资源下载寻求与具体标注方法及其注释元素 [英] Java seek a method with specific annotation and its annotation element

问题描述

假设我有这样的注释类

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface MethodXY {
    public int x();
    public int y();
}

public class AnnotationTest {
    @MethodXY(x=5, y=5)
    public void myMethodA(){ ... }

    @MethodXY(x=3, y=2)
    public void myMethodB(){ ... }
}

那么，有没有办法寻找到一个对象，求该方法与@MethodXY注释，在那里它的元素x = 3，Y = 2，并调用它？

So is there a way to look into an object, "seek" out the method with the @MethodXY annotation, where its element x = 3, y = 2, and invoke it?

感谢

推荐答案

下面是一个方法，它返回特定注释的方法：

Here is a method, which returns methods with specific annotations:

public static List<Method> getMethodsAnnotatedWith(final Class<?> type, final Class<? extends Annotation> annotation) {
    final List<Method> methods = new ArrayList<Method>();
    Class<?> klass = type;
    while (klass != Object.class) { // need to iterated thought hierarchy in order to retrieve methods from above the current instance
        // iterate though the list of methods declared in the class represented by klass variable, and add those annotated with the specified annotation
        final List<Method> allMethods = new ArrayList<Method>(Arrays.asList(klass.getDeclaredMethods()));       
        for (final Method method : allMethods) {
            if (method.isAnnotationPresent(annotation)) {
                Annotation annotInstance = method.getAnnotation(annotation);
                // TODO process annotInstance
                methods.add(method);
            }
        }
        // move to the upper class in the hierarchy in search for more methods
        klass = klass.getSuperclass();
    }
    return methods;
}

它可以很容易地修改您的特定需求。请注意，所提供的方法遍历类层次，以便找到与所需的注释的方法。

It can be easily modified to your specific needs. Pls note that the provided method traverses class hierarchy in order to find methods with required annotations.

下面是您的特定需求的方法：

Here is a method for your specific needs:

public static List<Method> getMethodsAnnotatedWithMethodXY(final Class<?> type) {
    final List<Method> methods = new ArrayList<Method>();
    Class<?> klass = type;
    while (klass != Object.class) { // need to iterated thought hierarchy in order to retrieve methods from above the current instance
        // iterate though the list of methods declared in the class represented by klass variable, and add those annotated with the specified annotation
        final List<Method> allMethods = new ArrayList<Method>(Arrays.asList(klass.getDeclaredMethods()));
        for (final Method method : allMethods) {
            if (method.isAnnotationPresent(MethodXY.class)) {
                MethodXY annotInstance = method.getAnnotation(MethodXY.class);
                if (annotInstance.x() == 3 && annotInstance.y() == 2) {         
                    methods.add(method);
                }
            }
        }
        // move to the upper class in the hierarchy in search for more methods
        klass = klass.getSuperclass();
    }
    return methods;
}

有关的发现方法（S）请参见的调用。这里的一个潜在困难是方法参数的数量，这可能会发现的方法和因此需要一些额外的处理之间变化。

For invocation of the found method(s) pls refer a tutorial. One of the potential difficulties here is the number of method arguments, which could vary between found methods and thus requiring some additional processing.

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