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Introduce @EnableLoadTimeWeaving
Issue: SPR-8317
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‎org.springframework.context/src/main/java/org/springframework/context/annotation/EnableLoadTimeWeaving.java

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/*
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* Copyright 2002-2011 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.context.annotation;
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import java.lang.annotation.Documented;
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import java.lang.annotation.ElementType;
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import java.lang.annotation.Retention;
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import java.lang.annotation.RetentionPolicy;
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import java.lang.annotation.Target;
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import org.springframework.context.weaving.DefaultContextLoadTimeWeaver;
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import org.springframework.instrument.classloading.LoadTimeWeaver;
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/**
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* Activates a Spring {@link LoadTimeWeaver} for this application context, available as
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* a bean with the name "loadTimeWeaver", similar to the {@code <context:load-time-weaver>}
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* element in Spring XML.
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* To be used
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* on @{@link org.springframework.context.annotation.Configuration Configuration} classes;
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* the simplest possible example of which follows:
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* <pre class="code">
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* &#064;Configuration
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* &#064;EnableLoadTimeWeaving
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* public class AppConfig {
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* // application-specific &#064;Bean definitions ...
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* }</pre>
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*
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* The example above is equivalent to the following Spring XML configuration:
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* <pre class="code">
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* {@code
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* <beans>
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* <context:load-time-weaver/>
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* <!-- application-specific <bean> definitions -->
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* </beans>
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* }</pre>
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*
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* <h2>The {@code LoadTimeWeaverAware} interface</h2>
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* Any bean that implements the {@link
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* org.springframework.context.weaving.LoadTimeWeaverAware LoadTimeWeaverAware} interface
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* will then receive the {@code LoadTimeWeaver} reference automatically; for example,
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* Spring's JPA bootstrap support.
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*
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* <h2>Customizing the {@code LoadTimeWeaver}</h2>
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* The default weaver is determined automatically. As of Spring 3.1: detecting
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* Sun's GlassFish, Oracle's OC4J, Spring's VM agent and any ClassLoader supported by
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* Spring's {@link
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* org.springframework.instrument.classloading.ReflectiveLoadTimeWeaver
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* ReflectiveLoadTimeWeaver} (for example, the {@link
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* org.springframework.instrument.classloading.tomcat.TomcatInstrumentableClassLoader
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* TomcatInstrumentableClassLoader}).
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*
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* <p>To customize the weaver used, the {@code @Configuration} class annotated with
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* {@code @EnableLoadTimeWeaving} may also implement the {@link LoadTimeWeaverConfigurer}
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* interface and return a custom {@code LoadTimeWeaver} instance through the
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* {@code #getLoadTimeWeaver} method:
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* <pre class="code">
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* &#064;Configuration
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* &#064;EnableLoadTimeWeaving
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* public class AppConfig implements LoadTimeWeaverConfigurer {
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* &#064;Override
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* public LoadTimeWeaver getLoadTimeWeaver() {
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* MyLoadTimeWeaver ltw = new MyLoadTimeWeaver();
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* ltw.addClassTransformer(myClassFileTransformer);
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* // ...
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* return ltw;
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* }
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* }</pre>
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*
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* <p>The example above can be compared to the following Spring XML configuration:
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* <pre class="code">
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* {@code
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* <beans>
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* <context:load-time-weaver weaverClass="com.acme.MyLoadTimeWeaver"/>
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* </beans>
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* }</pre>
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*
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* <p>The code example differs from the XML example in that it actually instantiates the
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* {@code MyLoadTimeWeaver} type, meaning that it can also configure the instance, e.g.
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* calling the {@code #addClassTransformer} method. This demonstrates how the code-based
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* configuration approach is more flexible through direct programmatic access.
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*
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* <h2>Enabling AspectJ-based weaving</h2>
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* AspectJ load-time weaving may be enabled with the {@link #aspectjWeaving()}
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* attribute, which will cause the {@linkplain
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* org.aspectj.weaver.loadtime.ClassPreProcessorAgentAdapter AspectJ class transformer} to
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* be registered through {@link LoadTimeWeaver#addTransformer}. AspectJ weaving will be
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* activated by default if a "META-INF/aop.xml" resource is present on the classpath.
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* Example:
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* <pre class="code">
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* &#064;Configuration
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* &#064;EnableLoadTimeWeaving(aspectjWeaving=ENABLED)
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* public class AppConfig {
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* }</pre>
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*
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* <p>The example above can be compared to the following Spring XML configuration:
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* <pre class="code">
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* {@code
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* <beans>
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* <context:load-time-weaver aspectj-weaving="on"/>
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* </beans>
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* }</pre>
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*
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* <p>The two examples are equivalent with one significant exception: in the XML case,
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* the functionality of {@code <context:spring-configured>} is implicitly enabled when
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* {@code aspectj-weaving} is "on". This does not occur when using
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* {@code @EnableLoadTimeWeaving(aspectjWeaving=ENABLED)}, although this may change in
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* future revisions.
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*
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* @author Chris Beams
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* @since 3.1
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* @see LoadTimeWeaver
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* @see DefaultContextLoadTimeWeaver
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* @see org.aspectj.weaver.loadtime.ClassPreProcessorAgentAdapter
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*/
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@Target(ElementType.TYPE)
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@Retention(RetentionPolicy.RUNTIME)
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@Documented
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@Import(LoadTimeWeavingConfiguration.class)
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public @interface EnableLoadTimeWeaving {
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/**
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* Whether AspectJ weaving should be enabled.
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*/
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AspectJWeaving aspectjWeaving() default AspectJWeaving.AUTODETECT;
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public enum AspectJWeaving {
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/**
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* Switches on Spring-based AspectJ load-time weaving.
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*/
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ENABLED,
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/**
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* Switches off Spring-based AspectJ load-time weaving (even if a
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* "META-INF/aop.xml" resource is present on the classpath).
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*/
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DISABLED,
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/**
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* Switches on AspectJ load-time weaving if a "META-INF/aop.xml" resource
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* is present in the classpath. If there is no such resource, then AspectJ
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* load-time weaving will be switched off.
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*/
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AUTODETECT;
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}
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}

