/*
* Copyright 2005 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.
*/
package org.drools.lang.dsl;
import java.io.IOException;
import java.io.Reader;
import java.util.HashMap;
import java.util.Map;
import org.drools.RuntimeDroolsException;
import org.drools.lang.Expander;
import org.drools.lang.ExpanderResolver;
/**
* The default expander resolver will provide instances of the DefaultExpander.
* The DefaultExpander uses templates to provide DSL and pseudo
* natural language support.
*/
public class DefaultExpanderResolver
implements
ExpanderResolver {
private final Map expanders = new HashMap();
/**
* Create an empty resolver, which you will then
* call addExpander multiple times, to map a specific expander
* with a name that will be found in the drl after the expander keyword.
*/
public DefaultExpanderResolver() {
}
/**
* This will load up a DSL from the reader specified.
* This will make the expander available to any parser
* regardless of name.
*
* The DSL expander will be the default expander.
*
* This is the constructor most people should use.
*/
public DefaultExpanderResolver(final Reader reader) throws IOException {
final DSLTokenizedMappingFile file = new DSLTokenizedMappingFile();
if ( file.parseAndLoad( reader ) ) {
final Expander expander = new DefaultExpander();
expander.addDSLMapping( file.getMapping() );
this.expanders.put( "*",
expander );
} else {
throw new RuntimeDroolsException( "Error parsing and loading DSL file." + file.getErrors() );
}
}
/**
* Add an expander with the given name, which will be used
* by looking for the "expander" keyword in the DRL.
*
* If a default expander is installed, it will always be returned
* if none matching the given name can be found.
*
* You don't need to use this unless you have multiple expanders/DSLs
* involved when compiling multiple rule packages at the same time.
* If you don't know what that sentence means, you probably don't need to use this method.
*/
public void addExpander(final String name,
final Expander expander) {
this.expanders.put( name,
expander );
}
public Expander get(final String name,
final String config) {
if ( this.expanders.containsKey( name ) ) {
return (Expander) this.expanders.get( name );
} else {
final Expander exp = (Expander) this.expanders.get( "*" );
if ( exp == null ) {
throw new IllegalArgumentException( "Unable to provide an expander for " + name + " or a default expander." );
}
return exp;
}
}
}