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univocity's open source parsers for processing different text formats using a consistent API
/*
* Copyright (c) 2015. uniVocity Software Pty Ltd
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.univocity.parsers.common.beans;
import java.lang.ref.*;
import java.lang.reflect.*;
import java.util.*;
import java.util.concurrent.*;
/**
* Helper class used to obtain property descriptors from annotated java beans whose values are set via reflection.
* This class was implemented to eliminate direct compile-time dependency with {@link java.beans.Introspector} and
* other classes in the {@code java.beans.*} package. This is required to allow Android developers to use uniVocity-parsers.
* Android developers should add have openbeans-1.0.jar
* in their classpath to be able to use uniVocity-parsers.
*
* When available, the classes from package {@code com.googlecode.openbeans.*} will be used, otherwise the
* bean introspection classes classes from {@code java.beans.*} package will be loaded.
*
* If everything fails, then the parser will try to manipulate fields in annotated java beans directly, instead
* of using their getters and setters.
*/
public final class BeanHelper {
private static final PropertyWrapper[] EMPTY = new PropertyWrapper[0];
private static final Class introspectorClass = findIntrospectorImplementationClass();
private static final Method beanInfoMethod = getBeanInfoMethod();
private static final Method propertyDescriptorMethod = getMethod("getPropertyDescriptors", beanInfoMethod, false);
static Method PROPERTY_WRITE_METHOD = getMethod("getWriteMethod", propertyDescriptorMethod, true);
static Method PROPERTY_READ_METHOD = getMethod("getReadMethod", propertyDescriptorMethod, true);
static Method PROPERTY_NAME_METHOD = getMethod("getName", propertyDescriptorMethod, true);
private static final Map, WeakReference> descriptors = new ConcurrentHashMap, WeakReference>();
private BeanHelper() {
}
/**
* Returns the property descriptors of all properties available from a class
* @param beanClass the class whose property descriptors should be returned
* @return an array of all property descriptors of the given class. Might be empty.
*/
public static PropertyWrapper[] getPropertyDescriptors(Class beanClass) {
if (propertyDescriptorMethod == null) {
return EMPTY;
}
PropertyWrapper[] out = null;
WeakReference reference = descriptors.get(beanClass);
if (reference != null) {
out = reference.get();
}
if (out == null) {
try {
Object beanInfo = beanInfoMethod.invoke(null, beanClass, Object.class);
Object[] propertyDescriptors = (Object[]) propertyDescriptorMethod.invoke(beanInfo);
out = new PropertyWrapper[propertyDescriptors.length];
for (int i = 0; i < propertyDescriptors.length; i++) {
out[i] = new PropertyWrapper(propertyDescriptors[i]);
}
} catch (Exception ex) {
out = EMPTY;
}
descriptors.put(beanClass, new WeakReference(out));
}
return out;
}
private static Class findIntrospectorImplementationClass() {
try {
return Class.forName("com.googlecode.openbeans.Introspector");
} catch (Throwable e1) {
try {
return Class.forName("java.beans.Introspector");
} catch (Throwable e2) {
return null;
}
}
}
private static Method getBeanInfoMethod() {
if (introspectorClass == null) {
return null;
}
try {
return introspectorClass.getMethod("getBeanInfo", Class.class, Class.class);
} catch (Throwable e) {
return null;
}
}
private static Method getMethod(String methodName, Method method, boolean fromComponentType) {
if (method == null) {
return null;
}
try {
Class returnType = method.getReturnType();
if (fromComponentType) {
returnType = returnType.getComponentType();
}
return returnType.getMethod(methodName);
} catch (Exception ex) {
return null;
}
}
}