‎org.springframework.context/src/main/java/org/springframework/context/annotation/LoadTimeWeavingConfiguration.java

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/*
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* Copyright 2002-2011 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.context.annotation;
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import static org.springframework.context.weaving.AspectJWeavingEnabler.ASPECTJ_AOP_XML_RESOURCE;
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import java.util.Map;
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import org.springframework.beans.factory.BeanClassLoaderAware;
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import org.springframework.beans.factory.annotation.Autowired;
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import org.springframework.beans.factory.config.BeanDefinition;
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import org.springframework.context.ConfigurableApplicationContext;
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import org.springframework.context.annotation.EnableLoadTimeWeaving.AspectJWeaving;
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import org.springframework.context.weaving.AspectJWeavingEnabler;
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import org.springframework.context.weaving.DefaultContextLoadTimeWeaver;
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import org.springframework.core.type.AnnotationMetadata;
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import org.springframework.instrument.classloading.LoadTimeWeaver;
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import org.springframework.util.Assert;
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/**
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* {@code @Configuration} class that registers a {@link LoadTimeWeaver} bean.
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*
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* <p>This configuration class is automatically imported when using the @{@link
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* EnableLoadTimeWeaving} annotation. See {@code @EnableLoadTimeWeaving} Javadoc for
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* complete usage details.
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*
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* @author Chris Beams
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* @since 3.1
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* @see LoadTimeWeavingConfigurer
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* @see ConfigurableApplicationContext#LOAD_TIME_WEAVER_BEAN_NAME
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*/
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@Configuration
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public class LoadTimeWeavingConfiguration implements ImportAware, BeanClassLoaderAware {
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private Map<String, Object> enableLTW;
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@Autowired(required=false)
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private LoadTimeWeavingConfigurer ltwConfigurer;
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private ClassLoader beanClassLoader;
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public void setImportMetadata(AnnotationMetadata importMetadata) {
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this.enableLTW = importMetadata.getAnnotationAttributes(EnableLoadTimeWeaving.class.getName(), false);
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Assert.notNull(this.enableLTW,
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"@EnableLoadTimeWeaving is not present on importing class " +
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importMetadata.getClassName());
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}
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public void setBeanClassLoader(ClassLoader beanClassLoader) {
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this.beanClassLoader = beanClassLoader;
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}
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@Bean(name=ConfigurableApplicationContext.LOAD_TIME_WEAVER_BEAN_NAME)
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@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
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public LoadTimeWeaver loadTimeWeaver() {
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LoadTimeWeaver loadTimeWeaver = null;
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if (ltwConfigurer != null) {
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// the user has provided a custom LTW instance
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loadTimeWeaver = ltwConfigurer.getLoadTimeWeaver();
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}
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if (loadTimeWeaver == null) {
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// no custom LTW provided -> fall back to the default
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loadTimeWeaver = new DefaultContextLoadTimeWeaver(this.beanClassLoader);
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}
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switch ((AspectJWeaving) this.enableLTW.get("aspectjWeaving")) {
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case DISABLED:
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// AJ weaving is disabled -> do nothing
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break;
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case AUTODETECT:
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if (this.beanClassLoader.getResource(ASPECTJ_AOP_XML_RESOURCE) != null) {
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// No aop.xml present on the classpath -> treat as 'disabled'
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break;
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}
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// aop.xml is present on the classpath -> fall through and enable
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case ENABLED:
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AspectJWeavingEnabler.enableAspectJWeaving(loadTimeWeaver, this.beanClassLoader);
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}
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return loadTimeWeaver;
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}
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}

