Struts example source code file (BaseTemplateEngine.java)

This example Struts source code file (BaseTemplateEngine.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 - Struts tags/keywords

default_theme_properties_file_name, default_theme_properties_file_name, file, filenotfoundexception, inputstream, inputstream, io, ioexception, logger, map, properties, properties, string, string, unable, util

The Struts BaseTemplateEngine.java source code

/*
 * $Id: BaseTemplateEngine.java 963612 2010-07-13 07:10:06Z lukaszlenart $
 *
 * 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.struts2.components.template;

import com.opensymphony.xwork2.util.ClassLoaderUtil;
import com.opensymphony.xwork2.util.logging.Logger;
import com.opensymphony.xwork2.util.logging.LoggerFactory;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;

/**
 * Base class for template engines.
 */
public abstract class BaseTemplateEngine implements TemplateEngine {

    private static final Logger LOG = LoggerFactory.getLogger(BaseTemplateEngine.class);

    /**
     * The default theme properties file name. Default is 'theme.properties'
     */
    public static final String DEFAULT_THEME_PROPERTIES_FILE_NAME = "theme.properties";

    final Map<String, Properties> themeProps = new HashMap();

    public Map getThemeProps(Template template) {
        synchronized (themeProps) {
            Properties props = themeProps.get(template.getTheme());
            if (props == null) {
                props = readNewProperties(template);
                themeProps.put(template.getTheme(), props);
            }
            return props;
        }
    }

    private Properties readNewProperties(Template template) {
        String propName = buildPropertyFilename(template);
        return loadProperties(propName);
    }

    private Properties loadProperties(String propName) {
        InputStream is = readProperty(propName);
        Properties props = new Properties();
        if (is != null) {
            tryToLoadPropertiesFromStream(props, propName, is);
        }
        return props;
    }

    private InputStream readProperty(String propName) {
        InputStream is = tryReadingPropertyFileFromFileSystem(propName);
        if (is == null) {
            is = readPropertyFromClasspath(propName);
        }
        return is;
    }

    /**
     * if its not in filesystem. let's try the classpath
     */
    private InputStream readPropertyFromClasspath(String propName) {
        return ClassLoaderUtil.getResourceAsStream(propName, getClass());
    }

    private void tryToLoadPropertiesFromStream(Properties props, String propName, InputStream is) {
        try {
            props.load(is);
        } catch (IOException e) {
            LOG.error("Could not load " + propName, e);
        } finally {
            tryCloseStream(is);
        }
    }

    private void tryCloseStream(InputStream is) {
        try {
            is.close();
        } catch (IOException io) {
            LOG.warn("Unable to close input stream", io);
        }
    }

    private String buildPropertyFilename(Template template) {
        return new StringBuilder().append(template.getDir())
                .append("/")
                .append(template.getTheme())
                .append("/")
                .append(getThemePropertiesFileName()).toString();
    }

    /**
     * WW-1292 let's try getting it from the filesystem
     */
    private InputStream tryReadingPropertyFileFromFileSystem(String propName) {
        File propFile = new File(propName);
        try {
            return createFileInputStream(propFile);
        } catch (FileNotFoundException e) {
            LOG.warn("Unable to find file in filesystem [" + propFile.getAbsolutePath() + "]");
            return null;
        }
    }

    private InputStream createFileInputStream(File propFile) throws FileNotFoundException {
        InputStream is = null;
        if (propFile.exists()) {
            is = new FileInputStream(propFile);
        }
        return is;
    }

    protected String getFinalTemplateName(Template template) {
        String t = template.toString();
        if (t.indexOf(".") <= 0) {
            return t + "." + getSuffix();
        }
        return t;
    }

    protected String getThemePropertiesFileName() {
        return DEFAULT_THEME_PROPERTIES_FILE_NAME;
    }

    protected abstract String getSuffix();

}