org.danann.cernunnos.spring.ApplicationContextTask.java Source code

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Here is the source code for org.danann.cernunnos.spring.ApplicationContextTask.java

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/*
 * Copyright 2008 Andrew Wills
 *
 * 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 org.danann.cernunnos.spring;

import java.net.URL;

import org.springframework.beans.factory.BeanIsAbstractException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.FileSystemXmlApplicationContext;

import org.danann.cernunnos.AbstractContainerTask;
import org.danann.cernunnos.EntityConfig;
import org.danann.cernunnos.Formula;
import org.danann.cernunnos.LiteralPhrase;
import org.danann.cernunnos.Phrase;
import org.danann.cernunnos.Reagent;
import org.danann.cernunnos.ReagentType;
import org.danann.cernunnos.ResourceHelper;
import org.danann.cernunnos.SimpleFormula;
import org.danann.cernunnos.SimpleReagent;
import org.danann.cernunnos.TaskRequest;
import org.danann.cernunnos.TaskResponse;

public final class ApplicationContextTask extends AbstractContainerTask {

    // Instance Members.
    private final ResourceHelper resource = new ResourceHelper();
    private Phrase cache;
    private URL prevUrl = null;
    private ApplicationContext prevBeans = null;

    /*
     * Public API.
     */

    public static final Reagent CACHE = new SimpleReagent("CACHE", "@cache", ReagentType.PHRASE, Boolean.class,
            "If true (the default), this task will retain and reuse an existing ApplicationContext "
                    + "unless/until either:  (1) a different XML file is specified;  or (2) this reagent "
                    + "becomes false.",
            new LiteralPhrase(Boolean.TRUE));

    public Formula getFormula() {
        Reagent[] reagents = new Reagent[] { ResourceHelper.CONTEXT_SOURCE, ResourceHelper.LOCATION_TASK, CACHE,
                AbstractContainerTask.SUBTASKS };
        final Formula rslt = new SimpleFormula(ApplicationContextTask.class, reagents);
        return rslt;
    }

    public void init(EntityConfig config) {

        super.init(config);

        // Instance Members.
        this.resource.init(config);
        this.cache = (Phrase) config.getValue(CACHE);

    }

    public void perform(TaskRequest req, TaskResponse res) {

        URL loc = resource.evaluate(req, res);

        ApplicationContext beans = getApplicationContext(loc, (Boolean) cache.evaluate(req, res));

        for (String name : beans.getBeanDefinitionNames()) {
            try {
                res.setAttribute(name, beans.getBean(name));
            } catch (BeanIsAbstractException biae) {
                // This is normal -- we can't ask for abstract beans...
                log.debug("Not adding bean '" + name + "' to TaskResponse because it is abstract.");
            }
        }

        super.performSubtasks(req, res);

    }

    /*
     * Implementation.
     */

    private synchronized ApplicationContext getApplicationContext(URL config, boolean useCache) {

        if (!useCache || !config.equals(prevUrl)) {
            prevBeans = new FileSystemXmlApplicationContext(config.toExternalForm());
            prevUrl = config;
        }

        return prevBeans;

    }

}