# ErrorHandler.java

    /*
     * 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.qi4j.library.rest.client.api;

    import java.util.LinkedHashMap;
    import java.util.Map;
    import org.qi4j.functional.Specification;
    import org.qi4j.functional.Specifications;
    import org.qi4j.library.rest.client.spi.ResponseHandler;
    import org.restlet.Response;
    import org.restlet.data.Status;
    import org.restlet.resource.ResourceException;

    /**
     * Implements a chained list of specification-&gt;handler. Add the most specific handlers first, and the most generic last.
     */
    public class ErrorHandler
        implements ResponseHandler
    {
        public static Specification<Response> AUTHENTICATION_REQUIRED = new Specification<Response>()
        {
            @Override
            public boolean satisfiedBy( Response item )
            {
                return item.getStatus().equals( Status.CLIENT_ERROR_UNAUTHORIZED );
            }
        };

        public static Specification<Response> RECOVERABLE_ERROR = new Specification<Response>()
        {
            @Override
            public boolean satisfiedBy( Response item )
            {
                return item.getStatus().isRecoverableError();
            }
        };

        LinkedHashMap<Specification<Response>, ResponseHandler> handlers = new LinkedHashMap<Specification<Response>, ResponseHandler>(  );

        public ErrorHandler()
        {
        }

        public ErrorHandler onError(Specification<Response> responseSpecification, ResponseHandler handler)
        {
            handlers.put( responseSpecification, handler );
            return this;
        }

        public ErrorHandler onError(ResponseHandler handler)
        {
            handlers.put( Specifications.<Response>TRUE(), handler );
            return this;
        }

        @Override
        public HandlerCommand handleResponse( Response response, ContextResourceClient client )
        {
            for( Map.Entry<Specification<Response>, ResponseHandler> specificationResponseHandlerEntry : handlers.entrySet() )
            {
                if (specificationResponseHandlerEntry.getKey().satisfiedBy( response ))
                {
                    return specificationResponseHandlerEntry.getValue().handleResponse( response, client );
                }
            }

            // No handlers, throw exception
            throw new ResourceException( response.getStatus() );
        }
    }