Develop Reference

How does a native calling application get a return value from JNLP?

I am launching a JNLP java application from a native client app (i.e. not a browser). When the JNLP finishes it's task, I need it to return a string to the calling app? How can I do this? Is it possible to return a value to a calling app - or do I need to have the calling app listen on a port and have the JNLP app write the value to that port through sockets?

Answering my own question!
I write to stdout from the child process (the JNLP)
The parent launches the child process
Process::Start
Read stdout from Parent
string ret = process.StandardOutput.ReadToEnd();
Process::WaitForExit();
Anyone sees any problem in this?

I like your idea to use sockets and think this is could be an easy solution.
It is not possible to get return values from a WebStart-application. Just see the help message from
javaws --help
There is no return-code available. (Sorry)
Have you thougth on a temporary file instead of the sockets?

It's a bit old but as fas as i know this is the exiting options to intercommunicate two process link.
I think the easiest way to solve your problem is use rmi, or jmx if you can, or just a simple socket

If the all-permissions element is specified, you could try to set an environment variable which you can read from your C# application.
Set environment variable in Java:
System.getenv().put("returnValue", "yourValue");
Read environment variable in C#:
ProcessStartInfo p = new ProcessStartInfo("start ....");
....
string returnValue = p.EnvironmentVariables["returnValue"];

ProgramCallDocument connecting to AS400 from Groovy Hangs

This question is specifically related to the JT400 class ProgramCallDocument, with it's method callProgram(String ProgramName)
I've tried wapping the call in a try/catch - but it's not throwing an exception, the debugger goes into the callProgram method, and just sits there indefinitely.
A small amount of specific information about the API is available here:
http://publib.boulder.ibm.com/infocenter/iadthelp/v7r0/index.jsp?topic=/com.ibm.etools.iseries.toolbox.doc/rzahhxpcmlusing.htm
Here's the code that I'm running:
AS400 as400System = AS400Factory.getAS400System()
ProgramCallDocument programCallDocument = new ProgramCallDocument(as400System, "com.sample.xpcml.Sample.xpcml")
programCallDocument.setStringValue("sampleProgramName.value", sampleValue)
Boolean didProgramCallDocumentRunSuccessfullyOnTheAS400 = programCallDocument.callProgram("sampleProgramName")
The last line of that snippet is the one that just sits there. I left out the try/catch for brevity.
The XPCML file that the ProgramCallDocument constructor uses is just a proprietary XML format that IBM uses for specifying the parameter lengths and types for a program call. I can come back and add it in if it would be helpful, but the ProgramCallDocument constructor runs validation on the XML, and it didn't come up with any validation errors. I'm not familiar with JT400, or how it does Program Calls, so any assistance would be wonderful.
As a further note, doing some more digging on a related issue today I also found this SO post:
Monitor and handle MSGW messages on a job on an IBM i-series (AS/400) from Java
I think it's relevant to this question, because it's about ways to trap MSGW status on the Java/Groovy side.

It's very likely the called program went into a MSGW status (error).
Check WRKACTJOB JOB(QZRCSRVS) to find the program call job and see the status as well as review the job log.
It may be easier to call a native program using the CommandCall class or as a JDBC stored procedure.
Here's an example of the CommandCall usage in Groovy:
sys = AS400Factory.AS400System
cmd = new CommandCall(sys)
if (!cmd.run "CALL MYLIB.MYPGM PARM('${sampleValue}')") {
println cmd.messageList
}

