Gets all values returned by appropriately annotated member variables or methods on the given object. - Java java.lang.annotation

Java examples for java.lang.annotation:Method Annotation

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Description

Gets all values returned by appropriately annotated member variables or methods on the given object.

Demo Code


//package com.java2s;
import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

public class Main {
    public static void main(String[] argv) throws Exception {
        Class annotationClass = String.class;
        Object object = "java2s.com";
        System.out.println(getAnnotationValues(annotationClass, object));
    }/*from www .  java2s .co  m*/

    /**
     * Gets all values returned by appropriately annotated member variables
     * or methods on the given object.
     */
    public static List<String> getAnnotationValues(Class annotationClass,
            Object object) {
        try {
            for (Method m : object.getClass().getMethods()) {
                for (Annotation a : m.getAnnotations()) {
                    if (a.annotationType().equals(annotationClass)) {
                        if (m.getParameterTypes().length != 0) {
                            throw new RuntimeException(
                                    "Methods annotated with "
                                            + annotationClass
                                            + " may not have parameters!");
                        }
                        if (m.getReturnType().equals(String[].class)) {
                            String[] values = (String[]) m.invoke(object);
                            if (values == null) {
                                return Collections.emptyList();
                            } else {
                                return Arrays.asList(values);
                            }
                        } else if (m.getReturnType().equals(String.class)) {
                            return Collections.singletonList((String) m
                                    .invoke(object));
                        } else {
                            throw new RuntimeException(
                                    m
                                            + " must not be annotated with "
                                            + annotationClass
                                            + " since it does not return a String or String[]");
                        }
                    }
                }
            }
            for (Field f : object.getClass().getFields()) {
                for (Annotation a : f.getAnnotations()) {
                    if (a.annotationType().equals(annotationClass)) {
                        if (f.getType().equals(String[].class)) {
                            String[] values = (String[]) f.get(object);
                            if (values == null) {
                                return Collections.emptyList();
                            } else {
                                return Arrays.asList(values);
                            }
                        } else if (f.getType().equals(String.class)) {
                            return Collections.singletonList((String) f
                                    .get(object));
                        } else {
                            throw new RuntimeException(
                                    f
                                            + " must not be annotated with "
                                            + annotationClass
                                            + " since it is not a String or String[]");
                        }
                    }
                }
            }
            throw new RuntimeException("No " + annotationClass.getName()
                    + " annotation found for class " + object.getClass()
                    + "!");
        } catch (InvocationTargetException e) {
            throw new RuntimeException(e);
        } catch (IllegalAccessException e) {
            throw new RuntimeException(e);
        }
    }
}

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