src/test/java/org/apache/sling/cli/impl/junit/SystemPropertiesRule.java

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 ~ Licensed to the Apache Software Foundation (ASF) under one
 ~ or more contributor license agreements.  See the NOTICE file
 ~ distributed with this work for additional information
 ~ regarding copyright ownership.  The ASF licenses this file
 ~ to you 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
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package org.apache.sling.cli.impl.junit;

import java.util.HashMap;
import java.util.Map;

import org.junit.rules.ExternalResource;

public class SystemPropertiesRule extends ExternalResource {

    private final Map<String, String> propsToRestore = new HashMap<>();
    private final Map<String, String> propsToOverride;

    public SystemPropertiesRule(Map<String, String> propsToOverride) {
        this.propsToOverride = propsToOverride;
    }
    
    @Override
    protected void before() {
        for (Map.Entry<String, String> prop : propsToOverride.entrySet() )
            propsToRestore.put(prop.getKey(), set(prop));
    }

    private String set(Map.Entry<String, String> prop) {
        if ( prop.getValue() != null )
            return System.setProperty(prop.getKey(), prop.getValue());
        
        return System.clearProperty(prop.getKey());
    }
    
    @Override
    protected void after() {
        for (Map.Entry<String, String> prop : propsToRestore.entrySet() )
            set(prop);
    }
}