de.unkrig.commons.util

Class CommandLineOptions

java.lang.Object

de.unkrig.commons.util.CommandLineOptions

public final class CommandLineOptions
extends java.lang.Object

Parses "command line options" from the args of your main() method and configures a Java bean accordingly.

See Also:

parse(String[], Object)

Method Summary

Modifier and Type	Method and Description
static int	applyCommandLineOption(java.lang.String optionName, java.lang.reflect.Method method, java.lang.String[] args, int optionArgumentIndex, java.lang.Object target) Parses the command line option's arguments from the args and invokes the method.
static java.lang.reflect.Method	getMethodForOption(java.lang.String option, java.lang.Class<?> targetClass) Determines the method of target.getClass() that is applicable for the given option.
static java.lang.String[]	parse(java.lang.String[] args, java.lang.Object target) Sets the target's properties from the args.
static void	printResource(java.lang.Class<?> clasS, java.lang.String name, java.nio.charset.Charset charset, java.io.PrintStream ps) Reads (and decodes) the contents of a resource, replaces all occurrences of "${system-property-name}" with the value of the system property, and writes the result to a PrintStream.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

parse

public static java.lang.String[] parse(java.lang.String[] args,
                                       java.lang.Object target)

Sets the target's properties from the args.

All public methods of the target (including those declared by superclasses) are regarded candidates iff they are annotated with the CommandLineOption annotation.

The possible "names" of the command line option are derived from the name element of the CommandLineOption annotation, or, if that is missing, from the method name.

When an element of args equals such a name, then the following elements in args are converted to match the parameter types of the method. After that, the method is invoked with the arguments, and the elements are removed from args.

Parsing terminates iff either

• The args are exhausted
• The special arg "--" is reached (which is consumed)
• The special arg "-" is reached (which is notconsumed)

Example:

   public
   class MyMain {

       // ...

       @CommandLineOption
       public static void
       setWidth(double width) {
           System.out.println("width=" + width);
       }
   }

   ...

   final MyMain main = new MyMain();

   String[] args = { "--width", "17.5", "a", "b" };
   System.out.println(Arrays.toString(args);            // Prints "[--width, 17.5, a, b]".

   args = MainBean.parseCommandLineOptions(args, main); // Prints "width=17.5".

   System.out.println(Arrays.toString(args);            // Prints "[a, b]".
 

Returns:

The args, less the elements that were parsed as "command line options"

Throws:

java.lang.IllegalArgumentException - An error occurred with parsing; typically a command-line application would print the message of the exception to STDERR and call "System.exit(1)"

java.lang.RuntimeException

getMethodForOption

@Nullable
public static java.lang.reflect.Method getMethodForOption(java.lang.String option,
                                                                     java.lang.Class<?> targetClass)

Determines the method of target.getClass() that is applicable for the given option.

Returns:

Null iff there is no applicable method

applyCommandLineOption

public static int applyCommandLineOption(java.lang.String optionName,
                                         java.lang.reflect.Method method,
                                         java.lang.String[] args,
                                         int optionArgumentIndex,
                                         @Nullable
                                         java.lang.Object target)

Parses the command line option's arguments from the args and invokes the method.

Iff the method is a varargs method, then all remaining arguments are converted to an array.

Parameters:

optionArgumentIndex - The position of the first option argument in args

Returns:

The position of the last option argument in args plus one

Throws:

java.lang.IllegalArgumentException - There are less option arguments available than the method requires

printResource

public static void printResource(java.lang.Class<?> clasS,
                                 java.lang.String name,
                                 @Nullable
                                 java.nio.charset.Charset charset,
                                 java.io.PrintStream ps)
                          throws java.io.IOException

Reads (and decodes) the contents of a resource, replaces all occurrences of "${system-property-name}" with the value of the system property, and writes the result to a PrintStream.

The resource is found through the clasS's class loader, and the name "package-name/simple-class-name.name", where all periods in the package-name have been replaced with slashes.

To ensure that the resource is decoded with the same charset as it was encoded, you should not use the JVM charset (which could be different in the build environment and the runtime environment).

Parameters:

charset - The charset to use for decoding the contents of the resource; null for the JVM default charset

Throws:

java.io.FileNotFoundException - The resource could not be found

java.io.IOException