org.kuali.rice.krad.uif.service
Interface ExpressionEvaluatorService

All Known Implementing Classes:

ExpressionEvaluatorServiceImpl

public interface ExpressionEvaluatorService

Provides evaluation of expression language statements against a given context

Used within the UI framework to allow conditional logic to be configured through the XML which can alter the values of component properties

Author:

Kuali Rice Team (rice.collab@kuali.org)

Method Summary

boolean	containsElPlaceholder(String value) Indicates whether or not the given string contains the el placholder (begin and end delimiters)
Object	evaluateExpression(Object contextObject, Map<String,Object> evaluationParameters, String expression) Evaluates the given el expression against the content object and parameters, and returns the result of the evaluation
String	evaluateExpressionTemplate(Object contextObject, Map<String,Object> evaluationParameters, String expressionTemplate) Evaluates the given expression template string against the context object and map of parameters
void	evaluateObjectExpressions(Object object, Object contextObject, Map<String,Object> evaluationParameters) Evaluates any el expressions that are found as a string property value for the object

Method Detail

evaluateObjectExpressions

void evaluateObjectExpressions(Object object,
                               Object contextObject,
                               Map<String,Object> evaluationParameters)

Evaluates any el expressions that are found as a string property value for the object

Using reflection the properties for the object are retrieved and if of String type the corresponding value is retrieved. If the value is not empty and contains the el placeholder see containsElPlaceholder(String) then the expression is evaluated using the given context object and parameters. The evaluated string is then set as the new property value, or in the case of a template (expression contained within a literal string), the expression part is replaced in the property value.

In addition to evaluating any property expressions, any configured PropertyReplacer for the object are also evaluated and if a match occurs those property replacements are made

Parameters:

object - - object whose properties should be checked for expressions and evaluated

contextObject - - context object for the expression evaluations

evaluationParameters - - map of parameters that may appear in expressions, the map key gives the parameter name that may appear in the expression, and the map value is the object that expression should evaluate against when that name is found

evaluateExpressionTemplate

String evaluateExpressionTemplate(Object contextObject,
                                  Map<String,Object> evaluationParameters,
                                  String expressionTemplate)

Evaluates the given expression template string against the context object and map of parameters

If the template string contains one or more el placeholders (see containsElPlaceholder(String)), the expression contained within the placeholder will be evaluated and the corresponding value will be substituted back into the property value where the placeholder occurred. If no placeholders are found, the string will be returned unchanged

Parameters:

contextObject - - context object for the expression evaluations

evaluationParameters - - map of parameters that may appear in expressions, the map key gives the parameter name that may appear in the expression, and the map value is the object that expression should evaluate against when that name is found

expressionTemplate - - string that should be evaluated for el expressions

Returns:

String formed by replacing any el expressions in the original expression template with their corresponding evaluation results

evaluateExpression

Object evaluateExpression(Object contextObject,
                          Map<String,Object> evaluationParameters,
                          String expression)

Evaluates the given el expression against the content object and parameters, and returns the result of the evaluation

The given expression string is assumed to be one el expression and should not contain the el placeholders. The returned result depends on the evaluation and what type is returns, for instance a boolean will be return for a boolean expression, or a string for string expression

Parameters:

contextObject - - context object for the expression evaluations

evaluationParameters - - map of parameters that may appear in expressions, the map key gives the parameter name that may appear in the expression, and the map value is the object that expression should evaluate against when that name is found

expression - - el expression to evaluate

Returns:

Object result of the expression evaluation

containsElPlaceholder

boolean containsElPlaceholder(String value)

Indicates whether or not the given string contains the el placholder (begin and end delimiters)

Parameters:

value - - String to check for contained placeholders

Returns:

boolean true if the string contains one or more placeholders, false if it contains none

See Also:

org.kuali.rice.krad.uif.UifConstants.EL_PLACEHOLDER_PREFIX, org.kuali.rice.krad.uif.UifConstants.EL_PLACEHOLDER_SUFFIX