java 获取泛型类
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Get class of generic
提问by kospiotr
My class starts with
我的课开始于
public abstract class LastActionHero<H extends Hero>(){
Now somewhere in the code I want to write H.classbut that isn't possible (like String.classor Integer.classis).
现在在我想写的代码中的某个地方，H.class但这是不可能的（就像String.class或是Integer.class）。
Can you tell me how I can get the Classof the generic?
你能告诉我如何获得Class泛型的吗？
采纳答案by Peter Lawrey
You can provide the type dynamically, however the compiler doesn't do this for you automagically.
您可以动态提供类型，但是编译器不会自动为您执行此操作。
public abstract class LastActionHero<H extends Hero>(){
protected final Class<H> hClass;
protected LastActionHero(Class<H> hClass) {
this.hClass = hClass;
}
// use hClass how you like.
}
BTW: It not impossible to get this dynamically, but it depends on how it is used. e.g
顺便说一句：动态获取它并非不可能，但这取决于它的使用方式。例如
public class Arnie extends LastActionHero<MuscleHero> { }
It is possible to determine that Arnie.class has a super class with a Generic parameter of MuscleHero.
可以确定 Arnie.class 有一个超类，其 Generic 参数为 MuscleHero。
public class Arnie<H extend Hero> extends LastActionHero<H> { }
The generic parameter of the super class will be just Hin this case.
超类的泛型参数就是H这种情况。
回答by kospiotr
We do it in the following way:
我们通过以下方式做到这一点：
private Class<T> persistentClass;
public Class<T> getPersistentClass() {
if (persistentClass == null) {
this.persistentClass = (Class<T>) ((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[0];
}
return persistentClass;
}
回答by Buhake Sindi
One way is to keep reference to your parameterized type like having an attribute of
一种方法是保留对参数化类型的引用，例如具有
private Class<H> clazz;
And create a setter or a constructor that takes in a Class<H>.
并创建一个接受Class<H>.
Parameterized Types are erased at runtime, hence why you can't do what you ask.
参数化类型在运行时被删除，因此为什么你不能按你的要求做。
回答by Peter Tseng
You can do it without passing in the class:
您可以在不传入类的情况下执行此操作：
public abstract class LastActionHero<H extends Hero>() {
Class<H> clazz = (Class<H>) DAOUtil.getTypeArguments(LastActionHero.class, this.getClass()).get(0);
}
You need two functions from this file: http://code.google.com/p/hibernate-generic-dao/source/browse/trunk/dao/src/main/java/com/googlecode/genericdao/dao/DAOUtil.java
您需要此文件中的两个函数：http: //code.google.com/p/hibernate-generic-dao/source/browse/trunk/dao/src/main/java/com/googlecode/genericdao/dao/DAOUtil。爪哇
For more explanation: http://www.artima.com/weblogs/viewpost.jsp?thread=208860
更多解释：http: //www.artima.com/weblogs/viewpost.jsp?thread= 208860
回答by Puppy
You can't- the type is erased at run-time and exists only at compile-time.
你不能 - 类型在运行时被擦除并且只在编译时存在。
