I have decompiled a jar file. Can we run this file using eclipse or some other IDE. Or any way to do this. Thanks in Advance.
It depends on a number of things, such as:
whether the original JAR was runnable,
whether the decompiler produced compilable Java code,
whether the decompiler produced correct Java code, and
whether you have all of the dependencies for the decompiled code.
Note that decompilers tend to have difficulty with code that has been obfuscated, and code that uses the latest Java language features.
It depends on the decompiler used: some do produce compileable code, some don't. If your decompiler's output can be recompiled you could include it in an eclipse-project and run the main-class (if there is any).
Make sure to have all other dependencies of the jar-file in the build-path.
Yes you can If it contains main method in any of it's classes.
Yes you can run the decompiled jar file. Right click on the class which contains main method and select Run as Java application. If required, adjust the classpath (You cand do this in eclipse using java build path and debug settings)
Related
I have some basic java knowledge and i decided to switch from Intellij to VS Code. I know how to compile and run a java file (which may use other imported .java files) from the terminal, but i want to run a java program using the run icon inside vs code.
I'm not a 100% sure, but i think that in order to run a java program inside vs code you need a extension. For this reason i downloaded the Java extension pack. Note that i already have installed the latest jdk on my computer.
After i installed the plugin, i could run the program using the "run without debugging"/clicking in the run icon. However, no .class files are produced. I control+h but there isnt any hidden folder that vs code may drop the .class files.
How does the program run in the first place?
How can i config vs code in order to compile the java files before running the one that has the main function?
Basically, when you run a java file normally, you compile it with javac and then run it with java (or something along those lines, there are many different variations of possible ways to do it). If you go ahead and try, it is possible to run java filename.java and skip the normal javac step. In the case of VSCode, it will differ based on what extensions you have, but some may run the code with a simple java filename.java and others may have different settings set. If you take a look at your extension preferences as well as your preferences for java by searching your settings, there may be an option, such as "Java Source Paths" enabled which changed where compiled files are saved by VSCode.
If your project is a folder containing Java source files. And no build tools(Maven/Gradle) are used.
If that is the case, you can trigger the command Java: Configure Classpath, then find the section output and then set a relative path to your workspace.
The output files are by default stored inside the workspace storage.
If after triggering the command, what you see is the native vs code setting page. Then try to search java.project.outputPath and then set a relative path to it.
I've been provided some external JAR libraries for a project I'm doing. I can access the compiled code but I can't really understand it as its not in the form I'm used to seeing. Any tips on how to 'de-code' and understand what's going on?
Thanks
Search the net for Java Decompilers (e.g. JAD). What you see in a jar is Java-Classes, i.e. the result of compiling .java files.
There are decomiplers you can use them to de-compile .class to .java. We are using JD Java decompiler.
NOTE: I think De-compilation (or) modifying de-compiled code is illegal in some countries. Be aware of it.
You could use a decompiler like JAD to decompile from .class file to .java files, but in my experience its use is quite limited
Try Java Decompiler (Yet another Fast Java decompiler) : http://java.decompiler.free.fr/ .
It can decompile your compiled library.
JAD is only supported up to 1.3.
There should be a documentation and/or source jar that you can attach to your IDE, which will allow you to access the documentation.
If not, you have to decompile it.
Keep in mind that it might be ok to treat this jar as a black box.
I was wondering ... I want to use a plugin-type thing with my Java program.
Here is the situation:
I have compiled a source file (.java) into a .jar file using MY .JAR program as a library. How to I make MY program run the other .jar file internally (using the main program as a reference).
I know this is weird (it sounds weird to me too), but if anyone understands what I am trying to say, please comment.
Thank you all in advance!
OK, here's a draft of how to do it.
Create an interface with a "run()" method.
Your .java plugin must implement that interface.
Load the all classes in classpath (help here Find Java classes implementing an interface)
run your plugin by executing the run method of the interface.
You would have to run the jar using the standard syntax. Your question is basically about running console commands inside java. Here is a nice answer to a similar question:
link!
This isn't necessarily exactly what you want, but it's goal is to put you on the right track, basically you would get the jar placement, then check for the system, then use the technique used there to run a command through the specific platform's console.
Background
I am writing a program that will do some bulk renaming of members and functions in a directory of java source code to de-obfuscate the code based on a look-up table .csv file passed in to the program.
What this is for is the source code I have was written against a obfuscated jar. I have a de-obfuscated version of the jar that was run through a customized version RetroGaurd and I would like to parse the mapping file that was passed in to RetroGaurd to de-obfuscate the function calls my source code makes in to the jar. If I just compile my code and run it through RetroGaurd too when I decompile I loose all of my nice commenting and formatting (unless there is a option on RetroGaurd that I missed).
Problem
I found the Abstract Syntax Tree parser built in to Eclipse and it looks perfect for my uses, however I am not planning on writing my program as a plugin for Eclipse, this is going to be a stand alone jar that can be run on any machine.
My main concern is as I write my code I am getting a lot of dependencies on internal jars that Eclipse uses. I know that if I conform to the EPL for the library jars I will have no issues distributing it, but I am concerned about this project getting bigger and bigger as I write it as more and more jars from Eclipse's SDK are required.
Are there any other projects out there that would give me the ability to parse Java source code to do find and replace reliably like AST will allow me to, or is there a way to use RetroGaurd (or a program like it) to run the same de-obfuscation but keep my comments and functions the same without needing to run the de-obfuscated program though a de-compiler afterwards?
If you're worried about the need to run Eclipse GUI to execute your code, then you could consider running the plugin in headless mode. This would allow your plugin to be run from command line. See this SO thread.
You could also use any other open source java compiler. For e.g., openjdk's Java compiler. Please refer to the Resources section.
Hope it helps.
Surprisingly enough I couldn't find the answer to this question.
I am trying to rebuild the java JRE from source. I obtain the java JRE source by extracting the src.zip file in the JDK.
After making any changes I need to make to the JRE, how do I compile the new source back into .java files (after which I can compress it into the rt.jar file).
Thanks.
You have better chances using OpenJDK (the base of Oracle/ Sun's future JDKs).
http://openjdk.java.net/
But what do you want to change actually? Maybe there is a better way...
Some of the Java sources that make up
rt.jar are generated during the build
process, from scripts and other means.
Some of the properties files are also
generated this way, and some of the
properties files are turned into Java
source that also contributes to
rt.jar. So without doing a complete
build first and populating the
'gensrc' directory, you won't have all
the sources that make up rt.jar.
Taken from:
http://www.java.net/forum/topic/jdk/java-se-snapshots-project-feedback/it-possible-just-build-rtjar
So when you say javac on all the java files inside src.zip it won't compile as the dependency graph is broken (missing generated files)
Also have a look at this: Where to get full source code for rt.jar?
If you want to change a number of class, you only need to compile those classes. You don't need to compile the whole JDK unless you intend to replace it.
If you just want to patch it, create a JAR of your changed classes and add this to the boot class path.
After revisiting the question. Javac on any of those files will allow you to rebuild them. Also you don't compile .java files into .java files they become .class files. You can write an ANT build script to handle the heavy work for you.