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Commons Digester example source code file (DigesterLoader.java)

This example Commons Digester source code file (DigesterLoader.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Commons Digester tags/keywords

annotatedelement, annotatedelement, annotation, annotation, annotationruleproviderfactory, class, class, digester, digesterloaderhandler, digesterloaderhandlerfactory, e, fromannotationsruleset, fromannotationsruleset, r, reflection

The Commons Digester DigesterLoader.java source code

/* $Id: DigesterLoader.java 992084 2010-09-02 19:52:17Z simonetripodi $
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.commons.digester.annotations;

import java.lang.annotation.Annotation;
import java.lang.reflect.AnnotatedElement;
import java.lang.reflect.Field;
import java.lang.reflect.Method;

import org.apache.commons.digester.Digester;
import org.apache.commons.digester.Rule;
import org.apache.commons.digester.RuleSet;
import org.apache.commons.digester.annotations.handlers.DefaultLoaderHandler;
import org.apache.commons.digester.annotations.internal.RuleSetCache;
import org.apache.commons.digester.annotations.reflect.MethodArgument;
import org.apache.commons.digester.annotations.spi.AnnotationRuleProviderFactory;
import org.apache.commons.digester.annotations.spi.DigesterLoaderHandlerFactory;
import org.apache.commons.digester.annotations.utils.AnnotationUtils;

/**
 * This class manages the creation of Digester instances analyzing target classes
 * annotated with digester annotations.
 *
 * @since 2.1
 */
public final class DigesterLoader {

    /**
     * In-memory LRU cache that stores already analyzed classes and relative
     * {@link RuleSet}.
     */
    private final RuleSetCache cachedRuleSet = new RuleSetCache();

    private final AnnotationRuleProviderFactory annotationRuleProviderFactory;

    private final DigesterLoaderHandlerFactory digesterLoaderHandlerFactory;

    /**
     * Creates a new {@link DigesterLoader} instance.
     *
     * @param annotationRuleProviderFactory
     * @param digesterLoaderHandlerFactory
     */
    protected DigesterLoader(AnnotationRuleProviderFactory annotationRuleProviderFactory,
            DigesterLoaderHandlerFactory digesterLoaderHandlerFactory) {
        this.annotationRuleProviderFactory = annotationRuleProviderFactory;
        this.digesterLoaderHandlerFactory = digesterLoaderHandlerFactory;
    }

    protected AnnotationRuleProviderFactory getAnnotationRuleProviderFactory() {
        return annotationRuleProviderFactory;
    }

    protected DigesterLoaderHandlerFactory getDigesterLoaderHandlerFactory() {
        return digesterLoaderHandlerFactory;
    }

    /**
     * Creates a new digester which rules are defined by analyzing the digester
     * annotations in the target class.
     *
     * @param target the class has to be analyzed.
     * @return a new Digester instance.
     */
    public Digester createDigester(final Class<?> target) {
        Digester digester = new Digester();
        digester.setClassLoader(target.getClassLoader());
        addRules(target, digester);
        return digester;
    }

    /**
     * Add rules to an already created Digester instance, analyzing the digester
     * annotations in the target class.
     *
     * @param target the class has to be analyzed.
     * @param digester the Digester instance reference.
     */
    public void addRules(final Class<?> target, final Digester digester) {
        RuleSet ruleSet = getRuleSet(target);
        ruleSet.addRuleInstances(digester);
    }

    /**
     * Builds a new {@link RuleSet} analyzing the digester annotations in the
     * target class.
     *
     * It avoids iterate the annotations analysis for already analyzed classes,
     * using an in-memory LRU cache.
     *
     * @param target the class has to be analyzed.
     * @return a new {@link RuleSet}.
     */
    public RuleSet getRuleSet(final Class<?> target) {
        if (this.cachedRuleSet.containsKey(target)) {
            return this.cachedRuleSet.get(target);
        }

