Java中的GetOpt操作

在shell工具中，有专门的getopt函数，使用方法如下所示：

while getopts "d:t:vh" opt; do
    case "${opt}" in
    "d")
        DATE="${OPTARG}"
        ;;
    "t")
        ID="${OPTARG}"
        ID2=`echo $ID | awk -F "_" '{print $2}'`
        ;;
    "v")
        printVersionInfo
        exit 0
        ;;
    "h")
        printHelpInfo
        exit 0
        ;;
    esac
done

其中的”d:t:vh”就是可以接收的选项类型，其中-d和-t意味着可以其后面可以接收参数，而-v和-h后面因为没有：，表示不可以接收参数，只用于单独使用。于是使用这个shell脚本的方式就大概如下：

./example.sh –d “d的参数” –t “t的参数”
./example.sh –h
./example.sh –v

GetOpt在Java1.8的全称为：

com.sun.org.apache.xalan.internal.xsltc.cmdline.getopt.GetOpt

Java程序员不能调用sun.*的相关包，以下是oracle给出的原因：

http://www.oracle.com/technetwork/java/faq-sun-packages-142232.html

既然不能够直接调用，就拷贝过来，反正依赖也不多。

只需要少许改动，解除与ErrorMsg类的依赖，删除一个MissingOptException（同样改成IllegalArgumentException），就可以直接使用了，以下就是修改后的代码：

/*
 * Copyright (c) 2007-2012, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/*
 * Copyright 2001-2004 The Apache Software Foundation.
 *
 * 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.
 */
/*
 * $Id: GetOpt.java,v 1.2.4.1 2005/08/31 11:46:04 pvedula Exp $
 */

import java.util.ArrayList;
import java.util.List;
import java.util.ListIterator;

/**
 * GetOpt is a Java equivalent to the C getopt() library function
 * discussed in man page getopt(3C). It provides command line
 * parsing for Java applications. It supports the most rules of the
 * command line standard (see man page intro(1)) including stacked
 * options such as '-sxm' (which is equivalent to -s -x -m); it
 * handles special '--' option that signifies the end of options.
 * Additionally this implementation of getopt will check for
 * mandatory arguments to options such as in the case of
 * '-d <file>' it will throw a MissingOptArgException if the
 * option argument '<file>' is not included on the commandline.
 * getopt(3C) does not check for this.
 *
 * @author G Todd Miller
 */
public class GetOpt {

    public static final String ILLEGAL_CMDLINE_OPTION_ERR = "ILLEGAL_CMDLINE_OPTION_ERR";

    public GetOpt(String[] args, String optString) {
        theOptions = new ArrayList();
        int currOptIndex = 0;
        theCmdArgs = new ArrayList();
        theOptionMatcher = new OptionMatcher(optString);
        // fill in the options list
        for (int i = 0; i < args.length; i++) {
            String token = args[i];
            int tokenLength = token.length();
            if (token.equals("--")) {         // end of opts
                currOptIndex = i + 1;         // set index of first operand
                break;                      // end of options
            } else if (token.startsWith("-") && tokenLength == 2) {
                // simple option token such as '-s' found
                theOptions.add(new Option(token.charAt(1)));
            } else if (token.startsWith("-") && tokenLength > 2) {
                // stacked options found, such as '-shm'
                // iterate thru the tokens after the dash and
                // add them to theOptions list
                for (int j = 1; j < tokenLength; j++) {
                    theOptions.add(new Option(token.charAt(j)));
                }
            } else if (!token.startsWith("-")) {
                // case 1- there are not options stored yet therefore
                // this must be an command argument, not an option argument
                if (theOptions.size() == 0) {
                    currOptIndex = i;
                    break;              // stop processing options
                } else {
                    // case 2-
                    // there are options stored, check to see if
                    // this arg belong to the last arg stored
                    int indexoflast = 0;
                    indexoflast = theOptions.size() - 1;
                    Option op = (Option) theOptions.get(indexoflast);
                    char opLetter = op.getArgLetter();
                    if (!op.hasArg() && theOptionMatcher.hasArg(opLetter)) {
                        op.setArg(token);
                    } else {
                        // case 3 -
                        // the last option stored does not take
                        // an argument, so again, this argument
                        // must be a command argument, not
                        // an option argument
                        currOptIndex = i;
                        break;                  // end of options
                    }
                }
            }// end option does not start with "-"
        } // end for args loop

        //  attach an iterator to list of options
        theOptionsIterator = theOptions.listIterator();

        // options are done, now fill out cmd arg list with remaining args
        for (int i = currOptIndex; i < args.length; i++) {
            String token = args[i];
            theCmdArgs.add(token);
        }
    }

    /**
     * debugging routine to print out all options collected
     */
    public void printOptions() {
        for (ListIterator it = theOptions.listIterator(); it.hasNext(); ) {
            Option opt = (Option) it.next();
            System.out.print("OPT =" + opt.getArgLetter());
            String arg = opt.getArgument();
            if (arg != null) {
                System.out.print(" " + arg);
            }
            System.out.println();
        }
    }

