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In the startup scripts generated by gradle's application plugin, how can I have the program name passed in to the application?

Executing the gradle application plugin's installDist task creates a directory build/install/my-application-name/bin that contains wrapper scripts, my-application-name and my-application-name.bat. Running either of these scripts runs the application, and arguments passed to these scripts are passed to the underlying application.
In UNIX shell scripts you can access the name that was used to execute the program as $0. In fact, the UNIX version of the gradle-generated startup script uses $0 several times.
How can I configure the gradle application plugin such that these scripts will pass the value of $0 (and whatever the Windows equivalent is on Windows) into the underlying application, perhaps as a Java system property?

Since parameter for obtaining the name of the script being run is referenced differently in Linux($0) and in Windows(%0), the most straightforward way to generate custom scripts would be to use separate custom templates for the respective start script generators:
startScripts {
unixStartScriptGenerator.template = resources.text.fromFile('unixStartScript.txt')
windowsStartScriptGenerator.template = resources.text.fromFile('windowsStartScript.txt')
}
The default templates are easy to obtain invoking e.g. unixStartScriptGenerator.template.asString()
Documentation on customizing the start scripts can be found here.

This is what I ended up doing, based on jihor's answer. I'm posting it here just so that there's a working answer for anyone else interested:
startScripts {
def gen = unixStartScriptGenerator
gen.template = resources.text.fromString(
gen.template.asString().replaceFirst('(?=\nDEFAULT_JVM_OPTS=.*?\n)') {
'\nJAVA_OPTS="\\$JAVA_OPTS "\'"-Dprogname=\\$0"\''
})
// TODO: do something similar for windowsStartScriptGenerator
}
This uses replaceFirst is instead of replace so we can match a pattern. This is a little less brittle, and also lets us use lookahead so we don't have to actually replace what we're looking for. (This is groovy's variant of replaceFirst that takes a closure, by the way. This requires far less escaping than the version that takes a replacement string in this case.)
Also, instead of:
JAVA_OPTS="$JAVA_OPTS -Dprogname=$0"
we actually need something like:
JAVA_OPTS="$JAVA_OPTS "'"-Dprogname=$0"'
This is because $0 may contains special character (like spaces), and the startup script removes one level of quoting in the value of $JAVA_OPTS using eval set --.
(If anyone knows how to make this work on Windows, pleas feel free to update this answer.)

I took an alternative approach. According to the documentation, as far back as Gradle 2.4 and all the way through Gradle 4.8, we should be able to set the following properties within the startScripts task:
applicationName
optsEnvironmentVar
exitEnvironmentVar
mainClassName
executableDir
defaultJvmOpts
appNameSystemProperty
appHomeRelativePath
classpath
Unfortunately, this is not true for the following properties, which seem to have never been exposed:
appNameSystemProperty
appHomeRelativePath
If appNameSystemProperty were exposed as the documentation describes, then we should be able to simply do the following:
startScripts {
applicationName = 'foo'
appNameSystemProperty = 'appName'
}
This would then result in the addition of -DappName=foo to the Java command constructed within both of the start scripts.
Since this is not the case, I took the following approach, which is a bit more verbose than the earlier solution to this question, but is perhaps less brittle because it does not rely on tweaking the out-of-box templates. Instead, it results in the documented behavior.
startScripts {
mainClassName = '...'
applicationName = 'foo'
unixStartScriptGenerator =
new CustomStartScriptGenerator(generator: unixStartScriptGenerator)
windowsStartScriptGenerator =
new CustomStartScriptGenerator(generator: windowsStartScriptGenerator)
}
class CustomStartScriptGenerator implements ScriptGenerator {
#Delegate
ScriptGenerator generator
void generateScript(JavaAppStartScriptGenerationDetails details,
Writer destination) {
details = new CustomDetails(details: details)
this.generator.generateScript(details, destination)
}
static class CustomDetails implements JavaAppStartScriptGenerationDetails {
#Delegate
JavaAppStartScriptGenerationDetails details
#Override
String getAppNameSystemProperty() { 'appName' }
}
}

