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* Fix #176 - Add support for java.util.Optional Support is implemented via a new resolver : OptionalELResolver The resolver is not included in the default ELResolvers. It must be explicitly added by the user if they wish to enable this functionality.
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| /* | ||
| * Licensed to the Apache Software Foundation (ASF) under one or more | ||
| * contributor license agreements. See the NOTICE file distributed with | ||
| * this work for additional information regarding copyright ownership. | ||
| * The ASF licenses this file to You under the Apache License, Version 2.0 | ||
| * (the "License"); you may not use this file except in compliance with | ||
| * the License. You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| package jakarta.el; | ||
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| import static jakarta.el.ELUtil.getExceptionMessageString; | ||
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| import java.util.Objects; | ||
| import java.util.Optional; | ||
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| /** | ||
| * Defines property resolution behaviour on {@link Optional}s. | ||
| * <p> | ||
| * This resolver handles base objects that are instances of {@link Optional}. | ||
| * <p> | ||
| * If the {@link Optional#isEmpty()} is {@code true} for the base object and the property is {@code null} then the | ||
| * resulting value is {@code null}. | ||
| * <p> | ||
| * If the {@link Optional#isEmpty()} is {@code true} for the base object and the property is not {@code null} then the | ||
| * resulting value is the base object (an empty {@link Optional}). | ||
| * <p> | ||
| * If the {@link Optional#isPresent()} is {@code true} for the base object and the property is {@code null} then the | ||
| * resulting value is the result of calling {@link Optional#get()} on the base object. | ||
| * <p> | ||
| * If the {@link Optional#isPresent()} is {@code true} for the base object 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: | ||
| * <ul> | ||
| * <li>The {@link ELContext} is the current context</li> | ||
| * <li>The base object is the result of calling {@link Optional#get()} on the current base object</li> | ||
| * <li>The property object is the current property object</li> | ||
| * </ul> | ||
| * <p> | ||
| * This resolver is always a read-only resolver. | ||
| */ | ||
| public class OptionalELResolver extends ELResolver { | ||
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| @Override | ||
| public Object getValue(ELContext context, Object base, Object property) { | ||
| Objects.requireNonNull(context); | ||
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| if (base instanceof Optional) { | ||
| context.setPropertyResolved(base, property); | ||
| if (((Optional<?>) base).isEmpty()) { | ||
| if (property == null) { | ||
| return null; | ||
| } else { | ||
| return base; | ||
| } | ||
| } else { | ||
| if (property == null) { | ||
| return ((Optional<?>) base).get(); | ||
| } else { | ||
| Object resolvedBase = ((Optional<?>) base).get(); | ||
| return context.getELResolver().getValue(context, resolvedBase, property); | ||
| } | ||
| } | ||
| } | ||
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| return null; | ||
| } | ||
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| /** | ||
| * {@inheritDoc} | ||
| * <p> | ||
| * If the base object is an {@link Optional} this method always returns {@code null} since instances of this | ||
| * resolver are always read-only. | ||
| */ | ||
| @Override | ||
| public Class<?> getType(ELContext context, Object base, Object property) { | ||
| Objects.requireNonNull(context); | ||
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| if (base instanceof Optional) { | ||
| context.setPropertyResolved(base, property); | ||
| } | ||
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| return null; | ||
| } | ||
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| /** | ||
| * {@inheritDoc} | ||
| * <p> | ||
| * 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); | ||
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| if (base instanceof Optional) { | ||
| throw new PropertyNotWritableException(getExceptionMessageString( | ||
| context, "resolverNotwritable", new Object[] { base.getClass().getName() })); | ||
| } | ||
| } | ||
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| /** | ||
| * {@inheritDoc} | ||
| * <p> | ||
| * If the base object is an {@link Optional} this method always returns {@code true} since instances of this | ||
| * resolver are always read-only. | ||
| */ | ||
| @Override | ||
| public boolean isReadOnly(ELContext context, Object base, Object property) { | ||
| Objects.requireNonNull(context); | ||
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| if (base instanceof Optional) { | ||
| context.setPropertyResolved(base, property); | ||
| return true; | ||
| } | ||
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| return false; | ||
| } | ||
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| /** | ||
| * {@inheritDoc} | ||
| * <p> | ||
| * If the base object is an {@link Optional} this method always returns {@code Object.class}. | ||
| */ | ||
| @Override | ||
| public Class<?> getCommonPropertyType(ELContext context, Object base) { | ||
| if (base instanceof Optional) { | ||
| return Object.class; | ||
| } | ||
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| return null; | ||
| } | ||
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| @Override | ||
| public <T> T convertToType(ELContext context, Object obj, Class<T> type) { | ||
| Objects.requireNonNull(context); | ||
| if (obj instanceof Optional) { | ||
| if (((Optional<?>) obj).isPresent()) { | ||
| Object 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; | ||
| } | ||
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| 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 ELUtil.isCoercibleFrom(). | ||
| */ | ||
| } | ||
| } else { | ||
| context.setPropertyResolved(true); | ||
| return null; | ||
| } | ||
| } | ||
| return null; | ||
| } | ||
| } |
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