define your own exceptions with overloaded constructors in scala

Question

In java exceptions have at least these four constructors:

Exception()  Exception(String message)  Exception(String message, Throwable cause)  Exception(Throwable cause)  

If you want to define your own extensions, you just have to declare a descendent exceptions and implement each desired constructor calling the corresponden super constructor

How can you achieve the same thing in scala?

so far now I saw this article and this SO answer, but I suspect there must be an easier way to achieve such a common thing

Answer 1

Default value for cause is null. And for message it is either cause.toString() or null:

val e1 = new RuntimeException()  e.getCause // res1: java.lang.Throwable = null  e.getMessage //res2: java.lang.String = null  val cause = new RuntimeException("cause msg") val e2 = new RuntimeException(cause)  e.getMessage() //res3: String = java.lang.RuntimeException: cause msg 

So you can just use default values:

class MyException(message: String = null, cause: Throwable = null) extends   RuntimeException(MyException.defaultMessage(message, cause), cause)  object MyException {   def defaultMessage(message: String, cause: Throwable) =     if (message != null) message     else if (cause != null) cause.toString()     else null }  // usage: new MyException(cause = myCause) // res0: MyException = MyException: java.lang.RuntimeException: myCause msg 

Answer 2

well, this is the best I've found so far

class MissingConfigurationException private(ex: RuntimeException) extends RuntimeException(ex) {   def this(message:String) = this(new RuntimeException(message))   def this(message:String, throwable: Throwable) = this(new RuntimeException(message, throwable)) }  object MissingConfigurationException {   def apply(message:String) = new MissingConfigurationException(message)   def apply(message:String, throwable: Throwable) = new MissingConfigurationException(message, throwable) } 

this way you may use the "new MissingConfigurationException" or the apply method from the companion object

Anyway, I'm still surprised that there isn't a simpler way to achieve it