I have some issues with debugging Java code. I have a Rascal module from where I am calling a linked Java method. This Java method contains a couple of System.err.println statements like suggested here: https://github.com/usethesource/rascal/wiki/Error-Reporting.
But where are they shown? When I execute the Rascal code from the Rascal debug console and call the linked Java method the messages are not shown. I even flush System.err directly after printing, but no luck. What am I doing wrong here?
Regards,
Nico
System.err is hard because Eclipse will hide it if you did not start Eclipse from a commandline console. So you should use evaluator.getStdErr() as suggested on https://github.com/usethesource/rascal/wiki/Error-Reporting.
First extend your Rascal function header to give access to the evaluator context:
#reflect{need access to stderr}
#javaClass{path.to.MyClass}
java int myFunction(int myParam);
Then change your interface in Java accordingly and retrieve a reference to the error stream:
public class MyClass {
public IValue myFunction(IInteger myParam, IEvaluatorContext ctx) {
ctx.getStdErr().println("Hello Rascal!");
}
}
Related
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Printing message on Console without using main() method
Can someone suggest how can a JAVA program run without writing a main method..
For eg:
System.out.println("Main not required to print this");
How can the above line be printed on console without using the public static void main(String arg[]) in the class.
Up to and including Java 6 it was possible to do this using the Static Initialization Block as was pointed out in the question Printing message on Console without using main() method. For instance using the following code:
public class Foo {
static {
System.out.println("Message");
System.exit(0);
}
}
The System.exit(0) lets the program exit before the JVM is looking for the main method, otherwise the following error will be thrown:
Exception in thread "main" java.lang.NoSuchMethodError: main
In Java 7, however, this does not work anymore, even though it compiles, the following error will appear when you try to execute it:
The program compiled successfully, but main class was not found.
Main class should contain method: public static void main (String[] args).
Here an alternative is to write your own launcher, this way you can define entry points as you want.
In the article JVM Launcher you will find the necessary information to get started:
This article explains how can we create a Java Virtual Machine
Launcher (like java.exe or javaw.exe). It explores how the Java
Virtual Machine launches a Java application. It gives you more ideas
on the JDK or JRE you are using. This launcher is very useful in
Cygwin (Linux emulator) with Java Native Interface. This article
assumes a basic understanding of JNI.
Up until JDK6, you could use a static initializer block to print the message. This way, as soon as your class is loaded the message will be printed. The trick then becomes using another program to load your class.
public class Hello {
static {
System.out.println("Hello, World!");
}
}
Of course, you can run the program as java Hello and you will see the message; however, the command will also fail with a message stating:
Exception in thread "main" java.lang.NoSuchMethodError: main
[Edit] as noted by others, you can avoid the NoSuchmethodError by simply calling System.exit(0) immediately after printing the message.
As of JDK6 onward, you no longer see the message from the static initializer block; details here.
public class X { static {
System.out.println("Main not required to print this");
System.exit(0);
}}
Run from the cmdline with java X.
Applets from what I remember do not need a main method, though I am not sure they are technically a program.
Hello I am trying to pass arguments to my ImageJ PlugIn. However it seems no matter what I pass, argument string will be considered as empty by the program. I couldn't find any documentation on the internet about THAT issue.
My Java plugIn looks like this, and compiles fine.
import ij.plugin.PlugIn;
public class Test implements PlugIn {
public void run(String args) {
IJ.log("Starting plugin Test");
IJ.log("args: ." + args + ".");
}
}
I compile, make a .jar file and put it into the ImageJ plugins folder.
I can call it with the ImageJ userInterface (Plugin>Segmentation>Test) and the macro recorder will put the command used:
run("Test");
Then my code is executed, the log window pops-up as expected:
Starting plugin Test
args: ..
I can manually run the same command in a .ijm file, and get the same result.
However, when I run the following macro command:
run("Test", "my_string");
I get the same results in the log window:
Starting plugin Test
args: .. // <- I would like to get "my_string" passed there
Where it should have displayed (at least what I expect it to do)
Starting plugin Test
args: .my_string.
So my question is: how can I pass parameters to PlugIn and especially how to access them?
Many thanks
EDIT
Hey I found a way to bypass that:
Using the Macro.getOptions() : this method will retrieve the string passed in argument to the plugin.
However, I still can't find a way to pass more than 1 string argument. I tried overloading the PlugIn.run() method but it doesn't work at all.
My quick fix is to put all my arguments in 1 string, and separating them by a space. Then I split this string:
String [] arguments = Macro.getOptions().split(" ");
I don't see a more convenient way to get around that. I can't believe how stupid this situation is.
Please, if you have a better solution, feel free to share! Thanks
You are confusing the run(String arg) method in ij.plugin.Plugin with the ImageJ macro command run("command"\[, "options"\]), which calls IJ.run(String command, String options).
In the documentation for ij.plugin.Plugin#run(String arg), it says:
This method is called when the plugin is loaded. 'arg', which may be blank, is the argument specified for this plugin in IJ_Props.txt.
So, arg is an optional argument that you can use in IJ_Props.txt or in the plugins.config file of your plugin to assign different menu commands to different functions of your plugin (see also the excellent documentation on the Fiji wiki).
To make use of the options parameter when running your plugin from macro code, you should use a GenericDialog to get the options, or (as you apparently learned the hard way) use the helper function Macro.getOptions().
