I'm prototyping a simple syntax which looks similar to an SQL query....

For example

select *:* from //


To do the query parsing, I've written the following grammer :

			

			

			

			header
			

			{
			

			package com.apptechsys.grammer;
			

			}
			

			

			class MyParser extends Parser;
			

			

			options
			

			{
			

			buildAST = true;
			

			k = 2;
			

			}
			

			

			tokens
			

			{
			

			SELECT_STATEMENT;
			

			FILTER_CLAUSE;
			

			FROM_CLAUSE;
			

			PATH_CLAUSE;
			

			FROM;
			

			FILTER;
			

			PATH;
			

			}
			

			

			statement
			

			: selectStatement
			

			;
			

			

			selectStatement :
			

			"select" filterClause fromClause SEMI!
			

			{ #selectStatement = #([SELECT_STATEMENT, "selectStatement"], #selectStatement); }
			

			;
			

			

			fromClause
			

			: "from" pathClause
			

			{ #fromClause = #([FROM_CLAUSE, "fromClause"], #fromClause); }
			

			;
			

			

			pathClause
			

			: SLASH (SLASH)? filterClause
			

			;
			

			

			filterClause
			

			: (STAR|ID)COLON(STAR|ID)
			

			{ #filterClause = #([FILTER_CLAUSE, "filterClause"], #filterClause); }
			

			;
			

			

			

			class MyLexer extends Lexer;
			

			

			options
			

			{
			

			k=2;
			

			charVocabulary = 'u0000'..'u007F';
			

			caseSensitive = false;
			

			}
			

			

			ID options { testLiterals = true; } :  ('a'..'z'|'0'..'9')+ ;
			

			

			SLASH: '/';
			

			

			COLON: ':';
			

			

			STAR: '*';
			

			

			SEMI: ';' ;
			

			

			WS     :
			

			(' '
			

			| ' '
			

			| '
			

			' '
			

			' { newline(); }
			

			| '
			

			'      { newline(); }
			

			)
			

			{ $setType(Token.SKIP); }
			

			;
			

			

			class MyTreeParser extends TreeParser;
			

			

			options
			

			{
			

			buildAST = true;
			

			}
			

			

			expr returns [ SelectObject selectObject = null; ]
			

			{
			

			}
			

			: selectObject = selectExpr
			

			;
			

			

			selectExpr
			

			returns [ SelectObject selectObject = null; ]
			

			:
			

			{ String string = null; }
			

			#(SELECT_STATEMENT "select" string = filterExpr )
			

			{
			

			selectObject = new SelectObject();
			

			selectObject.setFilter(string);
			

			}
			

			;
			

			

			filterExpr returns [ String s = null ]:
			

			#(FILTER_CLAUSE firstPart:starOrID secondPart:COLON thirdPart:starOrID )
			

			{ s = firstPart.getText() + secondPart.getText() + thirdPart.getText(); }
			

			;
			

			

			starOrID :
			

			(STAR|ID)
			

			;