org.kuali.rice.krad.uif.view

Interface ExpressionEvaluator

All Known Implementing Classes:

DefaultExpressionEvaluator

public interface ExpressionEvaluator

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)

Field Summary

Fields

Modifier and Type	Field and Description
static String	EMBEDDED_PROPERTY_NAME_ADD_INDICATOR Indicator that can be added to a property name to indicate the expression result should be added to the property (assumed to be a collection) instead of replaced

Method Summary

Modifier and Type	Method and Description
boolean	containsElPlaceholder(String value) Indicates whether or not the given string contains the el placeholder (begin and end delimiters)
Object	evaluateExpression(Map<String,Object> evaluationParameters, String expression) Evaluates the given el expression against the content object and parameters, and returns the result of the evaluation
void	evaluateExpressionsOnConfigurable(View view, UifDictionaryBean expressionConfigurable, Map<String,Object> evaluationParameters) Evaluates any el expressions that are found as a string property value for the object
String	evaluateExpressionTemplate(Map<String,Object> evaluationParameters, String expressionTemplate) Evaluates the given expression template string against the context object and map of parameters
void	evaluatePropertyExpression(View view, Map<String,Object> evaluationParameters, UifDictionaryBean expressionConfigurable, String propertyName, boolean removeExpression) Evaluates the configured expression for the given property name (if not exists) on the given configurable
List<String>	findControlNamesInExpression(String exp) Find the control names (ie, propertyNames) used in the passed in expression
void	initializeEvaluationContext(Object contextObject) Initializes the expression context for the given expression context object
String	parseExpression(String exp, List<String> controlNames, Map<String,Object> context) Takes in an expression and a list to be filled in with names(property names) of controls found in the expression.
void	populatePropertyExpressionsFromGraph(UifDictionaryBean expressionConfigurable, boolean buildRefreshGraphs) Pulls expressions within the expressionConfigurable's expression graph and moves them to the property expressions map for the expressionConfigurable or a nested expressionConfigurable (for the case of nested expression property names)
String	replaceBindingPrefixes(View view, Object object, String expression) Adjusts the property expressions for a given object

Field Detail

EMBEDDED_PROPERTY_NAME_ADD_INDICATOR

static final String EMBEDDED_PROPERTY_NAME_ADD_INDICATOR

Indicator that can be added to a property name to indicate the expression result should be added to the property (assumed to be a collection) instead of replaced

See Also:

Constant Field Values

Method Detail

initializeEvaluationContext

void initializeEvaluationContext(Object contextObject)

Initializes the expression context for the given expression context object

The object given here will form the default context for expression terms (terms without any variable prefix)

Parameters:

contextObject - instance of an Object

evaluateExpressionsOnConfigurable

void evaluateExpressionsOnConfigurable(View view,
                                       UifDictionaryBean expressionConfigurable,
                                       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:

view - view instance being rendered

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

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(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:

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

evaluatePropertyExpression

void evaluatePropertyExpression(View view,
                                Map<String,Object> evaluationParameters,
                                UifDictionaryBean expressionConfigurable,
                                String propertyName,
                                boolean removeExpression)

Evaluates the configured expression for the given property name (if not exists) on the given configurable

Parameters:

view - view instance the configurable is associated with, used to adjust binding prefixes

evaluationParameters - map that will be exposed as EL parameters

expressionConfigurable - configurable object to pull and evaluate the expression on

propertyName - name of the property whose expression should be evaluated

removeExpression - boolean that indicates whether the expression should be removed after evaluation

evaluateExpression

Object evaluateExpression(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:

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 placeholder (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:

UifConstants.EL_PLACEHOLDER_PREFIX, UifConstants.EL_PLACEHOLDER_SUFFIX

replaceBindingPrefixes

String replaceBindingPrefixes(View view,
                              Object object,
                              String expression)

Adjusts the property expressions for a given object

The UifConstants.NO_BIND_ADJUST_PREFIX prefix will be removed as this is a placeholder indicating that the property is directly on the form. The UifConstants.FIELD_PATH_BIND_ADJUST_PREFIX prefix will be replaced by the object's field path - this is only applicable to DataFields. The UifConstants.DEFAULT_PATH_BIND_ADJUST_PREFIX prefix will be replaced by the view's default path if it is set.

Parameters:

view - the parent view of the object

object - Object to adjust property expressions on

expression - The expression to adjust

Returns:

the adjusted expression String

populatePropertyExpressionsFromGraph

void populatePropertyExpressionsFromGraph(UifDictionaryBean expressionConfigurable,
                                          boolean buildRefreshGraphs)

Pulls expressions within the expressionConfigurable's expression graph and moves them to the property expressions map for the expressionConfigurable or a nested expressionConfigurable (for the case of nested expression property names)

Expressions that are configured on properties and pulled out by the org.kuali.rice.krad.uif.util.UifBeanFactoryPostProcessor and put in the UifDictionaryBean.getExpressionGraph() for the bean that is at root (non nested) level. Before evaluating the expressions, they need to be moved to the UifDictionaryBean.getPropertyExpressions() map for the expressionConfigurable that property is on.

Parameters:

expressionConfigurable - expressionConfigurable instance to process expressions for

buildRefreshGraphs - indicates whether the expression graphs for component refresh should be built

parseExpression

String parseExpression(String exp,
                       List<String> controlNames,
                       Map<String,Object> context)

Takes in an expression and a list to be filled in with names(property names) of controls found in the expression.

This method returns a js expression which can be executed on the client to determine if the original exp was satisfied before interacting with the server - ie, this js expression is equivalent to the one passed in.

There are limitations on the Spring expression language that can be used as this method. It is only used to parse expressions which are valid case statements for determining if some action/processing should be performed. ONLY Properties, comparison operators, booleans, strings, matches expression, and boolean logic are supported. Server constants and calls will be evaluated early. The isValueEmpty, listContains, and emptyList custom KRAD functions, however, will be converted to a js equivalent function. Properties must be a valid property on the form, and should have a visible control within the view.

Example valid exp: "account.name == 'Account Name'"

Parameters:

exp - the expression to convert to a js condition

controlNames - the list to populate with control names found in the expression (these may later be used to add js change handlers)

Returns:

the converted expression into an equivalent js condition

findControlNamesInExpression

List<String> findControlNamesInExpression(String exp)

Find the control names (ie, propertyNames) used in the passed in expression

Parameters:

exp - the expression to search

Returns:

the list of control names found (ie, propertyNames)