Question

我正在编写一个动态加载jar文件的应用程序并在jar文件中执行该类。我能够加载jar文件并获取方法。但是当我调用该方法时，我没有执行该方法，但没有例外。

我尝试执行的方法是公开的。

        URLClassLoader urlClassLoader;
      //no paramater
        Class noparams[] = {};
        try {
            urlClassLoader = new URLClassLoader(new URL[]{new URL("file:///C:/Users/jamju02/Desktop/today/jar2.jar")});
             Class pluiginClass = urlClassLoader.loadClass("plugintest.PluginTest");
            // Create a new instance from the loaded class
             Constructor<?> constructor = pluiginClass.getConstructor();

             Object classobject = constructor.newInstance();
             System.out.println(classobject.getClass().getName());
             //Method method = pluiginClass.getMethod("getName");
             Method[] m = pluiginClass.getDeclaredMethods();
                for (int i = 0; i < m.length; i++){
                    System.out.println(m[i].toString());
                    m[i].setAccessible(true);
                    m[i].invoke(classobject, null);
                }

            // method.invoke(object);

              //call the printIt method
                Method method = pluiginClass.getDeclaredMethod("getName", noparams);
                method.setAccessible(true);
                method.invoke(classobject);


        } catch (MalformedURLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (InstantiationException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (NoSuchMethodException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SecurityException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalArgumentException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }


package plugintest;

public class PluginTest implements SimplePlugin {
 public String getName() {
        return "I'm the plugin!";
    }
}

它打印类名和方法名，但不执行该方法。

Answer 1

try块中的最后一行需要更改为：

System.err.println((String) method.invoke(classobject));

使用URL类加载器

1 个答案: