BeanProperties

In Java-land many frameworks depend on Bean style properties. Scala has an extremely handy annotation that assists in interoperating with frameworks that require bean-style interfaces. In Scala 2.7 there are only a few annotations for helping:

• @BeanProperty - Generates getters and setters for a property. (Or just a getter if the bean is a val)
• @BeanInfo - Generates the associated BeanInfo for the class

Remember that if you want frameworks to be able to create the beans you need to make a 0-arg constructor and have the bean properties as fields.

Example with bean-properties as constructor arguments. This example requires Scala 2.8 because it uses BooleanBeanProperty. You can remove that and run with Scala 2.7.x.
In this example we define a bean class and use reflection to show that all the getters and setters are generated:

1. scala> import scala.reflect._
2. import scala.reflect._    
4. scala> case class MyBean(
5.      | @BeanProperty var mutable:String,  // getter and setter should be generated
6.      | @BooleanBeanProperty var boolProp:Boolean, // is getter and normal setter should be generated
7.      | @BeanProperty val readOnly:Int) // only a getter should be generated
9. defined class MyBean
11. scala> val beanClass = classOf[MyBean]
12. beanClass: java.lang.Class[MyBean] = class MyBean
14. scala> val beanMethods = beanClass.getDeclaredMethods.filter( _.getName.matches("(get|is|set).+"))
15. beanMethods: Array[java.lang.reflect.Method] = Array(public java.lang.String MyBean.getMutable(), public boolean MyBean.isBoolProp(), public int MyBean.getReadOnly(), public void MyBean.setBoolProp(boolean\
16. ), public void MyBean.setMutable(java.lang.String))
18. scala> println( beanMethods map (_.getName) mkString("\n"))
19. getMutable
20. isBoolProp
21. getReadOnly
22. setBoolProp
23. setMutable

This next example would not run in the REPL for some reason so you must copy-paste it into a file, compile and run. Instructions:

1. copy and paste code into bean.scala
2. scalac bean.scala
3. scala -cp . MyBean

1. import scala.reflect._
3. class MyBean{
4.   @BeanProperty
5.   var mutable:String = ""
6. }
8. object MyBean{
9.   def apply(mutable:String) = {
10.     val bean = new MyBean()
11.     bean.mutable = mutable
12.     bean
13.   }
15.   def main(args:Array[String]){
17.     import java.beans._
19.     val result = new java.io.ByteArrayOutputStream
20.     val encoder = new XMLEncoder(result)
21.     val bean = MyBean("hello")
22.     encoder.writeObject( bean )
23.     encoder.close
24.     println(result.toString)
25.   }
26. }