/*
* Copyright 2002-2010 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
*
* 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 org.springframework.context.expression;
import java.util.Map;
import org.springframework.expression.AccessException;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.PropertyAccessor;
import org.springframework.expression.TypedValue;
/**
* EL property accessor that knows how to traverse the keys
* of a standard {@link java.util.Map}.
*
* @author Juergen Hoeller
* @author Andy Clement
* @since 3.0
*/
public class MapAccessor implements PropertyAccessor {
public boolean canRead(EvaluationContext context, Object target, String name) throws AccessException {
Map map = (Map) target;
return map.containsKey(name);
}
public TypedValue read(EvaluationContext context, Object target, String name) throws AccessException {
Map map = (Map) target;
Object value = map.get(name);
if (value == null && !map.containsKey(name)) {
throw new MapAccessException(name);
}
return new TypedValue(value);
}
public boolean canWrite(EvaluationContext context, Object target, String name) throws AccessException {
return true;
}
@SuppressWarnings("unchecked")
public void write(EvaluationContext context, Object target, String name, Object newValue) throws AccessException {
Map map = (Map) target;
map.put(name, newValue);
}
public Class[] getSpecificTargetClasses() {
return new Class[] {Map.class};
}
/**
* Exception thrown from <code>read</code> in order to reset a cached
* PropertyAccessor, allowing other accessors to have a try.
*/
private static class MapAccessException extends AccessException {
private final String key;
public MapAccessException(String key) {
super(null);
this.key = key;
}
@Override
public String getMessage() {
return "Map does not contain a value for key '" + this.key + "'";
}
}
}
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