‎org.springframework.context/src/main/java/org/springframework/context/annotation/LoadTimeWeavingConfigurer.java

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/*
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* Copyright 2002-2011 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.context.annotation;
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import org.springframework.instrument.classloading.LoadTimeWeaver;
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/**
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* Interface to be implemented by @{@link org.springframework.context.annotation.Configuration
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* Configuration} classes annotated with @{@link EnableLoadTimeWeaving} that wish to
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* customize the {@link LoadTimeWeaver} instance to be used.
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*
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* <p>See @{@link EnableAsync} for usage examples and information on how a default
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* {@code LoadTimeWeaver} is selected when this interface is not used.
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*
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* @author Chris Beams
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* @since 3.1
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* @see LoadTimeWeavingConfiguration
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* @see EnableLoadTimeWeaving
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*/
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public interface LoadTimeWeavingConfigurer {
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/**
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* Create, configure and return the {@code LoadTimeWeaver} instance to be used. Note
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* that it is unnecessary to annotate this method with {@code @Bean}, because the
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* object returned will automatically be registered as a bean by
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* {@link LoadTimeWeavingConfiguration#loadTimeWeaver()}
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*/
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LoadTimeWeaver getLoadTimeWeaver();
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}

‎org.springframework.context/src/main/java/org/springframework/context/config/LoadTimeWeaverBeanDefinitionParser.java

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/*
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* Copyright 2002-2007 the original author or authors.
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* Copyright 2002-2011 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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import org.springframework.beans.factory.xml.AbstractSingleBeanDefinitionParser;
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import org.springframework.beans.factory.xml.ParserContext;
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import org.springframework.context.ConfigurableApplicationContext;
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import org.springframework.context.weaving.AspectJWeavingEnabler;
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import org.springframework.util.ClassUtils;
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/**
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private static final String ASPECTJ_WEAVING_ATTRIBUTE = "aspectj-weaving";
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private static final String ASPECTJ_AOP_XML_RESOURCE = "META-INF/aop.xml";
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private static final String DEFAULT_LOAD_TIME_WEAVER_CLASS_NAME =
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"org.springframework.context.weaving.DefaultContextLoadTimeWeaver";
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else {
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// Determine default...
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ClassLoader cl = parserContext.getReaderContext().getResourceLoader().getClassLoader();
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return (cl.getResource(ASPECTJ_AOP_XML_RESOURCE) != null);
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return (cl.getResource(AspectJWeavingEnabler.ASPECTJ_AOP_XML_RESOURCE) != null);
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}
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}
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