Package de.weltraumschaf.commons.shell

Sub package for a simple interactive shell.

See: Description

Interface Summary

Interface	Description
CommandType	Marker interface for shell command types.
CommandVerifier	Implementors verifies the passed command.
MainCommandType	Marker interface for shell main command types.
Parser	Parses input line from interactive shell.
Scanner	Scans the input line from an interactive shell.
SubCommandType	Marker interface for shell sub command types.

Class Summary

Class	Description
DefaultParser	Default parses implementation.
DefaultScanner	Default implementation for scanning the input line from an interactive shell.
LiteralCommandMap	Maps the literal string of an command to its enum type.
NullCommandVerifier	Verifies nothing.
Parsers	Factory to create parsers.
Scanners	Factory to create scanners.
ShellCommand	Describes a parsed mainCommand of the interactive shell.

Exception Summary

Exception	Description
SyntaxException	Signals syntax errors in the input scanned from an interactive shell.

Package de.weltraumschaf.commons.shell Description

Sub package for a simple interactive shell.

This package is a part of the open-source Commons

Contains:

• input scanner/parser
• helper classes for scanning
• shell command and token abstraction

Example

First define main and sub command types.

// CHECKSTYLE:OFF

public enum MyMainType implements MainCommandType {

     HELP("help"),
     FOO("foo"),
     EXIT("exit");

     // Literal command string used in shell.
     private final String literal;

     private NeuronMainType(final String name) {
         this.literal = name;
     }

     {@literal @}Override
     public String toString() {
         return literal;
     }
 }

 public enum MySubType implements SubCommandType {

     NONE(""), // Default for main commands w/o sub commands.
     BAR("bar"),
     BAZ("baz");

     // Literal sub command string used in shell.
     private final String literal;

     private NeuronSubType(final String name) {
         this.literal = name;
     }

     {@literal @}Override
     public String toString() {
         return literal;
     }
 }
 

// CHECKSTYLE:ON

And then define a literal to command map:

// CHECKSTYLE:OFF

public class MyLiteralCommandMap extends LiteralCommandMap {

     public MyLiteralCommandMap() {
         super(MySubType.NONE); // Default for main commands w/o sub commands.
     }

     {@literal @}Override
     protected void initCommandMap(Map<String, MainCommandType> map) {
         for (final MyMainType t : MyMainType.values()) {
             map.put(t.toString(), t);
         }
     }

     {@literal @}Override
     protected void initSubCommandMap(Map<String, SubCommandType> map) {
         for (final MySubType t : MySubType.values()) {
             if (t.toString().isEmpty()) {
                 continue; // Ignore to do not recognize empty strings as sub command in parser.
             }
             map.put(t.toString(), t);
         }
     }
 }
 

// CHECKSTYLE:ON

Now you can implement a simple REPL:

// CHECKSTYLE:OFF

Parser parser = Parsers.newParser(new MyLiteralCommandMap());
 BufferedReader input = new BufferedReader(new InputStreamReader(System.in));

 while (true) {
     System.out.println("prompt> ");
     final String inputLine = input.readLine();

     try {
         final ShellCommand cmd = parser.parse(inputLine);
         // Do something with the shell command...

         if (shellCmd.getCommand() == NeuronMainType.EXIT) {
             break;
         }
     } catch (SyntaxException ex) {
         System.out.println("Error: " + ex.getMessage());
     }
 }

 input.close();
 

// CHECKSTYLE:ON

If you want to verify the parsed commands, e.g. check if a command has a proper subcommand or arguments you must implement CommandVerifier and pass it to the parser factory.