        FromAnnotationsRuleSet ruleSet = new FromAnnotationsRuleSet(this);
        addRulesTo(target, ruleSet);
        this.cachedRuleSet.put(target, ruleSet);

        return ruleSet;
    }

    /**
     * Analyzes the target class and adds the {@link AnnotationRuleProvider}s to
     * the existing {@link FromAnnotationsRuleSet}.
     *
     * @param target the class has to be analyzed.
     * @param ruleSet the RuleSet where adding the providers.
     */
    public void addRulesTo(final Class<?> target, FromAnnotationsRuleSet ruleSet) {
        if (target == Object.class
                || target.isInterface()
                || ruleSet.mapsClass(target)) {
            return;
        }

        if (this.cachedRuleSet.containsKey(target)) {
            ruleSet.addRulesProviderFrom(this.cachedRuleSet.get(target));
            ruleSet.addMappedClass(target);
            return;
        }

        // current analyzed class
        handle(target, ruleSet);

        // class fields
        for (Field field : target.getDeclaredFields()) {
            handle(field, ruleSet);
        }

        // class methods
        for (Method method : target.getDeclaredMethods()) {
            handle(method, ruleSet);

            // method args
            Annotation[][] parameterAnnotations = method.getParameterAnnotations();
            Class<?>[] parameterTypes = method.getParameterTypes();
            for (int i = 0; i < parameterTypes.length; i++) {
                handle(new MethodArgument(i, parameterTypes[i], parameterAnnotations[i]), ruleSet);
            }
        }

        ruleSet.addMappedClass(target);
        addRulesTo(target.getSuperclass(), ruleSet);
    }

    /**
     * Executes an analysis for each annotation present in the element.
     *
     * @param element the current element under analysis.
     * @param ruleSet the ruleSet where add providers.
     */
    private void handle(AnnotatedElement element, FromAnnotationsRuleSet ruleSet) {
        for (Annotation annotation : element.getAnnotations()) {
            handle(annotation, element, ruleSet);
        }
    }

    /**
     * Handles the current visited element and related annotation, invoking the
     * right handler putting the rule provider in the rule set.
     *
     * @param annotation the current visited annotation.
     * @param element the current visited element.
     */
    @SuppressWarnings("unchecked")
    private <A extends Annotation, E extends AnnotatedElement, R extends Rule> void handle(A annotation,
            E element,
            FromAnnotationsRuleSet ruleSet) {
        Class<?> annotationType = annotation.annotationType();

        // check if it is one of the @*.List annotation
        if (annotationType.isAnnotationPresent(DigesterRuleList.class)) {
            Annotation[] annotations = AnnotationUtils.getAnnotationsArrayValue(annotation);
            if (annotations != null && annotations.length > 0) {
                // if it is an annotations array, process them
                for (Annotation ptr : annotations) {
                    handle(ptr, element, ruleSet);
                }
            }
        } else if (annotationType.isAnnotationPresent(DigesterRule.class)) {
            DigesterRule digesterRule = annotationType.getAnnotation(DigesterRule.class);

            if (DefaultLoaderHandler.class == digesterRule.handledBy()) {
                Class<? extends AnnotationRuleProvider providerType =
                    (Class<? extends AnnotationRuleProvider) digesterRule.providedBy();
                ruleSet.addRuleProvider(AnnotationUtils.getAnnotationPattern(annotation),
                        providerType,
                        annotation,
                        element);
            } else {
                Class<? extends DigesterLoaderHandler handlerType =
                    (Class<? extends DigesterLoaderHandler) digesterRule.handledBy();
                DigesterLoaderHandler<Annotation, AnnotatedElement> handler =
                    this.digesterLoaderHandlerFactory.newInstance(handlerType);

                // run!
                handler.handle(annotation, element, ruleSet);
            }
        }
    }

}

Other Commons Digester examples (source code examples)

Here is a short list of links related to this Commons Digester DigesterLoader.java source code file:



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