Struts example source code file (ELParser.jjt)

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and, choice, elparser, expression, expression, identifier, io, math, math, multiplication, null, token, token, unary, unary

The Struts ELParser.jjt source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
    Author:    Jacob Hookom
    Email:    jacob at hookom.net
*/

/* == Option Declaration == */
options
{
    STATIC=false;
    NODE_PREFIX="Ast";
    VISITOR_EXCEPTION="javax.el.ELException";
    VISITOR=false;
    MULTI=true;
    NODE_DEFAULT_VOID=true;
    JAVA_UNICODE_ESCAPE=false;
    UNICODE_INPUT=true;
    BUILD_NODE_FILES=true;
}

/* == Parser Declaration == */
PARSER_BEGIN( ELParser )
package org.apache.el.parser;
import java.io.StringReader;
import javax.el.ELException;
public class ELParser
{
    public static Node parse(String ref) throws ELException
    {
        try {
            return (new ELParser(new StringReader(ref))).CompositeExpression();
        } catch (ParseException pe) {
            throw new ELException(pe.getMessage());
        }
    }
}
PARSER_END( ELParser )

/*
 * CompositeExpression
 * Allow most flexible parsing, restrict by examining
 * type of returned node
 */
AstCompositeExpression CompositeExpression() #CompositeExpression : {}
{
    (DeferredExpression() | DynamicExpression() | LiteralExpression())* <EOF> { return jjtThis; }
}

/*
 * LiteralExpression
 * Non-EL Expression blocks
 */
void LiteralExpression() #LiteralExpression : { Token t = null; }
{
    t=<LITERAL_EXPRESSION> { jjtThis.setImage(t.image); }
}

/*
 * DeferredExpression
 * #{..} Expressions
 */
void DeferredExpression() #DeferredExpression : {}
{
    <START_DEFERRED_EXPRESSION> Expression() 
}

/*
 * DynamicExpression
 * ${..} Expressions
 */
void DynamicExpression() #DynamicExpression : {}
{
    <START_DYNAMIC_EXPRESSION> Expression() 
}

/*
 * Expression
 * EL Expression Language Root, goes to Choice
 */
void Expression() : {}
{
    Choice()
}

/*
 * Choice
 * For Choice markup a ? b : c, then Or
 */
void Choice() : {}
{
    Or() (LOOKAHEAD(3) <QUESTIONMARK> Choice()  Choice() #Choice(3))*
}

/*
 * Or
 * For 'or' '||', then And
 */
void Or() : {}
{
    And() ((<OR0>|) And() #Or(2))*
}

/*
 * And
 * For 'and' '&&', then Equality
 */
void And() : {}
{
    Equality() ((<AND0>|) Equality() #And(2))*
}

/*
 * Equality
 * For '==' 'eq' '!=' 'ne', then Compare
 */
void Equality() : {}
{
    Compare()
    (
        ((<EQ0>|) Compare() #Equal(2))
    |
        ((<NE0>|) Compare() #NotEqual(2))
    )*
}

/*
 * Compare
 * For a bunch of them, then Math
 */
void Compare() : {}
{
    Math()
    (
        ((<LT0>|) Math() #LessThan(2))
    |
        ((<GT0>|) Math() #GreaterThan(2))
    |
        ((<LE0>|) Math() #LessThanEqual(2))
    |
        ((<GE0>|) Math() #GreaterThanEqual(2))
    )*
}

/*
 * Math
 * For '+' '-', then Multiplication
 */
void Math() : {}
{
    Multiplication()
    (
        (<PLUS> Multiplication() #Plus(2))
    |
        (<MINUS> Multiplication() #Minus(2))
    )*
}

/*
 * Multiplication
 * For a bunch of them, then Unary
 */
void Multiplication() : {}
{
    Unary()
    (
        (<MULT> Unary() #Mult(2))
    |
        ((<DIV0>|) Unary() #Div(2))
    |
        ((<MOD0>|) Unary() #Mod(2))
    )*
}

/*
 * Unary
 * For '-' '!' 'not' 'empty', then Value
 */
void Unary() : {}
{
        <MINUS> Unary() #Negative
    |
        (<NOT0>|) Unary() #Not
    |
        <EMPTY> Unary() #Empty
    |
        Value()
}

/*
 * Value
 * Defines Prefix plus zero or more Suffixes
 */
void Value() : {}
{
    (ValuePrefix() (ValueSuffix())*) #Value(>1)
}

/*
 * ValuePrefix
 * For Literals, Variables, and Functions
 */
void ValuePrefix() : {}
{
    Literal()
    | NonLiteral()
}

/*
 * ValueSuffix
 * Either dot or bracket notation
 */
void ValueSuffix() : {}
{
    DotSuffix() | BracketSuffix()
}

/*
 * DotSuffix
 * Dot Property
 */
void DotSuffix() #DotSuffix : { Token t = null; }
{
    <DOT> t= { jjtThis.setImage(t.image); }
}

/*
 * BracketSuffix
 * Sub Expression Suffix
 */
void BracketSuffix() #BracketSuffix : {}
{
    <LBRACK> Expression() 
}