Py4j launch_gateway not connecting properly

I am trying to use py4j to open up a gateway that I can use to pass objects from java into python. When I try to open a gateway with the py4j function launch_gateway it does not seem to properly connect to my Java class. However, when I launch my java class in the command line and then connect to it in python using JavaGateway everything works as expected. I would like to be able to use the built in method as I am sure that I am not accounting for things that have already been considered in the design of py4j, but I'm just not sure what I'm doing wrong.
Let's say I wanted to create a gateway to the class sandbox.demo.solver.UtilityReporterEntryPoint.class. In the command line I can do this by executing the following:
java -cp /Users/grr/anaconda/share/py4j/py4j0.10.4.jar: sandbox.demo.solver.UtilityReporterEntryPoint py4j.GatewayServer
This launches as expected and I can use the methods in my class from within python after connecting to the gateway. So far so good.
My understanding of the py4j documentation would lead me to believe I should do the following to launch the gateway in python:
port = launch_gateway(classpath='sandbox.demo.solver.UtilityReporterEntryPoint')
params = GatewayParameters(port=port)
gateway= JavaGateway(gateway_parameters=params)
I get no errors when executing these three lines, but when I try to access my java class methods with gateway.entry_point.someMethod() it fails with the following error:
Py4JError: An error occurred while calling t.getReport. Trace:
py4j.Py4JException: Target Object ID does not exist for this gateway :t
at py4j.Gateway.invoke(Gateway.java:277)
at py4j.commands.AbstractCommand.invokeMethod(AbstractCommand.java:132)
at py4j.commands.CallCommand.execute(CallCommand.java:79)
at py4j.GatewayConnection.run(GatewayConnection.java:214)
at java.lang.Thread.run(Thread.java:745)
Obviously something is not getting called correctly within launch_gateway or I am feeding it the wrong information.
In the py4j source code for launch_gateway you can see that given the inputs you provide and those constructed by the function, a command is constructed that eventually gets called by subprocess.Popen. So given the input passed to launch_gateway above the command passed into Popen would be:
command = ['java', '-classpath', '/Users/grr/anaconda/share/py4j/py4j0.10.4.jar:sandbox.demo.solver.UtilityReporterEntryPoint', 'py4j.GatewayServer', '0']
Passing this command to Popen returns the listening port as expected. However, connecting to this listening port still does not allow access to my class methods.
Finally, passing the command as a single string to Popen without the final argument ('0'), properly launches a gateway which again operates as expected. Having taken a glance at the Java source code for py4j.GatewayServer.class this makes no sense as the main method seems to indicate that the class should exit with status 1 if the length of arguments is 0.
At this point I'm kind of at a loss. I can hack my way into a workable solution, but as I said I'm sure that ignores important aspects of the gateway behavior and I don't like hacky solutions. I'd love to tag #Barthelemy in this one, but hopefully he reads this. Thanks in advance for any help.
EDIT
For now I have been able to work around this issue with the following steps.
Package entire project including all external dependencies into a single jar file magABM-all.jar, with 'Main-Class' set to UtilityReporterEntryPoint.
Include if...else block regarding presence of --die-on-exit exactly like it is in GatewayServer.java
Use subprocess.Popen to call the command to run the project jar.
UtilityReporterEntryPoint.java
public static void main(String[] args) throws IOException {
GatewayServer server = new GatewayServer(new UtilityReporterEntryPoint());
System.out.println("Gateway Server Started");
server.start();
if (args[0].equals("--die-on-exit")) {
try {
BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in, Charset.forName("UTF-8")));
stdin.readLine();
System.exit(0);
} catch (java.io.IOException e) {
System.exit(1);
}
}
}
app.py
def setup_gateway()
"""Launch a py4j gateway using UtilityReporterEntryPoint."""
process = subprocess.Popen('java -jar magABM-all.jar --die-on-exit', shell=True)
time.sleep(0.5)
gateway = JavaGateway()
return gateway
In this way I can still use gateway.shutdown if necessary and if the python process that starts the py4j gateway dies or is closed the gateway will be closed.
N.B I would by no means consider this a final solution as py4j was written by much smarter individuals with a clear purpose in mind and I am sure that there is a way to manage this exact workflow within the confines of py4j. This is just a stopgap solution.

