獲得某個類的泛型

package com;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;


import org.springframework.core.ResolvableType;


interface Service2<N, M> {
}
class ABService2 implements Service2<A, B> {}


public class TestGenericClass2 {
	private Service<C, D> cdService;
	
	public static void main(String[] args) {
		//獲取ABService2實現的第一個介面(從0開始計數) 即Service2<A, B>
		ParameterizedType parameterizedType = (ParameterizedType) ABService2.class.getGenericInterfaces()[0];
		System.out.println(parameterizedType);
		//從Service2<A, B> 獲得第0個引數 即A
		Type genericType = parameterizedType.getActualTypeArguments()[0];
		System.out.println(genericType);
		System.out.println("*************");
		//下面的可以獲得被aop代理之前的型別
		//ClassUtils.getUserClass(myClass);
		ResolvableType resolvableType1 = ResolvableType.forClass(ABService2.class);  
		
		Class c=resolvableType1.as(Service2.class).getGeneric(0).resolve();
		Class d=resolvableType1.getInterfaces()[0].getGeneric(0).resolve();
		System.out.println("c   "+c);
		System.out.println("d   "+d);
		//上面的c與d一樣 說明resolvableType1.as(Service2.class)與resolvableType1.getInterfaces()[0]
		//是一樣的 都是返回resolvableType1 實現的某個介面
		
		System.out.println("__________");		
	}
}
 

輸出:
com.Service2<com.A, com.B>
class com.A
*************
c   class com.A
d   class com.A
---------------

上面程式碼裡,*************之前的是使用jdk的原始api,之後是使用spring為我們通過的泛型api


使用jdk原始的api,似乎有個問題,那就是如果,如果目標類是繼承(而不是實現)了某個泛型類,那就(似乎)沒法獲得引數型別了
(這個,我也不確定,如果諸位誰知道,麻煩告訴小弟一聲)

package com;


import org.springframework.core.ResolvableType;


interface Service3<N, M> {}
class ServiceImpl3<N,M> implements Service<N, M>{}

class C3 {}
class D3 {}

class CDService3 extends ServiceImpl<C3, D3> {}

public class TestGenericClass3 {
	
	public static void main(String[] args) {
		ResolvableType resolvableType1 = ResolvableType.forClass(CDService3.class);  
		Class c=resolvableType1.as(ServiceImpl.class).getGeneric(0).resolve();
		System.out.println("c   "+c);
	}
}
 

輸出
c   class com.C3
***********

獲得成員變數的泛型型別

package com;

import org.springframework.core.ResolvableType;
import org.springframework.util.ReflectionUtils;

interface Service4<N, M> {}
class ServiceImpl4<N,M> implements Service<N, M>{}

class C4 {}

class D4 {}

class CDService4 extends ServiceImpl4<C4, D4> {
}


public class TestGenericClass4 {
	private Service<C, D> cdService;
	
	public static void main(String[] args) {


		ResolvableType resolvableType2 =  
                ResolvableType.forField(ReflectionUtils.findField(TestGenericClass.class, "cdService")); 
		System.out.println(resolvableType2.getGeneric(0).resolve());
			
	}
}
 

輸出:
class com.C

在含泛型的父類中,獲得子類的引數

說的很模糊,大家看程式碼:

package com;

import org.springframework.core.ResolvableType;
import org.springframework.util.ClassUtils;

interface Service<N, M> {
}
class ServiceImpl<N,M> implements Service<N, M>{
	private Class<?> entityN;
	private Class<?> entityM;
	
	public ServiceImpl(){
		System.out.println("this is "+this.getClass());
		//用於避過aop 獲得原始的型別
		Class<?> childClass=ClassUtils.getUserClass(this.getClass());
		if (childClass.equals(this.getClass())) {
			System.out.println("一樣");
		}
		ResolvableType resolvableType1 = ResolvableType.forClass(childClass);  
		entityN=resolvableType1.as(ServiceImpl.class).getGeneric(0).resolve();
		entityM=resolvableType1.as(ServiceImpl.class).getGeneric(1).resolve();
		System.out.println(entityN+"  **  "+entityM);
	}
}
class A {}

class B {}


class ABService extends ServiceImpl<A, B> {


}


public class TestGenericClass {
	
	public static void main(String[] args) {
	
		Service<A, B> abService= (Service<A, B>) new ABService();
		System.out.println("************* "+abService);		
	}
}

輸出
this is class com.ABService
一樣
class com.A  **  class com.B
************* [email protected]


關於更多的泛型資料,請見參考資料
順便多說一句,開濤哥真牛。
感謝glt。

參考資料

http://jinnianshilongnian.iteye.com/blog/1993608