Summary of "Lec 11: Simple Object Access Protocol (SOAP)"

Summary of “Lec 11: Simple Object Access Protocol (SOAP)”

This lecture explains the fundamentals of SOAP (Simple Object Access Protocol), a messaging protocol used for communication between a client and a web service. It focuses on how SOAP messages are structured, sent, and received, and how SOAP enables remote procedure calls (RPC) over HTTP.

Main Ideas and Concepts

SOAP Overview

SOAP stands for Simple Object Access Protocol.
It is a messaging protocol that defines how messages are formatted and exchanged between a client and a web service.
SOAP messages are XML-based and sent over HTTP.
The client sends a SOAP request message, and the web service replies with a SOAP response message.

SOAP Message Structure

SOAP messages are enclosed in a SOAP Envelope, which acts like an envelope wrapping a letter.
The envelope contains two main parts:
- Header (optional): Contains routing information, security details, or other metadata needed to process the message.
- Body (mandatory): Contains the actual application-specific data, such as input parameters for a method or the output response.
Every SOAP message follows this structure: Envelope → Header (optional) + Body (mandatory)

Using WSDL (Web Services Description Language)

WSDL documents describe the web service methods, their input parameters, and output formats.
Clients use the WSDL to construct the correct SOAP request messages.
For example, if a method getStockPrice takes a stock symbol as input, the SOAP body will include this input in the defined XML format.

Example SOAP Request and Response

Request:

<soap:Envelope>
  <soap:Body>
    <getStockPrice>
      <stockName>IBM</stockName>
    </getStockPrice>
  </soap:Body>
</soap:Envelope>

Response:

<soap:Envelope>
  <soap:Body>
    <getStockPriceResponse>
      <price>34.5</price>
    </getStockPriceResponse>
  </soap:Body>
</soap:Envelope>

The request sends the stock symbol “IBM” and the response returns the stock price.

SOAP Communication Process

A client or service requester wants to invoke a remote procedure call (RPC) on a web service.
The RPC call is converted into a SOAP message by a SOAP engine.
The SOAP message is sent over HTTP using the POST method to the web service.
The web service’s SOAP engine extracts the procedure call, executes it, and returns the response wrapped in a SOAP message.
The response is sent back over HTTP to the client.

Analogy

SOAP message = Letter content HTTP = Postal service delivering the letter Procedure = Recipient who reads and replies to the letter

Tools

SOAP UI is a popular tool to generate and test SOAP requests.
By providing the WSDL file to SOAP UI, it automatically generates SOAP request templates.
Users can modify input values and send requests to the web service, receiving responses in the same SOAP format.

Detailed Methodology / Steps to Use SOAP

Understand the WSDL file: Identify the available methods and their input/output parameters.
Construct SOAP Request:
- Create a SOAP envelope.
- Optionally add a header if routing or security info is needed.
- Add the body with the method call and input parameters in XML format.
Send SOAP Request: Use HTTP POST to send the SOAP message to the web service endpoint.
Receive SOAP Response: The web service processes the request and sends back a SOAP response. The response is also an XML message inside a SOAP envelope and body.
Parse Response: Extract the output data from the SOAP body.
Use SOAP UI (optional):
- Load the WSDL file into SOAP UI.
- Automatically generate SOAP requests.
- Modify inputs and send requests without manual XML coding.

Speakers / Sources Featured

The lecture appears to be delivered by a single instructor (unnamed) explaining SOAP concepts in a step-by-step manner, possibly as part of a web services or distributed systems course.

This summary captures the key points and instructional content of the lecture on SOAP, focusing on its role, message structure, communication mechanism, and practical usage with tools like SOAP UI.