de.weltraumschaf.commons.application.Version Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of application Show documentation
Provides utilities to reduce boiler plate code when creating simple command line or swing applications.
There is a newer version: 2.2.0
/*
 * LICENSE
 *
 * "THE BEER-WARE LICENSE" (Revision 43):
 * "Sven Strittmatter"  wrote this file.
 * As long as you retain this notice you can do whatever you want with
 * this stuff. If we meet some day, and you think this stuff is worth it,
 * you can buy me a non alcohol-free beer in return.
 *
 * Copyright (C) 2012 "Sven Strittmatter" 
 */
package de.weltraumschaf.commons.application;

import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

/**
 * Reads the current version from a property file.
 *
 * 
 * The property files only defines one property. Import is to switch resource filtering on in your POM
 * for that properties file.
 * 
 *  *  version=1.0.0
 * 
 *
 * 
 * This property file may be processed by a Maven filter to provide the verison from
 * the pom.xml:
 * 
 *  *  version=${pom.version}
 * 
 *
 * 
 * If you save the file in src/main/resources/foo/bar/version.properties
 * you can use the version this way:
 * 
 *
 * {@code
 * Version version = new Version("/foo/bar/version.properties");
 * version.load()
 * println(version.getVersion);
 * }
 *
 * @since 1.0.0
 * @author Sven Strittmatter 
 */
public final class Version {

    /**
     * Location of property file.
     */
    private final String propertyFileName;

    /**
     * Indicates whether the properties are already loaded or not.
     */
    private boolean propertiesLoaded;

    /**
     * Properties.
     */
    private final Properties properties = new Properties();

    /**
     * Private constructor for singleton.
     *
     * @param propertyFileName Location of file, e.g. /de/weltraumschaf/commons/version.properties.
     */
    public Version(final String propertyFileName) {
        super();
        this.propertyFileName = propertyFileName;
    }

    /**
     * Opens the properties file and loads it.
     *
     * Only loads th property file once.
     *
     * @throws IOException On IO errors of the property file.
     */
    public void load() throws IOException {
        if (!propertiesLoaded) {
            loadImpl();
            propertiesLoaded = true;
        }
    }

    /**
     * Encapsulates the file loading.
     *
     * @throws IOException On IO errors of the property file.
     */
    void loadImpl() throws IOException {
        InputStream in = null;

        try {
            in = getClass().getResourceAsStream(propertyFileName);
            properties.load(in);
            in.close();
        } finally {
            if (null != in) {
                in.close();
            }
        }
    }

    /**
     * Get the version string.
     *
     * @return The version string.
     */
    public String getVersion() {
        return properties.getProperty(PropertyNames.VERSION.toString(),
                                      PropertyNames.VERSION.getDefaultValue());
    }

    /**
     * Returns the version string.
     *
     * @return Same as {@link #getVersion()}.
     */
    @Override
    public String toString() {
        return getVersion();
    }

    /**
     * Available properties in the file.
     */
    enum PropertyNames {

        /**
         * Version property.
         */
        VERSION("version", "n/a");

        /**
         * Property name.
         */
        private final String name;

        /**
         * Default value.
         */
        private final String defaultValue;

        /**
         * Initializes the enum with the property name.
         *
         * @param name The property name.
         * @param defaultValue Fall back value.
         */
        PropertyNames(final String name, final String defaultValue) {
            this.name = name;
            this.defaultValue = defaultValue;
        }

        /**
         * Returns the property name.
         *
         * @return String containing the property name.
         */
        @Override
        public String toString() {
            return name;
        }

        /**
         * Get the fallback value.
         *
         * @return Return default value string.
         */
        public String getDefaultValue() {
            return defaultValue;
        }

    }
}