I wrote a sample java agent that creates a "hello world" file in a specific place. I want it to run whenever any java applet is run (definitely including ones I didn't write myself.) How do I do that?
My agent works when I run it manually from the command line (as in, running another java file with the agent attached to it.) On the automatic front, I tried going into the java configuration panel -> Java -> View -> JRE Configuration Settings -> setting the optional arguments to attach my agent, but that doesn't seem to do the trick. I browse with FF to someplace that makes me run a java applet but no file is created.
I'm guessing I'm missing something basic here, because when I try to google this people all around various forums seem to answer it as if it's the most trivial thing: "just use -javaagent, read more about it in this (link)."
If it helps at all, this is the optional parameter I add in the configuration panel (which works when I use it manually):
-javaagent:C:\Users\admin\workspace\poc\bin\poc\myagent.jar
Update: I found out I can set an environment variable (JAVA_TOOL_OPTIONS) to -javaagent:(agentpath). Once again it works flawlessly with local java applications, but now when I browse over to a webpage with an applet, firefox auto-closes itself. IE declares the webpage broken. Chrome doesn't even display the applet. The agent itself at this point does nothing - it just has an empty premain method. Anyone?
Setting the environment variable JAVA_TOOLS_OPTIONS=-javagent:(path) is right.
My error was that I misconstructed the .jar file. Once I fixed that (simply used the jar.exe tool to make my .jar) it worked properly - locally and on all applets via firefox. Until then, that was what caused firefox to either hang or crash when encountering an applet.
Related
Hello!
The goal I have is pretty simple: I want to create an executable .jar file which should be able to bring up a form (made using swing) and write the put-in information into a well structurized plain text file. Due to portability/mobility reasons I will have to run this on an Android phone.
Since Android unfortunately doesn't have native Java support and I am unable to code a real Android application myself, I tried to use a Java emulator. Unfortunately, it appears that a working Java Emulator is hard to find to begin with. JBED instantly crashes on my Medion X701. Netmite's Website, which also seems to offer a .jar to .apk converter, appears to be down. JBlend seems to have installed properly, but I do not know how to work with the program now that it presents me nothing but an empty screen with the caption "0 Java ME Application(s)". On the web, I could not find a proper manual. PhoneME's official website was Java.net, which is no longer active. But during my research, I could find an older Version of PhoneME which seems to be running well.
As a test, I created a simple jar file that shows a maximized JFrame. Unfortunately, it isn't able to run my simple executable Jar file on my phone. The main reason for that should be the aforementioned error, which implies that the interpreter there is probably Java version 1.7, since PhoneME's last release was in 2015. There are more error messages referring to an "unknown source", which I believe originate from the first error. I tried to recompile my jar file using Eclipse, by setting the Compiler compliance level to 1.7 and choosing the jre 1.7 before exporting my project. Unfortunately, this didn't change the error messages I got on PhoneME!
As my last attempt, I created a Startup.class file which does the very same thing as my jar file.
import javax.swing.*;
public class Startup {
public static void main(String[] args) {
JFrame fishForm = new JFrame("Questionnaire");
fishForm.setExtendedState(JFrame.MAXIMIZED_BOTH);
fishForm.setVisible(true);
}
}
I compiled it using the command prompt in order to make sure that it is indeed using java 1.7 as the target. This .class file, which ran fine on my computer, leads me into a different error: "Main class name missing.", followed by multiple lines of usage explaination. The command line PhoneME presents doesn't seem to allow me to post command operations myself, as pressing Enter on the virtual keyboard does nothing.
My Questions
Is it even possible to run a Java application on Android which relies on the GUI libraries of Swing, or am I wasting my time?
Is there a different, up-to-date Java emulator for Android which I could use? Or is there a working jar2apk converter somewhere out there?
If not, then there's probably a reason why Java emulators ceased to exist. Is there a much simpler solution for my initial problem which I am missing?
I'll await your ideas eagerly!
Update: The problem was solved with the help of MathWorks. I've published the answer below.
I need to control a program (Zemax) from Matlab. Unfortunately, Zemax only supports DDE for such control, which Matlab does not support any more. It works, but stops working on 64 bit platform after a few (presumable 63) DDE calls.
I wonder if there are working solutions. I could probably program a DLL with correct DDE support and then use DDE in Matlab via this DLL. This is a major effort for me. A more suitable solution would be to use Java DDE methods. Following another post here, I've discovered the JDDE library. However I cannot make it work: Even if I am in the directory with the DLL and JAR files, executing
import pretty-tools.JDDE-2.0.3.*
works fine but calling
a = com.pretty_tools.dde.client.DDEClientConversation()
afterwards (as done here) results in
Undefined variable "com" or class "com.pretty_tools.dde.client.DDEClientConversation".
I have very limited writing privileges on my PC, so I have added the javaclasspath.txt file with the jar/dll location to the directory indicated by prefdir. The file looks like this:
C:\Users\xxxxxxxx\Documents\matlab toolbox\jdde\pretty-tools-JDDE-2.0.3.jar
Calling javaclasspath shows a long listing with the last lines being:
...
