If you want to declare a class in Zeppelin and create instance of it, you might be surprised:

class K

class K

defined class K

1	defined class K

classOf[K].newInstance()

1	classOf[K].newInstance()

java.lang.InstantiationException: K
at java.lang.Class.newInstance(Class.java:427)
... 52 elided
Caused by: java.lang.NoSuchMethodException: K.<init>()
at java.lang.Class.getConstructor0(Class.java:3082)
at java.lang.Class.newInstance(Class.java:412)
... 52 more

java.lang.InstantiationException: K

at java.lang.Class.newInstance(Class.java:427)

... 52 elided

Caused by: java.lang.NoSuchMethodException: K.<init>()

at java.lang.Class.getConstructor0(Class.java:3082)

at java.lang.Class.newInstance(Class.java:412)

... 52 more

What happened? Whatever you declare in Zeppelin notebook is a part of some internal class so the newly declared class K doesn’t have parameterless constructor because it expects the instance of enclosing type. There are two simple ways to handle this.

Quasiquotes

Just generate a class with scala’s quaisquotes:

import reflect.runtime._
import universe._
import tools.reflect.ToolBox

val tb = currentMirro.mkToolBox()
val l = tb.compile(q"""class L; classOf[L].newInstance()""")()

import reflect.runtime._

import universe._

import tools.reflect.ToolBox

val tb = currentMirro.mkToolBox()

val l = tb.compile(q"""class L; classOf[L].newInstance()""")()

l: Any = __wrapper$8$bb3239e978f24dc98e740075eecad313.__wrapper$8$bb3239e978f24dc98e740075eeacad313$L$1@7e2b9e13

1	l: Any = __wrapper$8$bb3239e978f24dc98e740075eecad313.__wrapper$8$bb3239e978f24dc98e740075eeacad313$L$1@7e2b9e13

Javax.tools

Use the following method to dynamically compile java code:

def generateClass(className: String, source: String): (Class[_], Any) = {
    val byteArrayOutputStream = new java.io.ByteArrayOutputStream()
    val simpleJavaFileObject = new javax.tools.SimpleJavaFileObject(java.net.URI.create(s"$className.java"), javax.tools.JavaFileObject.Kind.SOURCE) {
        override def getCharContent(ignoreEncodingErrors: Boolean):CharSequence = {
            return source;
        }
        override def openOutputStream(): java.io.OutputStream = {
            return byteArrayOutputStream;
        }
    };
    val standardManager = javax.tools.ToolProvider.getSystemJavaCompiler().getStandardFileManager(null, null, null);
    val customForwardingManager = new javax.tools.JavaFileManager {
        override def close() = standardManager.close()
        override def flush() = standardManager.flush()
        override def getClassLoader(location: javax.tools.JavaFileManager.Location) = standardManager.getClassLoader(location)
        override def getFileForInput(location: javax.tools.JavaFileManager.Location, packageName: String, relativeName: String) = standardManager.getFileForInput(location, packageName, relativeName)
        override def getFileForOutput(location: javax.tools.JavaFileManager.Location, packageName: String, relativeName: String, sibling: javax.tools.FileObject) = standardManager.getFileForOutput(location, packageName, relativeName, sibling)
        override def getJavaFileForInput(location: javax.tools.JavaFileManager.Location, className: String, kind: javax.tools.JavaFileObject.Kind) = standardManager.getJavaFileForInput(location, className, kind)
        override def getJavaFileForOutput(location: javax.tools.JavaFileManager.Location,
                                                   className: String,
                                                   kind: javax.tools.JavaFileObject.Kind,
                                                   sibling: javax.tools.FileObject): javax.tools.JavaFileObject = {
            return simpleJavaFileObject;
        }
        override def handleOption(current: String, remaining: java.util.Iterator[String]) = standardManager.handleOption(current, remaining)
        override def hasLocation(location: javax.tools.JavaFileManager.Location) = standardManager.hasLocation(location)
        override def inferBinaryName(location: javax.tools.JavaFileManager.Location, file: javax.tools.JavaFileObject) = standardManager.inferBinaryName(location, file)
        override def isSameFile(a: javax.tools.FileObject, b: javax.tools.FileObject) = standardManager.isSameFile(a, b)
        override def isSupportedOption(option: String) = standardManager.isSupportedOption(option)
        override def list(location: javax.tools.JavaFileManager.Location, packageName: String, kinds: java.util.Set[javax.tools.JavaFileObject.Kind], recurse: Boolean) = standardManager.list(location, packageName, kinds, recurse)
    }
    val list = new java.util.ArrayList[javax.tools.JavaFileObject]()
    list.add(simpleJavaFileObject)
    javax.tools.ToolProvider.getSystemJavaCompiler().getTask(null, customForwardingManager, null, null, null, list).call();
    val bytes = byteArrayOutputStream.toByteArray();
    val f = classOf[sun.misc.Unsafe].getDeclaredField("theUnsafe");
    f.setAccessible(true);
    val unsafe: sun.misc.Unsafe = f.get(null).asInstanceOf[sun.misc.Unsafe];
    val aClass = unsafe.defineClass(className, bytes, 0, bytes.length, null, null);
    val o = aClass.newInstance();
    (aClass, o)
}

