how to setup load-time weaving with Spring and Tomcat WITHOUT using the -javaagent on the command line

Question

I am using Spring 3.2.9, Tomcat 6.0.44

I am trying to configure my application's Spring instrumentation provider (e.g. spring-instrumentation.jar) for load-time weaving, when it is deployed on Tomcat.

I have a requirement to NOT use: "-javaagent:/path/path/spring-instrument.jar" on the command line to do the configuration.

I've read that I can configure the Spring instrumentation by modifying the <Context> element of my application's Tomcat configuration (in either Tomcat's server.xml or my web app's context.xml). Adding the appropriate <Context> element to the server.xml results in my application being correctly configured to run with Spring's instrumentation provider. Adding it to the context.xml (see below) does NOT result in a working setup.

I have a META-INF/aop.xml file, looks like this:

    <aspectj>
        <weaver options="-verbose -showWeaveInfo -debug">
            <include within="com.mv.xx.services..*"/>
            <exclude within="com.mv.xx.aop..*"/>
        </weaver>
        <aspects>
            <aspect name="com.mv.xx.aop.MyAspect"/>
        </aspects>
    </aspectj>

I also specify that I want to use load-time weaving by adding this to my Spring context config:

 <context:load-time-weaver />

And I add this jar to my application's classpath: spring-instrument-tomcat.jar

WHAT I HAVE TRIED:

When starting Tomcat, If I identify the location of the spring-instrument.jar on the command line using the -javaagent parameter like this:

-javaagent:/path/path2/spring-instrument-3.2.9.RELEASE.jar

Everything works fine.

---

Next I removed "-javaagent:/path/path2/spring-instrument-3.2.9.RELEASE.jar" from the command line. In Tomcat's server.xml file (located in $CATALINE_HOME/conf), I added a a <Context> element to the <Host> element, like this:

<Context path="/myApp" docBase="myApp">
    <Loader loaderClass="org.springframework.instrument.classloading.tomcat.TomcatInstrumentableClassLoader"/>
</Context>

With this configuration everything behaves properly. However I have a requirement to not modify Tomcat's server.xml, since I don't have control over the server.xml (DevOps does, and is reluctant to modify it).

---

Next I removed the <Context> element from Tomcat's server.xml. According to the Spring docs, I can add a /META-INF/context.xml to my webapp, and put the <Context> element that used to be in Tomcat's server.xml into the context.xml, like so:

        <Context>
            <Context path="/myApp" docBase="myApp">
                <Loader loaderClass="org.springframework.instrument.classloading.tomcat.TomcatInstrumentableClassLoader"/>
            </Context>
        </Context>

However when I restart Tomcat, I get an error message in the logs saying:

    SEVERE: Exception sending context initialized event to listener instance of class org.springframework.web.context.ContextLoaderListener
    org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.context.weaving.AspectJWeavingEnabler#0': Initialization of bean failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'loadTimeWeaver': Initialization of bean failed; nested exception is java.lang.IllegalStateException: ClassLoader [org.apache.catalina.loader.WebappClassLoader] does NOT provide an 'addTransformer(ClassFileTransformer)' method. Specify a custom LoadTimeWeaver or start your Java virtual machine with Spring's agent: -javaagent:org.springframework.instrument.jar

After digging around, I read something that suggested that I modify the <context:load-time-weaver/> element in my Spring config, like this:

        <context:load-time-weaver weaver-class="org.springframework.instrument.classloading.InstrumentationLoadTimeWeaver" />

And add the jar containing InstrumentationLoadTimeWeaver.class to my classpath.

However when I do that, I get this error message in the logs:

        SEVERE: Exception sending context initialized event to listener instance of class org.springframework.web.context.ContextLoaderListener
        java.lang.IllegalStateException: Must start with Java agent to use InstrumentationLoadTimeWeaver. See Spring documentation.
    etc....

Can anyone explain how to setup load-time weaving with Spring and Tomcat WITHOUT using the -javaagent on the command line, and WITHOUT modifying the server.xml?

Johppa

Same problem! Any solution? – Tonl

Answer 1

This is the code that I managed to use in order to removed the exception that you mentioned. Basically you have to implement the LoadTimeWeavingConfigurer and override the method getLoadTimeWeaver().

@Configuration
@ComponentScan(basePackages = "org.myproject")
@EnableAspectJAutoProxy
@EnableSpringConfigured
@EnableLoadTimeWeaving(aspectjWeaving = EnableLoadTimeWeaving.AspectJWeaving.AUTODETECT)
public class Config implements LoadTimeWeavingConfigurer {

    @Override
    public LoadTimeWeaver getLoadTimeWeaver() {
        return new ReflectiveLoadTimeWeaver();
    }

    @Bean
    public InstrumentationLoadTimeWeaver loadTimeWeaver()  throws Throwable {
        InstrumentationLoadTimeWeaver loadTimeWeaver = new InstrumentationLoadTimeWeaver();
        return loadTimeWeaver;
    }

}

Birkett

@Ryan I might achieve the same in xml config. Have a look at the spring doc - docs.spring.io/spring/docs/current/javadoc-api/org/… This might help. Thanks – Birkett

Thanks for the link. That looks more detailed than what I had found. It didn't work on my first attempt but nice to hear that its possible. – Hovey

Answer 2

I used invesdwin-instrument to perform that. It allows you to use Load time weaving instrumentation dynamically so that you don't have to use any javaagent.

It took me a bit of effort to make it work with Tomcat 8.5 though. But it finally work using this configuration with Spring Boot :

@SpringBootApplication
@EnableLoadTimeWeaving // instead of @ImportResource(locations = "classpath:/META-INF/ctx.spring.weaving.xml")
public class MySpringBootApplication {
    public static void main(final String[] args) {
        DynamicInstrumentationLoader.waitForInitialized(); //dynamically attach java agent to jvm if not already present
        DynamicInstrumentationLoader.initLoadTimeWeavingContext(); //weave all classes before they are loaded as beans
        SpringApplication.run(MySpringBootApplication.class, args); //start application, load some classes
    }
}

It should also work with previous version of Tomcat.

Regards

Jeanettajeanette

Answer 3

https://wiki.eclipse.org/EclipseLink/UserGuide/JPA/Advanced_JPA_Development/Performance/Weaving/Static_Weaving

Try maven plug-in from the above link. It's working

Evanesce

Whilst this may theoretically answer the question, it would be preferable to include the essential parts of the answer here, and provide the link for reference. – Rosenstein