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So using the common verbs of HTTP and Java object serialization, one can implement services and run them anywhere the HTTP protocol is implemented. The service developer or implementer simply creates methods for post, get, put, and delete, and a business collection such as a shopping cart, telephone directory, insurance form, or blog sites can be created. See the Tuscany module binding-rest-runtime for complete examples.

Mapping business interfaces to HTTP Operations using JAX-RS Standard Annotations

JAX-RS offers standards based annotations that allow properly configuration of the REST service endpoint and mappings of specific HTTP operations (e.g. get, put, post, delete) to java operations. The following subset of JAX-RS annotations are currently supported :

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@GET
@PUT
@POST
@DELETE

Enabling JAX-RS annotation processing

In order to enable JAX-RS

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annotation processing, a component need to be configured to use JAX-RS

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Operation Selector.

        <component name="Catalog">
		<implementation.java class="services.store.FruitsCatalogImpl"/> 
		<property name="currencyCode">USD</property>
		<service name="Catalog">
			<tuscany:binding.rest uri="http://localhost:8085/Catalog">
    		            <tuscany:wireFormat.json />
			    <tuscany:operationSelector.jaxrs />
    		        </tuscany:binding.rest>
   		</service>
		<reference name="currencyConverter" target="CurrencyConverter"/>	
	</component> 

Mapping RPC style calls over HTTP GET

In some cases, there isn't a simple mapping of a business operation as resources, but there is still a desire to take advantage of HTTP caching and other benefits that HTTP GET type of operations provide. In order to accomplish this, binding.rest has built in functionality that allows you to map RPC style calls to HTTP GET operations.

Client Invocation

The URL schema follows a simple pattern :

• <base service URI> ?method=<operation name>&parm1=<value>&parm2=<value>

http://localhost:8085/EchoService?method=echo&msg=Hello RPC

http://localhost:8085/EchoService?method=echoArrayString&msgArray=Hello RPC1&msgArray=Hello RPC2"

Mapping QueryStrings to Business Operation parameters

Standard JAX-RS annotation @QueryParam is used to map parameters sent over HTTP GET invocations using query string to business operation parameter

@Remotable
public interface Echo {

    String echo(@QueryParam("msg") String msg);

    int echoInt(int param);

    boolean echoBoolean(boolean param);

    String [] echoArrayString(@QueryParam("msgArray") String[] stringArray);

    int [] echoArrayInt(int[] intArray);

}

Enabling RPC to HTTP GET mapping

In order to enable automatically mapping, a component need to be configured to use RPC Operation Selector.

        <component name="Catalog">
		<implementation.java class="services.store.FruitsCatalogImpl"/> 
		<property name="currencyCode">USD</property>
		<service name="Catalog">
			<tuscany:binding.rest uri="http://localhost:8085/Catalog">
    		            <tuscany:wireFormat.json />
			    <tuscany:operationSelector.rpc />
    		        </tuscany:binding.rest>
   		</service>
		<reference name="currencyConverter" target="CurrencyConverter"/>	
	</component> 

Wire Formats

This binding will support two styles of wire formats and will be used to control what type of payload will be generated by the service:

• hardWired : where you hard code the wire format expectations in the composite when configuring the binding. In the example below, service will be using JSON payload.

<binding...>
   <wireFormat.json>
</binding...>

• dynamic : based on Content-Type header for request and Accept header for response. In the case below, the request content will be parsed based on the Content-Type request header and the response payload will be based on the request Accept header.

<binding...>
   <wireFormat.dynamic>
</binding...>

Cache control using ETags, Last-Modified and other HTTP Headers

The HTTP specification provides a set of methods for HTTP clients and servers to interact. These methods form the foundation of the World Wide Web. Tuscany implements many of these methods a binding interface to a collection. The main methods are:

• GET - retrieves an item from a collection
• POST - creates or adds an item to a collection
• PUT - updates or replaces an item in a collection
• DELETE - removes an item in a a collection

The HTTP specification (HTTP 1.1 Chapter 13 - Caching) also provides a mechanism by which these methods may be executed conditionally. To perform conditional methods, an HTTP client puts 3 items in the HTTP request header:

• ETag - entity tag, a unique identifier to an item in a collection. Normally created and returned by the server when creating (POST) a new item.
• LastModified - an updated field. Normally a string containing a date and time of the last modification of the item.
• Predicate - a logical test (e.g. IfModified, IfUnmodified) to use with the ETag and LastModified to determine whether to act.

