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/*
* ============LICENSE_START=======================================================
* ONAP
* ================================================================================
* Copyright (C) 2018-2019 AT&T Intellectual Property. All rights reserved.
* Modifications Copyright (C) 2019-2020 Nordix Foundation
* ================================================================================
* 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.
* ============LICENSE_END=========================================================
*/
package org.onap.policy.drools.pooling.extractor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Map;
import java.util.Properties;
import java.util.concurrent.ConcurrentHashMap;
import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.tuple.Pair;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Extractors for each object class. Properties define how the data is to be
* extracted for a given class, where the properties are similar to the
* following:
*
* <pre>
* <code><a.prefix>.<class.name> = ${event.reqid}</code>
* </pre>
*
* <p>For any given field name (e.g., "reqid"), it first looks for a public "getXxx()"
* method to extract the specified field. If that fails, then it looks for a public field
* by the given name. If that also fails, and the object is a <i>Map</i> subclass, then it
* simply uses the "get(field-name)" method to extract the data from the map.
*/
public class ClassExtractors {
private static final Logger logger = LoggerFactory.getLogger(ClassExtractors.class);
/**
* Properties that specify how the data is to be extracted from a given
* class.
*/
private final Properties properties;
/**
* Property prefix, including a trailing ".".
*/
private final String prefix;
/**
* Type of item to be extracted.
*/
private final String type;
/**
* Maps the class name to its extractor.
*/
private final ConcurrentHashMap<String, Extractor> class2extractor = new ConcurrentHashMap<>();
/**
* Constructor.
*
* @param props properties that specify how the data is to be extracted from
* a given class
* @param prefix property name prefix, prepended before the class name
* @param type type of item to be extracted
*/
public ClassExtractors(Properties props, String prefix, String type) {
this.properties = props;
this.prefix = (prefix.endsWith(".") ? prefix : prefix + ".");
this.type = type;
}
/**
* Gets the number of extractors in the map.
*
* @return gets the number of extractors in the map
*/
protected int size() {
return class2extractor.size();
}
/**
* Extracts the desired data item from an object.
*
* @param object object from which to extract the data item
* @return the extracted item, or {@code null} if it could not be extracted
*/
public Object extract(Object object) {
if (object == null) {
return null;
}
Extractor ext = getExtractor(object);
return ext.extract(object);
}
/**
* Gets the extractor for the given type of object, creating one if it
* doesn't exist yet.
*
* @param object object whose extracted is desired
* @return an extractor for the object
*/
private Extractor getExtractor(Object object) {
Class<?> clazz = object.getClass();
Extractor ext = class2extractor.get(clazz.getName());
if (ext == null) {
// allocate a new extractor, if another thread doesn't beat us to it
ext = class2extractor.computeIfAbsent(clazz.getName(), xxx -> buildExtractor(clazz));
}
return ext;
}
/**
* Builds an extractor for the class.
*
* @param clazz class for which the extractor should be built
*
* @return a new extractor
*/
private Extractor buildExtractor(Class<?> clazz) {
String value = properties.getProperty(prefix + clazz.getName(), null);
if (value != null) {
// property has config info for this class - build the extractor
return buildExtractor(clazz, value);
}
/*
* Get the extractor, if any, for the super class or interfaces, but
* don't add one if it doesn't exist
*/
Extractor ext = getClassExtractor(clazz, false);
if (ext != null) {
return ext;
}
/*
* No extractor defined for for this class or its super class - we
* cannot extract data items from objects of this type, so just
* allocated a null extractor.
*/
logger.warn("missing property {}{}", prefix, clazz.getName());
return new NullExtractor();
}
/**
* Builds an extractor for the class, based on the config value extracted
* from the corresponding property.
*
* @param clazz class for which the extractor should be built
* @param value config value (e.g., "${event.request.id}"
* @return a new extractor
*/
private Extractor buildExtractor(Class<?> clazz, String value) {
if (!value.startsWith("${")) {
logger.warn("property value for {}{} does not start with {}", prefix, clazz.getName(), "'${'");
return new NullExtractor();
}
if (!value.endsWith("}")) {
logger.warn("property value for {}{} does not end with '}'", prefix, clazz.getName());
return new NullExtractor();
}
// get the part in the middle
String val = value.substring(2, value.length() - 1);
if (val.startsWith(".")) {
logger.warn("property value for {}{} begins with '.'", prefix, clazz.getName());
return new NullExtractor();
}
if (val.endsWith(".")) {
logger.warn("property value for {}{} ends with '.'", prefix, clazz.getName());
return new NullExtractor();
}
// everything's valid - create the extractor
try {
ComponetizedExtractor ext = new ComponetizedExtractor(clazz, val.split("[.]"));
/*
* If there's only one extractor, then just return it, otherwise
* return the whole extractor.
*/
return (ext.extractors.length == 1 ? ext.extractors[0] : ext);
} catch (ExtractorException e) {
logger.warn("cannot build extractor for {}", clazz.getName(), e);
return new NullExtractor();
}
}
/**
* Gets the extractor for a class, examining all super classes and
* interfaces.
*
* @param clazz class whose extractor is desired
* @param addOk {@code true} if the extractor may be added, provided the
* property is defined, {@code false} otherwise
* @return the extractor to be used for the class, or {@code null} if no
* extractor has been defined yet
*/
private Extractor getClassExtractor(Class<?> clazz, boolean addOk) {
if (clazz == null) {
return null;
}
Extractor ext = null;
if (addOk) {
String val = properties.getProperty(prefix + clazz.getName(), null);
if (val != null) {
/*
* A property is defined for this class, so create the extractor
* for it.
