如何从通过类加载器加载的 class 调用构造函数

Question

I use classloader to load a class from a jar, but I get a "NoSuchMethodException" exception when trying to call the default constructor, which does exist.

The problem may to be that the loaded class is simply java.lang.Class?

How can I call the constructor?

Class<?> JRXlsExporter = urlClassLoader.loadClass("net.sf.jasperreports.engine.export.JRXlsExporter");
String classname = JRXlsExporter.getName();     //   looks good... it's net.sf.jasperreports.engine.export.JRXlsExporter
Class myclass = JRXlsExporter.getClass();           // this might be a a problem, the class is java.lang.Class
Constructor constructor = myclass.getConstructor();        // throws  java.lang.NoSuchMethodException: java.lang.Class.<init>()

Answer 1

Your JRXlsExporter is a Class - you can call getConstructor on it:

Constructor constructor = JRXlsExporter.getConstructor();