.handler;
	}

	@Override
	public int compareTo(final ErrorRegistrationStatus o)
	{
	return this.handler.compareTo(o.getHandler());
	}
	}

	private static boolean hasErrorCode(final ServletHandler handler, final String key)
	{
	for(final String val : handler.getServletInfo().getErrorPage())
	{
	if ( key.equals(val) )
	{
	return true;
	}
	}
	return false;
	}

	private static List<Long> hundredOf(final int start)
	{
	List<Long> result = new ArrayList<Long>();
	for (long i = start; i < start + 100; i++)
	{
	result.add(i);
	}
	return Collections.unmodifiableList(result);
	}

	private static long[] toLongArray(final Set<Long> set)
	{
	long[] codes = BuilderConstants.EMPTY_LONG_ARRAY;
	if ( !set.isEmpty() )
	{
	codes = new long[set.size()];
	int index = 0;
	for(final Long code : set)
	{
	codes[index++] = code;
	}
	}
	return codes;
	}

	private static Set<Long> toLongSet(final long[] codes)
	{
	final Set<Long> set = new TreeSet<Long>();
	for(final long c : codes)
	{
	set.add(c);
	}
	return set;
	}

	private static String[] toStringArray(final Set<String> set)
	{
	String[] array = BuilderConstants.EMPTY_STRING_ARRAY;
	if ( !set.isEmpty() )
	{
	array = set.toArray(new String[set.size()]);
	}
	return array;
	}

	private static Set<String> toStringSet(final String[] array)
	{
	final Set<String> set = new TreeSet<String>();
	for(final String s : array)
	{
	set.add(s);
	}
	return set;
	}

	private static String parseErrorCodes(final Set<Long> codes, final String string)
	{
	if (CLIENT_ERROR.equalsIgnoreCase(string))
	{
	codes.addAll(CLIENT_ERROR_CODES);
	}
	else if (SERVER_ERROR.equalsIgnoreCase(string))
	{
	codes.addAll(SERVER_ERROR_CODES);
	}
	else if (ERROR_CODE_PATTERN.matcher(string).matches())
	{
	codes.add(Long.parseLong(string));
	}
	else
	{
	return string;
	}
	return null;
	}

	/**
	* Parse the registration properties of the servlet for error handling
	* @param info The servlet info
	* @return An error registration object if the servlet handles errors
	*/
	public static @Nullable ErrorRegistration getErrorRegistration(@NotNull final ServletInfo info)
	{
	if ( info.getErrorPage() != null )
	{
	final Set<Long> errorCodes = new TreeSet<Long>();
	final Set<String> exceptions = new TreeSet<String>();

	for(final String val : info.getErrorPage())
	{
	final String exception = parseErrorCodes(errorCodes, val);
	if ( exception != null )
	{
	exceptions.add(exception);
	}
	}
	final long[] codes = toLongArray(errorCodes);
	final String[] exceptionsArray = toStringArray(exceptions);

	return new ErrorRegistration(codes, exceptionsArray);
	}
	return null;
	}

	/**
	* Add the servlet for error handling
	* @param handler The servlet handler.
	*/
	public synchronized void addServlet(@NotNull final ServletHandler handler)
	{
	final ErrorRegistration reg = getErrorRegistration(handler.getServletInfo());
	if ( reg != null )
	{
	final ErrorRegistrationStatus status = new ErrorRegistrationStatus(handler);
	for(final long code : reg.errorCodes)
	{
	addErrorHandling(handler, status, code, null);
	}
	for(final String exception : reg.exceptions)
	{
	addErrorHandling(handler, status, 0, exception);
	}
	final List<ErrorRegistrationStatus> newList = new ArrayList<ErrorPageRegistry.ErrorRegistrationStatus>(this.status);
	newList.add(status);
	Collections.sort(newList);
	this.status = newList;
	}
	}

	/**
	* Remove the servlet from error handling
	* @param info The servlet info.
	*/
	public synchronized void removeServlet(@NotNull final ServletInfo info, final boolean destroy)
	{
	final ErrorRegistration reg = getErrorRegistration(info);
	if ( reg != null )
	{
	final List<ErrorRegistrationStatus> newList = new ArrayList<ErrorPageRegistry.ErrorRegistrationStatus>(this.status);
	final Iterator<ErrorRegistrationStatus> i = newList.iterator();
	while ( i.hasNext() )
	{
	final ErrorRegistrationStatus status = i.next();
	if ( status.handler.getServletInfo().equals(info) )
	{
	i.remove();
	break;
	}
	}
	this.status = newList;

	for(final long code : reg.errorCodes)
	{
	removeErrorHandling(info, code, null);
	}
	for(final String exception : reg.exceptions)
	{
	removeErrorHandling(info, 0, exception);
	}
	}
	}

	public synchronized void cleanup()
	{
	this.errorMapping.clear();
	this.status = Collections.emptyList();
	}

	private void addErrorHandling(final ServletHandler handler, final ErrorRegistrationStatus status, final long code, final String exception)
	{
	final String key = (exception != null ? exception : String.valueOf(code));

	final List<ServletHandler> newList;
	final List<ServletHandler> list = errorMapping.get(key);
	if ( list == null )
	{
	newList = Collections.singletonList(handler);
	}
	else
	{
	newList = new ArrayList<ServletHandler>(list);
	newList.add(handler);
	Collections.sort(newList);
	}
	if ( newList.get(0) == handler )
	{
	// try to activate (and deactivate old handler)
	final int result = handler.init();
	addReason(status, code, exception, result);
	if ( result == -1 )
	{
	if ( list != null )
	{
	final ServletHandler old = list.get(0);
	old.destroy();
	errorMapping.put(key, newList);
	ErrorRegistrationStatus oldStatus = null;
	final Iterator<ErrorRegistrationStatus> i = this.status.iterator();
	while ( oldStatus == null && i.hasNext() )
	{
	final ErrorRegistrationStatus current = i.next();
	if ( current.handler.getServletInfo().equals(old.getServletInfo()) )
	{
	oldStatus = current;
	}
	}
	if ( oldStatus != null )
	{
	removeReason(oldStatus, code, exception, -1);
	boolean addReason = true;
	if ( exception == null )
	{
	if ( code >= 400 && code < 500 && oldStatus.usesClientErrorCodes && !status.usesClientErrorCodes )
	{
	addReason = false;
	}
	else if ( code >= 500 && code < 600 && oldStatus.usesServerErrorCodes && !status.usesServerErrorCodes )
	{
	addReason = false;
	}
	}
	if ( addReason )
	{
	addReason(oldStatus, code, exception, DTOConstants.FAILURE_REASON_SHADOWED_BY_OTHER_SERVICE);
	}
	}
	}
	else
	{
	errorMapping.put(key, newList);
	}
	}
	}
	else
	{
	// failure
	boolean addReason = true;
	if ( exception == null )
	{
	if ( code >= 400 && code < 500 && status.usesClientErrorCodes && !hasErrorCode(newList.get(0), CLIENT_ERROR) )
	{
	addReason = false;
	}
	else if ( code >= 500 && code < 600 && status.usesServerErrorCodes && !hasErrorCode(newList.get(0), SERVER_ERROR) )
	{
	addReason = false;
	}
	}
	if ( addReason )
	{
	addReason(status, code, exception, DTOConstants.FAILURE_REASON_SHADOWED_BY_OTHER_SERVICE);
	}
	errorMapping.put(key, newList);
	}
	}

	/**
	* Make an entry in the status object (which are used to create the DTOs)
	* @param status The status object
	* @param code Either the code
	* @param exception or the exception
	* @param reason The code for the failure reason or {@code -1} for success.
	*/
	private void addReason(final ErrorRegistrationStatus status,
	final long code,
	final String exception,
	final int reason)
	{
	ErrorRegistration reg = status.reasonMapping.get(reason);
	if ( reg == null )
	{
	if ( exception != null )
	{
	reg = new ErrorRegistration(BuilderConstants.EMPTY_LONG_ARRAY, new String[] {exception});
	}
	else
	{
	reg = new ErrorRegistration(new long[] {code}, BuilderConstants.EMPTY_STRING_ARRAY);
	}
	}
	else
	{
	long[] codes = reg.errorCodes;
	String[] exceptions = reg.exceptions;
	if ( exception != null )
	{
	final Set<String> set = toStringSet(exceptions);
	set.add(exception);
	exceptions = toStringArray(set);
	}
	else
	{
	final Set<Long> set = toLongSet(codes);
	set.add(code);
	codes = toLongArray(set);
	}

	reg = new ErrorRegistration(codes, exceptions);
	}
	status.reasonMapping.put(reason, reg);
	}

	private void removeReason(final ErrorRegistrationStatus status, final long code, final String exception, final int reason)
	{
	ErrorRegistration reg = status.reasonMapping.get(reason);
	if ( reg != null )
	{
	long[] codes = reg.errorCodes;
	String[] exceptions = reg.exceptions;
	if ( exception != null )
	{
	final Set<String> set = toStringSet(exceptions);
	set.remove(exception);
	exceptions = toStringArray(set);
	}
	else
	{
	final Set<Long> set = toLongSet(codes);
	set.remove(code);
	codes = toLongArray(set);
	}
	if ( codes.length == 0 && exceptions.length == 0 )
	{
	status.reasonMapping.remove(reason);
	}
	else
	{
	status.reasonMapping.put(reason, new ErrorRegistration(codes, exceptions));
	}
	}
	}

