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spring-el

Spel - is it possible to declare a new TokenKind value

Spring Spel supports the following set of the TokenKind elements. 

package org.springframework.expression.spel.standard;

/**
 * @author Andy Clement
 * @since 3.0
 */
enum TokenKind {
    // ordered by priority - operands first
    LITERAL_INT, LITERAL_LONG, LITERAL_HEXINT, LITERAL_HEXLONG, LITERAL_STRING, LITERAL_REAL, LITERAL_REAL_FLOAT, 
    LPAREN("("), RPAREN(")"), COMMA(","), IDENTIFIER,
    COLON(":"),HASH("#"),RSQUARE("]"), LSQUARE("["), 
    LCURLY("{"),RCURLY("}"),
    DOT("."), PLUS("+"), STAR("*"),  MINUS("-"), SELECT_FIRST("^["), SELECT_LAST("$["), QMARK("?"), PROJECT("!["),
    DIV("/"), GE(">="), GT(">"), LE("<="), LT("<"), EQ("=="), NE("!="),
    MOD("%"), NOT("!"), ASSIGN("="), INSTANCEOF("instanceof"), MATCHES("matches"), BETWEEN("between"),
    SELECT("?["),   POWER("^"),
    ELVIS("?:"), SAFE_NAVI("?."), BEAN_REF("@")
    ;

I'm wondering is it possible for us to declare a new TokenKind value and custom object which would handle the evaluation, which could be plugged into the existing Spel framework?

Solution

  • It's interest why you want to introduce a new TokenKind, if those provided just describe the SpEL DSL and play the languge tokens.

    I wonder why custom propertyAccessor, operatorOverloader or function isn't enough for you...

    Take a look into StandardEvaluationContext and try to find, why those hi-level hooks can't help you.