Understanding the following concepts
will help you work through the remainder of this tutorial, and better appreciate
the design and implementation decisions that OTN developers applied to the JAXBIPS
sample application:
Java Architecture for XML Binding (JAXB) provides API and
tools that make it easier to use Java applications that read, process and output
XML data. JAXB features a newer approach, and an easier way of authoring and
processing XML compared to SAX or DOM, by automating the mapping between XML
documents and Java objects. JAXB makes XML easy to use by compiling an XML schema
into one or more Java technology classes. The combination of the schema derived
classes and the binding framework enable one to perform the following operations
on an XML document:
Increased Productivity: Java developers using
JAXB are more productive because they are free from the burden of writing complex
parsing code.
About Unmarshaling
Unmarshaling, in data binding terms, refers to the conversion
of XML documents to Java object instances. To better understand the concepts
of Unmarshaling and Marshaling, one has to understand the key concepts behind
Data binding and Class generation.
Data binding refers to the mapping of XML documents to objects and vice-versa.
Other Java and XML API's (such as SAX, DOM, dom4J, JAXP, etc) achieve the
same thing, however they are document-centric, in that they are driven by
data in some XML representation. Data binding, on the other hand is data-centric,
and allows applications to manipulate data that has been serialized as XML,
thereby driving the business priority of the application.
Class generation refers to the generation of Java source files - it involves
the mapping between a structure that is laid out by the constraints in an
XML document and a set of Java classes. The Oracle JAXB implementation provides
a JAXB class generator that takes a set of XML constraints as input and creates
a set of Java source files. When these source files are compiled, you are
ready to start the process of Unmarshaling.
The Marshaling and Unmarshaling API's in the java.xml.bind package within
the JAXB API affects the Unmarshaling process in the Insurance Profile System
application. The Streamsource API's are used for unmarshaling data from the
XMLType tables in the database. The XML document to be converted should be
conformant with the structure of the generated Java classes.
The block diagram below summarizes the flow of the unmarshaling process:
About Marshaling
Marshaling works in an opposite fashion to the Unmarshaling
process - it converts a Java object into an XML document representation. Similar
to the unmarshaling process, the generated Java classes must be validated,
and checked for conformance with the existing Java classes before converting
them into XML. As with the Unmarshaling process, the Marshaling and Unmarshaling
API's in the java.xml.bind package within the JAXB API affects the marshaling
process in the Insurance Profile System application.
The block diagram below summarizes the flow of the Marshaling
process:
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