net.sf.zekr.engine.template.TemplateEngine.java Source code

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Here is the source code for net.sf.zekr.engine.template.TemplateEngine.java

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/*
 *               In the name of Allah
 * This file is part of The Zekr Project. Use is subject to
 * license terms.
 *
 * Author:         Mohsen Saboorian
 * Start Date:     Oct 14, 2004
 */

package net.sf.zekr.engine.template;

import java.io.StringWriter;
import java.io.Writer;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;

import net.sf.zekr.common.runtime.Naming;
import net.sf.zekr.engine.log.Logger;

import org.apache.commons.collections.ExtendedProperties;
import org.apache.velocity.Template;
import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.Velocity;

/**
 * An adapter class for velocity template engine.<br>
 * This class is not singleton due to thread-safety issues. A call to {@link #getInstance()} simply returns a
 * new instance.
 * 
 * @author Mohsen Saboorian
 */
public class TemplateEngine {
    VelocityContext context;
    private static TemplateEngine thisInstance;
    Template template;

    private TemplateEngine() {
        try {
            System.setProperty("zekr.home", Naming.getWorkspace());
            Velocity.setExtendedProperties(new ExtendedProperties("res/config/lib/velocity.properties"));
            Velocity.init();
            context = new VelocityContext();
        } catch (Exception e) {
            Logger.getLogger(this.getClass()).log(e);
        }
    }

    /**
     * @return a new template engine instance.
     */
    public static TemplateEngine getInstance() {
        return new TemplateEngine();
    }

    /**
     * @param name The file name of the desired template
     * @return The associated <code>Template</code> object
     * @throws Exception
     */
    public Template getTemplate(String name) throws Exception {
        return Velocity.getTemplate(name);
    }

    /**
     * Add a key-value pair to the template engine context.
     * 
     * @param key
     * @param value
     */
    public void put(String key, Object value) {
        context.put(key, value);
    }

    /**
     * Add a key-value pair to the template engine context. value should be of type <code>String</code>.
     * 
     * @param key
     * @param value
     */
    public void putWrappedString(String key, String value) {
        context.put(key, value);
    }

    /**
     * Add a collection of key-value pairs to the template engine context. Keys should be of type
     * <code>String</code>.
     */
    public void putAll(Map<String, Object> map) {
        for (Iterator<Entry<String, Object>> iter = map.entrySet().iterator(); iter.hasNext();) {
            Entry<String, Object> entry = iter.next();
            context.put(entry.getKey(), entry.getValue());
        }
    }

    /**
     * @param name the file name of the desired template
     * @return the result <code>String</code> after the context map is merged (applied) into the source
     *         template file.
     * @throws Exception
     */
    public String getUpdated(String name) throws Exception {
        template = Velocity.getTemplate(name);
        Writer writer = new StringWriter();
        template.merge(context, writer);
        return writer.toString();
    }

}