com.sqewd.open.dal.core.Env.java Source code

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Here is the source code for com.sqewd.open.dal.core.Env.java

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/**
 * Copyright 2012 Subho Ghosh (subho dot ghosh at outlook dot com)
 * 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 com.sqewd.open.dal.core;

import java.io.File;
import java.util.HashMap;

import org.apache.commons.configuration.XMLConfiguration;
import org.w3c.dom.Document;

import com.sqewd.open.dal.api.utils.XMLUtils;
import com.sqewd.open.dal.core.persistence.DataManager;

/**
 * Initializes the System Environment. Shared handles should be registered with
 * the Env instance.
 * 
 * @author subhagho
 * 
 */
public class Env {
    public static final String _CONFIG_XPATH_ROOT_ = "/configuration";

    public static final String _CONFIG_DIR_WORK_ = "env.work[@directory]";
    public static final String _CONFIG_DIR_TEMP_ = "env.temp[@directory]";

    private XMLConfiguration config = null;
    private String configf = null;
    private String workdir = null;
    private String tempdir = null;
    private final HashMap<String, Object> shared = new HashMap<String, Object>();

    private ClassLoader entityLoader = null;

    private Env(String filename) throws Exception {
        XMLUtils.validate(filename, "/schema/moong-dal.xsd");

        configf = filename;
        config = new XMLConfiguration(configf);

        workdir = config.getString(_CONFIG_DIR_WORK_);
        if (workdir == null || workdir.isEmpty())
            throw new Exception("Invalid Configuration : Missing parameter [" + _CONFIG_DIR_WORK_ + "]");
        tempdir = config.getString(_CONFIG_DIR_TEMP_);
        if (tempdir == null || tempdir.isEmpty())
            tempdir = System.getProperty("java.io.tmpdir");

    }

    /**
     * @return the config
     */
    public XMLConfiguration getConfig() {
        return config;
    }

    /**
     * Get the configuration handle as a XML document.
     * 
     * @return
     */
    public Document getConfigDom() {
        return config.getDocument();
    }

    /**
     * @return the configf
     */
    public String getConfigf() {
        return configf;
    }

    /**
     * @return the workdir
     */
    public String getWorkdir() {
        return workdir;
    }

    /**
     * @return the tempdir
     */
    public String getTempdir() {
        return tempdir;
    }

    /**
     * Get/Create a directory specified by the sub-path under the temp
     * directory.
     * 
     * @param folder
     *            - Sub-Path
     * @return
     * @throws Exception
     */
    public String getTempPath(String folder) throws Exception {
        String path = tempdir + "/" + folder;
        File di = new File(path);
        if (!di.exists()) {
            di.mkdirs();
        }
        return di.getAbsolutePath();
    }

    /**
     * Get/Create a directory specified by the sub-path under the work
     * directory.
     * 
     * @param folder
     *            - Sub-Path
     * @return
     * @throws Exception
     */
    public String getWorkPath(String folder) throws Exception {
        String path = workdir + "/" + folder;
        File di = new File(path);
        if (!di.exists()) {
            di.mkdirs();
        }
        return di.getAbsolutePath();
    }

    /**
     * Register an Object instance to the shared cache.
     * 
     * @param key
     *            - Search Key
     * @param obj
     *            - Object handle
     * @param overwrite
     *            - Overwrite if exists?
     * @throws Exception
     */
    public void register(String key, Object obj, boolean overwrite) throws Exception {
        if (shared.containsKey(key)) {
            if (overwrite) {
                shared.remove(key);
            } else {
                throw new Exception("Shared Cache : Key [" + key + "] already exists, and overwrite set to false.");
            }
        }
        shared.put(key, obj);
    }

    /**
     * Get an object handle from the shared cache.
     * 
     * @param key
     *            - Search Key
     * @return
     */
    public Object lookup(String key) {
        if (shared.containsKey(key))
            return shared.get(key);
        return null;
    }

    /**
     * @return the entityLoader
     */
    public ClassLoader getEntityLoader() {
        return entityLoader;
    }

    /**
     * @param entityLoader
     *            the entityLoader to set
     */
    public void setEntityLoader(ClassLoader entityLoader) {
        this.entityLoader = entityLoader;
    }

    // Instance
    private static Env _instance = null;
    private static Object _lock = new Object();

    /**
     * Initialize the environment handle. Should only be called once, at the
     * start of the application.
     * 
     * @param filename
     *            - Configuration filename.
     */
    public static void create(String filename) throws Exception {
        synchronized (_lock) {
            try {
                _instance = new Env(filename);
            } catch (Exception e) {
                e.printStackTrace();
                _instance = null;
                throw e;
            }
        }
    }

    /**
     * Get a handle to the environment.
     * 
     * @return
     * @throws Exception
     */
    public static Env get() throws Exception {
        synchronized (_lock) {
            if (_instance == null)
                throw new Exception("Environment hasn't been initialized or initialization failed.");
            return _instance;
        }
    }

    /**
     * Dispose the operating environment.
     */
    public static void dispose() {
        if (_instance != null) {
            DataManager.release();
            if (_instance.shared != null) {
                _instance.shared.clear();
            }
            _instance.config = null;
        }
        _instance = null;
    }

}