Web Services

Web Services

1. It is promoted as a new way to build network applications from distributed components that are language- and platform-independent

   • A web service is a message-based network service.
     • Web service protocol stack

2. SOAP

   • SOAP is a protocol which applies XML for message exchange in support of remote method calls over the Internet.
   • SOAP is web-based or “wired” and hence is not subject to firewall restrictions
   • SOAP Messages
   • The nature of the request
     • SOAP coating
     • the SOAP body
   • A SOAP response
     • A SOAP method call may fail, perhaps due to errors in specifying the method name or parameters.
   • Apache SOAP
     • As can be seen in the preceding descriptions, writing code to directly generate the XML syntax for SOAP requests and responses can be tedious and prone to errors. Consequently, numerous APIs for SOAP have appeared that provide the necessary abstraction to facilitate the programming that corresponds to SOAP requests / responses
       • The RPCMessage class
       • The Cali class
       • The Parameter class
       • The Response class
       • The Fault class

3. Servlets

   • are another type of Java program. While the applets are sent from the server to the HTTP client to be executed on the client machine, the servlets are server extensions and are executed on the server machine. In Chapter 9, They studied some server extension programs: CGI scripts. As you remember, CGI scripts are external programs that extend the capabilities of a server HTTP to support the processing of web forms
   • Session object
     • The Servlets API provides a special mechanism to maintain information from specific state of a particular session of an HTTP client. The mechanism is known as session objects.
       • The session object will persist during an inactivity interval that can be established by code, or by a default value that depends on the implementation. When the interval ends, the servlet container will invalidate the session object by what its content can no longer be accessed. The invalidation of a session object You can also start by program; it is good practice to do it in the code at www

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