---

GoogleOptions

GoogleOptions是来自 Bazel Project 的命令行参数解析器。将 com.google.devtools.common.options 包拆分为一个单独的 jar，用于通用实用程序。

环境搭建:

• 引入maven依赖

<dependency>
  <groupId>com.github.pcj</groupId>
  <artifactId>google-options</artifactId>
  <version>1.0.0</version>
</dependency>

• 引入官方提供的示例Demo

package example;

import com.google.devtools.common.options.Option;
import com.google.devtools.common.options.OptionsBase;

import java.util.List;

/**
 * Command-line options definition for example server.
 */
public class ServerOptions extends OptionsBase {

  @Option(
      name = "help",
      abbrev = 'h',
      help = "Prints usage info.",
      defaultValue = "true"
    )
  public boolean help;

  @Option(
      name = "host",
      abbrev = 'o',
      help = "The server host.",
      category = "startup",
      defaultValue = ""
  )
  public String host;

  @Option(
    name = "port",
    abbrev = 'p',
    help = "The server port.",
    category = "startup",
    defaultValue = "8080"
    )
    public int port;

  @Option(
    name = "dir",
    abbrev = 'd',
    help = "Name of directory to serve static files.",
    category = "startup",
    allowMultiple = true,
    defaultValue = ""
    )
    public List<String> dirs;

}

Option注解参数说明

• name:选项名称
• defaultValue:默认值
• abbrev:选项的单字符缩写
• help:使用信息的帮助字符串
• category:描述此选项所属的类别
• allowMultiple:一个标志，指示是否应允许选项类型在单个选项列表中多次出现。

实际使用:

package example;

import com.google.devtools.common.options.OptionsParser;
import java.util.Collections;

public class Server {
  //java -jar server.jar --host=127.0.0.1 --port=21 --dir=E:\test --dir=E:\demo
  public static void main(String[] args) {
    OptionsParser parser = OptionsParser.newOptionsParser(ServerOptions.class);
    parser.parseAndExitUponError(args);
    ServerOptions options = parser.getOptions(ServerOptions.class);
    if (options.host.isEmpty() || options.port < 0 || options.dirs.isEmpty()) {
      printUsage(parser);
      return;
    }

    System.out.format("Starting server at %s:%d...\n", options.host, options.port);
    for (String dirname : options.dirs) {
      System.out.format("\\--> Serving static files at <%s>\n", dirname);
    }
  }

  private static void printUsage(OptionsParser parser) {
    System.out.println("Usage: java -jar server.jar OPTIONS");
    System.out.println(parser.describeOptions(Collections.<String, String>emptyMap(),
                                              OptionsParser.HelpVerbosity.LONG));
  }

}