Commons CLI 所需的组 [英] Commons CLI required groups

问题描述

我正在用 Java 编写命令行应用程序，我选择了 Apache Commons CLI 来解析输入参数.

I am writing command line application in Java and I've chosen Apache Commons CLI to parse input arguments.

假设我有两个必需选项(即 -input 和 -output).我创建了新的 Option 对象并设置了 required 标志.现在一切都很好.但我有第三个，不是必需的选项，即.-帮助.使用我提到的设置，当用户想要显示帮助(使用 -help 选项)时，它会说-input 和 -output"是必需的.有没有办法实现这个(通过Commons CLI API，不是简单的 if (!hasOption) throw new XXXException()).

Let's say I have two required options (ie. -input and -output). I create new Option object and set required flag. For now it's all good. But I have third, not required option, ie. -help. With settings that I've mentioned, when user wants to show help (use -help option) it says "-input and -output" are required. Is there any way to implement this (via Commons CLI API, not simple if (!hasOption) throw new XXXException()).

推荐答案

在这种情况下，您必须定义两组选项并解析命令行两次.第一组选项包含位于所需组之前的选项(通常是 --help 和 --version)，第二组包含所有选项.

In this situation you have to define two sets of options and parse the command line twice. The first set of options contains the options that precede the required group (typically --help and --version), and the second set contains all the options.

您首先解析第一组选项，如果未找到匹配项，则继续处理第二组.

You start by parsing the first set of options, and if no match is found, you go on with the second set.

这是一个例子:

Options options1 = new Options();
options1.add(OptionsBuilder.withLongOpt("help").create("h"));
options1.add(OptionsBuilder.withLongOpt("version").create());

// this parses the command line but doesn't throw an exception on unknown options
CommandLine cl = new DefaultParser().parse(options1, args, true);

if (!cl.getOptions().isEmpty()) {

    // print the help or the version there.

} else {
    OptionGroup group = new OptionGroup();
    group.add(OptionsBuilder.withLongOpt("input").hasArg().create("i"));
    group.add(OptionsBuilder.withLongOpt("output").hasArg().create("o"));
    group.setRequired(true);

    Options options2 = new Options();
    options2.addOptionGroup(group);

    // add more options there.

    try {
        cl = new DefaultParser().parse(options2, args);

        // do something useful here.

    } catch (ParseException e) {
        // print a meaningful error message here.
    }
}

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