org.springframework.expression.common
Class TemplateAwareExpressionParser

java.lang.Object
  org.springframework.expression.common.TemplateAwareExpressionParser

All Implemented Interfaces:

ExpressionParser

Direct Known Subclasses:

InternalSpelExpressionParser, SpelExpressionParser

public abstract class TemplateAwareExpressionParser
extends java.lang.Object
implements ExpressionParser

An expression parser that understands templates. It can be subclassed by expression parsers that do not offer first class support for templating.

Since:

3.0

Author:

Keith Donald, Juergen Hoeller, Andy Clement

Nested Class Summary

private static class

TemplateAwareExpressionParser.Bracket This captures a type of bracket and the position in which it occurs in the expression.

Field Summary

private static ParserContext

NON_TEMPLATE_PARSER_CONTEXT Default ParserContext instance for non-template expressions.

Constructor Summary

TemplateAwareExpressionParser()

Method Summary

private Expression	createLiteralExpression(ParserContext context, java.lang.String text)
protected abstract Expression	doParseExpression(java.lang.String expressionString, ParserContext context) Actually parse the expression string and return an Expression object.
private boolean	isSuffixHere(java.lang.String expressionString, int pos, java.lang.String suffix) Return true if the specified suffix can be found at the supplied position in the supplied expression string.
Expression	parseExpression(java.lang.String expressionString) Parse the expression string and return an Expression object you can use for repeated evaluation.
Expression	parseExpression(java.lang.String expressionString, ParserContext context) Parse the expression string and return an Expression object you can use for repeated evaluation.
private Expression[]	parseExpressions(java.lang.String expressionString, ParserContext context) Helper that parses given expression string using the configured parser.
private Expression	parseTemplate(java.lang.String expressionString, ParserContext context)
private int	skipToCorrectEndSuffix(java.lang.String prefix, java.lang.String suffix, java.lang.String expressionString, int afterPrefixIndex) Copes with nesting, for example '${...${...}}' where the correct end for the first ${ is the final }.

Methods inherited from class java.lang.Object

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

Field Detail

NON_TEMPLATE_PARSER_CONTEXT

private static final ParserContext NON_TEMPLATE_PARSER_CONTEXT

Default ParserContext instance for non-template expressions.

Constructor Detail

TemplateAwareExpressionParser

public TemplateAwareExpressionParser()

Method Detail

parseExpression

public Expression parseExpression(java.lang.String expressionString)
                           throws ParseException

Description copied from interface: ExpressionParser

Parse the expression string and return an Expression object you can use for repeated evaluation.

Some examples:

     3 + 4
     name.firstName
 

Specified by:

parseExpression in interface ExpressionParser

Parameters:

expressionString - the raw expression string to parse

Returns:

an evaluator for the parsed expression

Throws:

ParseException - an exception occurred during parsing

parseExpression

public Expression parseExpression(java.lang.String expressionString,
                                  ParserContext context)
                           throws ParseException

Description copied from interface: ExpressionParser

Parse the expression string and return an Expression object you can use for repeated evaluation.

Some examples:

     3 + 4
     name.firstName
 

Specified by:

parseExpression in interface ExpressionParser

Parameters:

expressionString - the raw expression string to parse

context - a context for influencing this expression parsing routine (optional)

Returns:

an evaluator for the parsed expression

Throws:

ParseException - an exception occurred during parsing

parseTemplate

private Expression parseTemplate(java.lang.String expressionString,
                                 ParserContext context)
                          throws ParseException

Throws:

ParseException

parseExpressions

private Expression[] parseExpressions(java.lang.String expressionString,
                                      ParserContext context)
                               throws ParseException

Helper that parses given expression string using the configured parser. The expression string can contain any number of expressions all contained in "${...}" markers. For instance: "foo${expr0}bar${expr1}". The static pieces of text will also be returned as Expressions that just return that static piece of text. As a result, evaluating all returned expressions and concatenating the results produces the complete evaluated string. Unwrapping is only done of the outermost delimiters found, so the string 'hello ${foo${abc}}' would break into the pieces 'hello ' and 'foo${abc}'. This means that expression languages that used ${..} as part of their functionality are supported without any problem. The parsing is aware of the structure of an embedded expression. It assumes that parentheses '(', square brackets '[' and curly brackets '}' must be in pairs within the expression unless they are within a string literal and a string literal starts and terminates with a single quote '.

Parameters:

expressionString - the expression string

Returns:

the parsed expressions

Throws:

ParseException - when the expressions cannot be parsed

createLiteralExpression

private Expression createLiteralExpression(ParserContext context,
                                           java.lang.String text)

isSuffixHere

private boolean isSuffixHere(java.lang.String expressionString,
                             int pos,
                             java.lang.String suffix)

Return true if the specified suffix can be found at the supplied position in the supplied expression string.

Parameters:

expressionString - the expression string which may contain the suffix

pos - the start position at which to check for the suffix

suffix - the suffix string

Returns:

skipToCorrectEndSuffix

private int skipToCorrectEndSuffix(java.lang.String prefix,
                                   java.lang.String suffix,
                                   java.lang.String expressionString,
                                   int afterPrefixIndex)
                            throws ParseException

Copes with nesting, for example '${...${...}}' where the correct end for the first ${ is the final }.

Parameters:

prefix - the prefix

suffix - the suffix

expressionString - the expression string

afterPrefixIndex - the most recently found prefix location for which the matching end suffix is being sought

Returns:

the position of the correct matching nextSuffix or -1 if none can be found

Throws:

ParseException

doParseExpression

protected abstract Expression doParseExpression(java.lang.String expressionString,
                                                ParserContext context)
                                         throws ParseException

Actually parse the expression string and return an Expression object.

Parameters:

expressionString - the raw expression string to parse

context - a context for influencing this expression parsing routine (optional)

Returns:

an evaluator for the parsed expression

Throws:

ParseException - an exception occurred during parsing