Version.java

/*
 * Copyright 2013 The Skfiy Open Association.
 *
 * 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 org.skfiy.typhon;

/**
 * 版本对象. 通过{@code currentVersion() }方法可获取应用当前的版本号.
 * {@link #compareTo(org.skfiy.typhon.Version) }方法提供比较版本号操作,
 * 但是该方法只会比较{@code major, minor, incremental }部分, {@code qualifier }
 * 部分并不会参与比较. 当Version实例{@code major, minor, incremental }部分相同
 * 及使{@code qualifier }部分不相同, 这2个Version也会认为是相等的.
 *
 * @author Kevin Zou <kevinz@skfiy.org>
 */
public final class Version implements Comparable<Version> {

    private static final Version CURRENT_VERSION = new Version();
    private final int[] vers = {0, 0, 0};
    private String qualifier;

    /**
     * 获取系统默认版本号创建{@code Version }实例.
     * 默认版本号通过{@link Globals#PROP_VERSION }属性键在{@link System }中获取.
     */
    private Version() {
        this(System.getProperty(Globals.PROP_VERSION));
    }
    
    /**
     * 通过已存在的版本号创建{@code Version }实例.
     * 
     * @param ver 已经存在的字符版本号
     */
    public Version(String ver) {
        if (ver.indexOf("-") > 1) {
            String[] vals = ver.split("-");
            ver = vals[0];
            qualifier = vals[1];
        }

        String[] vals = ver.split("\\.");
        for (int i = 0; i < vals.length; i++) {
            vers[i] = Integer.valueOf(vals[i]);
        }
    }
    
    /**
     * 构造{@code Version }实例.
     *
     * @param major 主版本号,一个无符号的整数
     * @param minor 次版本号,一个无符号的整数
     * @param incremental 增量版本号,一个无符号的整数
     * @param qualifier 版本限定符,可为空
     */
    public Version(int major, int minor, int incremental, String qualifier) {
        if (major < 0 || minor < 0 || incremental < 0) {
            throw new IllegalArgumentException(
                    "major, minor, incremental 版本号标识必须为一个无符号的整数");
        }
        
        vers[0] = major;
        vers[1] = minor;
        vers[2] = incremental;
        this.qualifier = qualifier;
    }

    /**
     * 主版本号.
     *
     * @return 一个无符号的整数
     */
    public int getMajor() {
        return vers[0];
    }

    /**
     * 次版本号.
     *
     * @return 一个无符号的整数
     */
    public int getMinor() {
        return vers[1];
    }

    /**
     * 增量版本号.
     *
     * @return 一个无符号的整数
     */
    public int getIncremental() {
        return vers[2];
    }

    /**
     * 版本限定符.
     *
     * @return 一个字符串,可能为{@code null }
     */
    public String getQualifier() {
        return qualifier;
    }

    @Override
    public int compareTo(Version o) {
        if (o == null) {
            return -1;
        }
        
        int r = Integer.compare(getMajor(), o.getMajor());
        if (r != 0) {
            return r;
        }

        r = Integer.compare(getMinor(), o.getMinor());
        if (r != 0) {
            return r;
        }

        r = Integer.compare(getIncremental(), o.getIncremental());
        return r;
    }

    @Override
    public boolean equals(Object obj) {
        if (obj instanceof Version) {
            return compareTo((Version) obj) == 0;
        }
        return false;
    }

    @Override
    public int hashCode() {
        return getMajor() + getMinor() + getIncremental();
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append(getMajor());
        sb.append(".").append(getMinor());

        if (getIncremental() > 0) {
            sb.append(".").append(getIncremental());
        }
        if (getQualifier() != null && !getQualifier().isEmpty()) {
            sb.append("-").append(getQualifier());
        }
        return sb.toString();
    }

    /**
     * 获取当前应用的版本实例.
     *
     * @return Version实例
     */
    public static Version currentVersion() {
        return CURRENT_VERSION;
    }
}