JEST

JEST is a REST style access to any OpenJPA runtime.
REST (Representational State Transfer) is a foundational concept in the architecture for World Wide Web. JEST promotes REST style interaction between a client and an application based on OpenJPA. A JEST-enabled OpenJPA runtime embeds a specialized HTTP server such that a client (neither necessarily in Java nor having any definition of the persistent server objects) can send HTTP requests and receive persistent data as response in JSON, XML or other string based format.

Effectively there are three aspects to JEST

Protocol of client-server communication
Representation of persistent state
Transaction semantics

Protocol

The communication protocol for JEST is HTTP. The client sends request in standard HTTP URI (Uniform Resource Identifier) e.g. http://www.jpa.com:6789/find?Person&John to a JEST-enabled OpenJPA application to find a Person with primary key 'John'. The server will send a HTTP response back to the client. The content of the HTTP response can be formatted as XML or as JSON. The URI syntax governs the server response. Before describing the syntax in detail, here are few typical example URI and their associated effect on the server.

	Server Function	JEST URI
01	Get name of the persistent unit	http://www.jpa.com:6789/
02	List simple name of the domain classes	http://www.jpa.com:6789/domain
03	List the key-value properties of the persistent unit	http://www.jpa.com:6789/properties
04	Find an instance by key	http://www.jpa.com:6789/find?Person&123456789
05	Find an instance by key	http://www.jpa.com:6789/find?Person&ssn=123456789&name=John
06	Get the result of the query with no parameter	http://www.jpa.com:6789/query?select p from Person p
07	Get the result of the query with single parameter	http://www.jpa.com:6789/query?select p from Person p where p.name=:name&name=John
08.1	Get the result of the query with multiple parameters	http://www.jpa.com:6789/query?select p from Person p where p.name=:name and age > :age&name=John&age=20
08.2		http://www.jpa.com:6789/query?select p from Person p where p.first=:first and p.last=:last&first=John&last=Doe
09	Get the single result of the query	http://www.jpa.com:6789/query/single?select p from Person p where p.name=:name&name=John
10	Get the result of the named query	http://www.jpa.com:6789/query/named?QueryPersonByName&name=John
11.1	Get the single result of the named query	http://www.jpa.com:6789/query/single/named?QueryPersonByName&name=John
11.2	or	http://www.jpa.com:6789/query/named/single?QueryPersonByName&name=John
12	Get first 20 rows of query using a fetch plan	http://www.jpa.com:6789/query/fecthplan=myPlan/ignoreCache/maxResult=20?select p from Person p

URI syntax for JEST

   uri := http://host[:port]/action/[qualifier]*['?'[parameter]'&'*]

   qualifier := qualifier-key['='qualifier-value]
   parameter := parameter-key'='parameter-value 
   
   action    : denotes the JPA operation to be performed.
               For example, find, query, insert, merge, remove, properties, domain etc.

   qualifier : qualifies the action. 
               specific to the action, e.g. a query action can qualify with query/single to get a single result as in above ex09.
               zero or more qualifier can be specified. 
               qualifier may have value separated by '='  
               each qualifier is separated by '/' 
               qualifier ordering is not significant (see above ex11.1 and ex11.2)
            
   parameter  : parameter for the action
            For example, JPQL string is a parameter for a query action
            zero or more parameter can be specified
            parameter may have value separated by '='
            each parameter is separated by '&' 
            first parameter can have special semantics based on action, e.g. first parameter for 'query' is JPQL string, 
            or first parameter for 'find' is the entity name, etc.

Child pages

JEST

Protocol