Tutorial :Java commons-cli, options with list of possible values


How can I make an option accept only some specified values like in the following example:

$ java -jar Mumu.jar -a foo  OK  $ java -jar Mumu.jar -a bar  OK  $ java -jar Mumu.jar -a foobar  foobar is not a valid value for -a  


Since commons-cli doesn't support that directly, the simplest solution is probably to check the value of an option when you get it.


The other way can be to extend the Option class. At work we have made that:

    public static class ChoiceOption extends Option {          private final String[] choices;            public ChoiceOption(              final String opt,              final String longOpt,              final boolean hasArg,              final String description,              final String... choices) throws IllegalArgumentException {          super(opt, longOpt, hasArg, description + ' ' + Arrays.toString(choices));          this.choices = choices;         }          public String getChoiceValue() throws RuntimeException {          final String value = super.getValue();          if (value == null) {              return value;          }          if (ArrayUtils.contains(choices, value)) {              return value;          }          throw new RuntimeException( value " + describe(this) + " should be one of " + Arrays.toString(choices));       }          @Override        public boolean equals(final Object o) {          if (this == o) {              return true;          } else if (o == null || getClass() != o.getClass()) {              return false;          }          return new EqualsBuilder().appendSuper(super.equals(o))                  .append(choices, ((ChoiceOption) o).choices)                  .isEquals();       }          @Override        public int hashCode() {          return new ashCodeBuilder().appendSuper(super.hashCode()).append(choices).toHashCode();        }    }  


I've wanted this kind of behaviour before, and never came across a way to do this with an already provided method. That's not to say it doesn't exist. A kind of lame way, is to add the code yourself such as:

private void checkSuitableValue(CommandLine line) {      if(line.hasOption("a")) {          String value = line.getOptionValue("a");          if("foo".equals(value)) {              println("OK");          } else if("bar".equals(value)) {              println("OK");          } else {              println(value + "is not a valid value for -a");              System.exit(1);          }       }   }  

Obviously there would be nicer ways to do this than the long if/else, possibly with an enum, but that should be all you'd need. Also I've not compiled this, but I reckon it should work.

This example also does not make the "-a" switch mandatory, since that wasn't specified in the question.

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