KickJava   Java API By Example, From Geeks To Geeks.

Java > Open Source Codes > org > apache > servicemix > components > cache > CacheComponent


1 /*
2  * Licensed to the Apache Software Foundation (ASF) under one or more
3  * contributor license agreements. See the NOTICE file distributed with
4  * this work for additional information regarding copyright ownership.
5  * The ASF licenses this file to You under the Apache License, Version 2.0
6  * (the "License"); you may not use this file except in compliance with
7  * the License. You may obtain a copy of the License at
8  *
9  * http://www.apache.org/licenses/LICENSE-2.0
10  *
11  * Unless required by applicable law or agreed to in writing, software
12  * distributed under the License is distributed on an "AS IS" BASIS,
13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  */
17 package org.apache.servicemix.components.cache;
18
19 import java.util.Map JavaDoc;
20
21 import javax.jbi.JBIException;
22 import javax.jbi.messaging.Fault;
23 import javax.jbi.messaging.InOut;
24 import javax.jbi.messaging.MessageExchange;
25 import javax.jbi.messaging.MessagingException;
26 import javax.jbi.messaging.NormalizedMessage;
27
28 import org.apache.servicemix.components.util.TransformComponentSupport;
29 import org.apache.servicemix.expression.Expression;
30 import org.apache.servicemix.expression.PropertyExpression;
31 import org.apache.servicemix.jbi.NoOutMessageAvailableException;
32
33 /**
34  * Implements a caching layer on top of a service invocation to avoid calling an expensive remote service too often.
35  * The cache can be a simple Map based cache or a full <a HREF="http://www.jcp.org/en/jsr/detail?id=107">JCache</a> instance.
36  *
37  * @version $Revision: 426415 $
38  */
39 public class CacheComponent extends TransformComponentSupport {
40
41     public static final PropertyExpression KEY_PROPERTY_EXPRESSION = new PropertyExpression("org.apache.servicemix.key");
42
43     private Map JavaDoc cache;
44     private Expression keyExpression = KEY_PROPERTY_EXPRESSION;
45
46     public Map JavaDoc getCache() {
47         return cache;
48     }
49
50     public void setCache(Map JavaDoc cache) {
51         this.cache = cache;
52     }
53
54     public Expression getKeyExpression() {
55         return keyExpression;
56     }
57
58     public void setKeyExpression(Expression keyExpression) {
59         this.keyExpression = keyExpression;
60     }
61
62
63     // Implementation methods
64 //-------------------------------------------------------------------------
65 protected void init() throws JBIException {
66         super.init();
67         if (cache == null) {
68             throw new JBIException("You must specify a cache property");
69         }
70     }
71
72     protected boolean transform(MessageExchange exchange, NormalizedMessage in, NormalizedMessage out) throws MessagingException {
73         Object JavaDoc key = keyExpression.evaluate(exchange, in);
74         if (key != null) {
75             NormalizedMessage message = (NormalizedMessage) cache.get(key);
76             if (message != null) {
77                 getMessageTransformer().transform(exchange, message, out);
78                 return true;
79             }
80         }
81
82         InOut inOut = getExchangeFactory().createInOutExchange();
83         NormalizedMessage request = inOut.createMessage();
84         getMessageTransformer().transform(exchange, in, request);
85         inOut.setInMessage(request);
86         getDeliveryChannel().sendSync(inOut);
87
88         NormalizedMessage response = inOut.getOutMessage();
89         Fault fault = inOut.getFault();
90         Exception JavaDoc error = inOut.getError();
91         if (fault != null) {
92             fail(exchange, fault);
93         }
94         else if (error != null) {
95             fail(exchange, error);
96         }
97         else if (response != null) {
98             getMessageTransformer().transform(exchange, response, out);
99
100             if (key != null) {
101                 cache.put(key, response);
102             }
103         }
104         else {
105             throw new NoOutMessageAvailableException(exchange);
106         }
107         return true;
108     }
109
110 }
111
Popular Tags