/**
* 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 under the License.
*/
package org.apache.hadoop.hive.ql.exec;
import java.lang.reflect.Method;
import java.util.List;
import org.apache.hadoop.hive.serde2.typeinfo.TypeInfo;
/**
* The default UDF Method resolver. This resolver is used for resolving the UDF
* method that is to be used for evaluation given the list of the argument
* types. The getEvalMethod goes through all the evaluate methods and returns
* the one that matches the argument signature or is the closest match. Closest
* match is defined as the one that requires the least number of arguments to be
* converted. In case more than one matches are found, the method throws an
* ambiguous method exception.
*/
public class DefaultUDFMethodResolver implements UDFMethodResolver {
/**
* The class of the UDF.
*/
private final Class<? extends UDF> udfClass;
/**
* Constructor. This constructor sets the resolver to be used for comparison
* operators. See {@link UDFMethodResolver}
*/
public DefaultUDFMethodResolver(Class<? extends UDF> udfClass) {
this.udfClass = udfClass;
}
/**
* Gets the evaluate method for the UDF given the parameter types.
*
* @param argClasses
* The list of the argument types that need to matched with the
* evaluate function signature.
*/
@Override
public Method getEvalMethod(List<TypeInfo> argClasses) throws UDFArgumentException {
return FunctionRegistry.getMethodInternal(udfClass, "evaluate", false,
argClasses);
}
}