001/*
002 * Copyright 2002-2013 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.context.expression;
018
019import org.springframework.core.env.Environment;
020import org.springframework.expression.AccessException;
021import org.springframework.expression.EvaluationContext;
022import org.springframework.expression.PropertyAccessor;
023import org.springframework.expression.TypedValue;
024
025/**
026 * Read-only EL property accessor that knows how to retrieve keys
027 * of a Spring {@link Environment} instance.
028 *
029 * @author Chris Beams
030 * @since 3.1
031 */
032public class EnvironmentAccessor implements PropertyAccessor {
033
034        @Override
035        public Class<?>[] getSpecificTargetClasses() {
036                return new Class<?>[] {Environment.class};
037        }
038
039        /**
040         * Can read any {@link Environment}, thus always returns true.
041         * @return true
042         */
043        @Override
044        public boolean canRead(EvaluationContext context, Object target, String name) throws AccessException {
045                return true;
046        }
047
048        /**
049         * Access the given target object by resolving the given property name against the given target
050         * environment.
051         */
052        @Override
053        public TypedValue read(EvaluationContext context, Object target, String name) throws AccessException {
054                return new TypedValue(((Environment) target).getProperty(name));
055        }
056
057        /**
058         * Read-only: returns {@code false}.
059         */
060        @Override
061        public boolean canWrite(EvaluationContext context, Object target, String name) throws AccessException {
062                return false;
063        }
064
065        /**
066         * Read-only: no-op.
067         */
068        @Override
069        public void write(EvaluationContext context, Object target, String name, Object newValue) throws AccessException {
070        }
071
072}