org.springframework.core.env.ReadOnlySystemAttributesMap Maven / Gradle / Ivy
/*
* Copyright 2002-2013 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.core.env;
import java.util.Collection;
import java.util.Collections;
import java.util.Map;
import java.util.Set;
import org.springframework.util.Assert;
/**
* Read-only {@code Map} implementation that is backed by system
* properties or environment variables.
*
* Used by {@link AbstractApplicationContext} when a {@link SecurityManager} prohibits
* access to {@link System#getProperties()} or {@link System#getenv()}. It is for this
* reason that the implementations of {@link #keySet()}, {@link #entrySet()}, and
* {@link #values()} always return empty even though {@link #get(Object)} may in fact
* return non-null if the current security manager allows access to individual keys.
*
* @author Arjen Poutsma
* @author Chris Beams
* @since 3.0
*/
abstract class ReadOnlySystemAttributesMap implements Map {
@Override
public boolean containsKey(Object key) {
return (get(key) != null);
}
/**
* @param key the name of the system attribute to retrieve
* @throws IllegalArgumentException if given key is non-String
*/
@Override
public String get(Object key) {
Assert.isInstanceOf(String.class, key,
String.format("Expected key [%s] to be of type String, got %s", key, key.getClass().getName()));
return this.getSystemAttribute((String) key);
}
@Override
public boolean isEmpty() {
return false;
}
/**
* Template method that returns the underlying system attribute.
* Implementations typically call {@link System#getProperty(String)} or {@link System#getenv(String)} here.
*/
protected abstract String getSystemAttribute(String attributeName);
// Unsupported
@Override
public int size() {
throw new UnsupportedOperationException();
}
@Override
public String put(String key, String value) {
throw new UnsupportedOperationException();
}
@Override
public boolean containsValue(Object value) {
throw new UnsupportedOperationException();
}
@Override
public String remove(Object key) {
throw new UnsupportedOperationException();
}
@Override
public void clear() {
throw new UnsupportedOperationException();
}
@Override
public Set keySet() {
return Collections.emptySet();
}
@Override
public void putAll(Map map) {
throw new UnsupportedOperationException();
}
@Override
public Collection values() {
return Collections.emptySet();
}
@Override
public Set> entrySet() {
return Collections.emptySet();
}
}