[SPARK-22945][SQL] add java UDF APIs in the functions object

## What changes were proposed in this pull request?

Currently Scala users can use UDF like
```
val foo = udf((i: Int) => Math.random() + i).asNondeterministic
df.select(foo('a))
```
Python users can also do it with similar APIs. However Java users can't do it, we should add Java UDF APIs in the functions object.

## How was this patch tested?

new tests

Author: Wenchen Fan <[email protected]>

Closes apache#20141 from cloud-fan/udf.

sql/core/src/main/scala/org/apache/spark/sql/UDFRegistration.scala

@@ -17,7 +17,7 @@
 
 package org.apache.spark.sql
 
-import java.lang.reflect.{ParameterizedType, Type}
+import java.lang.reflect.ParameterizedType
 
 import scala.reflect.runtime.universe.TypeTag
 import scala.util.Try
@@ -110,29 +110,29 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
 
   /* register 0-22 were generated by this script
 
-    (0 to 22).map { x =>
+    (0 to 22).foreach { x =>
       val types = (1 to x).foldRight("RT")((i, s) => {s"A$i, $s"})
-      val typeTags = (1 to x).map(i => s"A${i}: TypeTag").foldLeft("RT: TypeTag")(_ + ", " + _)
+      val typeTags = (1 to x).map(i => s"A$i: TypeTag").foldLeft("RT: TypeTag")(_ + ", " + _)
       val inputTypes = (1 to x).foldRight("Nil")((i, s) => {s"ScalaReflection.schemaFor[A$i].dataType :: $s"})
       println(s"""
-        /**
-         * Registers a deterministic Scala closure of ${x} arguments as user-defined function (UDF).
-         * @tparam RT return type of UDF.
-         * @since 1.3.0
-         */
-        def register[$typeTags](name: String, func: Function$x[$types]): UserDefinedFunction = {
-          val ScalaReflection.Schema(dataType, nullable) = ScalaReflection.schemaFor[RT]
-          val inputTypes = Try($inputTypes).toOption
-          def builder(e: Seq[Expression]) = if (e.length == $x) {
-            ScalaUDF(func, dataType, e, inputTypes.getOrElse(Nil), Some(name), nullable, udfDeterministic = true)
-          } else {
-             throw new AnalysisException("Invalid number of arguments for function " + name +
-               ". Expected: $x; Found: " + e.length)
-          }
-          functionRegistry.createOrReplaceTempFunction(name, builder)
-          val udf = UserDefinedFunction(func, dataType, inputTypes).withName(name)
-          if (nullable) udf else udf.asNonNullable()
-        }""")
+        |/**
+        | * Registers a deterministic Scala closure of $x arguments as user-defined function (UDF).
+        | * @tparam RT return type of UDF.
+        | * @since 1.3.0
+        | */
+        |def register[$typeTags](name: String, func: Function$x[$types]): UserDefinedFunction = {
+        |  val ScalaReflection.Schema(dataType, nullable) = ScalaReflection.schemaFor[RT]
+        |  val inputTypes = Try($inputTypes).toOption
+        |  def builder(e: Seq[Expression]) = if (e.length == $x) {
+        |    ScalaUDF(func, dataType, e, inputTypes.getOrElse(Nil), Some(name), nullable, udfDeterministic = true)
+        |  } else {
+        |    throw new AnalysisException("Invalid number of arguments for function " + name +
+        |      ". Expected: $x; Found: " + e.length)
+        |  }
+        |  functionRegistry.createOrReplaceTempFunction(name, builder)
+        |  val udf = UserDefinedFunction(func, dataType, inputTypes).withName(name)
+        |  if (nullable) udf else udf.asNonNullable()
+        |}""".stripMargin)
     }
 
