This is a small vignette that demonstrates how to expose entities using Spring Data REST that use entity tags (ETags) for caching.
Entity Tags (ETags) are primarily used to implement caching of resources across the Internet. From RFC 7232:
Conditional requests are HTTP requests [RFC7231] that include one or more header fields indicating a precondition to be tested before applying the method semantics to the target resource. This document defines the HTTP/1.1 conditional request mechanisms in terms of the architecture, syntax notation, and conformance criteria defined in [RFC7230].
Conditional GET requests are the most efficient mechanism for HTTP cache updates [RFC7234]. Conditionals can also be applied to state-changing methods, such as PUT and DELETE, to prevent the "lost update" problem: one client accidentally overwriting the work of another client that has been acting in parallel.
Conditional request preconditions are based on the state of the target resource as a whole (its current value set) or the state as observed in a previously obtained representation (one value in that set). A resource might have multiple current representations, each with its own observable state. The conditional request mechanisms assume that the mapping of requests to a "selected representation" (Section 3 of [RFC7231]) will be consistent over time if the server intends to take advantage of conditionals. Regardless, if the mapping is inconsistent and the server is unable to select the appropriate representation, then no harm will result when the precondition evaluates to false.
The image below depicts the requests, headers and actions that are taken when ETags are used.
To begin, open and run the test TestEtagSupport.
This project uses the Embedded Mongo Database and the first time that you run it, it will download the appropriate binary. After that, things will be much faster.
Once you've run the first test, ClientExampleControllerTest demonstrates how to use ETags if you're calling a REST endpoint that supports them.
To run this from the command line, do
gradle bootRun
For now, this is setup to use the embedded MongoDB. To use your own MongoDB, change this line in build.gradle
compile('de.flapdoodle.embed:de.flapdoodle.embed.mongo:1.50.3')
to
testCompile('de.flapdoodle.embed:de.flapdoodle.embed.mongo:1.50.3')
You will also need to provide any configuration necessary to interact with your DB. See the Spring Data REST documentation for instructions.
POST this content with the header "Content-type" : "application/json"
{ "firstName" : "Phil", "lastName" : "Glebow", "email" : "p@g.com" }
to this endpoint
Search for the user that you've added by following this link
http://localhost:8080/users/search/findByLastName?lastName=Glebow
Follow the self/href link, e.g.,
to load the user. The status code will 200 and the user will be in the body of the response. If you inspect the headers, you'll find an ETag header. If you add this header
If-None-Match: "0"
and reload the entity, you'll get a status code of 304/Not modified and the body of the response will be empty. This indicates to the caller that the entity has not changed. The network will not have to transport the body which will improve the performance characteristics of the system.
Run the ClientExampleControllerTest
Look at the messages in the log; they describe the actions taken when attempting to retrieve a user.
OAUTH2 is a specification for authentication and authorization. See the references for a in-depth discussion of the framework.
This project uses Spring Security to perform a very basic authentication and authorization flow using Facebook and Github.
I've deployed two "applications" to demonstrate this - one on Facebook and one on Github.
The demo simply displays what data is made avaialble once a user authenticates via either platform.
The internal SSO version is being developed but we're having some difficulty with Ping Federate as of this writing.
| Description | Link |
|---|---|
| Spring Data REST Reference Page | http://projects.spring.io/spring-data-rest/ |
| RFC 7232: Conditional Requests (ETags) | https://tools.ietf.org/html/rfc7232 |
| de.flapdoodle.embed.mongo Embedded MongoDB | https://github.com/flapdoodle-oss/de.flapdoodle.embed.mongo |
| ETags and browser cache | http://thespringthing.blogspot.com/2015/06/etags-and-browser-cache.html |
| An Introduction to OAUTH2 | https://www.digitalocean.com/community/tutorials/an-introduction-to-oauth-2 |
| OAuth | https://oauth.net/2 |
| Spring Boot and OAuth2 | https://spring.io/guides/tutorials/spring-boot-oauth2/ |