Topics for Course Review

SOAP-based web services use XML so that heterogenous applications can communicate, thus providing interoperability.
SOAP messages have a strictly enforced format that requires at minimum, an <Envelope> and a <Body>. The SOAP specification requires that the Envelope and Body elements be namespace- qualified with a URL that identifies the SOAP version in use.
Most SOAP services provide a WSDL that gives clients enough information so that they can send and receive messages through the service. The WSDL itself is a well-formed XML document containing <message>, <portType>, <binding> and <service> elements.
The JAX-WS API gives Java developers an easy-to-use API for sending and receiving SOAP messages. JAX-WS uses annotations to make coding simple.
The SOAP with Attachments API (SAAJ) provides Java developers with a low-level, powerful API for working with SOAP messages, including those with attachments. It provides an alternative to JAX-WS that gives developers more control at expense of requiring much more Java coding.
The basic principles of the REST architecture include:
- Assigning unique resource IDs (URLs) to each REST resource, for example http://www.univ.edu/rest/students/1678.
- Providing multiple representations of resources, for example XML and JSON. This makes it easier to support diverse clients.
- Using links to connect resources, sometimes referred to as HATEOAS (Hypermedia as the Engine of Application State).
- Using standard HTTP verbs (methods) such as GET, POST, PUT and DELETE.
- Participants communicate statelessly to provide scalability. This makes techniques such as remembering a logged-in user more challenging, it's still feasible using tokens.
JSON is a format specification that's based on native JavaScript syntax. JSON is perhaps the most popular format used by REST applications. JSON has a simple syntax that supports defining objects using { and } and arrays using [ and ].
The REST community has come up with guidelines for creating RESTful applications that implement Create, Retrieve Update and Delete (CRUD) operations. The guidelines include:
- Using HTTP POST for create, GET for retrieve, PUT for update and DELETE for delete.
- Defining preferred HTTP return status codes for each operation, for example "201 Created" for a successful POST.
JAX-RS provides an easy-to-use API for writing RESTful resources (services) and clients in Java. It uses annotations such as @Path and @GET to make it easy to code. JAX-RS also provides an API for writing filters that let you intercept messages to to perform global operations such as security.
WS-Security is the specification for securing SOAP-based web services. It defines standard headers that describe how SOAP messages are signed and encrypted.
JSON Web Token (JWT) is an emerging standard for securing RESTful applications. It uses digital signatures to verify that message integrity and for authentication. Since the tokens are passed on every message, RESTful applications can remain stateless as recommended in the principles of the RESTful architecture.