/*
* Copyright 2002-2009 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.support;
import java.util.Collection;
import java.util.Map;
import java.util.Set;
/**
* Read-only {@code Map<String, String>} implementation that is backed by system properties or environment
* variables.
*
* <p>Used by {@link AbstractApplicationContext} when a {@link SecurityManager} prohibits access to {@link
* System#getProperties()} or {@link System#getenv()}.
*
* @author Arjen Poutsma
* @since 3.0
*/
abstract class ReadOnlySystemAttributesMap implements Map<String, String> {
public boolean containsKey(Object key) {
return get(key) != null;
}
public String get(Object key) {
if (key instanceof String) {
String attributeName = (String) key;
return getSystemAttribute(attributeName);
}
else {
return null;
}
}
public boolean isEmpty() {
return false;
}
/**
* Template method that returns the underlying system attribute.
*
* <p>Implementations typically call {@link System#getProperty(String)} or {@link System#getenv(String)} here.
*/
protected abstract String getSystemAttribute(String attributeName);
// Unsupported
public int size() {
throw new UnsupportedOperationException();
}
public String put(String key, String value) {
throw new UnsupportedOperationException();
}
public boolean containsValue(Object value) {
throw new UnsupportedOperationException();
}
public String remove(Object key) {
throw new UnsupportedOperationException();
}
public void clear() {
throw new UnsupportedOperationException();
}
public Set<String> keySet() {
throw new UnsupportedOperationException();
}
public void putAll(Map<? extends String, ? extends String> m) {
throw new UnsupportedOperationException();
}
public Collection<String> values() {
throw new UnsupportedOperationException();
}
public Set<Entry<String, String>> entrySet() {
throw new UnsupportedOperationException();
}
}
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