| /* |
| * 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.pig.builtin; |
| |
| import java.io.IOException; |
| |
| import org.apache.pig.EvalFunc; |
| import org.apache.pig.backend.executionengine.ExecException; |
| import org.apache.pig.data.DataType; |
| import org.apache.pig.data.Tuple; |
| import org.apache.pig.impl.logicalLayer.FrontendException; |
| import org.apache.pig.impl.logicalLayer.schema.Schema; |
| import org.apache.pig.impl.logicalLayer.schema.Schema.FieldSchema; |
| /** |
| * The generic Invoker class does all the common grunt work of setting up an invoker. |
| * Class-specific non-generic extensions of this class are needed for Pig to know what type |
| * of return to expect from exec, and to find the appropriate classes through reflection. |
| * All they have to do is implement the constructors that call into super(). Note that the |
| * no-parameter constructor is <b>required</b>, if seemingly nonsensical, for Pig to do its work. |
| * <p> |
| * The Invoker family of udfs understand the following class names (all case-independent): |
| * <li>String |
| * <li>Long |
| * <li>Float |
| * <li>Double |
| * <li>Int |
| * <p> |
| * Invokers can also work with array arguments, represented in Pig as DataBags of single-tuple |
| * elements. Simply refer to <code>string[]</code>, for example. |
| * <p> |
| * This UDF allows one to dynamically invoke Java methods that return a <code>T</code> |
| * <p> |
| * Usage of the Invoker family of UDFs (adjust as appropriate): |
| * <p> |
| *<pre> |
| * {@code |
| * -- invoking a static method |
| * DEFINE StringToLong InvokeForLong('java.lang.Long.valueOf', 'String') |
| * longs = FOREACH strings GENERATE StringToLong(some_chararray); |
| * |
| * -- invoking a method on an object |
| * DEFINE StringConcat InvokeForString('java.lang.String.concat', 'String String', 'false') |
| * concatenations = FOREACH strings GENERATE StringConcat(str1, str2); |
| * } |
| * </pre> |
| * <p> |
| * The first argument to the constructor is the full path to desired method.<br> |
| * The second argument is a list of classes of the method parameters.<br> |
| * If the method is not static, the first element in this list is the object to invoke the method on.<br> |
| * The second argument is optional (a no-argument static method is assumed if it is not supplied).<br> |
| * The third argument is the keyword "static" (or "true") to signify that the method is static. <br> |
| * The third argument is optional, and true by default.<br> |
| * <p> |
| * @param <T> |
| */ |
| public abstract class GenericInvoker<T> extends EvalFunc<T> { |
| |
| private Invoker<T> invoker_; |
| |
| public GenericInvoker() {} |
| |
| public GenericInvoker(String fullName) |
| throws ClassNotFoundException, FrontendException, SecurityException, NoSuchMethodException { |
| invoker_ = new Invoker<T>(fullName, ""); |
| } |
| |
| public GenericInvoker(String fullName, String paramSpecsStr) |
| throws ClassNotFoundException, FrontendException, SecurityException, NoSuchMethodException { |
| invoker_ = new Invoker<T>(fullName, paramSpecsStr); |
| } |
| |
| public GenericInvoker(String fullName, String paramSpecsStr, String isStatic) |
| throws ClassNotFoundException, FrontendException, SecurityException, NoSuchMethodException { |
| invoker_ = new Invoker<T>(fullName, paramSpecsStr, isStatic); |
| } |
| |
| @Override |
| public T exec(Tuple input) throws IOException { |
| if (invoker_ == null) { |
| throw new ExecException("exec() attempted on an unitialized invoker. " + |
| "Invokers must be constructed with the method to invoke, and parameter signature to same."); |
| } |
| return invoker_.invoke(input); |
| } |
| |
| @Override |
| public Schema outputSchema(Schema input) { |
| if (invoker_ == null) return null; |
| FieldSchema fs = new FieldSchema(null, DataType.findType(invoker_.getReturnType())); |
| return new Schema(fs); |
| } |
| } |