com.solarmetric.kodo.impl.jdbc.query.listen
Class GetColumn

java.lang.Object
  |
  +--com.solarmetric.kodo.impl.jdbc.query.listen.GetColumn

All Implemented Interfaces:

FilterListener, JDBCFilterListener

public class GetColumn

extends Object

implements JDBCFilterListener

Returns the SQL alias of the named column for use in a query. Note that to retrieve columns in the table of the candidate object, you must explicitly qualify the extension with this, as demonstrated in the second example below.

Examples:
"company.address.ext:getColumn (\"JDOID\") == 5"
"this.ext:getColumn (\"JDOCLASS\") == \"jdo.example.Person\""

Field Summary

static String

TAG

Constructor Summary

GetColumn()

Method Summary

Object	evaluate(Object target, Object arg, Object candidate, PersistenceManagerImpl 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.
void	where(QuerySQLBuffer buf, JDBCValue target, JDBCValue arg, ClassMapping type, PersistenceManagerImpl pm) Append the SQL for this expression or value.

Methods inherited from class java.lang.Object

, clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

TAG

public static final String TAG

Constructor Detail

GetColumn

public GetColumn()

Method Detail

getTag

public String getTag()

Description copied from interface: FilterListener

Return the tag that this extension listens for.

Specified by:

getTag in interface FilterListener

expectsArgument

public boolean expectsArgument()

Description copied from interface: FilterListener

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 ().

Specified by:

expectsArgument in interface FilterListener

expectsTarget

public boolean expectsTarget()

Description copied from interface: FilterListener

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.

Specified by:

expectsTarget in interface FilterListener

isExpression

public boolean isExpression()

Description copied from interface: FilterListener

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

Specified by:

isExpression in interface FilterListener

evaluate

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

Description copied from interface: FilterListener

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.

Specified by:

evaluate in interface FilterListener

Following copied from interface: com.solarmetric.kodo.query.FilterListener

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

where

public void where(QuerySQLBuffer buf,
                  JDBCValue target,
                  JDBCValue arg,
                  ClassMapping type,
                  PersistenceManagerImpl pm)

Description copied from interface: JDBCFilterListener

Append the SQL for this expression or value.

Specified by:

where in interface JDBCFilterListener

Following copied from interface: com.solarmetric.kodo.impl.jdbc.query.JDBCFilterListener

Parameters:

buf - the SQL buffer to append to

target - the target to act on; this will usually be a SQLPath, but depending on usage could also be other values; it will be null if the listener doesn't expect a target

arg - the value of the argument given in the filter; this will usually be a Constant, but will be null if this listener doesn't expect an argument

mapping - the class mapping for the query's candidate class

pm - the persistence manager that owns the query