1. Scheduled Tasks and Web Socket
Spring Cookbook
Scheduled Tasks and Web Socket
Spring Cookbook
SoftUni Team
Technical Trainers
Software University
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2. Table of Contents Scheduled Tasks Web Socket FixedRate FixedDelay Cron
SockJS, Stomp JS
Sending messages
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3. sli.do #JavaWeb Have a Question?
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4. Scheduled Tasks Creating Crons
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5. @Scheduled How to give resources every 5 seconds:
Execute method based on previous execution time:
@Scheduled(fixedRate = 5000) // 5000 milliseconds
public void giveGold() { … }
@Scheduled(fixedDelay = 5000) // 5000 milliseconds
public void doStuff() { … }
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6. @Scheduled (2)
Starting a task after waiting for all services to be initialized:
Create complex timer that will execute every hour 9 to 17 on weekdays
@Scheduled(initialDelay = 5000, fixedRate = 3000)
public void doStuff() { … }
@Scheduled(cron = " * * MON-FRI")
public void doStuff() { … }
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7. Crons Crons are date sequence generators
List of six single space-separated fields: representing second, minute, hour, day, month, weekday
"0 0 * * * *" = the top of every hour of every day.
"*/10 * * * * *" = every ten seconds.
" * * *" = 8, 9 and 10 o'clock of every day.
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8. Cron Syntax Crons expression symbols:
* - Every possible value of the field
? - The field won't be checked (used to avoid conflicts)
/X - Skips every Xth value
X-Y - Interval with all values between X and Y
X,Y,Z - List with the given values
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9. Web Socket Dynamic content
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10. Configuration Enabling Web socket: @EnableWebSocketMessageBroker
public class WebSocketConfig extends AbstractWebSocketMessageBrokerConfigurer { }
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11. Creating End-Point
STOMP is used to send text-based messages. STOMP is layer on top of TCP:
SockJS will pick the best transport available (websocket, xhr- streaming, xhr-polling, etc.).
@Override
public void registerStompEndpoints( StompEndpointRegistry registry) {
registry.addEndpoint("/game").withSockJS(); }
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12. Creating Message Broker
STOMP is used to send text-based messages. STOMP is layer on top of TCP:
@Override
public void configureMessageBroker( MessageBrokerRegistry config) {
config.enableSimpleBroker(
"/character/money", "/character/info"); }
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13. Sending Messages Spring provides an easy way to send messages:
By default, objects will be converted to JSON.
@Autowired
private final SimpMessagingTemplate template;
public void sendMoneyUpdate(CharacterMoneyModel character) {
this.template.convertAndSend(
"/character/money", character); }
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14. Receiving Messages with JS
Download or find a link to SockJS and StompJS.
Connecting to an end-point:
let socket = new SockJS('/game'); // /game is an end-point
let stompClient = Stomp.over(socket);
stompClient.connect({}, function (frame) { //Subscribe to message collections });
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15. Receiving Messages with JS (2)
Subscribing to message collections:
stompClient.connect({}, function (frame) { stompClient.subscribe('/character/money', function (data) {
// /character/money is the simple message broker we defined earlier
let obj = JSON.parse(data.body);
// Do something with the data
});
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16. Summary
You can schedule tasks in order to automate processes in your application
There are multiple ways to schedule a task using fixedRate, fixedDelay, cron, etc.
Web sockets can be used to dynamically change content of pages

17. Spring Cookbook https://softuni.bg/courses/java-mvc-frameworks-spring
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18. License
This course (slides, examples, demos, videos, homework, etc.) is licensed under the "Creative Commons Attribution- NonCommercial-ShareAlike 4.0 International" license
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19. Trainings @ Software University (SoftUni)
Software University – High-Quality Education, Profession and Job for Software Developers
softuni.bg
Software University Foundation
softuni.org
Software Facebook
facebook.com/SoftwareUniversity
Software University Forums
forum.softuni.bg
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