Spring, NotReadablePropertyException and Glassfish version

I am working on a web-application that uses Spring MVC.
It has been working fine on Glassfish 3.0.1, but when migrating to Glassfish 3.1, it started acting strange. Some pages are only partially showing, or showing nothing at all, and in the log, a lot of messages of this type:
[#|2012-08-30T11:50:17.582+0200|WARNING|glassfish3.1|javax.enterprise.system.container.web.com.sun.enterprise.web|_ThreadID=69;_ThreadName=Thread-1;|StandardWrapperValve[SpringServlet]: PWC1406: Servlet.service() for servlet SpringServlet threw exception
org.springframework.beans.NotReadablePropertyException: Invalid property 'something' of bean class [com.something.Something]: Bean property 'something' is not readable or has an invalid getter method: Does the return type of the getter match the parameter type of the setter?
at org.springframework.beans.BeanWrapperImpl.getPropertyValue(BeanWrapperImpl.java:729)
at org.springframework.beans.BeanWrapperImpl.getNestedBeanWrapper(BeanWrapperImpl.java:576)
at org.springframework.beans.BeanWrapperImpl.getBeanWrapperForPropertyPath(BeanWrapperImpl.java:553)
at org.springframework.beans.BeanWrapperImpl.getPropertyValue(BeanWrapperImpl.java:719)
at org.springframework.validation.AbstractPropertyBindingResult.getActualFieldValue(AbstractPropertyBindingResult.java:99)
at org.springframework.validation.AbstractBindingResult.getFieldValue(AbstractBindingResult.java:226)
at org.springframework.web.servlet.support.BindStatus.<init>(BindStatus.java:120)
at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getBindStatus(AbstractDataBoundFormElementTag.java:178)
at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getPropertyPath(AbstractDataBoundFormElementTag.java:198)
at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getName(AbstractDataBoundFormElementTag.java:164)
at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.writeDefaultAttributes(AbstractDataBoundFormElementTag.java:127)
at org.springframework.web.servlet.tags.form.AbstractHtmlElementTag.writeDefaultAttributes(AbstractHtmlElementTag.java:421)
at org.springframework.web.servlet.tags.form.TextareaTag.writeTagContent(TextareaTag.java:95)
at org.springframework.web.servlet.tags.form.AbstractFormTag.doStartTagInternal(AbstractFormTag.java:102)
at org.springframework.web.servlet.tags.RequestContextAwareTag.doStartTag(RequestContextAwareTag.java:79)
The error message isn't incorrect, because the property in question does not have a setter-method (gets its value through the constructor). But like I said, this has not been a problem when using Glassfish 3.0.1, only when using it on the new server with Glassfish 3.1.
Does anyone know if there is something in the Glassfish version that might cause this? Or is it some kind of configuration that is missing on the new server?
Some code:
Controller:
#ModelAttribute
public SomethingContainer retriveSomethingContainer(#PathVariable final long id {
return somethingContainerDao.retrieveSomethingContainer(id);
}
#InitBinder("somethingContainer")
public void initBinderForSomething(final WebDataBinder binder) {
binder.setAllowedFields(new String[] {
"something.title",
"something.description",
});
}
SomethingContainer:
#Embedded
private final Something something = new Something();
public Something getSomething() {
return something;
}
//no setter
public String getDescription() {
return something.getDescription();
}
Update:
Restarting Glassfish actually removes the problem - temporarily. I suspect that it might have something to do with the loading of the custom binders, we had some problems with out of memory errors, which I thought had something to do with it, but that has been fixed without fixing this problem.
Update 2:
On the 3.0.1 server, the one of the jvm arguments was -client. On the 3.1-server, it was -server. We changed it to -client, and this made the frequency of the error go down a lot, it was happening every other day with -server, took 2 weeks for it to happen with -client.
Update 3:
Some information about the servers (more can be added if requested..)
Server1 (the working one):
Windows Server 2003
Java jdk 6 build 35
Glassfish 3.0.1 build 22
-xmx 1024m
Server2 (the one with problems):
Windows Server 2008 64-bit
Java jdk 6 build 31
Glassfish 3.1 build 43
-xmx 1088m
-xms 1088m
We are using Spring version 3.1.0.
Update 4:
I recreated the error by renaming a field in a jsp to something that does not exist in the modelattribute.
But, more importantly, I noticed something: The fields where the system can't find the getters are often fields of superclasses of the ones that are referenced in the modelattribute. To continue my example, the SomthingContainer is really like this:
public class SuperSomethingContainer {
[...]
private Something something;
public Something getSomething() {
return something;
}
}
public class SomethingContainer extends SuperSomethingContainer {
[...]
}
The reference in the controller stays as is, so it's referencing a field that is in the superclass of the object in question.
Update 5:
I tried connecting to the production server with a debugger after the error occured. I put a breakpoint on the return statement of a controller-method returning the object with the error, and tried to see if I could access the field with problems at the time. And that I could, so the problem must lie within Spring MVC/the generated jsp-classes.
(Also, the field in error was of the type "someobject.something[0].somethingelse[0]", but when the somethingelse-list was empty, there was no error! To me, this implies that it somehow can't find the get-method of a list(?))
Update 6:
It seems that the problem has to do with the generation of Java-classes from the jsps. We have not used precompile jsps when deploying, so they are compiled when first used. The problem occurs the first time a page is visited, and the jsp compiled. I also noticed that once the problem has occured, jsps that are compiled after will all give errors. I've kept a few of the problem generated java files, and upon the next restart I will compare them to the working ones. Getting closer :)
Update 7:
Compared the compiled jsp java files that resulted in an error with ones that did not, and there was no difference. So that kinda leaves that out.
So, I now know that the Java object leaving the controller is fine (checked with debugger), and the java class generated from the jsp is fine. So it must be something in between, now I need to find out what...
Update 8:
Another round of debugging, and narrowed the problem down some more. It turns out that spring does some caching of the properties belonging to the various classes. In org.springframework.beans.BeanWrapperImpl, method getPropertyValue, there is the following:
private Object getPropertyValue(PropertyTokenHolder tokens) throws BeansException {
String propertyName = tokens.canonicalName;
String actualName = tokens.actualName;
PropertyDescriptor pd = getCachedIntrospectionResults().getPropertyDescriptor(actualName);
if (pd == null || pd.getReadMethod() == null) {
throw new NotReadablePropertyException(getRootClass(), this.nestedPath + propertyName);
}
The problem is that the cachedIntrospectionResults does not contain the property in question, it contains every other property of the class though. Will need to dig some more to try to find out why it is missing, if it's missing from the start or if it gets lost somewhere along the line.
Also, I've noticed that the missing properties are those that do not have setters, only getters. And, it seems to be context aware, as indicated by the stacktrace. So not finding a property when visiting one page does not mean that its not available when visiting another.
Update 9:
Another day, more debugging. Actually found some good stuff. The getCachedIntrospectionResults() call in the previous code block wounded up calling CachedIntrospectionResults#forClass(theClassInQuestion). This returned a CachedIntrospectionResults object, containing far from all of the properties expected (11 of 21). Going into the forClass-method, I found:
static CachedIntrospectionResults forClass(Class beanClass) throws BeansException {
CachedIntrospectionResults results;
Object value = classCache.get(beanClass);
if (value instanceof Reference) {
Reference ref = (Reference) value;
results = (CachedIntrospectionResults) ref.get();
}
else {
results = (CachedIntrospectionResults) value;
}
if (results == null) {
//build the CachedIntrospectionResults, store it in classCache and return it.
It turned out that the CachedIntrospectionResults returned was found by classCache.get(beanClass). So what was stored in the classCache was corrupted/did not contain all that it should. I put a breakpoint on the classCache.get(beanClass)-line, and tried running this through the debugger:
classCache.put(beanClass, null);
When allowing the method to finish, and rebuild the CachedIntrospectionResults, things started working again. So, what is being stored in the classCache is out of sync with what would and should be created if it was allowed to rebuild it. Whether this is due to something going wrong the first time it is built, or if the classCache is corrupted somewhere along the line I do not currently know.
I'm starting to suspect that this has something to do with classloaders, as I've previously experienced problems due to changes in the way the classloader works when updating Glassfish..

