Java的Actor框架--kilim

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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).

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