src/java/org/apache/velocity/texen/util/PropertiesUtil.java

package org.apache.velocity.texen.util;

/*
 * 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.    
 */

import java.io.FileInputStream;
import java.io.InputStream;
import java.util.Properties;
import java.util.StringTokenizer;

import org.apache.velocity.texen.Generator;

/**
 * A property utility class for the texen text/code generator
 * Usually this class is only used from a Velocity context.
 *
 * @author <a href="mailto:leon@opticode.co.za">Leon Messerschmidt</a>
 * @author <a href="mailto:sbailliez@apache.org">Stephane Bailliez</a>
 * @version $Id$
 */
public class PropertiesUtil
{
    /**
     * Load properties from either a file in the templatePath if there
     * is one or the classPath.
     *
     * @param propertiesFile the properties file to load through
     * either the templatePath or the classpath.
     * @return a properties instance filled with the properties found
     * in the file or an empty instance if no file was found.
     */
    public Properties load(final String propertiesFile)
    {
        Properties properties = null;

        String templatePath = Generator.getInstance().getTemplatePath();
        try
        {
            if (templatePath != null)
            {
                properties = loadFromTemplatePath(propertiesFile);
            }
            else
            {
                properties = loadFromClassPath(propertiesFile);
            }
        }
        catch (RuntimeException e)
        {
            throw e;
        }
        catch (Exception e)
        {
            throw new RuntimeException("Could not load properties: " + e.getMessage());
        }

        return properties;
    }

    /**
     * Load a properties file from the templatePath defined in the
     * generator. As the templatePath can contains multiple paths,
     * it will cycle through them to find the file. The first file
     * that can be successfully loaded is considered. (kind of
     * like the java classpath), it is done to clone the Velocity
     * process of loading templates.
     *
     * @param propertiesFile the properties file to load. It must be
     * a relative pathname.
     * @return a properties instance loaded with the properties from
     * the file. If no file can be found it returns an empty instance.
     * @throws Exception
     */
    protected Properties loadFromTemplatePath(final String propertiesFile)
    	throws Exception
    {
        Properties properties = new Properties();
        String templatePath = Generator.getInstance().getTemplatePath();

        // We might have something like the following:
        //
        // #set ($dbprops = $properties.load("$generator.templatePath/path/props")
        //
        // as we have in Torque but we want people to start using
        //
        // #set ($dbprops = $properties.load("path/props")
        //
        // so that everything works from the filesystem or from
        // a JAR. So the actual Generator.getTemplatePath()
        // is not deprecated but it's use in templates
        // should be.
        StringTokenizer st = new StringTokenizer(templatePath, ",");
        while (st.hasMoreTokens())
        {
            String templateDir = st.nextToken();
            InputStream stream = null;
            try
            {
                // If the properties file is being pulled from the
                // file system and someone is using the method whereby
                // the properties file is assumed to be in the template
                // path and they are simply using:
                //
                // #set ($dbprops = $properties.load("props") (1)
                //
                // than we have to tack on the templatePath in order
                // for the properties file to be found. We want (1)
                // to work whether the generation is being run from
                // the file system or from a JAR file.
                String fullPath = propertiesFile;

                // FIXME probably not that clever since there could be
                // a mix of file separators and the test will fail :-(
                if (!fullPath.startsWith(templateDir))
                {
                    fullPath = templateDir + "/" + propertiesFile;
                }

                stream = new FileInputStream(fullPath);
                properties.load(stream);
                // first pick wins, we don't need to go further since
                // we found a valid file.
                break;
            }
            finally
            {
        	if (stream != null)
        	{
        	    stream.close();
        	}
            }
        }
        return properties;
    }

    /**
     * Load a properties file from the classpath
     *
     * @param propertiesName the properties file to load.
     * @return a properties instance loaded with the properties from
     * the file. If no file can be found it returns an empty instance.
     * @throws Exception
     */
    protected Properties loadFromClassPath(final String propertiesName)
    	throws Exception
    {
        Properties properties = new Properties();
        ClassLoader classLoader = this.getClass().getClassLoader();

        InputStream inputStream = null;

        try
        {
            // This is a hack for now to make sure that properties
            // files referenced in the filesystem work in
            // a JAR file. We have to deprecate the use
            // of $generator.templatePath in templates first
            // and this hack will allow those same templates
            // that use $generator.templatePath to work in
            // JAR files.

            String propertiesFile = propertiesName.startsWith("$generator")
        	    ? propertiesName.substring("$generator.templatePath/".length())
    		    : propertiesName;

    	    inputStream = classLoader.getResourceAsStream(propertiesFile);
            properties.load(inputStream);
        }
        finally
        {
            if (inputStream != null)
            {
        	inputStream.close();
            }
        }
        return properties;
    }
}