C:\Program Files\MATLAB\R2012b\java\jarext\webservices\ws_client_core\mw-service-client-core.jar
C:\Users\kkarapet\Documents\matlab toolbox\jdde\pretty-tools-JDDE-2.0.3.jar
DYNAMIC JAVA PATH
<empty>
So path seems to be set correctly. What am I doing wrong?
With the help of MathWorks support, I've found the answer. Here is how to make JDDE work with Matlab 2012b, without admin privileges:
Download and unpack JDDE files (DLLs and JAR) into some folder. Let's say it's $path-to-jdde$\.
In Matlab, type prefdir. Open the resulting directory and create two files there, javaclasspath.txt and javalibrarypath.txt.
In javaclasspath.txt, add $path-to-jdde$\pretty-tools-JDDE-2.0.3.jar.
In javalibrarypath.txt, add $path-to-jdde$\.
Restart Matlab.
Now call ddeConv = com.pretty_tools.dde.client.DDEClientConversation; and start using the created object as described in JavaDoc. E.g. to connect to Zemax, run Zemax and then in call ddeConv.connect('Zemax', 'abc').
Step 2 above can only be done starting Matlab version R2012b. With an older version, if you have the write rights on the Matlab installation directory, you should be able to replace step 2 by editing the files librarypath.txt and classpath.txt in $MATLABROOT$\toolbox\local. I could not verify it so if you confirm it please let me know in the comment below.
Sometimes I am doing simple fixes for rather huge Java application and I don't want to open Eclipse for this task. Eclipse starts long and since the project is build out of large number of subprojects, which are build anyway by Maven, it takes ages before Eclipse is usable (at least ages in impatient Java developer scale).
Almost everything I need can be done in Sublime Text editor, however one place where Eclipse shines is debugger. My workflow is: make a fix, then test it running application (on server) using debugger, to check if everything is ok.
So is there any Sublime plugin, or other non-IDE solution for easy debugging of Java application.
Note: I have seen this post - its pretty old, maybe there is something better.
You could look for a standalone Java Debugger like JDebugTool.
Or you could simply create an additional Eclipse workspace with only the bare minimal you need for remote debugging your application (just one project with all the source jars linked in).
This workspace will start considerably faster than the full blown.
I have never worked with a standalone debugger for Java and personally I tend to keep the number of tools I have to learn as low as possible and Eclipse's debugger is pretty good.
JDebug - A Java Debugging plugin for Sublime Text
Debugging is a painful art. The programmers(coders) know about it. Even perfectly written code may misbehave sometimes and it is difficult to identify the piece of code causing the issue just by log statements. So the only possible way to identify the issue is to do step by step debugging of the code dynamically. There are so many debugging tools available for Java, some are standalone and few are integrated within the IDE like Eclipse. In this article, I will show you how to debug java codes remotely using JDebug in Sublime Text.
Setting up Sublime Text JDebug plugin can be installed using Package Control or manually. I will show you how to install JDebug plugin using Package Control. If you haven’t install the Package Control, you can install packages by installing package control.
Once you have the package control installed, you should start Sublime Text. Open up the command palette from the Preferences --> Package Control menu and search for “Install Package”.
Now you can search for any package you like. In our case, we are going to search for the package “JDebug”.
Setting up App Server (Weblogic/Tomcat/any other) in debug mode
Pass -Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=8000 as JVM argument to server startup command. You can change the debug port from 8000 to anything you prefer.
Tomcat
Add/update the JAVA_OPTS env variable in catalina.bat or catalina.sh set JAVA_OPTS=%JAVA_OPTS% -Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=8000
Weblogic
Add/update the SAVE_JAVA_OPTIONS env variable in catalina.bat or catalina.sh set SAVE_JAVA_OPTIONS=%JAVA_OPTIONS% -Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=8000
Setting up JDebug Setting up JDebug is very simple as it has only few settings to start with. You can copy and paste the default settings into user settings and update the following settings based on your environment.
workingdir - You need to set your current project directory like c:/worksapce/TestService (Windows) or /home/user/abc/workspace/TestService (Linux or Ubuntu)
commandline - Set the jdb command with arguments. If JDK/bin is not in your environment PATH then you need to specify full path to the jdb command. Also change the hostname and port in which the java application service is running and listening.
sourcepath - The path to the source file with in the project. For ant project it usually /src/ and for maven usually /src/main/java.
Breakpoints Ready to set the breakpoint?. Breakpoints are the way to inform the jvm to halt the execution at a particular point (line number or method in a class). When the execution halts, the application variables can be inspected.
Add a breakpoint using 'Toggle Breakpoint' menu option from context menu. Context menu can be accessible using right click. A circle icon will be placed on the line number gutter when a breakpoint is added
When the jvm hits the breakpoint during the execution, the gutter icon will be changed to 'pointer' to indicate that the breakpoint is hit.
Inspect Variables
Variables & expressions can be inspected using inline popup. Click on the variable or highlight the expression to evaluate/inspect inline.
