Github user cloud-fan commented on a diff in the pull request: https://github.com/apache/spark/pull/13969#discussion_r69146875 --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/JavaMethodReflect.scala --- @@ -0,0 +1,153 @@ +/* + * 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.spark.sql.catalyst.expressions + +import java.lang.reflect.Method + +import scala.util.Try + +import org.apache.spark.sql.catalyst.InternalRow +import org.apache.spark.sql.catalyst.analysis.TypeCheckResult +import org.apache.spark.sql.catalyst.analysis.TypeCheckResult.{TypeCheckFailure, TypeCheckSuccess} +import org.apache.spark.sql.catalyst.expressions.codegen.CodegenFallback +import org.apache.spark.sql.types._ +import org.apache.spark.unsafe.types.UTF8String +import org.apache.spark.util.Utils + +/** + * An expression that invokes a method on a class via reflection. + * + * @param children the first element should be a literal string for the class name, + * and the second element should be a literal string for the method name, + * and the remaining are input arguments to the Java method. + */ +// scalastyle:off line.size.limit +@ExpressionDescription( + usage = "_FUNC_(class,method[,arg1[,arg2..]]) calls method with reflection", + extended = "> SELECT _FUNC_('java.util.UUID', 'randomUUID');\nc33fb387-8500-4bfa-81d2-6e0e3e930df2") +// scalastyle:on line.size.limit +case class JavaMethodReflect(children: Seq[Expression]) + extends Expression with CodegenFallback { + import JavaMethodReflect._ + + override def prettyName: String = "reflect" + + override def checkInputDataTypes(): TypeCheckResult = { + if (children.size < 2) { + TypeCheckFailure("requires at least two arguments") + } else if (!children.take(2).forall(e => e.dataType == StringType && e.foldable)) { + // The first two arguments must be string type. + TypeCheckFailure("first two arguments should be string literals") + } else if (method == null) { + TypeCheckFailure("cannot find a method that matches the argument types") + } else { + TypeCheckSuccess + } + } + + override def deterministic: Boolean = false + override def nullable: Boolean = true + override val dataType: DataType = StringType + + override def eval(input: InternalRow): Any = { + var i = 0 + while (i < argExprs.length) { + buffer(i) = argExprs(i).eval(input).asInstanceOf[Object] + // Convert if necessary. Based on the types defined in typeMapping, string is the only + // type that needs conversion. + if (buffer(i).isInstanceOf[UTF8String]) { + buffer(i) = buffer(i).toString + } + i += 1 + } + UTF8String.fromString(String.valueOf(method.invoke(obj, buffer : _*))) + } + + @transient private lazy val argExprs: Array[Expression] = children.drop(2).toArray + + /** Name of the class -- this has to be called after we verify children has at least two exprs. */ + @transient private lazy val className = children(0).eval(null).asInstanceOf[UTF8String].toString + + /** The reflection method. */ + @transient lazy val method: Method = { + val methodName = children(1).eval(null).asInstanceOf[UTF8String].toString + findMethod(className, methodName, argExprs.map(_.dataType)).orNull + } + + /** If the class has a no-arg ctor, instantiate the object. Otherwise, obj is null. */ + @transient private lazy val obj: Object = instantiate(className).orNull.asInstanceOf[Object] + + /** A temporary buffer used to hold intermediate results returned by children. */ + @transient private lazy val buffer = new Array[Object](argExprs.length) +} + +object JavaMethodReflect { + /** Mapping from Spark's type to acceptable JVM types. */ + val typeMapping = Map[DataType, Seq[Class[_]]]( --- End diff -- What's hive's rule? This looks reasonable but I wanna make sure we don't miss anything.
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