def generateClass(className: String, source: String): (Class[_], Any) = {

val byteArrayOutputStream = new java.io.ByteArrayOutputStream()

val simpleJavaFileObject = new javax.tools.SimpleJavaFileObject(java.net.URI.create(s"$className.java"), javax.tools.JavaFileObject.Kind.SOURCE) {

override def getCharContent(ignoreEncodingErrors: Boolean):CharSequence = {

return source;

}

override def openOutputStream(): java.io.OutputStream = {

return byteArrayOutputStream;

}

};

val standardManager = javax.tools.ToolProvider.getSystemJavaCompiler().getStandardFileManager(null, null, null);

val customForwardingManager = new javax.tools.JavaFileManager {

override def close() = standardManager.close()

override def flush() = standardManager.flush()

override def getClassLoader(location: javax.tools.JavaFileManager.Location) = standardManager.getClassLoader(location)

override def getFileForInput(location: javax.tools.JavaFileManager.Location, packageName: String, relativeName: String) = standardManager.getFileForInput(location, packageName, relativeName)

override def getFileForOutput(location: javax.tools.JavaFileManager.Location, packageName: String, relativeName: String, sibling: javax.tools.FileObject) = standardManager.getFileForOutput(location, packageName, relativeName, sibling)

override def getJavaFileForInput(location: javax.tools.JavaFileManager.Location, className: String, kind: javax.tools.JavaFileObject.Kind) = standardManager.getJavaFileForInput(location, className, kind)

override def getJavaFileForOutput(location: javax.tools.JavaFileManager.Location,

className: String,

kind: javax.tools.JavaFileObject.Kind,

sibling: javax.tools.FileObject): javax.tools.JavaFileObject = {

return simpleJavaFileObject;

}

override def handleOption(current: String, remaining: java.util.Iterator[String]) = standardManager.handleOption(current, remaining)

override def hasLocation(location: javax.tools.JavaFileManager.Location) = standardManager.hasLocation(location)

override def inferBinaryName(location: javax.tools.JavaFileManager.Location, file: javax.tools.JavaFileObject) = standardManager.inferBinaryName(location, file)

override def isSameFile(a: javax.tools.FileObject, b: javax.tools.FileObject) = standardManager.isSameFile(a, b)

override def isSupportedOption(option: String) = standardManager.isSupportedOption(option)

override def list(location: javax.tools.JavaFileManager.Location, packageName: String, kinds: java.util.Set[javax.tools.JavaFileObject.Kind], recurse: Boolean) = standardManager.list(location, packageName, kinds, recurse)

}

val list = new java.util.ArrayList[javax.tools.JavaFileObject]()

list.add(simpleJavaFileObject)

javax.tools.ToolProvider.getSystemJavaCompiler().getTask(null, customForwardingManager, null, null, null, list).call();

val bytes = byteArrayOutputStream.toByteArray();

val f = classOf[sun.misc.Unsafe].getDeclaredField("theUnsafe");

f.setAccessible(true);

val unsafe: sun.misc.Unsafe = f.get(null).asInstanceOf[sun.misc.Unsafe];

val aClass = unsafe.defineClass(className, bytes, 0, bytes.length, null, null);

val o = aClass.newInstance();

(aClass, o)

}

Invoke it like this:

val (kClass, kInstance) = generateClass("K", """
public class K{
    public K(){}
}
""")

val (kClass, kInstance) = generateClass("K", """

public class K{

public K(){}

}

""")

kClass: Class[_] = class K
kInstance: Any = K@adfd330

1 2	kClass: Class[_] = class K kInstance: Any = K@adfd330

And you are done.