HystrixCommand vs HystrixObservableCommand

要想使用hystrix，只需要继承HystrixCommand或HystrixObservableCommand，简单用法见上面例子。两者主要区别是：

1. 前者的命令逻辑写在run()；后者的命令逻辑写在construct()
2. 前者的run()是由新创建的线程执行；后者的construct()是由调用程序线程执行
3. 前者一个实例只能向调用程序发送（emit）单条数据，比如上面例子中run()只能返回一个String结果；后者一个实例可以顺序发送多条数据，比如demo中顺序调用多个onNext()，便实现了向调用程序发送多条数据，甚至还能发送一个范围的数据集，下面举例说明

public class ObservableCommandNumbersToWords extends HystrixObservableCommand<ObservableCommandNumbersToWords.NumberWord>{    private final List<Integer> numbers;    // in the real world you'd probably want to replace this very simple code by using ICU or similar    static Map<Integer, String> dict = new HashMap<Integer, String>(11);    static    {        dict.put(0, "zero");        dict.put(1, "one");        dict.put(2, "two");        dict.put(3, "three");        dict.put(4, "four");        dict.put(5, "five");        dict.put(6, "six");        dict.put(7, "seven");        dict.put(8, "eight");        dict.put(9, "nine");        dict.put(10, "ten");    }    public ObservableCommandNumbersToWords(final List<Integer> numbers)    {        super(HystrixCommandGroupKey.Factory.asKey("hoho")        );        this.numbers = numbers;    }    protected Observable<NumberWord> construct()    {        System.out.println("construct! thread:" + Thread.currentThread().getName());        return Observable.from(numbers).map(new Func1<Integer, NumberWord>()        {            public NumberWord call(final Integer number)            {                System.out.println("call! thread:" + Thread.currentThread().getName());                return new NumberWord(number, dict.get(number));            }        });    }    static class NumberWord    {        private final Integer number;        private final String word;        public NumberWord(final Integer number, final String word)        {            super();            this.number = number;            this.word = word;        }        public Integer getNumber()        {            return number;        }        public String getWord()        {            return word;        }    }    public static void main(String[] args) throws Exception{        List<Integer> in = new LinkedList<Integer>();        in.add(2);        in.add(3);        Observable<NumberWord> hotObservable = new ObservableCommandNumbersToWords(in).observe();        hotObservable.subscribe(new Observer<NumberWord>() {            // 先执行onNext再执行onCompleted            // @Override            public void onCompleted() {                System.out.println("hotObservable of ObservableCommand completed");            }            // @Override            public void onError(Throwable e) {                System.out.println("hotObservable of ObservableCommand error");                e.printStackTrace();            }            // @Override            public void onNext(NumberWord v) {                System.out.println("hotObservable of ObservableCommand onNext: " + v.getWord());            }        });    }

运行结果是：
construct! thread:main
call! thread:main
call! thread:main
hotObservable of ObservableCommand onNext: two
hotObservable of ObservableCommand onNext: three
hotObservable of ObservableCommand completed