     (0 to 22).foreach { i =>
@@ -144,7 +144,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
       val funcCall = if (i == 0) "() => func" else "func"
       println(s"""
         |/**
-        | * Register a user-defined function with ${i} arguments.
+        | * Register a deterministic Java UDF$i instance as user-defined function (UDF).
         | * @since $version
         | */
         |def register(name: String, f: UDF$i[$extTypeArgs], returnType: DataType): Unit = {
@@ -689,7 +689,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 0 arguments.
+   * Register a deterministic Java UDF0 instance as user-defined function (UDF).
    * @since 2.3.0
    */
   def register(name: String, f: UDF0[_], returnType: DataType): Unit = {
@@ -704,7 +704,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 1 arguments.
+   * Register a deterministic Java UDF1 instance as user-defined function (UDF).
    * @since 1.3.0
    */
   def register(name: String, f: UDF1[_, _], returnType: DataType): Unit = {
@@ -719,7 +719,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 2 arguments.
+   * Register a deterministic Java UDF2 instance as user-defined function (UDF).
    * @since 1.3.0
    */
   def register(name: String, f: UDF2[_, _, _], returnType: DataType): Unit = {
@@ -734,7 +734,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 3 arguments.
+   * Register a deterministic Java UDF3 instance as user-defined function (UDF).
    * @since 1.3.0
    */
   def register(name: String, f: UDF3[_, _, _, _], returnType: DataType): Unit = {
@@ -749,7 +749,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 4 arguments.
+   * Register a deterministic Java UDF4 instance as user-defined function (UDF).
    * @since 1.3.0
    */
   def register(name: String, f: UDF4[_, _, _, _, _], returnType: DataType): Unit = {
@@ -764,7 +764,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 5 arguments.
+   * Register a deterministic Java UDF5 instance as user-defined function (UDF).
    * @since 1.3.0
    */
   def register(name: String, f: UDF5[_, _, _, _, _, _], returnType: DataType): Unit = {
@@ -779,7 +779,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 6 arguments.
+   * Register a deterministic Java UDF6 instance as user-defined function (UDF).
    * @since 1.3.0
    */
   def register(name: String, f: UDF6[_, _, _, _, _, _, _], returnType: DataType): Unit = {
@@ -794,7 +794,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 7 arguments.
+   * Register a deterministic Java UDF7 instance as user-defined function (UDF).
    * @since 1.3.0
    */
   def register(name: String, f: UDF7[_, _, _, _, _, _, _, _], returnType: DataType): Unit = {
@@ -809,7 +809,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 8 arguments.
+   * Register a deterministic Java UDF8 instance as user-defined function (UDF).
    * @since 1.3.0
    */
   def register(name: String, f: UDF8[_, _, _, _, _, _, _, _, _], returnType: DataType): Unit = {
@@ -824,7 +824,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 9 arguments.
+   * Register a deterministic Java UDF9 instance as user-defined function (UDF).
    * @since 1.3.0
    */
   def register(name: String, f: UDF9[_, _, _, _, _, _, _, _, _, _], returnType: DataType): Unit = {
@@ -839,7 +839,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 10 arguments.
+   * Register a deterministic Java UDF10 instance as user-defined function (UDF).
    * @since 1.3.0
    */
   def register(name: String, f: UDF10[_, _, _, _, _, _, _, _, _, _, _], returnType: DataType): Unit = {
@@ -854,7 +854,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 11 arguments.
+   * Register a deterministic Java UDF11 instance as user-defined function (UDF).
    * @since 1.3.0
    */
   def register(name: String, f: UDF11[_, _, _, _, _, _, _, _, _, _, _, _], returnType: DataType): Unit = {
@@ -869,7 +869,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 12 arguments.
+   * Register a deterministic Java UDF12 instance as user-defined function (UDF).
    * @since 1.3.0
    */
   def register(name: String, f: UDF12[_, _, _, _, _, _, _, _, _, _, _, _, _], returnType: DataType): Unit = {
@@ -884,7 +884,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 13 arguments.
+   * Register a deterministic Java UDF13 instance as user-defined function (UDF).
    * @since 1.3.0
    */
   def register(name: String, f: UDF13[_, _, _, _, _, _, _, _, _, _, _, _, _, _], returnType: DataType): Unit = {
@@ -899,7 +899,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 14 arguments.
+   * Register a deterministic Java UDF14 instance as user-defined function (UDF).
    * @since 1.3.0
    */
   def register(name: String, f: UDF14[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _], returnType: DataType): Unit = {
@@ -914,7 +914,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 15 arguments.
+   * Register a deterministic Java UDF15 instance as user-defined function (UDF).
    * @since 1.3.0
    */
   def register(name: String, f: UDF15[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _], returnType: DataType): Unit = {
@@ -929,7 +929,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 16 arguments.
+   * Register a deterministic Java UDF16 instance as user-defined function (UDF).
    * @since 1.3.0
    */
   def register(name: String, f: UDF16[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _], returnType: DataType): Unit = {
@@ -944,7 +944,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 17 arguments.
+   * Register a deterministic Java UDF17 instance as user-defined function (UDF).
    * @since 1.3.0
    */
   def register(name: String, f: UDF17[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _], returnType: DataType): Unit = {
@@ -959,7 +959,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 18 arguments.
+   * Register a deterministic Java UDF18 instance as user-defined function (UDF).
    * @since 1.3.0
    */
   def register(name: String, f: UDF18[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _], returnType: DataType): Unit = {
@@ -974,7 +974,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 19 arguments.
+   * Register a deterministic Java UDF19 instance as user-defined function (UDF).
    * @since 1.3.0
    */
   def register(name: String, f: UDF19[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _], returnType: DataType): Unit = {
@@ -989,7 +989,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 20 arguments.
+   * Register a deterministic Java UDF20 instance as user-defined function (UDF).
    * @since 1.3.0
    */
   def register(name: String, f: UDF20[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _], returnType: DataType): Unit = {
@@ -1004,7 +1004,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 21 arguments.
+   * Register a deterministic Java UDF21 instance as user-defined function (UDF).
    * @since 1.3.0
    */
   def register(name: String, f: UDF21[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _], returnType: DataType): Unit = {
@@ -1019,7 +1019,7 @@ class UDFRegistration private[sql] (functionRegistry: FunctionRegistry) extends
   }
 
   /**
-   * Register a user-defined function with 22 arguments.
+   * Register a deterministic Java UDF22 instance as user-defined function (UDF).
    * @since 1.3.0
    */
   def register(name: String, f: UDF22[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _], returnType: DataType): Unit = {

sql/core/src/main/scala/org/apache/spark/sql/expressions/UserDefinedFunction.scala

@@ -66,6 +66,7 @@ case class UserDefinedFunction protected[sql] (
    *
    * @since 1.3.0
    */
+  @scala.annotation.varargs
   def apply(exprs: Column*): Column = {
     Column(ScalaUDF(
       f,