2015 09 23

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Politecnico di Milano Middleware Technologies for Distributed Systems 23rd of September 2015 Rules: • You are not allowed to use books, notes, or other material. • You can answer in Italian or English. • Total time for the test: 1.5 hours. • Check the back of this page for any additional exercises. 1. Implement in Java the Executor class. At construction time the class receives a reference to a Runnable instance. After being created it executes the Runnable instance once a second until method stop() is invoked. You can assume that the Runnable passed at construction time only requires a short time to be executed. 2. Write in TinyOS a module PacketCounter that implements the receive interface and provides the Read<uint16_t> interface. It counts the number of received packets and returns the count when asked for it. Optional: automatically reset the counter every 10 seconds. The following interfaces may help you: interface Receive { event message_t* receive(message_t* msg, void* payload, uint8_t len); } interface Timer<precision_tag> { command void startPeriodic(uint32_t dt); command void startOneShot(uint32_t dt); command void stop(); event void fired(); } interface Read<val_t> { command error_t read(); event void readDone(error_t err, val_t val); } 3. Use RMI to expose a remote method capable of returning stock quote data given a stock quote symbol. The returned information should contain the stock's current (or last known) value, its opening value for the day, and its minimum and maximum values for the day. Provide both the server-side code required to implement and publish the service, and the client-side code required to access the remote method correctly. 4. What is WSDL, and what is its purpose? What are the main components of a WSDL file, and what information…