001    /*
002     * Copyright (c) 2007-2014 Concurrent, Inc. All Rights Reserved.
003     *
004     * Project and contact information: http://www.cascading.org/
005     *
006     * This file is part of the Cascading project.
007     *
008     * Licensed under the Apache License, Version 2.0 (the "License");
009     * you may not use this file except in compliance with the License.
010     * You may obtain a copy of the License at
011     *
012     *     http://www.apache.org/licenses/LICENSE-2.0
013     *
014     * Unless required by applicable law or agreed to in writing, software
015     * distributed under the License is distributed on an "AS IS" BASIS,
016     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
017     * See the License for the specific language governing permissions and
018     * limitations under the License.
019     */
020    
021    package cascading.operation.expression;
022    
023    import java.beans.ConstructorProperties;
024    import java.io.IOException;
025    import java.io.StringReader;
026    
027    import cascading.operation.OperationException;
028    import cascading.tuple.Fields;
029    import org.codehaus.commons.compiler.CompileException;
030    import org.codehaus.janino.ExpressionEvaluator;
031    import org.codehaus.janino.Scanner;
032    import org.codehaus.janino.ScriptEvaluator;
033    
034    import static cascading.tuple.coerce.Coercions.asClass;
035    
036    /**
037     * Class ExpressionOperation is the base class for {@link ExpressionFunction}, {@link ExpressionFilter},
038     * {@link cascading.operation.assertion.AssertExpression}.
039     */
040    public class ExpressionOperation extends ScriptOperation
041      {
042      @ConstructorProperties({"fieldDeclaration", "expression"})
043      protected ExpressionOperation( Fields fieldDeclaration, String expression )
044        {
045        this( fieldDeclaration, expression, new String[ 0 ], new Class[ 0 ] );
046        }
047    
048      @ConstructorProperties({"fieldDeclaration", "expression", "parameterType"})
049      protected ExpressionOperation( Fields fieldDeclaration, String expression, Class parameterType )
050        {
051        super( 1, fieldDeclaration, expression, asClass( fieldDeclaration.getType( 0 ) ), null,
052          new Class[]{parameterType} );
053        }
054    
055      @ConstructorProperties({"fieldDeclaration", "expression", "parameterNames", "parameterTypes"})
056      protected ExpressionOperation( Fields fieldDeclaration, String expression, String[] parameterNames, Class[] parameterTypes )
057        {
058        super( parameterTypes.length, fieldDeclaration, expression, asClass( fieldDeclaration.getType( 0 ) ), parameterNames, parameterTypes );
059        }
060    
061      @ConstructorProperties({"expression", "parameterType"})
062      protected ExpressionOperation( String expression, Class parameterType )
063        {
064        super( 1, expression, Object.class, null, new Class[]{parameterType} );
065        }
066    
067      @ConstructorProperties({"expression", "parameterNames", "parameterTypes"})
068      protected ExpressionOperation( String expression, String[] parameterNames, Class[] parameterTypes )
069        {
070        super( parameterTypes.length, expression, Object.class, parameterNames, parameterTypes );
071        }
072    
073      public String getExpression()
074        {
075        return getBlock();
076        }
077    
078      protected String[] guessParameterNames() throws CompileException, IOException
079        {
080        return ExpressionEvaluator.guessParameterNames( new Scanner( "expressionEval", new StringReader( block ) ) );
081        }
082    
083      @Override
084      protected ScriptEvaluator getEvaluator( Class returnType, String[] parameterNames, Class[] parameterTypes )
085        {
086        try
087          {
088          return new ExpressionEvaluator( block, getReturnType(), parameterNames, parameterTypes );
089          }
090        catch( CompileException exception )
091          {
092          throw new OperationException( "could not compile expression: " + block, exception );
093          }
094        }
095      }