Assuming you have a Java module that defines the following dependencies to SWT:
module com.test.mymodule {
requires org.eclipse.swt.win32.win32.x86;
}
If the module defined above is loaded within a 32-bit based JVM in Windows there are no issues, however within a 64-bit JVM this operation fails as the JVM tries to load native 32-bit libraries within the SWT JAR that then cause the JVM to crash. This will happen on the first line of code that references any SWT class (e.g. if you call Display.getShells). The JARs avaliable on Maven do not define the Atomatic-Module-Name property in the manifest so trying to add the 64-bit version of the library leads to Maven being unable to parse the name of the file correctly.
Furtmore adding a static to the requires has exactly the same effect, as the JVM insists on loading the module specified in the module-info file. Is there any generic SWT module that can be used instead of system-specific modules so that the mymodule module in this sample would load regardless of the bitness/OS of the underlying JVM?
JDK Version:11.0.2, Windows 10 64-Bit
Both the 32-bit and 64 bit versions of SWT binaries are available in Maven Central. The binaries are published to Maven Central for every release.
Links to 64-bit binaries:
https://mvnrepository.com/artifact/org.eclipse.platform/org.eclipse.swt.win32.win32.x86_64
https://mvnrepository.com/artifact/org.eclipse.platform/org.eclipse.swt.cocoa.macosx.x86_64
https://mvnrepository.com/artifact/org.eclipse.platform/org.eclipse.swt.gtk.linux.x86_64
Please note that Eclipse has dropped support for 32-bit since Eclipse 2018-12 (4.10) release.
Related
I’m trying to update my JavaFX project to be compatible with JRE 13 (until now it was set up to use JRE 1.8). I’m developing with Eclipse 2020-03, using a Mac.
The first big issue I’ve had to deal with is the migration from the included JavaFX libraries in JDK 1.8 to having to import JavaFX (14) as an external package for JDK 13.
The second issue is migration from using the classpath to using the modulepath. I’m new to the module path, so what I say about it may not make sense, but my current setup now is this:
modulepath:
<list of other .jar files>
JRE System Library [Java SE 13 [13.0.2]]
JavaFX 14
<list of .jar files I downloaded, including javafx-swt, javafx.base, javafx.controls, javafx.fxml, javafx.graphics, javafx.media, javafx.swing, javafx.web>
<I created a User Library from the above listed .jar’s>
Finally, all the compiler errors are now gone (I had to recompile some of the external .jar files I downloaded so there weren’t any split packages), but when I build and run the application class nothing happens.
Checking the Mac system console, the below output seems to reference why the app is not starting, but I checked he JDK path and the referenced java executable does exist.
com.apple.xpc.launchd[1] (com.apple.xpc.launchd.domain.pid.java.40558): Failed to bootstrap path: path = /Library/Java/JavaVirtualMachines/jdk-13.0.2.jdk/Contents/Home/bin/java, error = 2: No such file or directory
What is happening here? If you need more info about my project config, comment and I can add details.
I haven't done GWT development for a while and wanted to try again. In my Windows 10, I installed JDK 12 and Eclipse 2019-03. I installed GWT Eclipse Plugin (GWT 2.8.1).
From Eclipse, I created a hello world project this way:
Click on 'New GWT Application Project'
Project name: Gwt5, Package: com.foo, Use default SDK (GWT 2.8.1)
Click on 'GWT Compile Project'
I see this error:
Compiling module com.foo.Gwt5
[ERROR] Hint: Check that your module inherits 'com.google.gwt.core.Core' either directly or indirectly (most often by inheriting module 'com.google.gwt.user.User')
I didn't change my gwt.xml. I checked and "com.google.gwt.user.User" is there.
Any suggestion?
When language compliance level or JRE is set to higher than what GWT supports, this error occurs (The error message is not very helpful though).
