Java反射:根据参数和签名自动调用正确的重载方法 [英] Java reflection: automatically invoke the right overloaded method based on parameters and signature

问题描述

假设有一个名为 doTask 的重载方法:

Say have an overloaded method called doTask:

public class Game {
  void doTask(Joker joker);
  void doTask(Batman batman, Robin robin);
}

我想调用正确的方法，给出方法的名称 ("doTask") 和参数数组，其数量和类型事先未知.

I would like to invoke the right method, given the name of the method ("doTask") and an array of parameters whose number and types are not known a priori.

通常，这至少涉及三个步骤:
1. 找出参数的个数和类型，制作一个数组Class[] myTypes.
2. 识别正确的重载Method，即Method rightMethod = game.getClass().getMethod("doTask", myTypes);
3.调用方法:rightMethod.invoke(paramArray).

Normally, this involves three steps at least:
1. Find the number of the parameters and their types, and make an array Class[] myTypes.
2. Identify the correct overloaded Method, i.e. Method rightMethod = game.getClass().getMethod("doTask", myTypes);
3. Invoke the method: rightMethod.invoke(paramArray).

是否有一种工具可以让 Java 反射自动识别要使用的正确重载方法，并使我们不必执行步骤 1 和步骤 2?我认为理想情况下，这将是:
Library.invoke("doTask", paramArray);

Does there exist a facility to ask Java reflection to automatically identify the right overloaded method to use, and save us from having to do Steps 1 and 2? I'm thinking ideally, this would be like:
Library.invoke("doTask", paramArray);

推荐答案

有这样一个工具，java.beans.Statement，resp.表达式如果需要返回值:

There is such a facility, java.beans.Statement, resp. Expression if a return value is needed:

Game game = new Game();
Joker joker = new Joker();
Statement st = new Statement(game, "doTask", new Object[]{ joker });
st.execute();

然而，它只适用于 public 方法.

However, it only works for public methods.

此外，与 java.lang.reflect.Method 不同的是，该工具尚未调整为支持 varargs 参数，因此您必须手动创建参数数组.

Also, unlike java.lang.reflect.Method, this facility has not been adapted to support varargs parameters, so you have to create a parameter array manually.

可以证明，它可以根据参数类型选择正确的目标方法，这些参数类型不一定与参数类型相同:

It can be demonstrated, that it does the work of selecting the right target method based on the argument types, which are not necessarily identical to the parameter types:

ExecutorService es = Executors.newSingleThreadExecutor();
class Foo implements Callable<String> {
    public String call() throws Exception {
        return "success";
    }
}
// has to choose between submit(Callable) and submit(Runnable)
// given a Foo instance
Expression ex = new Expression(es, "submit", new Object[]{ new Foo() });
Future<?> f = (Future<?>)ex.getValue();
System.out.println(f.get());
es.shutdown();

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