ListELResolverpublic class ListELResolver extends ELResolver | Defines property resolution behavior on instances of {@link java.util.List}.
This resolver handles base objects of type java.util.List.
It accepts any object as a property and coerces that object into an
integer index into the list. The resulting value is the value in the list
at that index.
This resolver can be constructed in read-only mode, which means that
{@link #isReadOnly} will always return true and
{@link #setValue} will always throw
PropertyNotWritableException.
ELResolvers are combined together using
{@link CompositeELResolver}s, to define rich semantics for evaluating
an expression. See the javadocs for {@link ELResolver} for details.
|
| Fields Summary |
|---|
| private static Class | theUnmodifiableListClass | | private boolean | isReadOnly |
| Constructors Summary |
|---|
public ListELResolver()Creates a new read/write ListELResolver.
this.isReadOnly = false;
| public ListELResolver(boolean isReadOnly)Creates a new ListELResolver whose read-only status is
determined by the given parameter.
this.isReadOnly = isReadOnly;
|
| Methods Summary |
|---|
| public java.lang.Class | getCommonPropertyType(javax.el.ELContext context, java.lang.Object base)If the base object is a list, returns the most general type that
this resolver accepts for the property argument.
Otherwise, returns null.
Assuming the base is a List, this method will always
return Integer.class. This is because Lists
accept integers as their index.
if (base != null && base instanceof List) {
return Integer.class;
}
return null;
| | public java.util.Iterator | getFeatureDescriptors(javax.el.ELContext context, java.lang.Object base)Always returns null, since there is no reason to
iterate through set set of all integers.
The {@link #getCommonPropertyType} method returns sufficient
information about what properties this resolver accepts.
return null;
| | public java.lang.Class | getType(javax.el.ELContext context, java.lang.Object base, java.lang.Object property)If the base object is a list, returns the most general acceptable type
for a value in this list.
If the base is a List, the propertyResolved
property of the ELContext object must be set to
true by this resolver, before returning. If this property
is not true after this method is called, the caller
should ignore the return value.
Assuming the base is a List, this method will always
return Object.class. This is because Lists
accept any object as an element.
if (context == null) {
throw new NullPointerException();
}
if (base != null && base instanceof List) {
context.setPropertyResolved(true);
List list = (List) base;
int index = toInteger(property);
if (index < 0 || index >= list.size()) {
throw new PropertyNotFoundException();
}
return Object.class;
}
return null;
| | public java.lang.Object | getValue(javax.el.ELContext context, java.lang.Object base, java.lang.Object property)If the base object is a list, returns the value at the given index.
The index is specified by the property argument, and
coerced into an integer. If the coercion could not be performed,
an IllegalArgumentException is thrown. If the index is
out of bounds, null is returned.
If the base is a List, the propertyResolved
property of the ELContext object must be set to
true by this resolver, before returning. If this property
is not true after this method is called, the caller
should ignore the return value.
if (context == null) {
throw new NullPointerException();
}
if (base != null && base instanceof List) {
context.setPropertyResolved(true);
List list = (List) base;
int index = toInteger(property);
if (index < 0 || index >= list.size()) {
return null;
}
return list.get(index);
}
return null;
| | public boolean | isReadOnly(javax.el.ELContext context, java.lang.Object base, java.lang.Object property)If the base object is a list, returns whether a call to
{@link #setValue} will always fail.
If the base is a List, the propertyResolved
property of the ELContext object must be set to
true by this resolver, before returning. If this property
is not true after this method is called, the caller
should ignore the return value.
If this resolver was constructed in read-only mode, this method will
always return true.
If a List was created using
{@link java.util.Collections#unmodifiableList}, this method must
return true. Unfortunately, there is no Collections API
method to detect this. However, an implementation can create a
prototype unmodifiable List and query its runtime type
to see if it matches the runtime type of the base object as a
workaround.
if (context == null) {
throw new NullPointerException();
}
if (base != null && base instanceof List) {
context.setPropertyResolved(true);
List list = (List) base;
int index = toInteger(property);
if (index < 0 || index >= list.size()) {
throw new PropertyNotFoundException();
}
return list.getClass() == theUnmodifiableListClass || isReadOnly;
}
return false;
| | public void | setValue(javax.el.ELContext context, java.lang.Object base, java.lang.Object property, java.lang.Object val)If the base object is a list, attempts to set the value at the
given index with the given value. The index is specified by the
property argument, and coerced into an integer. If the
coercion could not be performed, an
IllegalArgumentException is thrown. If the index is
out of bounds, a PropertyNotFoundException is thrown.
If the base is a List, the propertyResolved
property of the ELContext object must be set to
true by this resolver, before returning. If this property
is not true after this method is called, the caller
can safely assume no value was set.
If this resolver was constructed in read-only mode, this method will
always throw PropertyNotWritableException.
If a List was created using
{@link java.util.Collections#unmodifiableList}, this method must
throw PropertyNotWritableException. Unfortunately,
there is no Collections API method to detect this. However, an
implementation can create a prototype unmodifiable List
and query its runtime type to see if it matches the runtime type of
the base object as a workaround.
if (context == null) {
throw new NullPointerException();
}
if (base != null && base instanceof List) {
context.setPropertyResolved(true);
List list = (List) base;
int index = toInteger(property);
if (isReadOnly) {
throw new PropertyNotWritableException();
}
try {
list.set(index, val);
} catch (UnsupportedOperationException ex) {
throw new PropertyNotWritableException();
} catch (IndexOutOfBoundsException ex) {
throw new PropertyNotFoundException();
} catch (ClassCastException ex) {
throw ex;
} catch (NullPointerException ex) {
throw ex;
} catch (IllegalArgumentException ex) {
throw ex;
}
}
| | private int | toInteger(java.lang.Object p)
if (p instanceof Integer) {
return ((Integer) p).intValue();
}
if (p instanceof Character) {
return ((Character) p).charValue();
}
if (p instanceof Boolean) {
return ((Boolean) p).booleanValue()? 1: 0;
}
if (p instanceof Number) {
return ((Number) p).intValue();
}
if (p instanceof String) {
return Integer.parseInt((String) p);
}
throw new IllegalArgumentException();
|
|