    /**
     * gets the next option found in the commandline. Distinguishes
     * between two bad cases, one case is when an illegal option
     * is found, and then other case is when an option takes an
     * argument but no argument was found for that option.
     * If the option found was not declared in the optString, then
     * an IllegalArgumentException will be thrown (case 1).
     * If the next option found has been declared to take an argument,
     * and no such argument exists, then a MissingOptArgException
     * is thrown (case 2).
     *
     * @return int - the next option found.
     * @throws IllegalArgumentException, MissingOptArgException.
     */
    public int getNextOption() throws IllegalArgumentException {
        int retval = -1;
        if (theOptionsIterator.hasNext()) {
            theCurrentOption = (Option) theOptionsIterator.next();
            char c = theCurrentOption.getArgLetter();
            boolean shouldHaveArg = theOptionMatcher.hasArg(c);
            String arg = theCurrentOption.getArgument();
            if (!theOptionMatcher.match(c)) {
//                ErrorMsg msg = new ErrorMsg(ErrorMsg.ILLEGAL_CMDLINE_OPTION_ERR,
//                                            new Character(c));
                throw (new IllegalArgumentException(String.format("%s : %s", ILLEGAL_CMDLINE_OPTION_ERR, new Character(c))));
            } else if (shouldHaveArg && (arg == null)) {
                throw (new IllegalArgumentException(String.format("%s : %s", ILLEGAL_CMDLINE_OPTION_ERR, new Character(c))));
            }
            retval = c;
        }
        return retval;
    }

    /**
     * gets the argument for the current parsed option. For example,
     * in case of '-d <file>', if current option parsed is 'd' then
     * getOptionArg() would return '<file>'.
     *
     * @return String - argument for current parsed option.
     */
    public String getOptionArg() {
        String retval = null;
        String tmp = theCurrentOption.getArgument();
        char c = theCurrentOption.getArgLetter();
        if (theOptionMatcher.hasArg(c)) {
            retval = tmp;
        }
        return retval;
    }

    /**
     * gets list of the commandline arguments. For example, in command
     * such as 'cmd -s -d file file2 file3 file4'  with the usage
     * 'cmd [-s] [-d <file>] <file>...', getCmdArgs() would return
     * the list {file2, file3, file4}.
     *
     * @return String[] - list of command arguments that may appear
     * after options and option arguments.
     * @params none
     */
    public String[] getCmdArgs() {
        String[] retval = new String[theCmdArgs.size()];
        int i = 0;
        for (ListIterator it = theCmdArgs.listIterator(); it.hasNext(); ) {
            retval[i++] = (String) it.next();
        }
        return retval;
    }

    private Option theCurrentOption = null;
    private ListIterator theOptionsIterator;
    private List theOptions = null;
    private List theCmdArgs = null;
    private OptionMatcher theOptionMatcher = null;

    ///////////////////////////////////////////////////////////
    //
    //   Inner Classes
    //
    ///////////////////////////////////////////////////////////

    // inner class to model an option
    class Option {
        private char theArgLetter;
        private String theArgument = null;

        public Option(char argLetter) {
            theArgLetter = argLetter;
        }

        public void setArg(String arg) {
            theArgument = arg;
        }

        public boolean hasArg() {
            return (theArgument != null);
        }

        public char getArgLetter() {
            return theArgLetter;
        }

        public String getArgument() {
            return theArgument;
        }
    } // end class Option

    // inner class to query optString for a possible option match,
    // and whether or not a given legal option takes an argument.
    //
    class OptionMatcher {
        public OptionMatcher(String optString) {
            theOptString = optString;
        }

        public boolean match(char c) {
            boolean retval = false;
            if (theOptString.indexOf(c) != -1) {
                retval = true;
            }
            return retval;
        }

        public boolean hasArg(char c) {
            boolean retval = false;
            int index = theOptString.indexOf(c) + 1;
            if (index == theOptString.length()) {
                // reached end of theOptString
                retval = false;
            } else if (theOptString.charAt(index) == ':') {
                retval = true;
            }
            return retval;
        }

        private String theOptString = null;
    } // end class OptionMatcher
}// end class GetOpt

我们先看GetOpt的构造函数，接收两个参数，第一个就是通过public static void main(String[] args)来指定的，也就是传过来的参数；第二个参数就更加重要了，这个是用来设置可接受选项类型的，这也是与shell中的getopt函数有着相同的含义。

下面就是一段关于getOpt函数的简单使用说明，对于每个选项，不用考虑其出现的顺序，这里也同样接收四种类型选项，其中d,t带具体的附加参数，而v,h没有附加参数，只作为帮助以及版本信息显示使用。

GetOpt getOpt = new GetOpt(args, "d:t:vh");
         while ((c = getOpt.getNextOption()) != -1) {
                System.out.println((char)c);
                switch (c) {
                    case 'd':
                        dateString = getOpt.getOptionArg();
                        break;
                    case 't':
                        campaignId = getOpt.getOptionArg();
                        break;
                    case 'h' :
                        printHelpInfo();
                        break;
                    case 'v':
                        printVersionInfo();
                        break;
                }
            }

使用getNextOption()函数来逐个获取下一个选项，直到返回-1表示没有下一个参数可以处理。通过switch/case语句对每个选项的附加参数进行区分，并结合getOptionArg()返回该选项中的附件参数，并进行处理。

如果输入了不合法的参数字符，就会抛出以下的错误信息（表明a是未定义的参数字符）：

java.lang.IllegalArgumentException: ILLEGAL_CMDLINE_OPTION_ERR : a
       at.utils.GetOpt.getNextOption(GetOpt.java:151)

以上就是java中使用getOpt函数的总体介绍，这对于处理linux形式的参数有着非常好的支持，并且符合程序员的习惯。