jodd.util.AnnotationDataReader Maven / Gradle / Ivy
// Copyright (c) 2003-present, Jodd Team (http://jodd.org)
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package jodd.util;
import java.lang.annotation.Annotation;
import java.lang.reflect.AccessibleObject;
/**
* Annotation reader reads an annotation and returns {@link AnnotationData annotation data object}
* populated with annotation element values. Can be used to simulate annotation inheritance,
* as such does not exist in Java.
*
* There are 3 ways how this class can be used. First, it can be used on single annotation,
* but that does not make much sense.
*
* Second way is with child and parent annotation. The parent annotation is default one,
* like a base class. Child annotation contains some predefined values different from parent.
* Note that child annotation does NOT have to specify all elements - all missing elements
* will be read from default parent annotation. So child annotation behaves like it is
* overriding the parent one.
*
* Third way is similar, except the child annotation is also annotated with parent annotation!
* Besides overriding features and default values, this way we can finalize some element value
* and prevent it from being modified by user.
*/
public abstract class AnnotationDataReader> {
protected final Annotation defaultAnnotation;
protected final Class annotationClass;
// ---------------------------------------------------------------- ctor
/**
* Creates new annotation data reader using annotation definition
* from class generics. Moreover, allows annotation to be annotated
* with default annotation, for convenient and fail-back value reading.
* @param annotationClass annotation type to read from
* @param defaultAnnotationClass optional default annotation type, used to annotate the annotation class.
*/
@SuppressWarnings( {"unchecked"})
protected AnnotationDataReader(Class annotationClass, Class defaultAnnotationClass) {
if (annotationClass == null) {
Class[] genericSupertypes = ReflectUtil.getGenericSupertypes(this.getClass());
if (genericSupertypes != null) {
annotationClass = genericSupertypes[0];
}
if (annotationClass == null || annotationClass == Annotation.class) {
throw new IllegalArgumentException("Missing annotation from generics supertype");
}
}
this.annotationClass = annotationClass;
// read default annotation
if (defaultAnnotationClass != null && defaultAnnotationClass != annotationClass) {
Annotation defaultAnnotation = annotationClass.getAnnotation(defaultAnnotationClass);
// no default annotation on parent, create annotation
if (defaultAnnotation == null) {
try {
defaultAnnotation = defaultAnnotationClass.newInstance();
} catch (Exception ignore) {
}
}
this.defaultAnnotation = defaultAnnotation;
} else {
this.defaultAnnotation = null;
}
}
// ---------------------------------------------------------------- methods
/**
* Returns annotation class.
*/
public Class getAnnotationClass() {
return annotationClass;
}
/**
* Returns true if annotation is present on
* given accessible object.
*/
public boolean hasAnnotation(AccessibleObject accessibleObject) {
return accessibleObject.isAnnotationPresent(annotationClass);
}
/**
* Reads {@link AnnotationData annotation data} on provided accessible object.
* If annotation is not presented, null is returned.
*/
public D readAnnotationData(AccessibleObject accessibleObject) {
A annotation = accessibleObject.getAnnotation(annotationClass);
if (annotation == null) {
return null;
}
return createAnnotationData(annotation);
}
/**
* Reads {@link AnnotationData annotation data} on provided type.
* If annotation is not presented, null is returned.
*/
public D readAnnotationData(Class type) {
A annotation = type.getAnnotation(annotationClass);
if (annotation == null) {
return null;
}
return createAnnotationData(annotation);
}
/**
* Creates annotation data from given annotation.
*/
protected abstract D createAnnotationData(A annotation);
// ---------------------------------------------------------------- read
/**
* Reads non-empty, trimmed, annotation element value. If annotation value is
* missing, it will read value from default annotation. If still missing,
* returns null.
*/
protected String readStringElement(A annotation, String name) {
Object annotationValue = ReflectUtil.readAnnotationValue(annotation, name);
if (annotationValue == null) {
if (defaultAnnotation == null) {
return null;
}
annotationValue = ReflectUtil.readAnnotationValue(defaultAnnotation, name);
if (annotationValue == null) {
return null;
}
}
String value = StringUtil.toSafeString(annotationValue);
return value.trim();
}
/**
* Reads annotation element as an object. If annotation value
* is missing, it will be read from default annotation.
* If still missing, returns null.
*/
protected Object readElement(A annotation, String name) {
Object annotationValue = ReflectUtil.readAnnotationValue(annotation, name);
if (annotationValue == null) {
if (defaultAnnotation != null) {
annotationValue = ReflectUtil.readAnnotationValue(defaultAnnotation, name);
}
}
return annotationValue;
}
/**
* Reads string element from the annotation. Empty strings are detected
* and default value is returned instead.
*/
protected String readString(A annotation, String name, String defaultValue) {
String value = readStringElement(annotation, name);
if (StringUtil.isEmpty(value)) {
value = defaultValue;
}
return value;
}
/**
* Reads boolean element from the annotation.
*/
protected boolean readBoolean(A annotation, String name, boolean defaultValue) {
Boolean value = (Boolean) readElement(annotation, name);
if (value == null) {
return defaultValue;
}
return value.booleanValue();
}
/**
* Reads int element from the annotation.
*/
protected int readInt(A annotation, String name, int defaultValue) {
Integer value = (Integer) readElement(annotation, name);
if (value == null) {
return defaultValue;
}
return value.intValue();
}
// ---------------------------------------------------------------- annotation data
/**
* Base class for annotation data, for holding annotation elements values.
*/
public abstract static class AnnotationData {
protected final N annotation;
protected AnnotationData(N annotation) {
this.annotation = annotation;
}
/**
* Returns annotation.
*/
public N getAnnotation() {
return annotation;
}
}
}