请问下java Method invoke 抛出异常，该怎么解决？

Question

在使用Method的invoke方法时，所调用的函数原有的异常如何按照原来的异常类型抛出？

Answer 1

InvocationTargetException异常由Method.invoke(obj, args...)方法抛出。当被调用的方法的内部抛出了异常而没有被捕获时，将由此异常接收。示例：package com.zzj.test.reflect;public class Reflect {public void run(int i) throws ZeroException {B b = new B();b.run(i);}}class B {public void run(int i) throws ZeroException {if (i < 0) {throw new ZeroException("参数不能小于零！");}System.out.println("参数：" + i);}}class ZeroException extends Exception {private static final long serialVersionUID = 1L;private String detailMessage;public ZeroException(String detailMessage) {this.detailMessage = detailMessage;}public String getMessage() {return detailMessage;}}测试：package com.zzj.test.reflect;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;public class Test {public static void main(String[] args) {try {Class<?> clazz = Class.forName("com.zzj.test.reflect.Reflect");Method method = clazz.getMethod("run", int.class);method.invoke(clazz.newInstance(), -1);} catch (ClassNotFoundException e) {e.printStackTrace();} catch (SecurityException e) {e.printStackTrace();} catch (NoSuchMethodException e) {e.printStackTrace();} catch (IllegalArgumentException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();} catch (InvocationTargetException e) {System.out.println("此处接收被调用方法内部未被捕获的异常");e.printStackTrace();} catch (InstantiationException e) {e.printStackTrace();}}}输出：此处接收被调用方法内部未被捕获的异常java.lang.reflect.InvocationTargetExceptionat sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)at java.lang.reflect.Method.invoke(Unknown Source)at com.zzj.test.reflect.Test.main(Test.java:11)Caused by: com.zzj.test.reflect.ZeroException: 参数不能小于零！at com.zzj.test.reflect.B.run(Reflect.java:13)at com.zzj.test.reflect.Reflect.run(Reflect.java:6)... 5 more也可以直接打印目标异常：package com.zzj.test.reflect;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;public class Test {public static void main(String[] args) {try {Class<?> clazz = Class.forName("com.zzj.test.reflect.Reflect");Method method = clazz.getMethod("run", int.class);method.invoke(clazz.newInstance(), -1);} catch (ClassNotFoundException e) {e.printStackTrace();} catch (SecurityException e) {e.printStackTrace();} catch (NoSuchMethodException e) {e.printStackTrace();} catch (IllegalArgumentException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();} catch (InvocationTargetException e) {System.out.println("此处接收被调用方法内部未被捕获的异常");Throwable t = e.getTargetException();// 获取目标异常t.printStackTrace();} catch (InstantiationException e) {e.printStackTrace();}}}输出：此处接收被调用方法内部未被捕获的异常com.zzj.test.reflect.ZeroException: 参数不能小于零！at com.zzj.test.reflect.B.run(Reflect.java:13)at com.zzj.test.reflect.Reflect.run(Reflect.java:6)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)at java.lang.reflect.Method.invoke(Unknown Source)at com.zzj.test.reflect.Test.main(Test.java:11)

Answer 2

java.lang.reflec.InvocationTargetException捕获这个异常，然后通过getTargetException() 方法获得异常，这个可以获得原方法抛出的异常。然后可以通过类型判断，判断到底抛出的是原异常的哪一个异常。

Answer 3

Class<?>[]getExceptionTypes()返回 Class 对象的数组，这些对象描述了声明将此 Method 对象表示的底层方法抛出的异常类型。Method对象通过该方法可以的到方法声明时异常抛出的类型，可以手工判断进行抛出，但是有一点给注意，如果在运行时抛出异常 如 RuntimeException类型的错误，如果再声明里没有写明，应该领去处理。