Obtain generic information through reflection.

Obtain generic information through reflection.

 

 

1 package com. coscon. reflectionTest; 2 3 import java. lang. reflect. method; 4 import java. lang. reflect. parameterizedType; 5 import java. lang. reflect. type; 6 import java. util. list; 7 import java. util. map; 8 9 // obtain generic information through reflection 10 public class ReflectionForGenerics {11 public void test01 (Map <String, User> map, List <User> users) {12 System. out. println ("test01"); 13} 14 15 public Map <Integer, User> test02 () {16 System. out. println ("test02"); 17 return null; 18} 19 20 public static void main (String [] args) {21 try {22 Class clazz = Class. forName ("com. coscon. reflectionTest. reflectionForGenerics "); 23 // obtain the generic information of the specified Method parameter 24 method = clazz. getMethod ("test01", Map. class, List. class); 25 // obtain the generic parameter 26 Type [] types = method. getGenericParameterTypes (); 27 for (Type type: types) {28 System. out. println ("#" + type); 29 if (type instanceof ParameterizedType) {30 Type [] actualTypeArguments = (ParameterizedType) type ). getActualTypeArguments (); 31 for (Type type2: actualTypeArguments) {32 System. out. println ("generic parameter type:" + type2); 33} 34} 35} 36 37 System. out. println ("--------------------------------------------------------------"); 38 Method method2 = clazz. getMethod ("test02", null); 39 // obtain the returned value generic information 40 Type returnType = method2.getGenericReturnType (); 41 System. out. println ("#" + returnType); 42 if (returnType instanceof ParameterizedType) {43 Type [] typeArguments = (ParameterizedType) returnType ). getActualTypeArguments (); 44 for (Type: typeArguments) {45 System. out. println ("returned value generic type:" + type); 46} 47} 48} catch (Exception e) {49 // TODO Auto-generated catch block50 e. printStackTrace (); 51} 52} 53}

Print results

# Java. util. Map <java. lang. String, com. coscon. reflectionTest. User>
Generic parameter type: class java. lang. String
Generic parameter type: class com. coscon. reflectionTest. User
# Java. util. List <com. coscon. reflectionTest. User>
Generic parameter type: class com. coscon. reflectionTest. User
--------------------------------------------------------------
# Java. util. Map <java. lang. Integer, com. coscon. reflectionTest. User>
Returned value generic type: class java. lang. Integer
Returned value generic type: class com. coscon. reflectionTest. User