Source Code Cross Referenced for LazyInitTargetSource.java in  » J2EE » spring-framework-2.5 » org » springframework » aop » target » Java Source Code / Java DocumentationJava Source Code and Java Documentation

01:        /*
02:         * Copyright 2002-2007 the original author or authors.
03:         *
04:         * Licensed under the Apache License, Version 2.0 (the "License");
05:         * you may not use this file except in compliance with the License.
06:         * You may obtain a copy of the License at
07:         *
08:         *      http://www.apache.org/licenses/LICENSE-2.0
09:         *
10:         * Unless required by applicable law or agreed to in writing, software
11:         * distributed under the License is distributed on an "AS IS" BASIS,
12:         * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13:         * See the License for the specific language governing permissions and
14:         * limitations under the License.
15:         */
16:
17:        package org.springframework.aop.target;
18:
19:        import org.springframework.beans.BeansException;
20:
21:        /**
22:         * {@link org.springframework.aop.TargetSource} that lazily accesses a
23:         * singleton bean from a {@link org.springframework.beans.factory.BeanFactory}.
24:         *
25:         * <p>Useful when a proxy reference is needed on initialization but
26:         * the actual target object should not be initialized until first use.
27:         * When the target bean is defined in an
28:         * {@link org.springframework.context.ApplicationContext} (or a
29:         * <code>BeanFactory</code> that is eagerly pre-instantiating singleton beans)
30:         * it must be marked as "lazy-init" too, else it will be instantiated by said
31:         * <code>ApplicationContext</code> (or <code>BeanFactory</code>) on startup.
32:         * <p>For example:
33:         *
34:         * <pre class="code">
35:         * &lt;bean id="serviceTarget" class="example.MyService" lazy-init="true"&gt;
36:         *   ...
37:         * &lt;/bean&gt;
38:         *
39:         * &lt;bean id="service" class="org.springframework.aop.framework.ProxyFactoryBean"&gt;
40:         *   &lt;property name="targetSource"&gt;
41:         *     &lt;bean class="org.springframework.aop.target.LazyInitTargetSource"&gt;
42:         *       &lt;property name="targetBeanName"&gt;&lt;idref local="serviceTarget"/&gt;&lt;/property&gt;
43:         *     &lt;/bean&gt;
44:         *   &lt;/property&gt;
45:         * &lt;/bean&gt;</pre>
46:         *
47:         * The "serviceTarget" bean will not get initialized until a method on the
48:         * "service" proxy gets invoked.
49:         *
50:         * <p>Subclasses can extend this class and override the {@link #postProcessTargetObject(Object)} to
51:         * perform some additional processing with the target object when it is first loaded.
52:         *
53:         * @author Juergen Hoeller
54:         * @author Rob Harrop
55:         * @since 1.1.4
56:         * @see org.springframework.beans.factory.BeanFactory#getBean
57:         * @see #postProcessTargetObject
58:         */
59:        public class LazyInitTargetSource extends
60:                AbstractBeanFactoryBasedTargetSource {
61:
62:            private Object target;
63:
64:            public synchronized Object getTarget() throws BeansException {
65:                if (this .target == null) {
66:                    this .target = getBeanFactory().getBean(getTargetBeanName());
67:                    postProcessTargetObject(this .target);
68:                }
69:                return this .target;
70:            }
71:
72:            /**
73:             * Subclasses may override this method to perform additional processing on
74:             * the target object when it is first loaded.
75:             * @param targetObject the target object that has just been instantiated (and configured)
76:             */
77:            protected void postProcessTargetObject(Object targetObject) {
78:            }
79:
80:        }