spring EnvironmentAccessor 源码
spring EnvironmentAccessor 代码
文件路径：/spring-context/src/main/java/org/springframework/context/expression/EnvironmentAccessor.java
/*
* 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 {
}
}
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