VariableExpander.java

/**
 *  Copyright 2007-2015 University Of Southern California
 *
 *  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 edu.isi.pegasus.common.util;

import org.apache.commons.lang3.text.StrSubstitutor;

import java.util.HashMap;
import java.util.Map;
import org.apache.commons.lang3.text.StrLookup;

/**
 * Utility class to allow for variable expansions in strings. 
 * 
 * @author  Karan Vahi
 */
public class VariableExpander {
    
    /**
     * The list of values mMap that need to be expanded.
     */
    private Map<String,String> mValuesMap;
    
    private StrSubstitutor mExpander;
    
    /**
     * The default constructor, which intializes the values from
     * the System environment variables, and has case sensitivity turned off.
     */
    public VariableExpander(){
        this( false );
    }
    
    /**
     * Overloaded constructor 
     * 
     * @param caseSensitive  boolean indicating whether you want lookups to be
     *                       case sensitive or not.
     */
    public VariableExpander( boolean caseSensitive ){
        mValuesMap = new HashMap(System.getenv());
        mExpander = new StrSubstitutor( mValuesMap, "${", "}", '\\' );
        mExpander.setVariableResolver( new CaseSensitiveStrLookup( this.mValuesMap, caseSensitive ));
        
    }
    
    /**
     * Overloaded  constructor. Constructs expander with case sensitivity turned off
     * 
     * @param map containing variable names and values that need to be expanded 
     */
    public VariableExpander(Map<String,String> map ){
        this( map, false );
    }
    
    /**
     * Overloaded  constructor
     * 
     * @param map containing variable names and values that need to be expanded 
     * @param caseSensitive  boolean indicating whether you want lookups to be
     *                       case sensitive or not.
     */
    public VariableExpander(Map<String,String> map, boolean caseSensitive ){
        mValuesMap = map;
        mExpander = new StrSubstitutor( map );
        mExpander.setVariableResolver( new CaseSensitiveStrLookup( this.mValuesMap, caseSensitive ));
    }
    
    /**
     * Expands the value passed with variable substitution 
     * 
     * @param text
     * 
     * @return expanded value
     */
    public String expand( String text ){
        return mExpander.replace(text);
    }
    
    public static void main( String[] args ){
        VariableExpander exp = new VariableExpander(  );
        System.out.println( exp.mValuesMap );
        
        System.out.println( exp.expand( "Pegasus developer $(USER) rocks "));
        System.out.println( exp.expand( "Pegasus developer $(USer) rocks "));
        //System.out.println( exp.expand( "Pegasus developer $(USER1) rocks "));
        System.out.println( exp.expand( "Pegasus developer \\$(USER) rocks "));
        
        
    }
    
}

/**
 * A case sensitive look up class to use in StrSubstitutor
 * @author vahi
 * @param <V> 
 */
class CaseSensitiveStrLookup<V> extends StrLookup<V> {

    private final Map<String, V> mMap;
    
    private final boolean mCaseSensitive ;

    CaseSensitiveStrLookup(final Map<String, V> map, boolean caseSensitive) {
        mCaseSensitive = caseSensitive;
        Map<String, V> setMap = new HashMap();
        //explicitly lower case all the key in there
        for( String key: map.keySet() ){
            V value = map.get(key);
            setMap.put( caseSensitive ? key : key.toLowerCase(), value);
        }
        this.mMap = setMap;
    }

    /**
     * Looks up the key and throws an exception if invalid value found 
     * 
     * @param key
     * @return 
     */
    public String lookup(final String key) {
        String casedKey = mCaseSensitive ? key : key.toLowerCase(); //lowercase the key you're looking for
        if (mMap == null) {
            return null;
        }
        final Object obj = mMap.get(casedKey);
        if (obj == null) {
            throw new RuntimeException( "Unable to expand variable " + key ); 
        }
        return obj.toString();
    }
}