JAVA高级面试进阶训练营视频教程

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 1 package Test;
 2 
 3 import java.lang.reflect.InvocationTargetException;
 4 import java.lang.reflect.Method;
 5 
 6 public class PrivateUtil {
 7 /** 
 8 * 利用递归找一个类的指定方法，如果找不到，去父亲里面找直到最上层Object对象为止。 
 9 * 
10 * @param clazz 
11 * 目标类 
12 * @param methodName 
13 * 方法名 
14 * @param classes 
15 * 方法参数类型数组 
16 * @return 方法对象 
17 * @throws Exception 
18 */ 
19 public static Method getMethod(Class clazz, String methodName, 
20 final Class[] classes) throws Exception { 
21 Method method = null; 
22 try { 
23 method = clazz.getDeclaredMethod(methodName, classes); 
24 } catch (NoSuchMethodException e) { 
25 try { 
26 method = clazz.getMethod(methodName, classes); 
27 } catch (NoSuchMethodException ex) { 
28 if (clazz.getSuperclass() == null) { 
29 return method; 
30 } else { 
31 method = getMethod(clazz.getSuperclass(), methodName, 
32 classes); 
33 } 
34 } 
35 } 
36 return method; 
37 } 
38 
39 /** 
40 * 
41 * @param obj 
42 * 调整方法的对象 
43 * @param methodName 
44 * 方法名 
45 * @param classes 
46 * 参数类型数组 
47 * @param objects 
48 * 参数数组 
49 * @return 方法的返回值 
50 * @throws Throwable 
51 */ 
52 public static Object invoke(final Object obj, final String methodName, 
53 final Class[] classes, final Object[] objects) throws Throwable { 
54 try { 
55 Method method = getMethod(obj.getClass(), methodName, classes); 
56 method.setAccessible(true);// 调用private方法的关键一句话 
57 return method.invoke(obj, objects); 
58 } catch (Exception e) { 
59 if(e instanceof InvocationTargetException){ 
60 Throwable throwable = ((InvocationTargetException) e).getTargetException(); //反射机制通常出现的的错误InvocationTargetException
61 throw throwable; 
62 }
63 throw new RuntimeException(e); 
64 } 
65 } 
66 
67 public static Object invoke(final Object obj, final String methodName, 
68 final Class[] classes) throws Throwable { 
69 return invoke(obj, methodName, classes, new Object[] {}); 
70 } 
71 
72 public static Object invoke(final Object obj, final String methodName) throws Throwable { 
73 return invoke(obj, methodName, new Class[] {}, new Object[] {}); 
74 } 
75 
76 }

总结：最近在做一个java的动态调用方法，遇到了两个问题：

       一：私有方法的访问需要设置: method.setAccessible(true);

　　 二：当java动态调用方法的方法体里有异常抛出，都会被打包成InvocationTargetException异常类并抛出。 

　　　　 因此，在Catch(捕捉异常)的时候进行以下处理:

1 try{
2  //doXXX
3 }catch (Exception e) { 
4   if(e instanceof InvocationTargetException){ 
5     Throwable throwable = ((InvocationTargetException) e).getTargetException(); //反射机制通常出现的的错误InvocationTargetException
6     throw throwable; 
7    }
8   throw new RuntimeException(e); 
9 }