It can be difficult for developers, architects, and managers to keep up with new software packages and releases. This can be especially true with fast moving technologies like Web services. This article provides an overview of the main technologies that comprise the Java Web Services Developer Pack (Java WSDP). For more in-depth knowledge of the WSDP, simply download it and walk through the examples or complete the Java Web Services Tutorial.

In an effort to standardize XML and Web services-related technologies, Sun Microsystems has developed implementations of popular standards and published them under the umbrella title of the WSDP. The toolkit's stated purpose is to simplify the development, testing, and deployment of secure and interoperable Web services. Version 1.5 is the latest release of the WSDP and contains many updates to existing technologies, new features, and a collection of bug fixes. This article will examine the main technologies provided in the WSDP and review their purpose and status.

Downloading/Installing the Java WSDP 1.5
The WSDP can be downloaded freely from Sun's WSDP site at http://java.sun.com/webservices/downloads/webservicespack.html.

On the server side, the WSDP runs within a container (WebSphere, JBoss, WebLogic, SunONE). Sun provides downloads for WSDP-ready containers from its site, including its own Sun Java System Application Server and Tomcat. Since the licensing is free and open, Tomcat is a good place to start. Sun offers a download of Tomcat for Java WSDP at http://java.sun.com/webservices/containers/tomcat_for_JWSDP_1_5.html.

Tomcat 5.0 for Java WSDP is built on Tomcat 5.0.19. The container supports JSP 2.0 and version 2.4 of the Servlet specification.

Related to the WSDP is the JDBC RowSet Implementations 1.0.1 JWSDP 1.5 Co-Bundle, which provides an implementation of a Web service?enabled rowset for remote access to databases. The Co-Bundle can be found at http://java.sun.com/products/jdbc/download.html#rowsetcobundle1_0.

Installing the WSDP is fairly straightforward once you have a container downloaded. One of the most notable weak points of the WSDP (in the opinion of this author) is that the installation is packaged as an executable (.exe) on Windows and is less transparent than most Java install scripts. A standard Ant-based installation would be helpful in porting the WSDP scripts to currently unsupported platforms.

WSDP 1.5 Technology
Below is a short description of the technologies that make up the WSDP 1.5. For each entry the purpose of the toolkit is summarized, the guiding JSRs listed, and the underlying XML specifications noted where applicable.

Sun Java Streaming XML Parser (SJSXP)
The WSDP includes the Sun Java Streaming XML Parser (SJSXP,) which is an implementation of JSR 173. The Streaming API for XML (StAX) found in JSR 173 provides a stream-based API for reading and writing XML documents. The StAX approach is also known as "pull" parsing because it is left to the programmer to pull the next event from the stream via an iterator-based approach. In cases where the current data/events will affect subsequent parsing steps, stream-based code may be easier to write than a typical SAX-based approach and still avoids the inefficiencies of the in-memory DOM-based approach. While pull parsing is not right for every parsing problem, the SJSXP implementation of StAX provides an additional and powerful tool for Java developers. SJSXP is nonvalidating and W3C XML 1.0 is Namespace 1.0 compliant. (See JSR 173: www.jcp.org/en/jsr/detail?id=173; XML Pull Parser: www.extreme.indiana.edu/xgws/xsoap/xpp/.)

XML Digital Signature Version 1.0 EA2
The XML Digital Signature package in the WSDP provides an implementation of JSR 105. JSR 105 provides a standard way for Java developers to access digital signature services and implements the W3C's XML-Signature Syntax and Processing specification. This specification defines the syntax and rules for creating and representing digital signatures associated with digital content (mainly XML). The specification provides support for enveloped and detached signatures and basic keying and management of digital information.

Using the XML Digital Signature APIs found in the WSDP, developers can sign and validate digital content and represent the signatures in an XML format. The signatures provide a standard way to verify that content originated from a known source and was not altered during transmission. The WSDP contains the core classes for using signatures as well as examples and documents. (See JSR 150: www.jcp.org/en/jsr/detail?id=105; XML-Signature Syntax and Processing: www.w3.org/TR/2002/REC-xmldsig-core-20020212/.)

