====== Glassfish Debugging, Caching, HATEOAS, RESTEasy ======

===== Glassfish application debugging =====
See how to debug an app on Glassfish:
[[https://docs.oracle.com/cd/E19798-01/821-1752/beafc/index.html|Glassfish Application Debug]]
[[https://www.jetbrains.com/idea/help/creating-run-debug-configuration-for-application-server.html|IntelliJ Tutorial]]

===== RESTEasy =====

Another JAX-RS implementation except Jersey JBoss: http://www.jboss.org/resteasy

Uses the same API and package //javax.ws.rs.*//

Simple dependencies with JSON for Maven:
<code>
<dependencies>
	<dependency>
		<groupId>org.jboss.resteasy</groupId>
		<artifactId>resteasy-jaxrs</artifactId>
		<version>2.2.1.GA</version>
	</dependency>

	<dependency>
		<groupId>org.jboss.resteasy</groupId>
		<artifactId>resteasy-jackson-provider</artifactId>
		<version>2.2.1.GA</version>
	</dependency>
</dependencies>

<repositories>
	<repository>
		<id>JBOSS_NEXUS</id>
		<url>http://repository.jboss.org/nexus/content/groups/public</url>
	</repository>
</repositories>
</code>

===== REST architecture constraints =====

  * Client-Server
  * Stateless
  * Cacheable
  * Layered system
  * Code on demand (optional)
  * Uniform interface

Talk on the topic given by  doc. Ing. Tomáš Vitvar, Ph.D (FIT):
{{:courses:a4m36aos:cviceni:lecture8.pdf|HATEOAS-Vitvar}}

==== Caching ====

=== HTTP Headers Cache-Control, Last-Modified, ETag, If-Modified-Since, If-None-Match ===

== Cache-Control ==

Defines caching setting for client, proxy

  * **private** proxy can't cache, client can
  * **public** both client and proxy can cache
  * **no-cache** should not be cached
  * **no-store** cache should not be persistent
  * **no-transform** no data transformation (compression)
  * **max-age** cache validity
  * **s-maxage** cache validity for proxy

== Last-Modified ==

Response header, defines when the resource was last modified.


== If-Modified-Since ==

Request header, defines that the resource returns ok (200), if modified since the given date, 304 otherwise.

== ETag ==

Response header, defines the tag (hash) of the returned resource.

== If-None-Match ==

Request header, defines, that the resource should be returned if the tag was modified, otherwise returns 304

=== Example ===

{{:courses:a4m36aos:cviceni:caching.zip|caching.zip}}
=== Concurrency Control ===

Lze možné tyto caching headers použít i pro Concurrency Control?

== If-Unmodified-Since ==

Request header (for Last-Modified response header) - if holds, 200 / 204, otherwise 412 Precondition Failed

== If-Match ==

Request header (for ETag response header) - if holds, 200 / 204, otherwise 412 Precondition Failed


==== HATEOAS ====

**Hypertext as the Engine for Application State**

  * How is the state of the stateful application stored?
  * How can we achieve the same behavior in stateless application?

HATEOAS - using links and headers we can store the state of the application.

=== Stateless ordering system design ===

Download the RESTEasy project: {{:courses:a4m36aos:cviceni:hateoas.zip|HATEOAS}}

Resources:
  * **POST /orders** Creates a new order and returns URI of the order in the Location header
  * **GET /orders/id** Returns an order with given ID
  * **POST /orders/id {"name":"car"}** Creates a new item in the order
  * **GET /orders/id/itemId** Returns an item of the order with given ID
  * **PUT /orders/id/itemId {"name":"car"}** Modifies the item in the order
  * **DELETE /orders/id/itemId** Deletes item of the order with given ID.