org.springframework.context.expression.EnvironmentAccessor.java Source code

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Here is the source code for org.springframework.context.expression.EnvironmentAccessor.java

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/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed 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
 *
 *      https://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 org.springframework.context.expression;

import org.springframework.core.env.Environment;
import org.springframework.expression.AccessException;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.PropertyAccessor;
import org.springframework.expression.TypedValue;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;

/**
 * Read-only EL property accessor that knows how to retrieve keys
 * of a Spring {@link Environment} instance.
 *
 * @author Chris Beams
 * @since 3.1
 */
public class EnvironmentAccessor implements PropertyAccessor {

    @Override
    public Class<?>[] getSpecificTargetClasses() {
        return new Class<?>[] { Environment.class };
    }

    /**
     * Can read any {@link Environment}, thus always returns true.
     * @return true
     */
    @Override
    public boolean canRead(EvaluationContext context, @Nullable Object target, String name) throws AccessException {
        return true;
    }

    /**
     * Access the given target object by resolving the given property name against the given target
     * environment.
     */
    @Override
    public TypedValue read(EvaluationContext context, @Nullable Object target, String name) throws AccessException {
        Assert.state(target instanceof Environment, "Target must be of type Environment");
        return new TypedValue(((Environment) target).getProperty(name));
    }

    /**
     * Read-only: returns {@code false}.
     */
    @Override
    public boolean canWrite(EvaluationContext context, @Nullable Object target, String name)
            throws AccessException {
        return false;
    }

    /**
     * Read-only: no-op.
     */
    @Override
    public void write(EvaluationContext context, @Nullable Object target, String name, @Nullable Object newValue)
            throws AccessException {
    }

}