java 方法中带有超类参数的Java getMethod
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Java getMethod with superclass parameters in method
提问by Jonathon Faust
Given:
鉴于：
class A
{
public void m(List l) { ... }
}
Let's say I want to invoke method mwith reflection, passing an ArrayList as the parameter to m:
假设我想m通过反射调用方法，将 ArrayList 作为参数传递给m：
List myList = new ArrayList();
A a = new A();
Method method = A.class.getMethod("m", new Class[] { myList.getClass() });
method.invoke(a, Object[] { myList });
The getMethodon line 3 will throw NoSuchMethodExceptionbecause the runtime type of myList is ArrayList, not List.
第getMethod3 行将抛出，NoSuchMethodException因为 myList 的运行时类型是 ArrayList，而不是 List。
Is there a good generic way around this that doesn't require knowledge of class A's parameter types?
是否有一个很好的通用方法来解决这个问题，不需要了解 A 类的参数类型？
回答by Bozho
If you know the type is List, then use List.classas argument.
如果您知道类型是List，则List.class用作参数。
If you don't know the type in advance, imagine you have:
如果您事先不知道类型，请想象您有：
public void m(List l) {
// all lists
}
public void m(ArrayList l) {
// only array lists
}
Which method should the reflection invoke, if there is any automatic way?
如果有任何自动方式，反射应该调用哪个方法？
If you want, you can use Class.getInterfaces()or Class.getSuperclass()but this is case-specific.
如果需要，您可以使用Class.getInterfaces()or ，Class.getSuperclass()但这是特定于案例的。
What you can do here is:
你可以在这里做的是：
public void invoke(Object targetObject, Object[] parameters,
String methodName) {
for (Method method : targetObject.getClass().getMethods()) {
if (!method.getName().equals(methodName)) {
continue;
}
Class<?>[] parameterTypes = method.getParameterTypes();
boolean matches = true;
for (int i = 0; i < parameterTypes.length; i++) {
if (!parameterTypes[i].isAssignableFrom(parameters[i]
.getClass())) {
matches = false;
break;
}
}
if (matches) {
// obtain a Class[] based on the passed arguments as Object[]
method.invoke(targetObject, parametersClasses);
}
}
}
回答by user207421
See java.beans.Expression and java.beans.Statement.
请参阅 java.beans.Expression 和 java.beans.Statement。
回答by Matt Ball
Instead of myList.getClass(), why not just pass in List.class? That iswhat your method is expecting.
相反myList.getClass()，为什么不直接传入List.class？这就是您的方法所期望的。
