org.apache.beehive.netui.script
Interface ExpressionEvaluator

public interface ExpressionEvaluator

An interface for evaluating expressions in NetUI. Different languages may implement this to expose the language for use in the NetUI JSP tags.

evaluateStrict

Object evaluateStrict(String expression,
                      VariableResolver variableResolver)
                      throws ExpressionEvaluationException

Evaluate an expression and return the result.

Parameters:

expression - the expression to evaluate

variableResolver - the set of contexts that may be used in expression evaluation. This set is not necessarily complete as some objects that can be used as top-level expression contexts may be contained within an object available in this JavaBean.

Throws:

ExpressionEvaluationException - when an error occurs

update

void update(String expression,
            Object value,
            VariableResolver variableResolver,
            boolean requestParameter)
            throws ExpressionUpdateException

Update an expression with the given value. This will apply the parameter value to the object referenced by the expression expression. The requestParameter flag is used by a caller to restrict the set of contexts into which an update can occur on the request.

Parameters:

expression - the expression whose value to update

value - the new value for the update

variableResolver - the set of contexts that may be used in expression evaluation. This set is not necessarily complete as some objects that can be used as top-level expression contexts may be contained within an object available in this JavaBean.

requestParameter - a boolean that marks this update as occurring from data in the request, if true or simply as a regular update.

Throws:

ExpressionUpdateException

changeContext

String changeContext(String expression,
                     String oldContext,
                     String newContext,
                     int lookupIndex)
                     throws ExpressionEvaluationException

Change the evaluation context of an expression. This is used to rewrite some expressions that need to be qualified into a different context for evaluation. The context of an expression is its first identifier, up to the first delimiter.

Parameters:

expression - the expression whose context to change

oldContext - the old context to replace, if present

newContext - the new context to replace if the expression starts with the oldContext

lookupIndex - an index used to qualify an expression into an array look-up.

Throws:

ExpressionEvaluationException

qualify

String qualify(String contextName,
               String expression)
               throws ExpressionEvaluationException

Qualify the expression into the given context. This will take the expression and simply qualify it into the new context contextName.

Parameters:

contextName - the new context

expression - the expression to qualify

Throws:

ExpressionEvaluationException

isExpression

boolean isExpression(String expression)

Checks to see if a particular String is exactly an expression.

Parameters:

expression - the expression to check

Returns:

true if the expression is exactly an expression; false otherwise.

Throws:

IllegalExpressionException - if the given expression expression is not legal.

containsExpression

boolean containsExpression(String expression)

Checks to see if a particular expression contains an expression. This method will return true if there is an expression surrounded by whitespace, other expressions, or literal text.

Parameters:

expression - the expression to check

Returns:

true if the expression contains an expression; false otherwise.

parseExpression

Expression parseExpression(String expression)

Parse an atomic expression into a common parsed expression representation.

Parameters:

expression - the String expression to parse

Returns:

the parsed expression