Building Services using Java EE

Today, Web Services is a popular technology for implementing service-oriented applications. Java EE has become a popular platform for deploying Web services applications. Also, j2ee1.4 has developed standards for building and deploying Web Services applications on the Java platform.

In this article, I'll show you how to build interoperable, lightweight and flexible services using j2ee1.4 between application servers that implement the j2ee1.4 specification, such as Oracle Application Server 10g.

Web Services Architecture

Before delving into the details of Web services development and deployment on the Java platform, let's take a brief look at the architecture of the Web service.

Web services have many definitions, but in short, Web services are independent, self-describing components that can be published, discovered, and invoked over the network. As shown in Figure 1, a Web service may perform a simple function, such as accounting for bank deposit records, or a complex task spanning multiple business processes.

Figure 1. How a Web service works

There are two ways to interact with Web services: RPC types and document types. Initially, RPC-type Web services was popular in industry, but in recent years it has been overtaken by document-type Web services, which is considered the preferred method of exchanging information in Web services.

RPC-type Web services proposes to simulate data interchange as a remote procedure call (RPC). This is very common in commercial applications. For remote invocations and their return values, let the exchanged messages follow a well-defined guideline. In contrast, a document-type Web services simulates the exchange of XML documents, which are defined by both the sending and receiving applications. A document-type service is more adaptable to applications that require the exchange of commercial or other types of documents, and unlike RPC-type Web services, the sender does not need to expect or wait for an immediate response.

Most developers will agree that Web services is an effective technology for implementing SOA because it provides interoperability between different platforms and lightweight technologies that rely on XML,SOAP and HTTP.

Platform independence and technology implementation are the main reasons for Web services popularization. The client does not have to understand the implementation of the technology, but simply invoke the service over the network. For example, even if you use JAVA/J2EE technology to create a service and deploy it on a Java EE server, such as Oracle Application Server Container for Java EE (oc4j), clients can also use Microsoft. NET schema creation.

Now that we have a basic understanding of Web services, let's focus on the basic elements that make up a Web service.