本文转载http://blog.sina.com.cn/s/blog_6151984a0100kwy0.html

反射机制出现的InstantiationException异常

做反射机制时,执行如下的语句:
Class class1 = Class.forName(className);
Object o1 = class1.newInstance();

出下面的异常:
Exception in thread "main" java.lang.InstantiationException: classtest.PersonServiceBean
    at java.lang.Class.newInstance0(Class.java:340)
    at java.lang.Class.newInstance(Class.java:308)
    at classtest.JustTest.classInstanceTest(JustTest.java:33)
    at classtest.JustTest.main(JustTest.java:13)

进行debug调试:   
程序运行到Class.class文件,try {
        Class[] empty = {};
           final Constructor<T> c = getConstructor0(empty,Member.DECLARED); 
                                    //执行到此句时,出noSuchMethod异常,跳到catch
                java.security.AccessController.doPrivileged
                    (new java.security.PrivilegedAction() {
                            public Object run() {
                                c.setAccessible(true);
                                return null;
                            }
                        });
                cachedConstructor = c;
            } catch (NoSuchMethodException e) {     //出现noSuchMethod异常
                throw new InstantiationException(getName());    
                     //抛出的是java.lang.InstantiationException
            }
        }

解决:
显示的定义一个无参构造方法

备注:InstantiationException也发生在对Interface,SuperClass调用反射机制实例化对象的时候.