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package javax.faces.event;
import javax.el.
ELContext;
import javax.el.
MethodExpression;
import javax.el.
MethodNotFoundException;
import javax.faces.context.
FacesContext;
import javax.faces.component.
StateHolder;
/**
* <p><strong><span class="changed_modified_2_0
* changed_modified_2_0_rev_a
* changed_modified_2_2">MethodExpressionValueChangeListener</span></strong>
* is a {@link ValueChangeListener} that wraps a {@link
* MethodExpression}. When it receives a {@link ValueChangeEvent}, it
* executes a method on an object identified by the {@link
* MethodExpression}.</p>
*/
public class
MethodExpressionValueChangeListener implements
ValueChangeListener,
StateHolder {
// ------------------------------------------------------ Instance Variables
private
MethodExpression methodExpressionOneArg = null;
private
MethodExpression methodExpressionZeroArg = null;
private boolean
isTransient;
private final static
Class[]
VALUECHANGE_LISTENER_ZEROARG_SIG = new
Class[] { };
public
MethodExpressionValueChangeListener() { }
/**
* <p><span class="changed_modified_2_0">Construct</span> a {@link
* ValueChangeListener} that contains a {@link
* MethodExpression}.<span
* class="changed_added_2_0">To accomodate method expression targets
* that take no arguments instead of taking a {@link
* ValueChangeEvent} argument</span>, the implementation of this
* class must take the argument <code>methodExpressionOneArg</code>,
* extract its expression string, and create another
* <code>MethodExpression</code> whose expected param types match
* those of a zero argument method. The usage requirements for both
* of these <code>MethodExpression</code> instances are described in
* {@link #processValueChange}.</span></p>
*
* @param methodExpressionOneArg a <code>MethodExpression</code>
* that points to a method that returns <code>void</code> and takes
* a single argument of type {@link ValueChangeEvent}.
*/
public
MethodExpressionValueChangeListener(
MethodExpression methodExpressionOneArg) {
super();
this.
methodExpressionOneArg =
methodExpressionOneArg;
FacesContext context =
FacesContext.
getCurrentInstance();
ELContext elContext =
context.
getELContext();
this.
methodExpressionZeroArg =
context.
getApplication().
getExpressionFactory().
createMethodExpression(
elContext,
methodExpressionOneArg.
getExpressionString(),
Void.class,
VALUECHANGE_LISTENER_ZEROARG_SIG);
}
/**
* <p>Construct a {@link ValueChangeListener} that contains a {@link MethodExpression}.</p>
*/
public
MethodExpressionValueChangeListener(
MethodExpression methodExpressionOneArg,
MethodExpression methodExpressionZeroArg) {
super();
this.
methodExpressionOneArg =
methodExpressionOneArg;
this.
methodExpressionZeroArg =
methodExpressionZeroArg;
}
// ------------------------------------------------------- Event Method
/**
* <p><span
* class="changed_modified_2_0 changed_modified_2_2">Call</span>
* through to the {@link MethodExpression} passed in our
* constructor. <span class="changed_added_2_0">First, try to
* invoke the <code>MethodExpression</code> passed to the
* constructor of this instance, passing the argument {@link
* ValueChangeEvent} as the argument. If a {@link
* MethodNotFoundException} is thrown, call to the zero argument
* <code>MethodExpression</code> derived from the
* <code>MethodExpression</code> passed to the constructor of this
* instance. <span class="changed_deleted_2_2"><del>If that fails
* for any reason, throw an {@link AbortProcessingException},
* including the cause of the failure.</del></span></span></p>
*
* @throws NullPointerException if the argument valueChangeEvent is null.
* @throws AbortProcessingException {@inheritDoc}
*/
public void
processValueChange(
ValueChangeEvent valueChangeEvent) throws
AbortProcessingException {
if (
valueChangeEvent == null) {
throw new
NullPointerException();
}
FacesContext context =
FacesContext.
getCurrentInstance();
ELContext elContext =
context.
getELContext();
// PENDING: The corresponding code in MethodExpressionActionListener
// has an elaborate message capture, logging, and rethrowing block.
// Why not here?
try {
methodExpressionOneArg.
invoke(
elContext, new
Object[] {
valueChangeEvent});
} catch (
MethodNotFoundException mnf) {
if (null !=
methodExpressionZeroArg) {
// try to invoke a no-arg version
methodExpressionZeroArg.
invoke(
elContext, new
Object[]{});
}
}
}
// ------------------------------------------------ Methods from StateHolder
/**
* <p class="changed_modified_2_0">Both {@link MethodExpression}
* instances described in the constructor must be saved.</p>
*/
public
Object saveState(
FacesContext context) {
if (
context == null) {
throw new
NullPointerException();
}
return new
Object[] {
methodExpressionOneArg,
methodExpressionZeroArg };
}
/**
* <p class="changed_modified_2_0">Both {@link MethodExpression}
* instances described in the constructor must be restored.</p>
*/
public void
restoreState(
FacesContext context,
Object state) {
if (
context == null) {
throw new
NullPointerException();
}
if (
state == null) {
return;
}
methodExpressionOneArg = (
MethodExpression) ((
Object[])
state)[0];
methodExpressionZeroArg = (
MethodExpression) ((
Object[])
state)[1];
}
public boolean
isTransient() {
return
isTransient;
}
public void
setTransient(boolean
newTransientValue) {
isTransient =
newTransientValue;
}
}