	private void removeErrorHandling(final ServletInfo info, final long code, final String exception)
	{
	final String key = (exception != null ? exception : String.valueOf(code));

	final List<ServletHandler> list = errorMapping.get(key);
	if ( list != null )
	{
	int index = 0;
	final Iterator<ServletHandler> i = list.iterator();
	while ( i.hasNext() )
	{
	final ServletHandler handler = i.next();
	if ( handler.getServletInfo().equals(info) )
	{
	final List<ServletHandler> newList = new ArrayList<ServletHandler>(list);
	newList.remove(handler);

	if ( index == 0 )
	{
	handler.destroy();

	index++;
	while ( index < list.size() )
	{
	final ServletHandler next = list.get(index);
	ErrorRegistrationStatus nextStatus = null;
	for(final ErrorRegistrationStatus s : this.status)
	{
	if ( s.handler.getServletInfo().equals(next.getServletInfo()) )
	{
	nextStatus = s;
	break;
	}
	}
	this.removeReason(nextStatus, code, exception, DTOConstants.FAILURE_REASON_SHADOWED_BY_OTHER_SERVICE);
	final int reason = next.init();
	this.addReason(nextStatus, code, exception, reason);
	if ( reason == -1 )
	{
	break;
	}
	else
	{
	newList.remove(next);
	}
	}
	}
	if ( newList.isEmpty() )
	{
	errorMapping.remove(key);
	}
	else
	{
	errorMapping.put(key, newList);
	}

	break;
	}
	index++;
	}
	}
	}

	/**
	* Get the servlet handling the error (error code or exception).
	* If an exception is provided, a handler for the exception is searched first.
	* If no handler is found (or no exception provided) a handler for the error
	* code is searched.
	* @param exception Optional exception
	* @param errorCode Error code
	* @return The servlet handling the error or {@code null}
	*/
	public ServletHandler get(final Throwable exception, final int errorCode)
	{
	ServletHandler errorHandler = this.get(exception);
	if (errorHandler != null)
	{
	return errorHandler;
	}

	return get(errorCode);
	}

	/**
	* Get the servlet handling the error code
	* @param errorCode Error code
	* @return The servlet handling the error or {@code null}
	*/
	private ServletHandler get(final long errorCode)
	{
	final List<ServletHandler> list = this.errorMapping.get(String.valueOf(errorCode));
	if ( list != null )
	{
	return list.get(0);
	}
	return null;
	}

	/**
	* Get the servlet handling the exception
	* @param exception Error exception
	* @return The servlet handling the error or {@code null}
	*/
	private ServletHandler get(final Throwable exception)
	{
	if (exception == null)
	{
	return null;
	}

	ServletHandler servletHandler = null;
	Class<?> throwableClass = exception.getClass();
	while ( servletHandler == null && throwableClass != null )
	{
	final List<ServletHandler> list = this.errorMapping.get(throwableClass.getName());
	if ( list != null )
	{
	servletHandler = list.get(0);
	}
	if ( servletHandler == null )
	{
	throwableClass = throwableClass.getSuperclass();
	if ( !Throwable.class.isAssignableFrom(throwableClass) )
	{
	throwableClass = null;
	}
	}

	}
	return servletHandler;
	}

	/**
	* Get DTOs for error pages.
	* @param dto The servlet context DTO
	* @param failedErrorPageDTOs The failed error page DTOs
	*/
	public void getRuntimeInfo(final ServletContextDTO dto,
	final Collection<FailedErrorPageDTO> failedErrorPageDTOs)
	{
	final List<ErrorPageDTO> errorPageDTOs = new ArrayList<ErrorPageDTO>();
	final List<ErrorRegistrationStatus> statusList = this.status;
	for(final ErrorRegistrationStatus status : statusList)
	{
	for(final Map.Entry<Integer, ErrorRegistration> entry : status.reasonMapping.entrySet())
	{
	final ErrorPageDTO state = ErrorPageDTOBuilder.build(status.getHandler(), entry.getKey());
	state.errorCodes = Arrays.copyOf(entry.getValue().errorCodes, entry.getValue().errorCodes.length);
	state.exceptions = Arrays.copyOf(entry.getValue().exceptions, entry.getValue().exceptions.length);

	if ( entry.getKey() == -1 )
	{
	errorPageDTOs.add(state);
	}
	else
	{
	failedErrorPageDTOs.add((FailedErrorPageDTO)state);
	}
	}
	}
	if ( !errorPageDTOs.isEmpty() )
	{
	dto.errorPageDTOs = errorPageDTOs.toArray(new ErrorPageDTO[errorPageDTOs.size()]);
	}
	}
	}