There are a few issues:
The classpath parameter in launch_gateway should be a directory or a jar file, not a class name. For example, if you want to include additional Java libraries, you would add them to the classpath parameter.
The error you receive when you call gateway.entry_point.someMethod() means that you have no entry point. When you call launch_gateway, the JVM is started with GatewayServer.main, which launches a GatewayServer with no entry point: GatewayServer server = new GatewayServer(null, port). It is not possible currently to use launch_gateway and specify an entry point.
When you start the JVM with java -cp /Users/grr/anaconda/share/py4j/py4j0.10.4.jar: sandbox.demo.solver.UtilityReporterEntryPoint py4j.GatewayServer I believe the JVM uses UtilityReporterEntryPoint as the main class. Although you did not provide the code, I assume that this class has a main method and that it launches a GatewayServer with an instance of UtilityReporterEntryPoint as the entry point. Note that there is a whitespace between the colon and the class name so UtilityReporterEntryPoint is seen as the main class and not as being part of the classpath.

Run python script using Pyrolite from java

I have a simple python script in my local machine, which returns a string. I want to run this script from java application and get the return value. I'm trying to do this using Pyrolite. I downloaded the jar files and added them to my java class path. But I'm not able to run the script.
I got the below sample code from readme.txt
NameServerProxy ns = NameServerProxy.locateNS(null);
PyroProxy remoteobject = new PyroProxy(ns.lookup("Your.Pyro.Object"));
Object result = remoteobject.call("pythonmethod", 42, "hello", new int[]{1,2,3});
String message = (String)result; // cast to the type that 'pythonmethod' returns
System.out.println("result message="+message);
remoteobject.close();
ns.close();
But this is not working for me. My system configuration is
OS: Windows 8
JDK: jdk1.7.0_51
Python: 2.6
Please help me with this.
This is how I have edited the code:
NameServerProxy ns = NameServerProxy.locateNS(null);
PyroProxy remoteobject = new PyroProxy();
Object result = remoteobject.call("C:\\trail1.py", null);
String message = (String)result; // cast to the type that 'pythonmethod' returns
System.out.println("result message="+message);
remoteobject.close();
ns.close();

I'm not positive that I understand what you're trying to do.
If you carefully read the tutorial, you'll see that you can't use Pyrolite the way you are. It specifies that you must have a python script running as a server, WITH a name server, where you must define some classes (for example Your.Pyro.Object).
Then you'll be able to call those objects you defined in that python script, but not the script itself.
To do what you want to do you'll need to call a function like C's fork(). Then you're able to call an executable, and you don't need Pyrolite.

Environment variable problem using java

Steps using runtime api
echo %PATH% (output will be something like "c:\windows\system32;d:\test")
execute ping or any system command, the output will be success
delete one value for the path like d:\test
echo %PATH% (output will be "%system32%\system32;")
Now if I execute the same command executed in step 2 like ping, then I get "command not found."
Plesae note:- all steps executed in same java process
Anybody suggest whats going wrong in this process

Looks like variables are not being expanded the second time you show the PATH (step 4). Probably you are corrupting the path when you delete one value in step 3.
Show us a code snippet demonstrating the problem.

Are you using ProcessBuilder for this? That allows simple access to the environment variables passed to sub-processes. It sounds like you are trying to modify the global environment, which is likely not what you want to do.
Here's an example:
ProcessBuilder pb = new ProcessBuilder();
Map<String, String> env = pb.environment();
System.out.println("Current environment: " + env.toString());
String path = env.get("PATH");
path = path.substring(0, path.indexOf("d:\\test")) + path.substring(path.indexOf("d:\\test") + "d:\\test".length());
env.put("PATH", path);
pb.command("ping");
Process p = pb.start();
// ...
Because it sounds like you are on Windows, you'll need to be a bit more careful about finding the path variable in the environment, since the Windows environment is case-insensitive, but Map.get() is case-sensitive. Probably best to loop through the keys looking for a equalsIgnoreCase("PATH").
Also, you may want to clean up the path before putting it back into the map (make sure it doesn't contain extra System.getProperty("path.separator")s.

