{"id":41938,"date":"2015-07-25T15:00:34","date_gmt":"2015-07-25T12:00:34","guid":{"rendered":"http:\/\/www.javacodegeeks.com\/?p=41938"},"modified":"2015-07-21T11:52:45","modified_gmt":"2015-07-21T08:52:45","slug":"websocket-client-api-in-java-ee-7","status":"publish","type":"post","link":"https:\/\/www.javacodegeeks.com\/2015\/07\/websocket-client-api-in-java-ee-7.html","title":{"rendered":"WebSocket Client API in Java EE 7"},"content":{"rendered":"

In this post, let\u2019s explore the less talked about Web Socket Client API<\/em> and how to leverage it within a Java EE 7 container itself.<\/p>\n

Web Socket Server API rules<\/h2>\n

The server side API of JSR 356<\/a> (Web Socket API for Java) is most commonly used for building Web Socket endpoint implementations. More often than not, from a client perspective, the standard JavaScript Web Socket API is leveraged by the HTML5 (browser) based clients which attach themselves to web socket server end points and enjoy bi-directional and full-duplex communication. You would have seen common examples such applications such as live maps, stock tickers, games, screen sharing etc \u2013 all these use cases are perfect for Web Sockets and Java EE 7 is the ideal platform for building scalable Web Socket driven back end.<\/p>\n

What about the Web Socket client side API ?<\/h2>\n

The Web Socket specification includes a client side API as well and its mandatory for all JSR 356 (e.g. Tyrus<\/a>, Undertow <\/a>etc) implementations to provide one. There are quite a few use cases wherein a browser based \/ end user facing web socket client might not be<\/em> required.<\/p>\n

Example<\/h4>\n

Consider a scenario where you want to connect to a third party Web Socket end point, consume it\u2019s information and persist it for later use ? Maybe for further analysis ? In such cases, its useful to leverage the client API within the Java EE container itself.<\/p>\n

Let\u2019s explore this with a simple example.<\/p>\n

(annotated) Web Socket Client<\/h4>\n

Note:<\/strong> the logic for @OnMessage was excluded on purpose and has been implemented in a different way (clarified later)<\/p>\n

package blog.abhirockzz.wordpress.com;\r\n\r\nimport javax.websocket.ClientEndpoint;\r\nimport javax.websocket.OnClose;\r\nimport javax.websocket.OnError;\r\nimport javax.websocket.Session;\r\n\r\n@ClientEndpoint\r\npublic class StockTickerClient {\r\n\r\n    @OnClose\r\n    public void closed(Session session) {\r\n        System.out.println(\"Session \" + session + \" closed\");\r\n\r\n    }\r\n\r\n    @OnError\r\n    public void error(Throwable error) {\r\n        System.out.println(\"Error: \" + error.getMessage());\r\n\r\n    }\r\n\r\n}<\/pre>\n
A Stock Ticker (info) JPA entity<\/h4>\n
package blog.abhirockzz.wordpress.com;\r\n\r\nimport java.io.Serializable;\r\nimport javax.persistence.Entity;\r\nimport javax.persistence.GeneratedValue;\r\nimport javax.persistence.GenerationType;\r\nimport javax.persistence.Id;\r\nimport javax.persistence.Table;\r\n\r\n@Entity\r\n@Table(name = \"STOCK_TICK\")\r\npublic class StockTick implements Serializable {\r\n\r\n    @Id\r\n    @GeneratedValue(strategy = GenerationType.AUTO)\r\n    private Long id;\r\n\r\n    private String name;\r\n    private String price;\r\n\r\n    public StockTick(String name, String price) {\r\n        this.name = name;\r\n        this.price = price;\r\n    }\r\n\r\n    public StockTick() {\r\n        \/\/for JPA\r\n    }\r\n\r\n    \/\/getters and setters omitted ...\r\n}<\/pre>\n
A Stateless bean<\/h4>\n