What is XMLBeans?

XMLBeans is a tool that allows you to access the full power of XML in a Java friendly way. The idea is that you can take advantage of the richness and features of XML and XML Schema and have these features mapped as naturally as possible to the equivalent Java language and typing constructs. XMLBeans uses XML Schema to compile Java interfaces and classes that you can then use to access and modify XML instance data.

Using XMLBeans is similar to using any other Java interface/class, you will see things like getFoo or setFoo just as you would expect when working with Java. While a major use of XMLBeans is to access your XML instance data with strongly typed Java classes there are also API's that allow you access to the full XML infoset (XMLBeans keeps XML Infoset fidelity) as well as to allow you to reflect into the XML schema itself through an XML Schema Object model.

What Makes XMLBeans Different

There are at least two major things that make XMLBeans unique from other XML-Java binding options.

1. Full XML Schema support. XMLBeans fully supports XML Schema and the corresponding java classes provide constructs for all of the major functionality of XML Schema. This is critical since often times you do not have control over the features of XML Schema that you need to work with in Java. Also, XML Schema oriented applications can take full advantage of the power of XML Schema and not have to restrict themselvs to a subset.
2. Full XML Infoset fidelity.When unmarshalling an XML instance the full XML infoset is kept and is available to the developer. This is critical because because of the subset of XML that is not easily represented in java. For example, order of the elements or comments might be needed in a particular application.

A major objective of XMLBeans has been to be applicable in all non-streaming (in memory) XML programming situations. You should be able to compile your XML Schema into a set of java classes and know that 1) you will be able to use XMLBeans for all of the schemas you encounter (even the warped ones) and 2) that you will be able to get to the XML at whatever level is necessary - and not have to resort to multple tools to do this.

To accomplish this XMLBeans provides three major APIs:

• XmlObject The java classes that are generated from an XML Schema are all derived from XmlObject. These provide strongly typed getters and setters for each of the elements within the defined XML. Complex types are in turn XmlObjects. For example getCustomer might return a CustomerType (which is an XmlObject). Simple types turn into simple getters and setters with the correct java type. For example getName might return a String.
• XmlCursor From any XmlObject you can get an XmlCursor. This provides efficient, low level access to the XML Infoset. A cursor represents a position in the XML instance. You can move the cursor around the XML instance at any level of granularity you need from individual characters to Tokens.
• SchemaType XMLBeans provides a full XML Schema object model that you can use to reflect on the underlying schema meta information. For example, you might want to generate a sample XML instance for an XML schema or perhaps find the enumerations for an element so that you can display them.

All of this was built with performance in mind. Informal benchmarks and user feedback indicate that XMLBeans is extremely fast.

XMLBeans provides several ways to get at the XML, including:

·        Through XML schema that has been compiled to generate Java types that represent schema types. In this way, you can access instances of the schema through JavaBeans-style accessors after the fashion of "getFoo" and "setFoo". The XMLBeans API also allows you to reflect into the XML schema itself through an XML Schema Object model.

·        A cursor model through which you can traverse the full XML infoset.

·        Support for XML DOM.

·        It provides a familiar Java object-based view of XML data without losing access to the original, native XML structure.

·        The XML's integrity as a document is not lost with XMLBeans. XML-oriented APIs commonly take the XML apart in order to bind to its parts. With XMLBeans, the entire XML instance document is handled as a whole. The XML data is stored in memory as XML. This means that the document order is preserved as well as the original element content with whitespace.

·        With types generated from schema, access to XML instances is through JavaBean-like accessors, with get and set methods.

·        It is designed with XML schema in mind from the beginning — XMLBeans supports all XML schema definitions.

·        Access to XML is fast.
 

Features are:

Accessing XML Using Its Schema

To get a glimpse of the kinds of things you can do with XMLBeans, take a look at an example using XML for a purchase order. The purchase order XML contains data exchanged by two parties, such as two companies. Both parties need to be able to rely on a consistent message shape, and a schema specifies the common ground. This XML includes a root element, purchase-order, that has three kinds of child elements: customer, date, line-item, and shipper. An intuitive, object-based view of this XML would provide an object representing the purchase-order element, and it would have methods for getting the date and for getting subordinate objects for customer, line-item, and shipper elements. Each of the last three would have its own methods for getting the data inside them as well.

Looking at the Schema

The following XML is the the schema for the preceding purchase order XML. It defines the XML's "shape" — what its elements are, what order they appear in, which are children of which, and so on. This schema describes the purchase order XML instance by defining the following:

·        Definitions for three complex types — customer, line-item, and shipper. These are the types used for the children of the purchase-order element. In schema, a complex type is one that defines an element that may have child elements and attributes. The sequence element nested in the complex type lists its child elements. These are also global types. They are global because they are at the top level of the schema (in other words, just beneath the schema root element). This means that they may be referenced from anywhere else in the schema.

·        Use of simple types within the complex types. The name, address, and description elements (among others) are typed as simple types. As it happens, these are also built-in types. A built-in type (here, one with the "xs" prefix) is part of the schema specification. (The specification defines 46 built-in types.)

·        A global element called purchase-order. This element definition includes a nested complex type definition that specifies the child elements for a purchase-order element. Notice that the complex type includes references to the other complex types defined in this schema.