How to get a global object which has been set in a Java Servlet Context

Question

I am working on a Tomcat application which populates a HashMap on startup. I set it in the ServletContext using ServletContext.setAttribute. However, I have some non Java EE classes also in this application (basically my webservice calls call those methods). I want to access this HashMap in those Methods. What is the best way to do it?

Either send them the hashMap and let them do whatever you want to do, or even better: expose a service that handles the map. — Nir Alfasi, Jul 15 '14 at 23:40
Is there a way I can do it without setting it in the Context? Is there a way I can keep a handle to an Object through out the lifetime of my Tomcat application? — Anuja Khemka, Jul 15 '14 at 23:53
yes, that's what I said: create a service (could be a singleton) that handles that map. You can access the service from anywhere and that service will "hide" the hashmap and expose only its functionalities. — Nir Alfasi, Jul 16 '14 at 00:45

score 0 · Answer 1 · answered Jul 15 '14 at 23:40

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Fetch the HashMap in your web service class and pass on the same as method argument to your non Java EE classes.

answered Jul 15 '14 at 23:40

Juned Ahsan

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Is there a way I can do it without setting it in the Context? Is there a way I can keep a handle to an Object through out the lifetime of my Tomcat application? – Anuja Khemka Jul 15 '14 at 23:53
ServletContext is used for saving things that you want to use across different application. ServletConfig is used to store things that you want to access only in a particular application. – Juned Ahsan Jul 16 '14 at 00:00
Is there a reason you don't want to use ServletContext? – Juned Ahsan Jul 16 '14 at 00:01
I want to use ServletContext but was unable to retrieve ServletContext as it is a non Tomcat Class. However now I am using ServletContextAware to retrieve it. – Anuja Khemka Jul 18 '14 at 00:17

score 0 · Accepted Answer · answered Jul 16 '14 at 00:15

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Your web service should have access to HTTP Request and Response where you can get ServletContext. When web services call these non J2EE methods, you can pass the map as a argument parameter.

answered Jul 16 '14 at 00:15

sendon1982

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I wish I could but the code is managed by spring and generated by CXF and didnot want to disturb that. – Anuja Khemka Jul 18 '14 at 00:18
You can add a ServletContextListener in the web xml file. In this listener, you can load your items into a static HashMap where later your POJO will have access to them. – sendon1982 Jul 18 '14 at 03:59
I ended up doing something very similar to what you said. – Anuja Khemka Jul 22 '14 at 17:16

score 0 · Answer 3 · edited May 23 '17 at 10:33

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You can make your map available to all classes of your application:

Using a Singleton

See What is an efficient way to implement a singleton pattern in Java?
Using Tomcat global JNDI tree (not recommended, but you can do it).

See How do you save name-value pairs in Tomcat environment? and Apache Tomcat 7 - JNDI Resources HOW-TO

edited May 23 '17 at 10:33

Community

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answered Jul 16 '14 at 02:49

Paul Vargas

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I thought of singleton but wanted a more efficient way. – Anuja Khemka Jul 18 '14 at 00:18

score 0 · Answer 4 · answered Jul 18 '14 at 00:19

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Thank you all for the suggestions. However what I was trying to achieve was achieved by the following example:

http://www.xinotes.net/notes/note/1772/

It gave me a method to retrieve the context in non-Tomcat handled classes.

answered Jul 18 '14 at 00:19

Anuja Khemka

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How to get a global object which has been set in a Java Servlet Context

4 Answers4