*/
return class2extractor.computeIfAbsent(clazz.getName(), xxx -> buildExtractor(clazz));
}
}
// see if the superclass has an extractor
if ((ext = getClassExtractor(clazz.getSuperclass(), true)) != null) {
return ext;
}
// check the interfaces, too
for (Class<?> clz : clazz.getInterfaces()) {
if ((ext = getClassExtractor(clz, true)) != null) {
break;
}
}
return ext;
}
/**
* Extractor that always returns {@code null}. Used when no extractor could
* be built for a given object type.
*/
private class NullExtractor implements Extractor {
@Override
public Object extract(Object object) {
logger.info("cannot extract {} from {}", type, object.getClass());
return null;
}
}
/**
* Component-ized extractor. Extracts an object that is referenced
* hierarchically, where each name identifies a particular component within
* the hierarchy. Supports retrieval from {@link Map} objects, as well as
* via getXxx() methods, or by direct field retrieval.
*
* <p>Note: this will <i>not</i> work if POJOs are contained within a Map.
*/
private class ComponetizedExtractor implements Extractor {
/**
* Extractor for each component.
*/
private final Extractor[] extractors;
/**
* Constructor.
*
* @param clazz the class associated with the object at the root of the
* hierarchy
* @param names name associated with each component
* @throws ExtractorException extractor exception
*/
public ComponetizedExtractor(Class<?> clazz, String[] names) throws ExtractorException {
this.extractors = new Extractor[names.length];
Class<?> clz = clazz;
for (int x = 0; x < names.length; ++x) {
String comp = names[x];
Pair<Extractor, Class<?>> pair = buildExtractor(clz, comp);
extractors[x] = pair.getLeft();
clz = pair.getRight();
}
}
/**
* Builds an extractor for the given component of an object.
*
* @param clazz type of object from which the component will be
* extracted
* @param comp name of the component to extract
* @return a pair containing the extractor and the extracted object's
* type
* @throws ExtractorException extrator exception
*/
private Pair<Extractor, Class<?>> buildExtractor(Class<?> clazz, String comp) throws ExtractorException {
Pair<Extractor, Class<?>> pair = getMethodExtractor(clazz, comp);
if (pair == null) {
pair = getFieldExtractor(clazz, comp);
}
if (pair == null) {
pair = getMapExtractor(clazz, comp);
}
// didn't find an extractor
if (pair == null) {
throw new ExtractorException("class " + clazz + " contains no element " + comp);
}
return pair;
}
@Override
public Object extract(Object object) {
Object obj = object;
for (Extractor ext : extractors) {
if (obj == null) {
break;
}
obj = ext.extract(obj);
}
return obj;
}
/**
* Gets an extractor that invokes a getXxx() method to retrieve the
* object.
*
* @param clazz container's class
* @param name name of the property to be retrieved
* @return a new extractor, or {@code null} if the class does not
* contain the corresponding getXxx() method
* @throws ExtractorException if the getXxx() method is inaccessible
*/
private Pair<Extractor, Class<?>> getMethodExtractor(Class<?> clazz, String name) throws ExtractorException {
Method meth;
String nm = "get" + StringUtils.capitalize(name);
try {
meth = clazz.getMethod(nm);
Class<?> retType = meth.getReturnType();
if (retType == void.class) {
// it's a void method, thus it won't return an object
return null;
}
return Pair.of(new MethodExtractor(meth), retType);
} catch (NoSuchMethodException expected) {
// no getXxx() method, maybe there's a field by this name
logger.debug("no method {} in {}", nm, clazz.getName(), expected);
return null;
} catch (SecurityException e) {
throw new ExtractorException("inaccessible method " + clazz + "." + nm, e);
}
}
/**
* Gets an extractor for a field within the object.
*
* @param clazz container's class
* @param name name of the field whose value is to be extracted
* @return a new extractor, or {@code null} if the class does not
* contain the given field
* @throws ExtractorException if the field is inaccessible
*/
private Pair<Extractor, Class<?>> getFieldExtractor(Class<?> clazz, String name) throws ExtractorException {
Field field = getClassField(clazz, name);
if (field == null) {
return null;
}
return Pair.of(new FieldExtractor(field), field.getType());
}
/**
* Gets an extractor for an item within a Map object.
*
* @param clazz container's class
* @param key item key within the map
* @return a new extractor, or {@code null} if the class is not a Map
* subclass
*/
private Pair<Extractor, Class<?>> getMapExtractor(Class<?> clazz, String key) {
if (!Map.class.isAssignableFrom(clazz)) {
return null;
}
/*
* Don't know the value's actual type, so we'll assume it's a Map
* for now. Things should still work OK, as this is only used to
* direct the constructor on what type of extractor to create next.
* If the object turns out not to be a map, then the MapExtractor
* for the next component will just return null.
*/
return Pair.of(new MapExtractor(key), Map.class);
}
/**
* Gets field within a class, examining all super classes and
* interfaces.
*
* @param clazz class whose field is desired
* @param name name of the desired field
* @return the field within the class, or {@code null} if the field does
* not exist
* @throws ExtractorException if the field is inaccessible
*/
private Field getClassField(Class<?> clazz, String name) throws ExtractorException {
if (clazz == null) {
return null;
}
try {
return clazz.getField(name);
} catch (NoSuchFieldException expected) {
// no field by this name - try super class & interfaces
logger.debug("no field {} in {}", name, clazz.getName(), expected);
return null;
} catch (SecurityException e) {
throw new ExtractorException("inaccessible field " + clazz + "." + name, e);
}
}
}
}
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