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.NoTypeConversionAvailableException;
023    import org.apache.camel.TypeConverter;
024    import org.apache.camel.impl.converter.DefaultTypeConverter;
025    import org.apache.camel.util.UuidGenerator;
026    
027    /**
028     * A base class for implementation inheritence providing the core
029     * {@link Message} body handling features but letting the derived class deal
030     * with headers.
031     *
032     * Unless a specific provider wishes to do something particularly clever with
033     * headers you probably want to just derive from {@link DefaultMessage}
034     *
035     * @version $Revision: 749956 $
036     */
037    public abstract class MessageSupport implements Message {
038        private static final UuidGenerator DEFALT_ID_GENERATOR = new UuidGenerator();
039        private Exchange exchange;
040        private Object body;
041        private String messageId;
042    
043        public Object getBody() {
044            if (body == null) {
045                body = createBody();
046            }
047            return body;
048        }
049    
050        @SuppressWarnings("unchecked")
051        public <T> T getBody(Class<T> type) {
052            return getBody(type, getBody());
053        }
054    
055        @SuppressWarnings("unchecked")
056        protected <T> T getBody(Class<T> type, Object body) {
057            Exchange e = getExchange();
058            if (e != null) {
059                CamelContext camelContext = e.getContext();
060                if (camelContext != null) {
061                    boolean tryConvert = true;
062                    TypeConverter converter = camelContext.getTypeConverter();
063                    // if its the default type converter then use a performance shortcut to check if it can convert it
064                    // this is faster than getting throwing and catching NoTypeConversionAvailableException
065                    // the StreamCachingInterceptor will attempt to convert the payload to a StremCache for caching purpose
066                    // so we get invoked on each node the exchange passes. So this is a little performance optimization
067                    // to avoid the excessive exception handling
068                    if (body != null && converter instanceof DefaultTypeConverter) {
069                        DefaultTypeConverter defaultTypeConverter = (DefaultTypeConverter) converter;
070                        // we can only check if there is no converter meaning we have tried to convert it beforehand
071                        // and then knows for sure there is no converter possible
072                        tryConvert = !defaultTypeConverter.hasNoConverterFor(type, body.getClass());
073                    }
074                    if (tryConvert) {
075                        try {
076                            // lets first try converting the body itself first
077                            // as for some types like InputStream v Reader its more efficient to do the transformation
078                            // from the body itself as its got efficient implementations of them, before trying the
079                            // message
080                            return converter.convertTo(type, e, body);
081                        } catch (NoTypeConversionAvailableException ex) {
082                            // ignore
083                        }
084                    }
085                    // fallback to the message itself
086                    return converter.convertTo(type, this);
087                }
088            }
089            return (T)getBody();
090        }
091    
092        public void setBody(Object body) {
093            this.body = body;
094        }
095    
096        public <T> void setBody(Object value, Class<T> type) {
097            Exchange e = getExchange();
098            if (e != null) {
099                T v = e.getContext().getTypeConverter().convertTo(type, e, value);
100                if (v != null) {
101                    value = v;
102                }
103            }
104            setBody(value);
105        }
106    
107        public Message copy() {
108            Message answer = newInstance();
109            answer.copyFrom(this);
110            return answer;
111        }
112    
113        public void copyFrom(Message that) {
114            setMessageId(that.getMessageId());
115            setBody(that.getBody());
116            getHeaders().putAll(that.getHeaders());
117            getAttachments().putAll(that.getAttachments());
118        }
119    
120        public Exchange getExchange() {
121            return exchange;
122        }
123    
124        public void setExchange(Exchange exchange) {
125            this.exchange = exchange;
126        }
127    
128        /**
129         * Returns a new instance
130         */
131        public abstract Message newInstance();
132    
133        /**
134         * A factory method to allow a provider to lazily create the message body
135         * for inbound messages from other sources
136         *
137         * @return the value of the message body or null if there is no value
138         *         available
139         */
140        protected Object createBody() {
141            return null;
142        }
143    
144        public String getMessageId() {
145            if (messageId == null) {
146                messageId = createMessageId();
147            }
148            return this.messageId;
149        }
150    
151        public void setMessageId(String messageId) {
152            this.messageId = messageId;
153        }
154    
155        /**
156         * Lets allow implementations to auto-create a messageId
157         */
158        protected String createMessageId() {
159            return DEFALT_ID_GENERATOR.generateId();
160        }
161    }