As of May 2019, GWT supports only up to Java 8, and that is provided by JDK 1.8. For example, to make GWT work with Oracle's JDK, you need to download an older version of JDK (Java SE), than set both the Compiler compliance level and Installed JRE to:
Compiler compliance level: 1.8
JRE Home: C:\Program Files\Java\jdk1.8.0_202\
I created a jar file (compiled it using jdk1.7). When I used this jar in a project(using JRE 1.6), I get the following exception- unsupported major.minor version 51.0 (I suppose 51.0 is meant for jdk1.7). I used eclipse IDE for all these operations.
I am wondering whether this exception is a norm (in this kind of situation) or is it coming just because class loading in eclipse works differently
This is expected. Bytecode specifically compiled for a java version, can't be executed on a lower version. This is because it might have bytecode instructions and/or features not supported by an earlier Java version.
To compile for a lower java version, you need to explicitly specify the target version of compilation, eg:
javac -target 1.6 ...
In Eclipse you can set this under Properties > Java Compiler > "Generated .class files compatibility". However in general it is advisable to just use a Java 6 compiler to make sure you are actually only using features and libraries included in Java 6.
Class loading is performed by the JVM, both within eclipse and outside of it. This error simply indicates the the file format of class files has changed in Java 7, and a Java 6 virtual machine does't know the class file format from the future.
You can instruct the Java compiler to use the class file format of a previous java version (in eclipse, you can find the setting under Properties -> Java Compiler -> JDK compliance).
In addition, you'll want to verify that you only use API elements that also existed in JDK 6.
I try to deploy a simple "Hello Word" in my local server GlasshFish 3, but at the deploy the console print this message
[#|2013-01-15T15:00:02.458+0100|SEVERE|glassfish3.1.2|
javax.enterprise.system.tools.admin.org.Exception while deploying the app
[HelloWorldEJB] :UnsupportedClassVersionError: Class ejb_other.PlaceAuctionItemBean
as unsupported major or minor version numbers, which are greater than those found
in the Java Runtime Environment version 1.6.0_27|#]
My JAVA_HOME has java version 1.6.0_27 (it refers to _C:\Program Files\Java\jdk1.6.0_27_), my Eclipse (indigo) project refers to java 1.6.0_27.
I think (i don't know how to verify) that GlasshFish refers to JAVA_HOME.
In my PC (Windows 7) I found 2 directory having java.exe:
C:\Windows\SysWOW64>java -version -->>java version "1.6.0_29"
C:\Windows\System32>java -version -->>java version "1.6.0_27"
I found more discussions about this exception (f.e. this or this ), but I need of something more specific for Eclipse/Glasshfish, because I can't to solve. I see that the JVM is the same for compilation and execution.
Post Scriptim
I add the screenshot about the places where I declare JVM: it's always 1.6.
one:
two:
three:
Where can I see that I compile with java 7 or it runs with another JVM?
ejb_other.PlaceAuctionItemBean was obviously compiled for Java 7 which won't work if you run it in a Java 6 JVM.
Found solution
There's another place where setting the compiler's options:
how do I get eclipse to use a different compiler version for Java?
I created a Drools project in Eclipse (Indigo) configured to use JRE 1.7. But I get an error pointing to my .drl file:
com/sample/DroolsTest$Message : Unsupported major.minor version 51.0
The com.sample.DroolsTest.Message class is imported by the .drl file. The Drools runtime was 5.2.1 (also tried with 5.3.0.Final).
Any help would be appreciated. Thanks.
This exception doesn't seem to have to do anything with Drools in particular, but is a generic Java error. It occurs if you try to execute a Java class with a JRE that is older than the JDK that was used to compile it. For example, if you compiled the class with a JDK7 and then tried to execute it with a JDK6, you would get this error.
Just to detail above answer and comment. I had both JRE6 and JRE7 installed, with JRE7 being the default. I had to do two things to remove the error from the drools sample project.
Set the JRE for the project to 1.6
Project properties->Java Build Path->Libraries. Remove JRE System Library 1.7 and Add Library->JRE System Library->Alternate JRE->JRE6
Set the compiler compliance level for the project at 1.6.
Project properties->Java Compiler->check Enable Project specific settings and set Compiler compliance level at 1.6.