Sharing data between JAX-RS filters

This is a quick post which points out how to share contextual user-defined (custom) data between JAX-RS filters

Filter execution

• It is chain based: one filter gets executed after another
• Request filters are executed before Response filters
• If a filter throws an exception, the chain breaks and other filters are skipped i.e. an exception from a Request filter will auto-abort all other Request filters. The same is applicable to Response filters

For more info, please do check out one of my existing blog posts which discussed JAX-RS server side processing pipeline in depth

Sharing data b/w filters

JAX-RS API enables sharing of user-defined data amongst filters associated with a particular request

• It is abstracted in the form of a Map<String,Object> (pretty natural choice) via the ContainerRequestContext interface
• Get all the custom properties using the getPropertyNames() method
• The value of a specific property can be fetched (from the Map) using getProperty(String name)
• Overwrite an existing property or a add a new one using setProperty(String name, Object val)

Examples

Here is how multiple Request filters can share user-defined contextual data amongst themselves

Another example where a Response filter uses the contextual data set by a Request filter

To be noted…

The same capability is available in the Client side JAX-RS filters as well. The only difference is that you would be interacting with an instance of the ClientRequestContext

Further reading

• For more discussion on Filters and other JAX-RS 2.0 stuff you can peek into this article in the latest Java Magazine edition
• I had discussed different binding strategies for JAX-RS filters in my previous post
• Check out the JAX-RS 2.0 specification doc

Cheers !

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