There may be more than one possible reason. I am not sure about the actual but I can give you the way to find out the problem
Step 1: on server 2 machine deploy application on Glassfish 3.0.1 build 22 , now if it works fine on the server 2 machine that it means there might be problem with the libraries of Glass fish, following can be reason for this problem
Any library that is missing in the Glassfish 3.1 build 43 that is in Glassfish 3.0.1 build 22. you can solve by copying all libraries from working Glassfish server to new server.
My be the libraries of Glassfish is conflicting with spring version. [Similliar kind of problem I have faced on tomcat and when i replaced my spring libraires from 3.0.1 to 3.0.3 it worked for me] , so replace your spring libraries with latest one.
Step 2: and if the result of step1 is that application is not running on server 2 machin on Glassfish 3.0.1 build 22 there may be following reason
if any libraries that you have pasted on java lib either not included in this server machine or having different versions.
Any folders that are set on classpath or using any environment variables on server 1, either does not exist on server 2 or don't have the jars or having jars with diff versions

I got a colleague of mine investigate the error, and he was able to recreate it in a unit test. This was done by invoking the method that builds CachedIntroSpectionResults for a class, while at the same time stressing the jvm by adding strings to the memory, with very low memory settings. This approach made it fail 20/30000 times.
As to the cause of it, I only got an oral explanation, so I don't have all the details, but it was something like this: Java has its own introspection-results, and these are wrapped by Spring. The problem is that the java-results utilize soft references, which make them prone to garbage collections. So, when Spring was building its wrappers around these soft references at the exact same time that the garbage collector ran, it actually cleared some of the basis of what Spring was using, leading to properties being "lost".
The solution seems to be upgrading from Spring 3.1.0.RELEASE to Spring 3.1.3.RELEASE. Here, there are some changes, and Spring no longer wraps soft references when determining the properties of a class (soft reference are used in rare, special cases, instead of all the time). After upgrading the version of Spring, the error has not been reproducable through the unit test, it remains to see if this is the case through in practice use.
Update: It's been a few weeks, an no sign of the error. So updating Spring version worked :)

