jakarta.el.OptionalELResolver Maven / Gradle / Ivy
/*
* Copyright (c) 2024 Contributors to the Eclipse Foundation
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0, which is available at
* http://www.eclipse.org/legal/epl-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception, which is available at
* https://www.gnu.org/software/classpath/license.html.
*
* SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
*/
package jakarta.el;
import static jakarta.el.ELUtil.getExceptionMessageString;
import java.util.Objects;
import java.util.Optional;
/**
* Defines property resolution, method invocation and type conversion behaviour on {@link Optional}s.
*
* This resolver handles base objects that are instances of {@link Optional}.
*
* This resolver is always a read-only resolver since {@link Optional} instances are immutable.
*/
public class OptionalELResolver extends ELResolver {
/**
* {@inheritDoc}
*
* @return If the base object is an {@link Optional} and {@link Optional#isEmpty()} returns {@code true} then the
* resulting value is {@code null}.
*
* If the base object is an {@link Optional}, {@link Optional#isPresent()} returns {@code true} and the
* property is {@code null} then the resulting value is the result of calling {@link Optional#get()} on
* the base object.
*
* If the base object is an {@link Optional}, {@link Optional#isPresent()} returns {@code true} and the
* property is not {@code null} then the resulting value is the result of calling
* {@link ELResolver#getValue(ELContext, Object, Object)} using the {@link ELResolver} obtained from
* {@link ELContext#getELResolver()} with the following parameters:
*
* - The {@link ELContext} is the current context
* - The base object is the result of calling {@link Optional#get()} on the current base object
* - The property object is the current property object
*
*
* If the base object is not an {@link Optional} then the return value is undefined.
*/
@Override
public Object getValue(ELContext context, Object base, Object property) {
Objects.requireNonNull(context);
if (base instanceof Optional) {
context.setPropertyResolved(base, property);
if (((Optional) base).isEmpty()) {
if (property == null) {
return null;
}
} else {
if (property == null) {
return ((Optional) base).get();
} else {
Object resolvedBase = ((Optional) base).get();
return context.getELResolver().getValue(context, resolvedBase, property);
}
}
}
return null;
}
/**
* {@inheritDoc}
*
* @return If the base object is an {@link Optional} this method always returns {@code null} since instances of this
* resolver are always read-only.
*
* If the base object is not an {@link Optional} then the return value is undefined.
*/
@Override
public Class getType(ELContext context, Object base, Object property) {
Objects.requireNonNull(context);
if (base instanceof Optional) {
context.setPropertyResolved(base, property);
}
return null;
}
/**
* {@inheritDoc}
*
* If the base object is an {@link Optional} this method always throws a {@link PropertyNotWritableException} since
* instances of this resolver are always read-only.
*/
@Override
public void setValue(ELContext context, Object base, Object property, Object value) {
Objects.requireNonNull(context);
if (base instanceof Optional) {
throw new PropertyNotWritableException(getExceptionMessageString(
context, "resolverNotwritable", new Object[] { base.getClass().getName() }));
}
}
/**
* {@inheritDoc}
*
* @return If the base object is an {@link Optional} this method always returns {@code true} since instances of this
* resolver are always read-only.
*
* If the base object is not an {@link Optional} then the return value is undefined.
*/
@Override
public boolean isReadOnly(ELContext context, Object base, Object property) {
Objects.requireNonNull(context);
if (base instanceof Optional) {
context.setPropertyResolved(base, property);
return true;
}
return false;
}
/**
* {@inheritDoc}
*
* @return If the base object is an {@link Optional} this method always returns {@code Object.class}.
*
* If the base object is not an {@link Optional} then the return value is undefined.
*/
@Override
public Class getCommonPropertyType(ELContext context, Object base) {
if (base instanceof Optional) {
return Object.class;
}
return null;
}
/**
* {@inheritDoc}
*
* @return If the base object is an {@link Optional} and {@link Optional#isEmpty()} returns {@code true} then this
* method returns the result of coercing {@code null} to the requested {@code type}.
*
* If the base object is an {@link Optional} and {@link Optional#isPresent()} returns {@code true} then
* this method returns the result of coercing {@code Optional#get()} to the requested {@code type}.
*
* If the base object is not an {@link Optional} then the return value is undefined.
*/
@Override
public T convertToType(ELContext context, Object obj, Class type) {
Objects.requireNonNull(context);
if (obj instanceof Optional) {
Object value = null;
if (((Optional) obj).isPresent()) {
value = ((Optional) obj).get();
// If the value is assignable to the required type, do so.
if (type.isAssignableFrom(value.getClass())) {
context.setPropertyResolved(true);
@SuppressWarnings("unchecked")
T result = (T) value;
return result;
}
}
try {
Object convertedValue = context.convertToType(value, type);
context.setPropertyResolved(true);
@SuppressWarnings("unchecked")
T result = (T) convertedValue;
return result;
} catch (ELException e) {
/*
* TODO: This isn't pretty but it works. Significant refactoring would be required to avoid the
* exception. See also Util.isCoercibleFrom().
*/
}
}
return null;
}
/**
* {@inheritDoc}
*
* @return If the base object is an {@link Optional} and {@link Optional#isEmpty()} returns {@code true} then this
* method returns {@code null}.
*
* If the base object is an {@link Optional} and {@link Optional#isPresent()} returns {@code true} then
* this method returns the result of invoking the specified method on the object obtained by calling
* {@link Optional#get()} with the specified parameters.
*
* If the base object is not an {@link Optional} then the return value is undefined.
*/
@Override
public Object invoke(ELContext context, Object base, Object method, Class[] paramTypes, Object[] params) {
Objects.requireNonNull(context);
if (base instanceof Optional && method != null) {
context.setPropertyResolved(base, method);
if (((Optional) base).isEmpty()) {
return null;
} else {
Object resolvedBase = ((Optional) base).get();
return context.getELResolver().invoke(context, resolvedBase, method, paramTypes, params);
}
}
return null;
}
}