Construct a web service using J2EE

In this article, I will introduce service-oriented architecture (SOA) to java developers ), I will explain how to use J2EE 1.4 to create a web service so that it can be operated and conveniently adapt to the Application service through J2EE1.4 (for example, Oracle Application Server ).
Web Services Architecture
Before learning how to deploy J2EE platform on web services, let's first understand the main structure of web service.
Through the network, we can find some definitions, releases, and calls for web services. A web service, as shown in Figure 1
Figure 1
There are two types of web services: "RPC style and document style". RPC-style web services were initially popular. However, in recent years, document-style has become the first choice for web services.
RPC-style web services is a remote program call that represents mutual interaction. RPC-style web services must comply with a clear signature before calling and returning in interaction information, which is inconvenient for applications. Instead, document-style web services uses xml to change the sending and receiving applications.
Many developers think that web services is a dynamic technology that inherits SOA. Because it provides an interaction between different platforms and lightweight technology. For example, xml, soap, and http.
What Are Web Services Made?
In web service, you must first define the Web Services Definition Language (WSDL; pronounced "wizdle") document.
This WSDL provides a complete description of the web service, including ports, operations, and information types.
Here is a simple example of a WSDL document that describes a HelloWorld web service:
<Definitions
Name = "HelloService"
TargetNamespace = "http://oracle.j2ee.ws/ejb/Hello"