java反射中捕获特定异常

Question

给定一个具有静态方法的类并引发一些异常

class Foo {
    public static void doThis() throws CannotDoThisException {
        //do something
    }
}

我使用下面的反射来调用doThis方法

public class Bar {
    Class c = Class.forName("Foo");
    Method m = c.getDeclaredMethod("doThis",null);
    try {
        m.invoke(null,null);
    } catch (CannotDoThisException e) {
       //Compiler says this is unreachable block.
    }
}

如何捕获异常CannotDothis异常

Answer 1

无法捕获该异常的原因是Method::invoke（javadoc）不会抛出它

如果通过invoke调用的方法抛出任何异常，反射层将捕获它，然后创建并抛出一个InvocationTargetException（javadoc），原始异常作为异常的cause

所以这就是你需要做的：

public class Bar {
    Class c = Class.forName("Foo");
    Method m = c.getDeclaredMethod("doThis",null);
    try {
        m.invoke(null,null);
    } catch (InvocationTargetException e) {
       if (e.getCause() instanceof CannotDoThisException) {
           // do something about it
       } else {
           // do something else
           // if the `cause` exception is unchecked you could rethrow it.
       }
    }
}