/*
* Copyright 2006 JBoss Inc
*
* 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.
*
* Created on Jun 12, 2007
*/
package org.drools.base.extractors;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import org.drools.base.AccessorKey;
import org.drools.base.ValueType;
import org.drools.base.ClassFieldAccessorCache.CacheEntry;
import org.drools.common.InternalWorkingMemory;
import org.drools.spi.InternalReadAccessor;
import org.mvel2.MVEL;
import org.mvel2.compiler.CompiledExpression;
import org.mvel2.compiler.ExpressionCompiler;
/**
* A class field extractor that uses MVEL engine to extract the actual value for a given
* expression. We use MVEL to resolve nested accessor expressions.
*
* @author etirelli
*/
public class MVELClassFieldReader extends BaseObjectClassFieldReader {
private static final long serialVersionUID = 400L;
private CompiledExpression mvelExpression = null;
private Map extractors = null;
public MVELClassFieldReader() {
}
public MVELClassFieldReader(Class cls,
String fieldName,
CacheEntry cache) {
super( -1, // index
Object.class, // fieldType
ValueType.determineValueType( Object.class ) ); // value type
this.extractors = new HashMap();
ExpressionCompiler compiler = new ExpressionCompiler( fieldName );
this.mvelExpression = compiler.compile();
Set inputs = compiler.getParserContextState().getInputs().keySet();
for ( Iterator it = inputs.iterator(); it.hasNext(); ) {
String basefield = (String) it.next();
if ( "this".equals( basefield ) ) {
continue;
}
InternalReadAccessor extr = cache.getReadAccessor( new AccessorKey( cls.getName(),
basefield,
AccessorKey.AccessorType.FieldAccessor ),
cls );
this.extractors.put( basefield,
extr );
}
}
// public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
// super.readExternal(in);
// mvelExpression = (CompiledExpression)in.readObject();
// extractors = (Map)in.readObject();
// }
//
// public void writeExternal(ObjectOutput out) throws IOException {
// super.writeExternal(out);
// out.writeObject(mvelExpression);
// out.writeObject(extractors);
// }
/* (non-Javadoc)
* @see org.drools.base.extractors.BaseObjectClassFieldExtractor#getValue(java.lang.Object)
*/
public Object getValue(InternalWorkingMemory workingMemory,
Object object) {
Map variables = new HashMap();
for ( Iterator it = this.extractors.entrySet().iterator(); it.hasNext(); ) {
Map.Entry entry = (Map.Entry) it.next();
String var = (String) entry.getKey();
InternalReadAccessor extr = (InternalReadAccessor) entry.getValue();
variables.put( var,
extr.getValue( workingMemory,
object ) );
}
return MVEL.executeExpression( mvelExpression,
object,
variables );
}
}