Relationship Between Web Service, SOAP and WSDL

Source: Internet
Author: User

Recently, there have been a lot of projects, and a person who does not do the Web will start to look at various web-related things. Hohoho... these concepts have been in use recently. Record them. I summarized and analyzed various sources of materials including the garden, Wikipedia, Baidu encyclopedia, ESRI documentation library, and experienced colleagues. Some articles from the Wiki or document library will not be translated, and the original text is already in place.


Web Service
Web services provide the ability for applications to communicate using messaging over protocol different protocols. because web services provide a means to communicate between applications that are written both in the same programming language as well as in different programming languages, a language neutral means of communication was needed. XML is the format used to hold the information carried between the applications. the XML message is carried using SOAP (Simple Object Access Protocol ). SOAP defines the headers and the valid means for passing messages. that passing of messages usually takes place over HTTP but it can actually be over any well know protocol, such as SMTP, FTP, or DCOM. SOAP takes the xml message and wraps it so that it can be routed to the processing application and appropriaptely processed.


Simple Object Access Protocol (SOAP) is a lightweight, simple, XML-based protocol designed to exchange structured information on the WEB. SOAP can be used in combination with many existing Internet protocols and formats, including Hypertext Transfer Protocol (HTTP), Simple Mail Transfer Protocol (SMTP), and multi-purpose Internet Mail Extension protocol (MIME ). It also supports a large number of applications from the message system to Remote Process calling (RPC.

WIKIPEDIA: SOAP, originally defined as Simple Object Access Protocol, is a protocol specification for exchanging structured information in the implementation of Web Services in computer networks. it relies on XML for its message format, and usually relies on other Application Layer protocols, most notably Hypertext Transfer Protocol (HTTP) and Simple Mail Transfer Protocol (SMTP ), for message negotiation and transmission.

Simple Object Access Protocol (SOAP) is a Note organized by W3C. It describes a lightweight protocol for exchanging information in a distributed or distributed environment. SOAP is an XML-based protocol. It consists of three parts: SOAP encapsulation (Envelop), which defines a description of the content in a message and who sent the message, framework for who should accept and process it and how to process it; the SOAP Encoding rule (Encoding Rules) is used to represent the Data Type instances required by the application; RPC Representation indicates the protocol for remote process calls and responses. SOAP can be bound to multiple transmission protocols and exchange information using the underlying protocol.

SOAP messages are basically unidirectional transmission from the sending end to the receiving end, but they are often combined to execute a mode similar to request/response. All SOAP messages are encoded in XML format. A soap message is an XML file that contains an essential SOAP encapsulation package, an optional SOAP header, and a required SOAP block.

Based on the HTTP protocol, SOAP writes xml request parameters and submits them to the web service Server (SERVLET, ASP or something) on the http body, the results are also written in XML as RESPONSE and sent back to the user end. To make the user end and web service correspond to each other, you can use WSDL as the description file for this communication method, the WSDL tool can be used to automatically generate WS and user-end framework files. SOAP can be used to serialize complex objects and bind them to XML.

SOAP can also be bound to TCP and UDP protocols.


WSDL describes what a web service does, what methods it contains, what parameters and types it knows how to use, and which ports it is using for communication. the WSDL defines the valid contents of the XML messages to be passed over SOAP. the WSDL acts as a specification, like IDL, to describe the interfaces and parameters on a web service. the methods available are usually grouped together in a "port", which can be thought of as a view to web services where different operations are exposed. a wsdl can contain one or more ports.


Link Summary

In short, SOAP is a protocol specification for structured data exchange and is used for WebService. SOAP is based on XML. Most SOAP applications are based on HTTP because HTTP protocol is widely supported (protocol supported and port 80 is reachable.

SOAP is the layer in the message stack that is located above the HTTP protocol. After a Service is called to the server, it obtains its own Payload at the TCP/IP, HTTP, and SOAP levels in turn, the program, combined with the WebService structure information described in the WSDL, finally generates/obtains the corresponding object and initiates a call.

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