kodo.query
Interface FilterListener

All Superinterfaces:

Serializable

All Known Subinterfaces:

JDBCFilterListener

public interface FilterListener

extends Serializable

A filter listener extends JDOQL filters with custom functionality.

Method Summary

Object	evaluate(Object target, Object arg, Object candidate, KodoPersistenceManager pm) Evaluate the given expression.
boolean	expectsArgument() Return true if this extension expects an argument 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.
boolean	isExpression() Return true if this extension is an expression; i.e.

Method Detail

getTag

public String getTag()

Return the tag that this extension listens for.

expectsArgument

public boolean expectsArgument()

Return true if this extension expects an argument 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

public 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.

isExpression

public boolean isExpression()

Return true if this extension is an expression; i.e. if it evaluates to true or false on its own.

evaluate

public Object evaluate(Object target,
                       Object arg,
                       Object candidate,
                       KodoPersistenceManager pm)

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

arg - the value of the argument given in the filter; will be null if this extension does not expect an argument

candidate - the candidate object being evaluated

pm - a persistence manager to use if needed

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:

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