The complete list of predicates is given in the HTTP specification.

The most common use of conditional methods is to prevent two requests to the server instead of one conditional request. For example, a common scenario is to check if an item has been modified, if not changed update it with a new version, if changed do not update it. With a conditional PUT method (using the IfUnmodifed predicate and a LastModified date), this can be done in one action. Another common use is to prevent multiple GETs of an item to ensure we have a valid copy. Rather than doing a second request of a large item, one can do a conditional GET request (using an IfModified predicate and a LastModified date), and avoid the second request if our object is still valid. The server responds with either a normal response body, or status code 304 (Not Modified), or status code 412 (precondition failed).

Default cache control is done by using generated ETags based on response content checksum. To avoid data to be overwriten during concurrent updates, include an HTTP If-Match header that contains the original content ETag value. If you want to force an update regardless of whether someone else has updated it since you retrieved it, then use If-Match: * and don't include the ETag.

Declarative cache control

In order to allow for better flexibility, and re-usability of the components exposed as REST services, there is an option to declare cache controls when configuring the REST Binding as show the example below :

	<component name="CustomerService">
		<implementation.java class="services.customer.CustomerServiceImpl"/> 
		<service name="CustomerService">
			<tuscany:binding.rest uri="http://localhost:8085/Customer">
    		    <tuscany:wireFormat.xml />
			    <tuscany:operationSelector.jaxrs />
			    <tuscany:http-headers>
			       <tuscany:header name="Cache-Control" value="no-cache"/>
			       <tuscany:header name="Expires" value="-1"/>
			       <tuscany:header name="X-Tuscany" value="tuscany"/> 
			    </tuscany:http-headers>
    		</tuscany:binding.rest>
   		</service>
	</component>

Wire Formats

This binding will support two styles of wire formats and will be used to control what type of payload will be generated by the service:

• hardWired : where you hard code the wire format expectations in the composite when configuring the binding. In the example below, service will be using JSON payload.

<binding...>
   <wireFormat.json>
</binding...>

• dynamic : based on Content-Type header for request and Accept header for response. In the case below, the request content will be parsed based on the Content-Type request header and the response payload will be based on the request Accept header.

<binding...>
   <wireFormat.dynamic>
</binding...>

Cache control using ETags, Last-Modified and other HTTP Headers

The HTTP specification provides a set of methods for HTTP clients and servers to interact. These methods form the foundation of the World Wide Web. Tuscany implements many of these methods a binding interface to a collection. The main methods are:

• GET - retrieves an item from a collection
• POST - creates or adds an item to a collection
• PUT - updates or replaces an item in a collection
• DELETE - removes an item in a a collection

The HTTP specification (HTTP 1.1 Chapter 13 - Caching) also provides a mechanism by which these methods may be executed conditionally. To perform conditional methods, an HTTP client puts 3 items in the HTTP request header:

• ETag - entity tag, a unique identifier to an item in a collection. Normally created and returned by the server when creating (POST) a new item.
• LastModified - an updated field. Normally a string containing a date and time of the last modification of the item.
• Predicate - a logical test (e.g. IfModified, IfUnmodified) to use with the ETag and LastModified to determine whether to act.

The complete list of predicates is given in the HTTP specification.

The most common use of conditional methods is to prevent two requests to the server instead of one conditional request. For example, a common scenario is to check if an item has been modified, if not changed update it with a new version, if changed do not update it. With a conditional PUT method (using the IfUnmodifed predicate and a LastModified date), this can be done in one action. Another common use is to prevent multiple GETs of an item to ensure we have a valid copy. Rather than doing a second request of a large item, one can do a conditional GET request (using an IfModified predicate and a LastModified date), and avoid the second request if our object is still valid. The server responds with either a normal response body, or status code 304 (Not Modified), or status code 412 (precondition failed).

Default cache control is done by using generated ETags based on response content checksum. To avoid data to be overwriten during concurrent updates, include an HTTP If-Match header that contains the original content ETag value. If you want to force an update regardless of whether someone else has updated it since you retrieved it, then use If-Match: * and don't include the ETag.

Store scenarios goes REST - Catalog Services using binding.rest

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