I hava an application which deployed on J2EE application server , inside the application there is implementation of class loader loading jar files into the JVM, inside those jar files there are Test Cases which implements common interface, by java reflection i dynamically invoke (by name) those test cases, the problem is that is like a black box and if test case fails i need to work hard to find what went worng throw the application server logger , is there any way to debug the test cases code? or any suggestion at all? thank you sorry for the long story..
You should be able to use Java's remote debugging facility. I've done something similar before and I would simply set a breakpoint in the test that failed. This page describes how to set up remote debugging in eclipse. How you enable debugging depends on the app server you're using.
You can connect to a remote Java EE app server with IntelliJ and step through the code line by line.
Related
I have an executable jar and I was trying to create a Windows Service using sc.exe. I used the below code for creating service:
sc create "TestService" binPath= "C:\Program Files\Java\jdk1.6.0_03\jre\bin\java.exe -jar C:\abc\MainClass.jar"
The service got created but when I was trying to start the service I got the below error:
Error 1053: The service did not respond to the start or control request in a timely fashion.
Later I tried to use Java Service Wrapper (Community Edition), the service starts for some time but is getting stopped everytime. The wrapper log tells something like:
Advice:
The Wrapper consists of a native component as well as a set of classes
which run within the JVM that it launches. The Java component of the
Wrapper must be initialized promptly after the JVM is launched or the
Wrapper will timeout, as just happened. Most likely the main class
specified in the Wrapper configuration file is not correctly initializing
the Wrapper classes:
com.MainClass
While it is possible to do so manually, the Wrapper ships with helper
classes to make this initialization processes automatic.
Please review the integration section of the Wrapper's documentation
for the various methods which can be employed to launch an application
within the Wrapper
Could anyone please tell me how can I run jar as a Windows Service without using external software as I can't use any third party app on Client's prod env.
If not what other configs I need to do in Java Service Wrapper to make the service start.
I tried to find some info related to this on stackoverflow but I did not get anything thing. If any one has anything on stackoverflow please feel free to put this in comment.
I have used this approach before in a productive environment, so I can assure you it is safe to use.
The Jar-File is wrapped in an exe and then it is added to the windows service scheduler (or however you want to call this). If you have a maven project this is also really easy to accomplish.
https://dzone.com/articles/installing-a-java-application-as-a-windows-service
Edit: you said you can’t use external software. With this approach everything that is needed is packed in the exe file. Including a JRE, I hope that that is allowed by your client’s policy.
I am currently helping a small hosting company. There is no experience existing in regards to writing Java code.
They now have the order of a customer to host a complicated product using Tomcat, which needs some prelimanary work to be done beforehands. In detail, some Java Proxy classes need to be created using NetBeans (and Eclipse).
I think this is subject to be done by the software manufacturer. However when starting to work with this topic following a documentation of the manufacturer I see that i.e. when creating a WSDL the connect to an internal server (inclusing user name/password) is necessary.
So I wonder how to have this work to be done by the manufacturer without having access to our webserver? I.e. creating a WAR-file?
Usually, the developers should create a deployable artifact that - if the Tomcat itself is configured correctly - simply needs to be deployed and will run out of the box. That is the war file! So basically there is no need to access the hosting company server itself, neither to write any code in Eclipse/NetBeans to get the application up and running. If the customers say so, they either have a really weird code base there, or they simply do not know what they are talking about.
My application code will run on one box. I have a tool that will be executed on a different box. Here I want to access my application code specific class method in the tool where it will executed on different box. How can I do this?
I don't want to change any existing code on the application side, I only want to add code on tool side to access the application class method. The class that I want to access is a regular java bean class.
We used to have a somehow similar issue.
We end up creating a simple library that allow us to distribute classes over several JVMs and to call methods in remote JVM.
You can have a look on https://github.com/plantuml/remotejvm to see if it can help you.
May be you need to have a look at Remote Method Invocation. Also take care of which version you are using, versions before Java 5.0 required the RMI stubs to be compiled separately.
Java RMI Tutorial
RMI online training
You would want to take a look at remote method invocation(RMI). It is not possible without adding code on the application side since you need to register the application with the RMI registry. The RMI registry is sort of a directory lookup to allow remote applications to access the application.
You could also use RMI-IIOP but it has the same constraints. You need to register the application with tnameserv
Link: https://docs.oracle.com/javase/8/docs/technotes/guides/rmi/index.html
We have a web application which sometimes (quite rarely, several times a day) gives an
error in production. It is deployed on Tomcat, uses Spring+Hibernate, the error is caused
by a Hibernate exception which is hard to understand without actually logging the
parameters passed to the method of the Hibernate class. It is not possible to replace
the Hibernate library with a modified version which logs the parameters, and spring-aop
cannot be used since the "beans" are not managed. I have seen an example of byte code
instrumentation using javassist, on http://today.java.net/pub/a/today/2008/04/24/add-logging-at-class-load-time-with-instrumentation.html, however trying to run it under
tomcat, the instrumented code does not seem to run, probably due to classloader problems
which I currently don't understand.
What I am asking then, is this: does anyone know of a more or less simple way to instrument
the byte code under tomcat for such a task as logging the parameters of methods in
external libraries? is there some further insight you may give on this problem?
Have a look at BTrace.
It will allow you to log calls to other classes/functions without slowing down the main application.
You could (temporarily) enable JDWP on the production Tomcat, attach a debugger, and place a breakpoint on the offending code. But I'd recommend avoiding doing that on the actual production machine -- better to clone the production environment to another machine that you can tinker with.
At work, I use a Java application (I have located compiled/executable jars on the C-drive). I want to be able to grab some information from this application through code. The application itself probably does not store information, so it must communicate with legacy systems some way, I am not sure how, I have seen traces of a Servlet(?) Hence, I suspect the application also has built-in "encryption"(?)
I do not want to get involved in encryption and login procedures etc., so I am thinking I could just build a Java project around the current executable jars, and launch the application as I usually do (through the "main" entry point, "Start.jar", but then after execution call the functions that I want to (i.e. the application just runs as usual in the background)...
Would that be possible? Is there another way? Can one, for example, hook up to an already executed Java application and issue commands?
What I have tried so far
Downloaded Eclipse, and created a new project
Made Eclipse "reference" external jars (there was a wizard in Eclipse)
Created a new class in my new project, in which I launch the "main" entry point of the "main" executable jar (the structure of all the jars pops up with "IntelliSense"). I have also found out which argument I need to supply to the main procedure using JD-GUI (Java Decompiler)...
It seems that from inside the main procedure a call is made to another procedure, which resides in a different jar, in the debug window of Eclipse I just see an error, which made me doubt that my current approach is viable... Maybe the problem arises because the command is issued from a compiled jar? Could there be an issue with the "class path"? Does this at all seem like a solution? But then again, I have no experience with Java (mostly VBA and some C#).
You can start your JVM for the application with options, which enable remote debugging. Then you can connect the eclipse debugger to this JVM.
http://www.eclipsezone.com/eclipse/forums/t53459.html
Based on your question, I am going to guess that your application does not have a Java API you can code against. That would, of course, be the easiest way. So, if you have not checked, do that first.
Assuming you don't have an API to code against, I think your approach is correct. But it could be hard to do, since you are basically flying blind trying to figure out what the application is doing. Remote debugging might solve part of that problem.
There might be a slightly easier solution, if you are sure it is sending requests across the network. You can use a tool like Wireshark to see what it is creating. Then, you can have your application create requests that look like that and send them to that destination. This assumes of course that the requests aren't encrypted. In that case you are probably out of luck.