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: 749962 $
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        protected <T> T getBody(Class<T> type, Object body) {
056            Exchange e = getExchange();
057            if (e != null) {
058                CamelContext camelContext = e.getContext();
059                if (camelContext != null) {
060                    boolean tryConvert = true;
061                    TypeConverter converter = camelContext.getTypeConverter();
062                    // if its the default type converter then use a performance shortcut to check if it can convert it
063                    // this is faster than getting throwing and catching NoTypeConversionAvailableException
064                    // the StreamCachingInterceptor will attempt to convert the payload to a StremCache for caching purpose
065                    // so we get invoked on each node the exchange passes. So this is a little performance optimization
066                    // to avoid the excessive exception handling
067                    if (body != null && converter instanceof DefaultTypeConverter) {
068                        DefaultTypeConverter defaultTypeConverter = (DefaultTypeConverter) converter;
069                        // we can only check if there is no converter meaning we have tried to convert it beforehand
070                        // and then knows for sure there is no converter possible
071                        tryConvert = !defaultTypeConverter.hasNoConverterFor(type, body.getClass());
072                    }
073                    if (tryConvert) {
074                        try {
075                            // lets first try converting the body itself first
076                            // as for some types like InputStream v Reader its more efficient to do the transformation
077                            // from the body itself as its got efficient implementations of them, before trying the
078                            // message
079                            return converter.convertTo(type, e, body);
080                        } catch (NoTypeConversionAvailableException ex) {
081                            // ignore
082                        }
083                    }
084                    // fallback to the message itself
085                    return converter.convertTo(type, this);
086                }
087            }
088            return (T)getBody();
089        }
090    
091        public void setBody(Object body) {
092            this.body = body;
093        }
094    
095        public <T> void setBody(Object value, Class<T> type) {
096            Exchange e = getExchange();
097            if (e != null) {
098                T v = e.getContext().getTypeConverter().convertTo(type, e, value);
099                if (v != null) {
100                    value = v;
101                }
102            }
103            setBody(value);
104        }
105    
106        public Message copy() {
107            Message answer = newInstance();
108            answer.copyFrom(this);
109            return answer;
110        }
111    
112        public void copyFrom(Message that) {
113            setMessageId(that.getMessageId());
114            setBody(that.getBody());
115            getHeaders().putAll(that.getHeaders());
116            getAttachments().putAll(that.getAttachments());
117        }
118    
119        public Exchange getExchange() {
120            return exchange;
121        }
122    
123        public void setExchange(Exchange exchange) {
124            this.exchange = exchange;
125        }
126    
127        /**
128         * Returns a new instance
129         */
130        public abstract Message newInstance();
131    
132        /**
133         * A factory method to allow a provider to lazily create the message body
134         * for inbound messages from other sources
135         *
136         * @return the value of the message body or null if there is no value
137         *         available
138         */
139        protected Object createBody() {
140            return null;
141        }
142    
143        public String getMessageId() {
144            if (messageId == null) {
145                messageId = createMessageId();
146            }
147            return this.messageId;
148        }
149    
150        public void setMessageId(String messageId) {
151            this.messageId = messageId;
152        }
153    
154        /**
155         * Lets allow implementations to auto-create a messageId
156         */
157        protected String createMessageId() {
158            return DEFALT_ID_GENERATOR.generateId();
159        }
160    }