001    /**
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.camel.impl;
018    
019    import org.apache.camel.CamelContext;
020    import org.apache.camel.Exchange;
021    import org.apache.camel.Message;
022    import org.apache.camel.TypeConverter;
023    import org.apache.camel.util.UuidGenerator;
024    
025    /**
026     * A base class for implementation inheritence providing the core
027     * {@link Message} body handling features but letting the derived class deal
028     * with headers.
029     *
030     * Unless a specific provider wishes to do something particularly clever with
031     * headers you probably want to just derive from {@link DefaultMessage}
032     *
033     * @version $Revision: 46968 $
034     */
035    public abstract class MessageSupport implements Message {
036        private static final UuidGenerator DEFALT_ID_GENERATOR = new UuidGenerator();
037        private Exchange exchange;
038        private Object body;
039        private String messageId;
040    
041        public Object getBody() {
042            if (body == null) {
043                body = createBody();
044            }
045            return body;
046        }
047    
048        @SuppressWarnings({"unchecked" })
049        public <T> T getBody(Class<T> type) {
050            return getBody(type, getBody());
051        }
052    
053        protected <T> T getBody(Class<T> type, Object body) {
054            Exchange e = getExchange();
055            if (e != null) {
056                CamelContext camelContext = e.getContext();
057                if (camelContext != null) {
058                    TypeConverter converter = camelContext.getTypeConverter();
059                    T answer = converter.convertTo(type, e, body);
060                    if (answer == null) {
061                        // lets first try converting the message itself first
062                        // as for some types like InputStream v Reader its more efficient to do the transformation
063                        // from the Message itself as its got efficient implementations of them, before trying the
064                        // payload
065                        answer = converter.convertTo(type, this);
066                    }
067                    return answer;
068                }
069            }
070            return (T)getBody();
071        }
072    
073        public void setBody(Object body) {
074            this.body = body;
075        }
076    
077        public <T> void setBody(Object value, Class<T> type) {
078            Exchange e = getExchange();
079            if (e != null) {
080                T v = e.getContext().getTypeConverter().convertTo(type, e, value);
081                if (v != null) {
082                    value = v;
083                }
084            }
085            setBody(value);
086        }
087    
088        public Message copy() {
089            Message answer = newInstance();
090            answer.copyFrom(this);
091            return answer;
092        }
093    
094        public void copyFrom(Message that) {
095            setMessageId(that.getMessageId());
096            setBody(that.getBody());
097            getHeaders().putAll(that.getHeaders());
098            getAttachments().putAll(that.getAttachments());
099        }
100    
101        public Exchange getExchange() {
102            return exchange;
103        }
104    
105        public void setExchange(Exchange exchange) {
106            this.exchange = exchange;
107        }
108    
109        /**
110         * Returns a new instance
111         */
112        public abstract Message newInstance();
113    
114        /**
115         * A factory method to allow a provider to lazily create the message body
116         * for inbound messages from other sources
117         *
118         * @return the value of the message body or null if there is no value
119         *         available
120         */
121        protected Object createBody() {
122            return null;
123        }
124    
125        public String getMessageId() {
126            if (messageId == null) {
127                messageId = createMessageId();
128            }
129            return this.messageId;
130        }
131    
132        public void setMessageId(String messageId) {
133            this.messageId = messageId;
134        }
135    
136        /**
137         * Lets allow implementations to auto-create a messageId
138         */
139        protected String createMessageId() {
140            return DEFALT_ID_GENERATOR.generateId();
141        }
142    }