I think I've actually found a candidate for the cause of this.
After getting the error on one of the test-servers after a very short duration and little use, we did some additional checks on the cause. It turned out that the test-server had just half the available memory, which turned us into looking at it a bit more thoroughly. It turned out that it hadn't used up all its memory, but when using JConsole to investigate the memory usage of the different part of the new generation space on the heap, it turned out that one of the surivior spaces was packed full. I'm guessing that this made parts of it overflow, leading to the overflowed parts to be GC-ed or unreachable by not being where it was supposed to.
We have yet to verify that this is in fact the problem in the production environment as well, but once the error turns up again we will check, and if it is the case we will change some memory settings to allow more space for survival areas of the new generation heap. (-XX:SurvivorRatio=6 or something like that).
So it seems that larger Spring MVC applications has a need for a large survivor space, specially in newer versions of Glassfish.

Indeed, there had been an issue with the new introduced ExtendedBeanInfo class in Spring 3.1.0, which had been fixed in Spring 3.1.1 - see (https://jira.spring.io/browse/SPR-8347).

Using Windows API call in Java using "native"

I've tried to solve this issue by referring possible duplicates but none of them seem to be helpful.
Here's a code that I'm using to call Win API methods in Java to get current Windows User Name, and a native Windows MessageBox, but I'm getting UnsatisfiedLinkError that says that my code is unable to locate the native method I'm trying to call.
public class TestNative
{
public static void main(String[] args)
{
long[] buffer= { 128 };
StringBuffer username = new StringBuffer((int)buffer[0]);
GetUserNameA(username,buffer);
System.out.println("Current User : "+username);
MessageBoxA(0,"UserName : "+username,"Box from Java",0);
}
/** #dll.import("ADVAPI32") */
static native void GetUserNameA(StringBuffer username,long[] buffer);
/** #dll.import("USER32") */
private static native int MessageBoxA(int h,String txt,String title,int style);
}
What can be my possible (relatively simple) solution to call native Windows methods in Java. I realize that it will kill the very reason of Java being a cross-platform language, but I need to work on a project for Windows, to be developed in Java.
Thanks.
Update
As David Heffernan suggested, I've tried changing the method signature of MessageBox to MessageBoxA, but still it's not working.

I would guess it's related to the signatures not matching completely.
The GetUserName function takes two parameters: a LPTSTR and a LPDWORD. Java will likely not handle the StringBuffer acting as a TCHAR array for you.
Also, why bother using the Windows API for this? Java can probably get the user's logon name (quick google says: System.getProperty("user.name")), and Swing can make a message box (even one that looks like a Windows one).

Have you tried https://github.com/twall/jna. I have heard good things and its supposed to make jni that bit easier with many conveniences and simplifications.

Do you have a -Djava.library.path VM arg set with the path to your DLL's? Alternatively, you can have it in your system PATH.

The error is because there is no MessageBox. You presumably mean MessageBoxA.

Accessing Windows Registry [duplicate]

This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
read/write to Windows Registry using Java
I need to access Windows registry from Java.. Also I need to copy some registry entries and may have to enter new registry variables using Java..
some one help me please...

I'd recommend the Java Native Access (JNA) library. It's a pretty nice wrapper around JNI. According to this mailing list post, they've already got a contributed wrapper around the native Windows registry function calls.
If you add the JNA libraries to your project, the relevant source you'll want is the Registry.java class. From there, just call methods on that class to investigate the Windows registry.
As a side note, make sure when you use JNA that you use Platform.isXxx() to make sure your code can actually query the registry on the particular platform.

An example will be like this:
import com.ice.jni.registry.*;
public class DeleteEnvironmentVar{
public DeleteEnvironmentVar(String variable, String value) throws Exception {
RegistryKey machine = Registry.getTopLevelKey("HKEY_LOCAL_MACHINE");
RegistryKey environment = machine.openSubKey("SYSTEM\\CurrentControlSet\\Control\\Session Manager\\Environment", RegistryKey.ACCESS_WRITE);
try {
if ( value == null ) { //Delete the variable in case value is empty
environment.deleteValue(variable);
}
}
catch( NoSuchValueException nsve ) {}
catch( NoSuchKeyException nske ) {}
}
}

The Preferences class is the Java preferred way of writing to the registry. However, I haven't actually used it, so I don't know if it allows access to the entire registry or just a section specific to the JVM or your application. If it doesn't, then it sounds like for your purpose you'll be needing to look at the JNI solutions posited by others here. If it does work, then you have a platform-independent method of storing off your settings if you ever port it.