javassist | Java bytecode engineering toolkit | Bytecode library

You have to use the information SLF4J provide you and back trace the dependency using dependency:tree and its includes option.

This message:

Thanks to Holger's comment, I was able to figure out that I actually needed a StackMapTable, not a StackMap. And I indeed need a stack map table entry at every branch destination.

From previous comments:

The unfound classes are dynamic proxies which are heavily used by the Spring Framework in order to implement AOP. Spring can use both JDK dynamic interface proxies and CGLIB proxies, the latter of which is what we are seeing here. Maybe you should simply ignore those types of classes. They are in fact created dynamically, hence the name. But they are rather a result of dynamic (sub-)class generation than of bytecode transformation.

Yes, I have considered just ignoring those dynamically generated classes, but the whole point of my application was to capture every single method invocation as a user interacts with the web application (such as clicking on a button, etc). In this case, would it be okay to ignore these types of dynamically generated classes? I want to make sure I do not miss any method calls.

As those classes are just dynamic proxies, they will either forward the calls to the original methods or call some AOP or interceptor logic first/instead. Either way, you would not miss anything essential, those proxies are more like switchboards or routers, the actual show happens somewhere else. I recommend you to simply try in a little playgrounds project with an aspect or two.

You also asked how to detect and ignore dynamic proxies by their names:

• CGLIB proxies: Spring's CGLIB proxies contain substrings like $$FastClassBySpringCGLIB$$ or $$EnhancerBySpringCGLIB$$, followed by 8 characters representing 4 hexadecimal bytes. You could either match with a regular expression of just keep it simple and match the substring BySpringCGLIB$$. If non-Spring CGLIB proxies are also in use somewhere in your application, you would have to watch for other naming patterns. But probably you would get similar errors as before when not filtering them, so you would notice automatically.

• JDK proxies: If your Spring application also happens to use JDK proxies, you can identify them easily using JRE API call Proxy.isProxyClass(Class). Thanks to Johannes Kuhn for his comment.

• JDK proxies (old answer): You can filter class names beginning with $Proxy, usually something like com.sun.proxy.$Proxy2 (the trailing number being different). According to the JDK documentation: "The unqualified name of a proxy class is unspecified. The space of class names that begin with the string "$Proxy" is, however, to be reserved for proxy classes." At least for Oracle and probably OpenJDK, you can match for that naming pattern. If that holds true for all JVMs, is up to you to test, if chances are that in your environments others are being used. I quickly tried with Semeru OpenJ9, and the proxy naming pattern is identical, even the package name com.sun.proxy. Pleasae note that in more recent JDK versions, JDK proxies will have fully qualified names like jdk.proxy2.$Proxy25, so in e.g. Java 16 or 17 you should not rely on package name com.sun.proxy. Either add more cases or limit matching to the leading $Proxy in the simple class name.

Update 2022-02-26: Because there was activity on this question, I decided to add some more information about Spring-specific tools which can determine whether an object (or a class) is an AOP proxy (class) and, more specifically, if it is a CGLIB or JDK proxy:

Take a look at tool class AopUtils and its handy methods

• isAopProxy(Object),
• isCglibProxy(Object),
• isJdkDynamicProxy(Object).

No more String matching, simply ask Spring.

BTW, there is also a method net.sf.cglib.proxy.Proxy.isProxyClass(Class) directly in CGLIB, which is supposed to do the same, but within Spring it does not work, probably because Spring uses CGLIB in a non-canonical way. Because Spring embeds a package-relocated CGLIB in its core, the corresponding method org.springframework.cglib.proxy.Proxy.isProxyClass(Class) yields the same faulty result. So if you are working within Spring, please do not use those methods, better use AopUtils.

Here is some example code for your convenience, showing how to determine Spring AOP proxy types (JDK vs. CGLIB proxies) using AopUtils. See also my answer here for how to configure Spring in order to use both proxy types.

BTW, instead of Javassist you could also use AspectJ for your purpose. It sounds like a pretty typical use case.

Acording to this answer: https://stackoverflow.com/a/51236918/16651073 tomcat falls back to default logging if it can resolve the location

Can you try to save the properties without the spaces.

Like this: logging.file.name=application.logs

You simply need to use the correct classpath. This is wrong, because you are pointing into a package subdirectory rather than straight to the root:

It was an Intelli-J issue!

So, cleaning the Intelli-J dependency spaghetti up solved it!

1. File > Invalidate cache ... and restart. Helped a bit.
2. Closing the Intelli-J project. Then removed manually the ".idea" folder and any *.iml file.

Yes, I did option 1 previously. Especially doing action 2 solved it within a minute.

These messages usually mean that your application is importing multiple versions of the same files, or that each of these files in imported multiple times. From the message in this case, it looks like you have identical files located in the same place or being overwritten by the same files.

In which context do you see these files? (IDE, building, running server, etc) If you see these in your IDE (Eclipse?), you may have a project configuration issue, such as importing the same library folder twice through different path.

Additionally, the zkbind dependency will itself transitively load other ZK dependencies. I'd recommend running a mvn clean dependency:tree command locally to see which dependencies are being added to your application, and from which parent.

Questions not presenting any of your own code but asking others for complete sample code or other resources are likely to be closed as off-topic. At the time of writing this, your question already attracted 2 of 3 necessary close votes. Please remember what I told you in your other question about how to ask good questions and how an MCVE helps you do that.

Because you are new to Java instrumentation, I want to elaborate a little more on Johannes' correct comments: I recommend you to not just read the Baeldung article but also some related javadocs.

For example, the Java 8 API documentation for Instrumentation.redefineClasses clearly states the limitations when redefining classes:

The redefinition may change method bodies, the constant pool and attributes. The redefinition must not add, remove or rename fields or methods, change the signatures of methods, or change inheritance. These restrictions maybe be lifted in future versions.

Alas, the restrictions have not been lifted as of Java 17. The same method is described there as follows:

The supported class file changes are described in JVM TI RedefineClasses.

The document pointed to basically says the same as the Java 8 documentation, only in some more detail:

The redefinition may change method bodies, the constant pool and attributes (unless explicitly prohibited). The redefinition must not add, remove or rename fields or methods, change the signatures of methods, change modifiers, or change inheritance. The redefinition must not change the NestHost, NestMembers, Record, or PermittedSubclasses attributes. These restrictions may be lifted in future versions.

Besides, the very same restrictions apply to Instrumentation.retransformClasses, the difference basically being that you do not start from scratch there but use existing class bytes as an input and can chain multiple transformers in order to incrementally instrument your existing class. But even with redefinition, the base line stays the original class, if it was loaded before.

As far as I know there are multiple things that can cause this

• Your Java POJO Mapping class may not have the empty/default constructor
• Any collections you have should have the default constructor or overridden hashcode and equals method. That is, the same rules apply for any joined collections/parent-children.

If you have your constructors right for POJO classes than check hibernate.properties file and try changing