JAXB Version 1.0.4 (Java Architecture for XML Binding)
The Java Architecture for XML Binding (JAXB) project is the implementation of JSR 33 that provides a standard API for automating the mapping between XML documents and Java objects. Using JAXB, a developer can compile a schema into Java classes that provide support for marshaling, unmarshaling, accessing, updating, and validating. The main goal of JAXB is to relieve the developer of these tasks so that they can be more productive and be exposed to fewer XML-oriented issues. JAXB 1.0.4 provides support for a subset of XML Schema and experimental support for RelaxNG. RelaxNG is a simplified XML schema system sponsored by the Oasis group. JAXB is currently integrated with JAX-RPC for easily transporting objects across the wire. JAXB 2.0 (governed under JSR 222) will focus on further integration with JAX-RPC, broader schema support, and underlying use of StAX for XML handling. (See JSR 31: http://jcp.org/en/jsr/detail?id=31; JSR 222: http://jcp.org/en/jsr/detail?id=222; XML Schema Part 1: www.w3.org/TR/xmlschema-1/; XML Schema Part 2: www.w3.org/TR/xmlschema-2/; RelaxNG: www.oasis-open.org/committees/relax-ng/; UBL: www.oasisopen.org/committees/tc_home.php?wg_abbrev=ubl_l.)

JAXP Version 1.2.6_01 (Java API for XML Processing)
The JAXP package (Java API for XML Processing) provides an implementation-neutral way of accessing XML-related tools like SAX2 and DOM Level 2 XML parsers, XSLT processors (via TrAX) and XML utility standards for XBase, XLink, XPath, and XPointer. Developers using JAXP can access implementations of these tools by their interface and keep their code from directly depending on a particular implementation. For example, XML parsers are pluggable and can be switched out to fix bugs, improve speed, or alter the memory profile without a code change or recompilation. The JAXP 1.2 specification is a maintenance release of JAXP 1.1 and adds support for W3C XML Schema. (See JAXP: http://java.sun.com/xml/jaxp; JSR 63: www.jcp.org/en/jsr/detail?id=63; JSR 5: www.jcp.org/en/jsr/detail?id=5; SAX2: www.saxproject.org/; DOM Level 2: www.w3.org/TR/DOM-Level-2-Core/.)

JAXR Version 1.0.7 (Java API for XML Registries)
The Java API for XML Registries (JAXR) provides a uniform facade for accessing XML-based registries and was developed under JSR 93. Registries are useful for organizing, relating, and adding metadata to services and resources. The unifying approach of JAXR is useful because there are several similar and overlapping service registries in the Web services space. The JAXR API provides facilities for establishing connections to, querying, and updating registries. The current JAXR specification includes bindings for UDDI 2.0. Additional registries such as ebXML and eCo Framework can be developed and plugged in in a straightforward manner. (See UDDI: http://uddi.org/pubs/ProgrammersAPI-V2.04-Published-20020719.htm; JSR 93: http://jcp.org/en/jsr/detail?id=93; ebXML: www.oasis-open.org/committees/tc_home.php?wg_abbrev=regrep.)

JAX-RPC Version 1.1.2_01 (Java API for XML-based RPC)
The JAX-RPC project provides a uniform API for building Web services and Web service clients that use remote procedure calls (RPCs) with XML as a transport. JAX-RPC was originally developed under JSR 101 and is currently being developed under JSR 224 for JAX-RPC 2.0. A developer using JAX-RPC can either consume a remote Web service as a client or expose a Web service from the server side. The resulting code is RPC protocol independent. Web service based RPC protocols such as SOAP can be plugged into the JAX-RPC framework as needed. The 2.0 version of JAX?RPC is being increasingly integrated with the 2.0 version of the JAXB specification. (See JSR 101: www.jcp.org/en/jsr/detail?id=101; JSR 224: www.jcp.org/en/jsr/detail?id=224; SOAP: www.w3.org/TR/soap/.)

JDBC RowSet Implementations: Java Web Services Pack v1.5 Co-Bundle
The WSDP Co-Bundle provides a basic JDBC rowset implementation and several disconnected JDBC rowset implementations that can be used to access and update data in a relational database. Several of the rowset implementations provided are disconnected, that is they are not directly connected to the underlying database. The WebRowSet class is disconnected and can marshal and unmarshal itself to/from XML according to the WebRowSet schema. A developer can expose the WebRowSet via Web services and allow clients easy, powerful, and secure access to a remote database. (See Co-Bundle: http://java.sun.com/products/jdbc/download.html#rowsetcobundle1_0.)

WSDP Recap
The WSDP provides a rich set of utilities for the XML and Web services developer. Developers can use the current implementation of the WSDP to build sophisticated Web service implementations in a standard fashion. As the WSDP expands over time to include additional security tools and updated XML-related standards, developers will continue to find it a valuable resource. For the latest information on the WSDP and Sun's Web service efforts, see http://java.sun.com/webservices.

Additional Resources