org.apache.openjpa.kernel.exps

Interface FilterListener

All Superinterfaces:

Serializable

All Known Subinterfaces:

JDBCFilterListener

All Known Implementing Classes:

GetColumn, JDBCStringContains, JDBCWildcardMatch, SQLEmbed, SQLExpression, SQLValue, StringContains, WildcardMatch

public interface FilterListener
extends Serializable

A filter listener extends expression filters with custom functionality.

Author:

Steve Kim, Abe White

Method Summary

Modifier and Type	Method and Description
Object	evaluate(Object target, Class targetClass, Object[] args, Class[] argClasses, Object candidate, StoreContext ctx) Evaluate the given expression.
boolean	expectsArguments() Return true if this extension expects arguments to act on.
boolean	expectsTarget() Return true if this extension expects a target to act on.
String	getTag() Return the tag that this extension listens for.
Class	getType(Class targetClass, Class[] argClasses) Return the expected type of the result of this listener.

Method Detail

getTag

String getTag()

Return the tag that this extension listens for.

expectsArguments

boolean expectsArguments()

Return true if this extension expects arguments to act on. Some extensions may not need arguments; for example, an extension to switch a string to upper case might be of the form: field.ext:toUpperCase ().

expectsTarget

boolean expectsTarget()

Return true if this extension expects a target to act on. Some extensions act on a field or object value; others stand alone. field.ext:toUpperCase () acts on the target field but has no arguments, while another possible form, ext:toUpperCase (field) has no target but does have an argument.

evaluate

Object evaluate(Object target,
                Class targetClass,
                Object[] args,
                Class[] argClasses,
                Object candidate,
                StoreContext ctx)

Evaluate the given expression. This method is used when evaluating in-memory expressions. The method used when evaluating data store expressions will change depending on the data store in use.

Parameters:

target - the target object / field value to act on; will be null if this extension does not expect a target

targetClass - the expected class of the target; given in case the target evaluates to null and typing is needed

args - the values of the arguments given in the filter; will be null if this extension does not expect an argument

argClasses - the expected classes of the arguments; given in case an argument evaluates to null and typing is needed

candidate - the candidate object being evaluated

ctx - the persistence context

Returns:

the value of the extension for this candidate; if this extension is an expression, this method should return Boolean.TRUE or Boolean.FALSE

Throws:

UserException - if this extension does not support in-memory operation

getType

Class getType(Class targetClass,
              Class[] argClasses)

Return the expected type of the result of this listener.

Parameters:

targetClass - the expected class of the target, or null if no target

argClasses - the expected classes of the arguments, or null if no arguments