I want to create a GUI app in java for signing j2me app which is done by JadTool.jar but it is a Command Line Interface Apps. So I just want to use it as library and pass the parameters in program. How it can be done?
Check out Runtime. It will allow you to execute a command. You can use this to start your command line interface library.
Edit:
Ah, I didn't read care carefully earlier. If you're using a Java library starting a separate process is not the best solution.
Just reference the JadTool jar from your project. If the functionality you need isn't accessible in the library, edit the source and recompile. Make sure JadTool's license allows this.
If you're against editing the source (or not allowed) try using reflection to invoke the private run method you need.
A jar is just a library of classes, the fact that it can be run from the command line is caused by the presence of a main method in a class. As jadtool's source is available it's easy to see its very simple main:
public static void main(String[] args) {
int exitStatus = -1;
try {
new JadTool().run(args);
exitStatus = 0;
} catch (Exception e) {
System.err.println("\n" + e.getMessage() + "\n");
}
System.exit(exitStatus);
}
Unfortunately, that run() method is private, so calling it directly from another class won't work, leading to a reduced set of options:
#WilliamMorrison 's solution of going via Runtime - not really a library call, but it would work.
see Any way to Invoke a private method?
I'm working on java application which perform some Runtime sub-process on files, for some files I got error cause the Send error report to Microsoft window to appear ,I need to handle this error programmatically, without showing this window to user. Please can anyone help ?
To Suppress windows error reporting the .exe that is being invoked should not terminate with an unhandled exception. This only works if you have access to the source of the application.
Based on the WER Reference - you should use the Win32 API call WerAddExcludedApplication to add the specific .exe files that you are intending to ignore to the per-user ignore list - you could create a simple stub-application that allows you to add applications by name to the ignore list. Then when you invoke the application it does not trigger the error.
Similarly you could create another application to remove them using the WerRemoveExcludedApplication.
Alternatives are to use JNI/JNA to make a class to encapsulate this functionality rather than using Runtime.exec
Here is a simple example using Java Native Access (JNA), which is a simpler version of JNI (no C++ needed for the most part). Download the jna.jar and make it part of your project.
import com.sun.jna.Native;
import com.sun.jna.WString;
import com.sun.jna.win32.StdCallLibrary;
public class JNATest {
public interface CLibrary extends StdCallLibrary {
CLibrary INSTANCE = (CLibrary) Native.loadLibrary("wer.dll",
CLibrary.class);
int WerAddExcludedApplication(WString name, boolean global);
int WerRemoveExcludedApplication(WString name, boolean global);
}
public static void main(String[] args) {
CLibrary.INSTANCE.WerAddExcludedApplication(new WString("C:\\foo.exe"), false);
CLibrary.INSTANCE.WerRemoveExcludedApplication(new WString("C:\\foo.exe"), false);
}
}
Basically, replace the new WString(...) value with the name of the application that you are intending to ignore. It should be ignored for the purposes of windows error reporting at that point.
Bear in mind that the wer.dll is only on Windows Vista and newer, so if this is a problem, then you may need to edit the registry entries manually.
You can always use try-catch-finally statement:
try
{
some code here (the code that is causing the error);
}
catch (Exception x)
{
handle exception here;
}
It works for me...
EDIT Here is the link that can help you a little bit more:
http://www.exampledepot.com/egs/Java%20Language/TryCatch.html
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Printing message on Console without using main() method
Can someone suggest how can a JAVA program run without writing a main method..
For eg:
System.out.println("Main not required to print this");
How can the above line be printed on console without using the public static void main(String arg[]) in the class.
Up to and including Java 6 it was possible to do this using the Static Initialization Block as was pointed out in the question Printing message on Console without using main() method. For instance using the following code:
public class Foo {
static {
System.out.println("Message");
System.exit(0);
}
}
The System.exit(0) lets the program exit before the JVM is looking for the main method, otherwise the following error will be thrown:
Exception in thread "main" java.lang.NoSuchMethodError: main
In Java 7, however, this does not work anymore, even though it compiles, the following error will appear when you try to execute it:
The program compiled successfully, but main class was not found.
Main class should contain method: public static void main (String[] args).
Here an alternative is to write your own launcher, this way you can define entry points as you want.
In the article JVM Launcher you will find the necessary information to get started:
This article explains how can we create a Java Virtual Machine
Launcher (like java.exe or javaw.exe). It explores how the Java
Virtual Machine launches a Java application. It gives you more ideas
on the JDK or JRE you are using. This launcher is very useful in
Cygwin (Linux emulator) with Java Native Interface. This article
assumes a basic understanding of JNI.
Up until JDK6, you could use a static initializer block to print the message. This way, as soon as your class is loaded the message will be printed. The trick then becomes using another program to load your class.
public class Hello {
static {
System.out.println("Hello, World!");
}
}
Of course, you can run the program as java Hello and you will see the message; however, the command will also fail with a message stating:
Exception in thread "main" java.lang.NoSuchMethodError: main
[Edit] as noted by others, you can avoid the NoSuchmethodError by simply calling System.exit(0) immediately after printing the message.
As of JDK6 onward, you no longer see the message from the static initializer block; details here.
public class X { static {
System.out.println("Main not required to print this");
System.exit(0);
}}
Run from the cmdline with java X.
Applets from what I remember do not need a main method, though I am not sure they are technically a program.