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/*
* EnvironmentFilter.java May 2006
*
* Copyright (C) 2006, Niall Gallagher
*
* 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.simpleframework.xml.filter;
/**
* The EnvironmentFilter
object is used to provide a
* filter that will replace the specified values with an environment
* variable from the OS. This can be given a delegate filter which
* can be used to resolve replacements should the value requested
* not match an environment variable from the OS.
*
* @author Niall Gallagher
*/
public class EnvironmentFilter implements Filter {
/**
* Filter delegated to if no environment variable is resolved.
*/
private Filter filter;
/**
* Constructor for the EnvironmentFilter
object. This
* creates a filter that resolves replacements using environment
* variables. Should the environment variables not contain the
* requested mapping this will return a null value.
*/
public EnvironmentFilter() {
this(null);
}
/**
* Constructor for the EnvironmentFilter
object. This
* creates a filter that resolves replacements using environment
* variables. Should the environment variables not contain the
* requested mapping this will delegate to the specified filter.
*
* @param filter the filter delegated to should resolution fail
*/
public EnvironmentFilter(Filter filter) {
this.filter = filter;
}
/**
* Replaces the text provided with the value resolved from the
* environment variables. If the environment variables fail this
* will delegate to the specified Filter
if it is
* not a null object. If no match is found a null is returned.
*
* @param text this is the text value to be replaced
*
* @return this will return the replacement text resolved
*/
public String replace(String text) {
String value = System.getenv(text);
if(value != null) {
return value;
}
if(filter != null) {
return filter.replace(text);
}
return null;
}
}