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gw.lang.annotation.Annotations Maven / Gradle / Ivy
/*
* Copyright 2014 Guidewire Software, Inc.
*/
package gw.lang.annotation;
import gw.lang.reflect.TypeSystem;
import gw.util.SpaceEfficientHashMap;
import java.lang.annotation.Annotation;
import gw.util.Array;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.Arrays;
import java.util.Map;
public class Annotations {
private Annotations() {
}
/**
* Returns a builder that can be used to construct an annotation instance.
*/
public static Builder builder(Class annotationType) {
return new Builder(annotationType);
}
/**
* Convenience method that constructs an annotation instance with a single "value" element.
*/
public static T create(Class annotationType, Object value) {
return new Builder(annotationType).withValue(value).create();
}
/**
* Convenience method that constructs an annotation instance with no elements.
*/
public static T create(Class annotationType) {
return new Builder(annotationType).create();
}
public static class Builder {
private final Class _annotationType;
private final Map _configuredElements;
private Builder(Class annotationType) {
_annotationType = annotationType;
_configuredElements = new SpaceEfficientHashMap();
}
public Builder withElement(String name, Object value) {
Method elementMethod;
try {
elementMethod = _annotationType.getMethod(name);
} catch (NoSuchMethodException e) {
throw new IllegalArgumentException(
"No such element \"" + name + "\" defined on annotation type " + _annotationType.getName());
}
if (elementMethod.getReturnType().isPrimitive()) {
if (!TypeSystem.isBoxedTypeFor(TypeSystem.get(elementMethod.getReturnType()), TypeSystem.getFromObject(value))) {
throw new IllegalArgumentException(
"Element \"" + name + "\" on annotation type " + _annotationType.getName() + " must be of type " +
elementMethod.getReturnType() + ". Got " + value +
(value == null ? "" : " (type " + value.getClass().getName() + ")"));
}
} else if ( elementMethod.getReturnType().isArray() &&
elementMethod.getReturnType().getComponentType().isInstance( value ) ) {
//TODO-dp review this with Scott
// IType fromObject = TypeSystem.getFromObject( value );
// Object arr = fromObject.makeArrayInstance( 1 );
// fromObject.setArrayComponent( arr, 0, value );
Object arr = Array.newInstance(value.getClass(), 1);
Array.set(arr, 0, value);
value = arr;
} else if (value == null && elementMethod.getDefaultValue() != null) {
value = elementMethod.getDefaultValue();
} else if (!elementMethod.getReturnType().isInstance(value)) {
throw new IllegalArgumentException(
"Element \"" + name + "\" on annotation type " + _annotationType.getName() + " must be of type " +
elementMethod.getReturnType() + ". Got " + value +
(value == null ? "" : " (type " + value.getClass().getName() + ")"));
} else if (value instanceof Object[] && hasNullElements((Object[]) value)) {
throw new IllegalArgumentException(
"Object arrays can't have null elements. Got " + Arrays.toString((Object[]) value) + " for element \"" +
name + "\"");
}
_configuredElements.put(elementMethod, new Element(value));
return this;
}
public Builder withValue(Object value) {
return withElement("value", value);
}
private static class Element {
private final Object _value;
private final int _arrayLength;
private final Class _componentType;
Element(Object value) {
assert value != null;
Class valueClass = value.getClass();
_arrayLength = valueClass.isArray() ? Array.getLength(value) : -1;
_componentType = valueClass.getComponentType();
_value = copyValueIfNecessary(value, _arrayLength, _componentType);
}
/**
* Protects a value from outside modification. Incoming and outgoing values must be copied if necessary in
* order to preserve the contract of annotations.