Watch Expressions Expressions can be evaluated using the 'Add Expression' context menu. You can enter any valid expression to evaluate.
Enter the Expression
JDebug Variables It is interesting to watch the variables in the 'JDebug Variables' window. If a variable is complex object it will be displayed with '+' icon on gutter. These variables can be expanded further to get the additional details using 'Expand' context menu. The 'Expand' context menu will be enabled only in 'JDebug' variables window.
How to Continue?
The application execution can be continued using one of the following menu options
Step Over Continue execution to next line
Step Into Continue the execution into a method call
Step Out Step out of the current method and continue
Continue Continue to next breakpoint or till completion
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I'm writing a Java Swing application for the Mac using Java 1.6. I've read a number of tutorials that step you through how to better integrate your Java application with OS X, but there's one thing I haven't been able to get working. I can't get the application name (the first, bolded menu item in the Mac menu bar) to display. By default, the fully-qualified class name of the main class is shown and I can't get it to change.
This site says that you have to set the following property:
System.setProperty("com.apple.mrj.application.apple.menu.about.name", "AppName");
But that doesn't work (I'm running 10.6, so maybe the property name changed?).
When I create a new Java project in XCode (I normally use Eclipse), the name somehow magically gets set! (it starts you out with a runnable, boiler-plate application) I've looked all around the XCode project for how this is done, but I can't figure it out!
My guess is that it only sets the application name if you wrap your Java application up in a Mac *.app package, but was wondering if anyone knew the answer. Thanks.
EDIT: Interestingly, it sets the application name if I package my application in a runnable JAR file, but not if I run it from Eclipse.
You should do the following during app initialization, before GUI is built:
// take the menu bar off the jframe
System.setProperty("apple.laf.useScreenMenuBar", "true");
// set the name of the application menu item
System.setProperty("com.apple.mrj.application.apple.menu.about.name", "AppName");
// set the look and feel
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
UPDATE.
Above code works in Java 1.5, this code may not work in 1.6
For new java see documentation:
Either use -Xdock:name command-line property: -Xdock:name=YourAppName
Or set CFBundleName in information property list file (plist)
On Mac 10.7.5, programatically setting the property will work with with Java 1.6 but not with Java 1.7.
I am working on a team project in Java. One requirement is that we dynamically populate a drop-down menu of all classes that implement a certain interface. New classes can be added after compile time. To accomplish this we are using reflection.
Problem: All of the drop-down menus are blank on my system. I cannot for the life of me figure out why they are not populating. All other 5 team members have it working on their system.
Things I tired that didn't work:
1) Installing most recent eclipse (galileo) because rest team was using it
2) Re-install most recent java release (jdk1.6.0-17 and jre6)
3) Check PATH and JAVA_HOME variables
Any thoughts as to what else I can try or if something I did should have solved it and didn't? It is driving me crazy.
Edit:
I should have been clearer that we are developing in a team. We are using SVN for version control and we are all running the exact same source code. I even tried checking out a fresh copy of the entire tree from SVN, but I had the same issue with reflection on my system while it worked for teammates.
The team created an executable jar and that ran on everyone's system fine except for mine. Everything worked for me except the reflection bit.
You need to debug your application. This means you have to systematically explore possible causes of the problem. Here are some things that come to mind:
Could your GUI be failing rather than reflection? What if you output with System.out.println() rather than your menu?
Is your reflection code throwing an exception, and are you ignoring it?
Is your reflection code actually being called? Toss a println() in there to be sure!
Is the test for the interface suffering from a typo or similar error that's causing it to fail? Try finding classes that implement Serializable instead!
Is your reflection test running in the main thread and trying to update your GUI? You need to use SwingUtilities.invokeAndWait to get an update to the Swing worker thread.
You're working with Eclipse; Eclipse has a fantastic debugger. Set a breakpoint near where your main action is and then single step through the code.
PATH and JAVA_HOME won't help. PATH only affects dynamically-linked libraries ("native code"). JAVA_HOME is a scripting variable that happens to be used by some Java-based utilities like Ant and Tomcat; it means nothing to the Java runtime itself.
You need to be investigating the classpath, which should be specified by the -classpath option to the java command, in the Build Path in your Eclipse project properties, or in the Class-Path attribute of the main section of a JAR file if you're launching java with the -jar option.
From within your code, you should be able to list the contents of your classpath by examining the system property, "java.class.path"
System.out.println(System.getProperty("java.class.path"));
Problem solution:
Classpath leading to source code must have no spaces in it.
I am running windows XP and, for whatever reason, if the classpath that leads to the jar file or source code that is using reflection has any spaces in it, then the reflection fails.
I took the jar file that works for the rest of my team and ran it from C:\ on my system and the reflection worked perfectly fine.
I do not know why this is so please comment if you know what is happening.
Might be a long shot, but look for differences in security settings for you and your team mates. Article describing more details http://www.ibm.com/developerworks/library/j-dyn0603/ heading "Security and reflection"