javax.faces.event.MethodExpressionValueChangeListener Maven / Gradle / Ivy
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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;
/**
* MethodExpressionValueChangeListener
* 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}.
*/
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() { }
/**
* Construct a {@link
* ValueChangeListener} that contains a {@link
* MethodExpression}.To accommodate method expression targets
* that take no arguments instead of taking a {@link
* ValueChangeEvent} argument, the implementation of this
* class must take the argument methodExpressionOneArg,
* extract its expression string, and create another
* MethodExpression whose expected param types match
* those of a zero argument method. The usage requirements for both
* of these MethodExpression instances are described in
* {@link #processValueChange}.
*
* @param methodExpressionOneArg a MethodExpression
* that points to a method that returns void 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);
}
/**
* Construct a {@link ValueChangeListener} that contains a {@link MethodExpression}.
*
* @param methodExpressionOneArg a method expression that takes one argument
* @param methodExpressionZeroArg a method expression that takes zero arguments
*/
public MethodExpressionValueChangeListener(MethodExpression methodExpressionOneArg,
MethodExpression methodExpressionZeroArg) {
super();
this.methodExpressionOneArg = methodExpressionOneArg;
this.methodExpressionZeroArg = methodExpressionZeroArg;
}
// ------------------------------------------------------- Event Method
/**
* Call
* through to the {@link MethodExpression} passed in our
* constructor. First, try to
* invoke the MethodExpression 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
* MethodExpression derived from the
* MethodExpression passed to the constructor of this
* instance. If that fails
* for any reason, throw an {@link AbortProcessingException},
* including the cause of the failure.
*
* @throws NullPointerException if the argument valueChangeEvent is null.
* @throws AbortProcessingException {@inheritDoc}
*/
@Override
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
/**
* Both {@link MethodExpression}
* instances described in the constructor must be saved.
*/
@Override
public Object saveState(FacesContext context) {
if (context == null) {
throw new NullPointerException();
}
return new Object[] { methodExpressionOneArg, methodExpressionZeroArg };
}
/**
* Both {@link MethodExpression}
* instances described in the constructor must be restored.
*/
@Override
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];
}
@Override
public boolean isTransient() {
return isTransient;
}
@Override
public void setTransient(boolean newTransientValue) {
isTransient = newTransientValue;
}
}