Questions tagged [byte-buddy]

Byte Buddy is a code generation and manipulation library for creating and modifying Java classes during the runtime of a Java application and without the help of a compiler. Byte Buddy allows the creation of arbitrary classes and is not limited to implementing interfaces for the creation of runtime proxies. Furthermore, Byte Buddy offers a convenient API for changing classes either manually, using a Java agent or during a build.

Byte Buddy is a code generation and manipulation library for creating and modifiying Java classes during the runtime of a Java application and without the help of a compiler. Other than the code generation utilities that ship with the Java Class Library, Byte Buddy allows the creation of arbitrary classes and is not limited to implementing interfaces for the creation of runtime proxies. Furthermore, Byte Buddy offers a convenient API for changing classes either manually, using a Java agent or during a build.

In order to use Byte Buddy, one does not require an understanding of Java byte code or the class file format. In contrast, Byte Buddy's API aims for code that is concise and easy to understand for everybody. Nevertheless, Byte Buddy remains fully customizable down to the possibility of defining custom byte code. Furthermore, the API was designed to be as non-intrusive as possible and as a result, Byte Buddy does not leave any trace in the classes that were created by it. For this reason, the generated classes can exist without requiring Byte Buddy on the class path. Because of this feature, Byte Buddy's mascot was chosen to be a ghost.

Byte Buddy is written in Java 6 but supports the generation of classes for any Java version. Byte Buddy is a light-weight library and only depends on the visitor API of the Java byte code parser library ASM which does itself not require any further dependencies.

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Bytebuddy: method interception doesn't work in Kotlin

Consider the following bytebuddy program to intercept method call load(): public class ByteJavaBuddyTest { public static class MemoryDatabase { public List load(String info) { return Arrays.asList(info + ": foo", info…
Kshitiz Sharma
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How to define a new method and intercept and delegate a call to that method?

I am solving a problem for a school work. let us say I have a class as follows class test { public String foo(int i) { printvalue(i); return "foo"; } public void printvalue(int i) { System.out.println(i); } } class Solution { public static void…
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How to attach bytebuddy agent to the dynamic class, especially, when dynamic class are loaded from signed jar file

I tried attach bytebuddy agent to the old applet. In some runtime stage, that old applet receives a signed jar file from the other host and load them dynamically. The problem is that the agent doesn't work in that dynamic loading stage. I think …
boun
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How to attach bytebuddy agent when target application load classes from uRLConnection.getInputStream

I made a java agent with bytebuddy. It works well untill target application load classes form uRLConnection.getInputStream. The target app works well without attachment the agent, but shows exception [java.lang.ClassNotFoundException] when the agent…
boun
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How to create dynamic proxy of class with no public constructor using ByteBuddy

I want to create a dynamic proxy of class Sample which has two no public constructor, it's not working and giving the error. But if I make the constructor as Public then it works fine. Is it possible in byte buddy to achieve that? Also is it…
Hemant Singh
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Instrument Java system class with byteBuddy

I am new to bytebuddy. I tried to follow the link here to instrument a java system class, java.lang.String without success. Below is the code, AgentBuilder agentBuilder = new AgentBuilder.Default() …
Sams2018
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instrumentation of Java System class

I am new to instrumentation. I need to add a static variable and maybe a static method later on in one of bootstrap classes, java.lang.String. I tried both Javassist and ASM but both report error, > Exception in thread "main"…
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How to generate bytecode of existing class at Runtime in Java?

How to generate bytecode of existing class at Runtime in Java? My Existing class is say Foo.java public class Foo { public String saySomething() { return "Hello World"; } } Now I want to generate byte code of this existing class…
user1870400
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ByteBuddy implement method using other fields

My use case is to implement a method that combines some fields with a string concatenation. Basically the equivalent of: String doAThing(){ return this.a + " " + this.b; } in the examples i can only find static values (for example the Stack…
Shaharko
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ByteBuddy javaAgent has conflict with javassist agent

I am using two javaagents (one is based on Byte Buddy and the other is based on Javassist) to enhance one method. If the Javassist agent load first, both agents will work. If the Byte Buddy agent loads first, the Byte Buddy agent can not work (the…
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Redefining JDK Bootstrap classes

Is it possible to redefine Bootstrap classes using Java agent during runtime? To be more specific, I want to redefine some classes in java.io package during runtime after they have been loaded.
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How to subclass an abstract class with 1+ args constructor using ByteBuddy

I would like to proxy java.net.HttpURLConnection which has one constructor: HttpURLConnection(URL u). How can I subclass such a class with ByteBuddy without creating custom "Empty" class with the non-arg constructor? new…
Peter Jurkovic
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Use of ByteBuddy's MemberSubstitution class

I am using ByteBuddy to substitute a field reference by another one into methods of a class. In another question I was suggested to use the class net.bytebuddy.asm.MemberSubstitution. I have been looking for examples about how to use this in mi java…
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MethodHandler in Hibernate using ByteBuddy proxies gets stuck in endless loop

I'm currently migrating an old tool for Hibernate to automate prefetching based on entity statistics. The old tool used Hibernate 3.1, so there's some job to be done. Traditionally, Hibernate used CGlib proxies, but as I'm developing for the latest…
Jssson
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"duplicate class" error in a Bytebuddy agent applying Advice

I've got some ByteBuddy-based instrumentation that I want to provide both for embedded use and as an agent. The code goes something like this: public static void premain(String arguments, Instrumentation instrumentation) { installedInPremain =…
ddimitrov
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