*/
Object getValue() {
return copyValueIfNecessary(_value, _arrayLength, _componentType);
}
boolean valueEquals(Object otherValue) {
boolean result;
if (isArray()) {
if (otherValue.getClass().isArray()) {
if (_arrayLength == Array.getLength(otherValue)) {
boolean allElementsEqual = true;
for (int i = 0; i < _arrayLength; i++) {
if (!Array.get(_value, i).equals(Array.get(otherValue, i))) {
allElementsEqual = false;
break;
}
}
result = allElementsEqual;
} else {
result = false;
}
} else {
result = false;
}
} else {
result = _value.equals(otherValue);
}
return result;
}
int valueHashCode() {
int hash;
if (isArray()) {
int arrayHash = 1;
for (int i = 0; i < _arrayLength; i++) {
Object arrayElement = Array.get(_value, i);
arrayHash = 31 * arrayHash + arrayElement.hashCode();
}
hash = arrayHash;
} else {
hash = _value.hashCode();
}
return hash;
}
void valueToString(StringBuilder buf) {
if (isArray()) {
buf.append('[');
for (int i = 0; i < _arrayLength; i++) {
if (i > 0) {
buf.append(", ");
}
buf.append(Array.get(_value, i));
}
buf.append(']');
} else {
buf.append(_value);
}
}
private boolean isArray() {
return _componentType != null;
}
private static Object copyValueIfNecessary(Object value, int arrayLength, Class componentType) {
Object result;
if (arrayLength > 0) {
result = Array.newInstance(componentType, arrayLength);
//noinspection SuspiciousSystemArraycopy
System.arraycopy(value, 0, result, 0, arrayLength);
} else {
// 0-length arrays are immutable, and
// all other types allowed in annotation elements are immutable
result = value;
}
return result;
}
}
public T create() {
final Map elements = buildElements();
ClassLoader cl = determineClassLoader();
return _annotationType.cast(Proxy.newProxyInstance( cl,
new Class[] { _annotationType },
new AnnotationInvocationHandler( elements, _annotationType ) ));
}
private ClassLoader determineClassLoader()
{
// First see if the context class loader can see the annotation and
// use it if so (needed for some hibernate insanity)
if( canLoadAnnotation( Thread.currentThread().getContextClassLoader() ) )
{
return Thread.currentThread().getContextClassLoader();
}
else
{
// Otherwise, use the annotation types class loader, which actually makes sense
return _annotationType.getClassLoader();
}
}
private boolean canLoadAnnotation( ClassLoader cl )
{
Class loadedVersion = null;
if(cl != null)
{
try
{
loadedVersion = Class.forName(_annotationType.getName(), false, cl);
}
catch( ClassNotFoundException e )
{
//ignore
}
}
return loadedVersion == _annotationType;
}
private boolean hasNullElements(Object[] array) {
for (Object o : array) {
if (o == null) {
return true;
}
}
return false;
}
private Map buildElements() {
Map elements = new SpaceEfficientHashMap();
if(_annotationType != null) {
for (Method elementMethod : TypeSystem.getDeclaredMethods( _annotationType )) {
Element value = _configuredElements.get(elementMethod);
if (value == null) {
Object defaultValue = elementMethod.getDefaultValue();
if (defaultValue == null) {
throw new IllegalStateException(
"Can't create annotation of type " + _annotationType.getName() + ": missing value for element \"" +
elementMethod.getName() + "\"");
}
value = new Element(defaultValue);
}
elements.put(elementMethod, value);
}
}
return elements;
}
public static class AnnotationInvocationHandler implements InvocationHandler
{
private final Map _elements;
private final Class _annotationType;
public AnnotationInvocationHandler( Map elements, Class annotationType )
{
_elements = elements;
_annotationType = annotationType;
}
public Class getAnnotationType() {
return _annotationType;
}
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
Object result;
if (Object.class.equals(method.getDeclaringClass())) {
if ("equals".equals(method.getName())) {
result = equalsImpl(args[0]);
} else if ("hashCode".equals(method.getName())) {
result = hashCodeImpl();
} else {
boolean b = "toString".equals(method.getName());
assert b;
result = toStringImpl();
}
} else if ( Annotation.class.equals(method.getDeclaringClass())) {
boolean b = "annotationType".equals(method.getName());
assert b;
result = _annotationType;
} else {
boolean b = _annotationType.equals(method.getDeclaringClass());
assert b;
result = _elements.get(method).getValue();
}
return result;
}
/**
* @see java.lang.annotation.Annotation#toString()
*/
private String toStringImpl() {
StringBuilder buf = new StringBuilder();
buf.append('@').append(_annotationType.getName());
// print elements in deterministic order
Method[] elementMethods = TypeSystem.getDeclaredMethods( _annotationType );
if (elementMethods.length > 0) {
buf.append('(');
for (int i = 0; i < elementMethods.length; i++) {
if (i > 0) {
buf.append(", ");
}
Method elementMethod = elementMethods[i];
buf.append(elementMethod.getName()).append('=');
_elements.get(elementMethod).valueToString(buf);
}
buf.append(')');
}
return buf.toString();
}
/**
* @see java.lang.annotation.Annotation#hashCode()
*/
private int hashCodeImpl() {
int hash = 0;
for ( Map.Entry entry : _elements.entrySet()) {
hash += hashElement(entry.getKey(), entry.getValue());
}
return hash;
}
private int hashElement(Method elementMethod, Element element) {
return (127 * elementMethod.getName().hashCode()) ^ element.valueHashCode();
}
/**
* @see java.lang.annotation.Annotation#equals(Object)
*/
private boolean equalsImpl(Object obj) throws Throwable {
if (!_annotationType.isInstance(obj)) {
return false;
}
for (Map.Entry entry : _elements.entrySet()) {
Object otherValue = getElementValue(obj, entry.getKey());
if (!entry.getValue().valueEquals(otherValue)) {
return false;
}
}
return true;
}
private Object getElementValue(Object annotation, Method elementMethod) throws Throwable {
try {
return elementMethod.invoke(annotation);
} catch ( InvocationTargetException e) {
throw e.getTargetException();
}
}
}
}
}
