What is SOAP ? . SOAP stands for Simple Object Access Protocol. It is a communication protocol that facilitates the interaction between applications and web services located on remote computers. It is a specification for a messaging system where data is represented as a text and defined as a data type. The text that contains the data is called SOAP message, which is written in XML.
There are three parts of SOAP message, they are the envelope, the header and body. The header is an optional XML tag that contains metadata. The body of the SOAP message is a required part, this contains the text of the message. The SOAP envelope contains the SOAP message.
A J2ee application that uses web services, requests service from a component by referencing the component’s URL in a request sent using SOAP, which is typically transmitted using the HTTP transmission protocol. The web services component replies to the request using SOAP and HTTP once the request has been processed.
The Java API for XML Messaging(JAXM) is used to create a JAXM message by making Java API calls.
There are two types of SOAP messages they are SOAP messages without attachments and SOAP messages with attachments. This two type of messages contain one or multiple parts. The first part of both types of messages is called the SOAP Part. The SOAP messages with attachments have a SOAP Part of the message and also one or more attachment part. The AttachmentPart class creates attachments.
A JAXM message is send over a connection either directly to the receiver or to a messaging provider that forwards the message to the receiver. A messaging provider is an intermediary process that transmits and routes the messages. There are two kinds of connection classes available in JAXM. They are the SOAPConnection class and the ProviderConnection class. The SOAPConnection class is used in a point-to-point connection between the requester and receiver. A SOAPConnection does not need to run in a container.
A SOAPConnection requires that the messages to be sent using a methode call. A methode call is a form of request-response messaging where the requestor is blocked until the response is received from the receiver.
The ProviderConnection class is used to connect to a messaging provider. A J2ee application that uses a messaging provider sends messages to the messaging provider.
SOAP messages can be placed within other protocols that add features to the messaging capabilities of SOAP.
Thus SOAP is simple and extensible communication protocol which is platform independent.