spring-framework / org.springframework.context.annotation / EnableLoadTimeWeaving

EnableLoadTimeWeaving

@Target([AnnotationTarget.CLASS, AnnotationTarget.FILE]) @Import(LoadTimeWeavingConfiguration) class EnableLoadTimeWeaving

Activates a Spring LoadTimeWeaver for this application context, available as a bean with the name "loadTimeWeaver", similar to the <context:load-time-weaver> element in Spring XML.

To be used on @org.springframework.context.annotation.Configuration classes; the simplest possible example of which follows: 

 @Configuration @EnableLoadTimeWeaving public class AppConfig { // application-specific @Bean definitions ... }
The example above is equivalent to the following Spring XML configuration: 
<beans> <context:load-time-weaver/> <!-- application-specific <bean> definitions --> </beans>
The LoadTimeWeaverAware interface Any bean that implements the interface will then receive the LoadTimeWeaver reference automatically; for example, Spring's JPA bootstrap support. Customizing the LoadTimeWeaver The default weaver is determined automatically: see DefaultContextLoadTimeWeaver.

To customize the weaver used, the @Configuration class annotated with @EnableLoadTimeWeaving may also implement the LoadTimeWeavingConfigurer interface and return a custom LoadTimeWeaver instance through the #getLoadTimeWeaver method: 

 @Configuration @EnableLoadTimeWeaving public class AppConfig implements LoadTimeWeavingConfigurer { @Override public LoadTimeWeaver getLoadTimeWeaver() { MyLoadTimeWeaver ltw = new MyLoadTimeWeaver(); ltw.addClassTransformer(myClassFileTransformer); // ... return ltw; } }

The example above can be compared to the following Spring XML configuration: 

<beans> <context:load-time-weaver weaverClass="com.acme.MyLoadTimeWeaver"/> </beans>

The code example differs from the XML example in that it actually instantiates the MyLoadTimeWeaver type, meaning that it can also configure the instance, e.g. calling the #addClassTransformer method. This demonstrates how the code-based configuration approach is more flexible through direct programmatic access.

Enabling AspectJ-based weaving AspectJ load-time weaving may be enabled with the #aspectjWeaving() attribute, which will cause the to be registered through LoadTimeWeaver#addTransformer. AspectJ weaving will be activated by default if a "META-INF/aop.xml" resource is present on the classpath. Example: 
 @Configuration @EnableLoadTimeWeaving(aspectjWeaving=ENABLED) public class AppConfig { }

The example above can be compared to the following Spring XML configuration: 

<beans> <context:load-time-weaver aspectj-weaving="on"/> </beans>

The two examples are equivalent with one significant exception: in the XML case, the functionality of <context:spring-configured> is implicitly enabled when aspectj-weaving is "on". This does not occur when using @EnableLoadTimeWeaving(aspectjWeaving=ENABLED). Instead you must explicitly add @EnableSpringConfigured (included in the spring-aspects module)

Author
Chris Beams

Since
3.1

See Also
LoadTimeWeaverDefaultContextLoadTimeWeaverorg.aspectj.weaver.loadtime.ClassPreProcessorAgentAdapter

Constructors

<init>

 EnableLoadTimeWeaving(aspectjWeaving: AspectJWeaving)

Activates a Spring LoadTimeWeaver for this application context, available as a bean with the name "loadTimeWeaver", similar to the <context:load-time-weaver> element in Spring XML.

To be used on @org.springframework.context.annotation.Configuration classes; the simplest possible example of which follows: 

 @Configuration @EnableLoadTimeWeaving public class AppConfig { // application-specific @Bean definitions ... }
The example above is equivalent to the following Spring XML configuration: 
<beans> <context:load-time-weaver/> <!-- application-specific <bean> definitions --> </beans>
The LoadTimeWeaverAware interface Any bean that implements the interface will then receive the LoadTimeWeaver reference automatically; for example, Spring's JPA bootstrap support. Customizing the LoadTimeWeaver The default weaver is determined automatically: see DefaultContextLoadTimeWeaver.

To customize the weaver used, the @Configuration class annotated with @EnableLoadTimeWeaving may also implement the LoadTimeWeavingConfigurer interface and return a custom LoadTimeWeaver instance through the #getLoadTimeWeaver method: 

 @Configuration @EnableLoadTimeWeaving public class AppConfig implements LoadTimeWeavingConfigurer { @Override public LoadTimeWeaver getLoadTimeWeaver() { MyLoadTimeWeaver ltw = new MyLoadTimeWeaver(); ltw.addClassTransformer(myClassFileTransformer); // ... return ltw; } }

The example above can be compared to the following Spring XML configuration: 

<beans> <context:load-time-weaver weaverClass="com.acme.MyLoadTimeWeaver"/> </beans>

The code example differs from the XML example in that it actually instantiates the MyLoadTimeWeaver type, meaning that it can also configure the instance, e.g. calling the #addClassTransformer method. This demonstrates how the code-based configuration approach is more flexible through direct programmatic access.

Enabling AspectJ-based weaving AspectJ load-time weaving may be enabled with the #aspectjWeaving() attribute, which will cause the to be registered through LoadTimeWeaver#addTransformer. AspectJ weaving will be activated by default if a "META-INF/aop.xml" resource is present on the classpath. Example: 
 @Configuration @EnableLoadTimeWeaving(aspectjWeaving=ENABLED) public class AppConfig { }

The example above can be compared to the following Spring XML configuration: 

<beans> <context:load-time-weaver aspectj-weaving="on"/> </beans>

The two examples are equivalent with one significant exception: in the XML case, the functionality of <context:spring-configured> is implicitly enabled when aspectj-weaving is "on". This does not occur when using @EnableLoadTimeWeaving(aspectjWeaving=ENABLED). Instead you must explicitly add @EnableSpringConfigured (included in the spring-aspects module)

Properties

aspectjWeaving

 val aspectjWeaving: AspectJWeaving

Whether AspectJ weaving should be enabled.