Your question is not clear to me but i do see some problem :
%System32% is usually c:\windows\system32.
In your example,assuming the environment is set of %system32% correctly, the step(4) "%system32%\system32;" will resolve to c:\windows\system32\system32
Which may not what you want.

How to detect that code is running inside eclipse IDE

How to detect that code is running inside eclipse IDE

I am not aware of a generic way to get this kind of information.
One suggestion:
When you start a Java program (or a web server) inside Tomcat, simply add an argument that will indicate that this program is launched by Eclipse.
You can do that by opening the "Open Run Dialog" ("Run" menu), then select your type of application and add in the "Arguments" tab a -DrunInEclipse=true.
In your Java code, you can check the value of the property:
String inEclipseStr = System.getProperty("runInEclipse");
boolean inEclipse = "true".equalsIgnoreCase(inEclipseStr);
This way, if the program is not running inside Eclipse (or unfortunately if you forgot to set the property) the property will be null and then the boolean inEclipse will be equal to false.

Although I agree that having the code detecting a single IDE as the dev env is not an optimal solution, the following code works.
Like others proposed, using a flag at runtime is better.
public static boolean isEclipse() {
boolean isEclipse = System.getProperty("java.class.path").toLowerCase().contains("eclipse");
return isEclipse;
}

1) Create a helper method like:
public boolean isDevelopmentEnvironment() {
boolean isEclipse = true;
if (System.getenv("eclipse42") == null) {
isEclipse = false;
}
return isEclipse;
}
2) Add an environment variable to your launch configuration:
3) Usage example:
if (isDevelopmentEnvironment()) {
// Do bla_yada_bla because the IDE launched this app
}

Actually the code is not being run inside Eclipse, but in a separate Java process started by Eclipse, and there is per default nothing being done by Eclipse to make it any different than any other invocation of your program.
Is the thing you want to know, if your program is being run under a debugger? If so, you cannot say for certain. You CAN, however, inspect the arguments used to invoke your program and see if there is anything in there you do not like.

If your workspace matches some pattern like "/home/user/workspace/Project" you can use the code below:
Boolean desenv = null;
boolean isDevelopment() {
if (desenv != null) return desenv;
try {
desenv = new File(".").getCanonicalPath().contains("workspace");
}
catch (IOException e) {
e.printStackTrace();
}
return desenv;
}

A more generic and precise way, that can be used on any IDE would be loop at:
ManagementFactory.getRuntimeMXBean().getInputArguments()
looking for "-Xdebug" || (starting with) "-agentlib:jdwp=".
I came with this from #saugata comment here.
This is excellent if you want to throw a conditional exception preventing the application from simply exiting. Use a boolean like "ideWait" and add it to Eclipse watch expressions as ideWait=false, so whenever you stop at that throw, and "drop to frame" you can continue debugging happily (I mean it!)

I don't think there is any way to do this. But what I would suggest is just a command line argument such as 'debug'. Then in your main method just do
if (args.length > 0 && args[0].equalsIgnoreCase("debug")) {
// do whatever extra work you require here or set a flag for the rest of the code
}
This way you can also get your extra code to run whenever you want just by specifiying the debug parameter but under normal conditions it will never execute.

This might work if your alternative execution work flow provides a different set of dependencies:
boolean isRunningInEclipe = false;
try {
Workbench.getInstance();
isRunningInEclipe = true;
} catch (NoClassDefFoundError error) {
//not running in Eclipse that would provide the Workbench class
}

You could detect if you're inside a JAR or not, as per Can you tell on runtime if you're running java from within a jar?
Eclipse will run your app from the classes/ dir, whereas most of your end users will be running the app from a JAR.

System.out.println("Is my parent eclipse[.exe]? " +
ProcessHandle.current()
.parent()
.flatMap(parent -> parent.info().command())
.orElse("")
.matches("^.*eclipse(\\.exe)?$"));

You may try something like this:
if (ClassLoader.getSystemResource("org/eclipse/jdt/core/BindingKey.class")!=null){
System.out.println("Running within Eclipse!!!");
} else {
System.out.println("Running outside Eclipse!!!");
}