/*
 * NonLiteral
 * For Grouped Operations, Identifiers, and Functions
 */
void NonLiteral() : {}
{
    <LPAREN> Expression() 
    | LOOKAHEAD((<IDENTIFIER> )?  ) Function()
    | Identifier()
}

/*
 * Identifier
 * Java Language Identifier
 */
void Identifier() #Identifier : { Token t = null; }
{
    t=<IDENTIFIER> { jjtThis.setImage(t.image); }
}

/*
 * Function
 * Namespace:Name(a,b,c)
 */
void Function() #Function :
{
    Token t0 = null;
    Token t1 = null;
}
{
    (LOOKAHEAD(2) t0=<IDENTIFIER> )? t1=
    {
        if (t0 != null) {
            jjtThis.setPrefix(t0.image);
            jjtThis.setLocalName(t1.image);
        } else {
            jjtThis.setLocalName(t1.image);
        }
    }
    <LPAREN> (Expression() ( Expression())*)? 
}

/*
 * Literal
 * Reserved Keywords
 */
void Literal() : {}
{
    Boolean()
    | FloatingPoint()
    | Integer()
    | String()
    | Null()
}

/*
 * Boolean
 * For 'true' 'false'
 */
void Boolean() : {}
{
    <TRUE> #True
    | <FALSE> #False
}

/*
 * FloatinPoint
 * For Decimal and Floating Point Literals
 */
void FloatingPoint() #FloatingPoint : { Token t = null; }
{
    t=<FLOATING_POINT_LITERAL> { jjtThis.setImage(t.image); }
}

/*
 * Integer
 * For Simple Numeric Literals
 */
void Integer() #Integer : { Token t = null; }
{
    t=<INTEGER_LITERAL> { jjtThis.setImage(t.image); }
}

/*
 * String
 * For Quoted Literals
 */
void String() #String : { Token t = null; }
{
    t=<STRING_LITERAL> { jjtThis.setImage(t.image); }
}

/*
 * Null
 * For 'null'
 */
void Null() #Null : {}
{
    <NULL>
}


/* ==================================================================================== */
<DEFAULT> TOKEN :
{
  < LITERAL_EXPRESSION:
    ((~["\\", "$", "#"])
      | ("\\" ("\\" | "$" | "#"))
      | ("$" ~["{", "$"])
      | ("#" ~["{", "#"])
    )+
    | "$"
    | "#"
  >
|
  < START_DYNAMIC_EXPRESSION: "${" > : IN_EXPRESSION
|
  < START_DEFERRED_EXPRESSION: "#{" > : IN_EXPRESSION
}

<DEFAULT> SKIP : { "\\" }

<IN_EXPRESSION> SKIP : { " " | "\t" | "\n" | "\r" }

<IN_EXPRESSION> TOKEN :
{
    < INTEGER_LITERAL: ["0"-"9"] (["0"-"9"])* >
|    < FLOATING_POINT_LITERAL: (["0"-"9"])+ "." (["0"-"9"])* (
|    < GT1 : "gt" >
|    < LT0 : "<" >
|    < LT1 : "lt" >
|    < GE0 : ">=" >
|    < GE1 : "ge" >
|    < LE0 : "<=" >
|    < LE1 : "le" >
|    < EQ0 : "==" >
|    < EQ1 : "eq" >
|    < NE0 : "!=" >
|    < NE1 : "ne" >
|    < NOT0 : "!" >
|    < NOT1 : "not" >
|    < AND0 : "&&" >
|    < AND1 : "and" >
|    < OR0 : "||" >
|    < OR1 : "or" >
|    < EMPTY : "empty" >
|    < INSTANCEOF : "instanceof" >
|    < MULT : "*" >
|    < PLUS : "+" >
|    < MINUS : "-" >
|    < QUESTIONMARK : "?" >
|    < DIV0 : "/" >
|    < DIV1 : "div" >
|    < MOD0 : "%" >
|    < MOD1 : "mod" >
|    < IDENTIFIER : () (|)* >
|    < FUNCTIONSUFFIX : (
|    < #IMPL_OBJ_START: "#" >
|    < #LETTER:
        [
        "\u0024",
        "\u0041"-"\u005a",
        "\u005f",
        "\u0061"-"\u007a",
        "\u00c0"-"\u00d6",
        "\u00d8"-"\u00f6",
        "\u00f8"-"\u00ff",
        "\u0100"-"\u1fff",
        "\u3040"-"\u318f",
        "\u3300"-"\u337f",
        "\u3400"-"\u3d2d",
        "\u4e00"-"\u9fff",
        "\uf900"-"\ufaff"
        ]
    >
|    < #DIGIT:
        [
        "\u0030"-"\u0039",
        "\u0660"-"\u0669",
        "\u06f0"-"\u06f9",
        "\u0966"-"\u096f",
        "\u09e6"-"\u09ef",
        "\u0a66"-"\u0a6f",
        "\u0ae6"-"\u0aef",
        "\u0b66"-"\u0b6f",
        "\u0be7"-"\u0bef",
        "\u0c66"-"\u0c6f",
        "\u0ce6"-"\u0cef",
        "\u0d66"-"\u0d6f",
        "\u0e50"-"\u0e59",
        "\u0ed0"-"\u0ed9",
        "\u1040"-"\u1049"
        ]
    >
|    < ILLEGAL_CHARACTER: (~[]) >
}