Dynamic loading of class from external jar and NoClassDefFoundError

[daniele licitra]

Hi to all.
I don't know if this is the correct thread to post in my question.

What is the situation?
I've a web application, we call it WA, that uses JSF. WA run on Glassfish 3.
This application has some panel (extended from primefaces.Panel) and i want to bind the panel to some object P:

<p:panel ... binding="{bean.panel}" />

The panel must be loaded dynamically from an external jar.

The P class is something like

public class ModTest {

    public BssPanel pannello;
    
    public ModTest() {
        this.pannello = new BssPanel();
        BssOutputText testo = new BssOutputText();
        testo.setValue("modulo vuoto, di test");
        this.pannello.setHeader("Modulo di Test");
        this.pannello.getChildren().add(testo);
    }
    
    //setter and getter
    
}

The ModTest class is in another jar file, called ModTest.jar. I want to load the class at runtime from the external jar so i can change the "panel" without recompile WA.

So, I built a bean B that read from database the path of jar file and the classname.
B then must instantiate an object A of tipe P and return A.pannello to show it on screen.

The loader function is:

public static Object caricaClasse(String jar, String nomeClasse){
        File jarFile = new File(jar);
        Object instance = null;
        try {
            URL jarpath = jarFile.toURI().toURL();
            String jarUrl = "jar:"+jarpath+"!/";
            URL urls[] = {new URL(jarUrl)};
            URLClassLoader child = new URLClassLoader(urls);
            Class classToLoad = Class.forName(nomeClasse, true, child);
            instance = classToLoad.newInstance();
        } catch (MalformedURLException ex) {
            Logger.getLogger(BssLoader.class.getName()).log(Level.SEVERE, null, ex);
        } catch(ClassNotFoundException ex){
            Logger.getLogger(BssLoader.class.getName()).log(Level.SEVERE, null, ex);
        } catch(IllegalAccessException | InstantiationException ex){
            Logger.getLogger(BssLoader.class.getName()).log(Level.SEVERE, null, ex);
        }
        return instance;
    }

What is the problem?
It works untill instance = classToLoad.newInstance(); at this time throw java.lang.NoClassDefFoundError: com/bss/primefaces/panel/BssPanel.
com/bss/primefaces/panel/BssPanel is missing or it is not found. That class is in another library, component.jar.
The ModTest.jar hasn't component.jar inside but WA.war has it.

What are the questions?
- ModTest.jar is a maven project so, how i can force to put all dependency jar in ModTest.jar? It solve the problem? I need to create a normal java project?
otherwise
- There is a way to provide the necessary jar without modifing ModTest.jar, like read it from glassfish's lib directory? How I must provide all the dependencies in the correct way?

Thanks, sorry for my bad English.

[daniele licitra]

Solved.

In external jar ModTest.jar, in pom.xml, put the maven plugin:
<plugin> <artifactId>maven-assembly-plugin</artifactId> <configuration> <descriptorRefs> <descriptorRef>jar-with-dependencies</descriptorRef> </descriptorRefs> </configuration> <executions> <execution> <id>make-assembly</id> <phase>package</phase> <goals> <goal>attached</goal> </goals> </execution> </executions> </plugin>

now all dependency are exploded inside the jar. It works.