一个Java的Actor框架：kilim

除了Akka以外，另外一个将类似Erlang和Scala的Actor的并发模型引入Java的开源框架：kilim/kilim - GitHub，其使用了一种mailbox跨线程共享内存，没有锁或同步。

消息消费者代码如下，监听mailbox：


public class Calculator extends Task{
 
 private Mailbox<calculation> mailbox;
 
 public Calculator(Mailbox<calculation> mailbox) {
  super();
  this.mailbox = mailbox;
 }
 
 @[author]Override[/author]
 public void execute() throws Pausable, Exception {
  while (true) {   
   Calculation calc = mailbox.get(); // blocks
   if (calc.getAnswer() == null) {
    calc.setAnswer(calc.getDividend().divide(calc.getDivisor(), 8, 
      RoundingMode.HALF_UP));    
    System.out.println("Calculator determined answer");
    mailbox.putnb(calc);
   }
   Task.sleep(1000);
  }
 }
}

消息发生者，向mailbox发送消息：


public class DeferredDivision extends Task {
 
 private Mailbox<calculation> mailbox;
 
 public DeferredDivision(Mailbox<calculation> mailbox) {
  super();
  this.mailbox = mailbox;
 }
 
 @[author]Override[/author]
 public void execute() throws Pausable, Exception {
  Random numberGenerator = new Random(new Date().getTime());
  MathContext context = new MathContext(8);
  while (true) {
   System.out.println("I need to know the answer of something");
   mailbox.putnb(new Calculation(
     new BigDecimal(numberGenerator.nextDouble(), context), 
     new BigDecimal(numberGenerator.nextDouble(), context)));
   Task.sleep(1000);
   Calculation answer = mailbox.getnb(); // no block
   if (answer != null && answer.getAnswer() != null) {
    System.out.println("Answer is: " + answer.printAnswer());
   }
  }
 }
}

需要使用Ant调用 Kilim's weaver(byte code enhancer)：
<target name="weave" depends="compile" description="handles Kilim byte code weaving">
<java classname="kilim.tools.Weaver" fork="yes">
<classpath refid="classpath">
<arg value="-d">
<arg value="./target/classes">
<arg line="./target/classes">
</arg></arg></arg></classpath></java>
</target>

客户端测试代码：


 Mailbox<calculation> sharedMailbox = new Mailbox<calculation>();
 
  Task deferred = new DeferredDivision(sharedMailbox);
  Task calculator = new Calculator(sharedMailbox);
 
  deffered.start();
  calculator.start();

在"events vs. threads"争论提及两个问题：线程是重量的；其次线程范式隐式的和共享内存锁联系在一起，导致性能陷阱；而Kilim 试图证明线程也可以和状态机一样轻量，甚至提供一个自动的线程stack管理特性(也就没有必要的 "return to the mainloop" 返回主循环的编程习惯).