B4J Question B4J user external library (Jar)

[Roberto P.]

where can I find an example or tuturial for B4J that uses a library Jar outside?
thanks

 

[rwblinn]

Hi Roberto,

external libraries can be included by using the #AdditionalJar Parameter in the Project Attribute section.
You can start with the B4J jSQL Library Tutorial here or have a look at my B4J HOWTOs > Inline Java > select the HOWTO Ext Library JSch or JSoup.
Important is that you copy the external library (jar file) you want to use to the B4J external library folder.

 

[Roberto P.]

thanks Rob

 

[Roberto P.]

I can import every single class? or, I can transform a class in a jar?
I do not know these features of Java!
thanks

 

[rwblinn]

Yes you can - have made a simple example showing how to do:
See attached Java Project (Package > Class > 2 methods and the jar file) and the B4J Project using this external library.
Please read the b4j project file for further information.

 

[Roberto P.]

thank you. I see, though, you need to have to compile the Jar.
thanks again

p.s.
just for info, your example by mistake.


Program started.
ExtLibEx
Hello World
main._appstart (java line: 57)
java.lang.UnsupportedClassVersionError: rwblinn/extlibex/ExtLibExClass : Unsupported major.minor version 52.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:190)
at anywheresoftware.b4j.object.JavaObject.getCorrectClassName(JavaObject.java:272)
at anywheresoftware.b4j.object.JavaObject.InitializeStatic(JavaObject.java:73)
at b4j.example.main._appstart(main.java:57)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:93)
at anywheresoftware.b4a.BA.raiseEvent(BA.java:84)
at b4j.example.main.start(main.java:36)
at com.sun.javafx.application.LauncherImpl$5.run(LauncherImpl.java:319)
at com.sun.javafx.application.PlatformImpl$5.run(PlatformImpl.java:216)
at com.sun.javafx.application.PlatformImpl$4$1.run(PlatformImpl.java:179)
at com.sun.javafx.application.PlatformImpl$4$1.run(PlatformImpl.java:176)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl$4.run(PlatformImpl.java:176)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:76)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.access$100(WinApplication.java:17)
at com.sun.glass.ui.win.WinApplication$3$1.run(WinApplication.java:67)
at java.lang.Thread.run(Thread.java:744)

 

[rwblinn]

Hi,

this message occurs because of a higher JDK during compile time (I used JDK 1.8.0_45) and lower JDK during runtime. Which means you probably have a lower Java version.
To Fix: Upgrade your Java runtime or recompile the class using your local Java compiler.

 

[Roberto P.]

ok, thanks you