Android notes-Web Service Basics

I,Web ServiceWhat is it?

It is a network service. According to W3C definition, WebServices (Web Service) is a software system used to support interoperability between different machines on the network, it is a self-contained, self-describing, and modular application that can be described, published, and called on the network, it can be viewed as a network-based, distributed modular component.

Web ServicesIs based on general protocols, includingHTTP,SOAP,UDDI,WSDL. WhereWebServiceThe three elements areSOAP,WSDLAndUDDI. SOAPUsed to describe the format of transmitted information,WSDLUsed to describe how to access a specific interface,UDDIUsed for management, distribution, and queryWebService.

(The above content in bold is from Baidu encyclopedia)

The advantage of WebServices is that it provides interoperability between different application platforms, which makes the combination of component-based development and Web best. It is based on the HTTP protocol. Call requests and response messages can both pass through the firewall without changing the firewall settings. This avoids the problem that the firewall cannot be crossed when special ports are used for communication.

 

Summary --A Web service is an application that exposes an API that can be called through the Web..

 

In fact, to put it bluntly, a server can be understood as a website. A function or method is enabled (that is, open to the public, through web service programming, we can obtain the public information for our own use. For example, if a weather website exposes its weather interface, we can use the web service to obtain the weather conditions on a daily basis. It should be noted that the web service is based on common protocols, which is the same as JAVA,Good cross-platform and cross-language features!But in this case, is Web Service really like this? I don't know how to use it because I have little practice, but the following blog post illustrates it in the form of a historical biography.

Some things. For details, see --

SOAPAndWebServiceOf

 

 

II,SOAP,WSDLAndUDDI

As mentioned above, SOAP, WSDL, and UDDI are the three major components of Web Service. SOAP and WSDL are mandatory, and UDDI is optional. So we need to first understand these protocols.

 

(1)SOAP

Simple Object Access Protocol (Simple Object Access Protocol) is a lightweight Protocol used to exchange XML (a subset of standard General Markup Language) encoding information. Currently, two common versions are available: SOAP1.1 and SOAP 1.2. The advantage of SOAP is that it can run on any other protocol, such as SMTP and HTTP.

(2)WSDL

Web Services DescriptionLanguage (Web Service Description Language) is an XML language used to describe Web Services. It describes the functions, interfaces, parameters, and returned values of Web Services, this allows you to easily bind and call services. It defines operations and messages related to a given Web service call and response in a language-independent manner.

WSDL is what we can see. It is an xml document used to describe all aspects of a WebSerivce.

If you still cannot understand the WSDL after reading the above text, please read the following content: (from a netizen, there is a source below)

How will you introduce the functions of your Webservice and the parameters used for each function call? You may write a set of documents on your own. You may even verbally tell people who need your Webservice. These informal methods have at least one serious problem: when programmers sit in front of a computer and want to use your Web service, their tools (such as Visual Studio) cannot provide them with any help, because these tools do not know your Web service at all. The solution is to provide a formal description document that can be read by machines. The Webservice Description Language (WSDL) is an XML-based language used to describe Webservice and its functions, parameters, and return values. Because it is based on XML, WSDL is both readable and readable, which is a great benefit. Some of the latest development tools can generate a WSDL document based on your Webservice, and import the WSDL document to generate code that calls the corresponding Web service.Therefore, WSDL was born.

 

Source Document

 

 

(3)UDDI

The full name is: Universal Description, Discovery andIntegration. The Chinese translation is "general Description, Discovery and integration service", or "unified Description, Discovery and Integration Protocol ". It feels abstract, right? So do I, haha. It doesn't matter. Let's continue.

The following description is too professional and hard to understand. Therefore, the original article references --

Understand Web Service Specifications: Part 1: unified description, discovery, and integration (UDDI)

 

When all applications are local, it is very easy to find the required features. However, you cannot obtain the benefits of a central registration center when using distributed systems such as Web Services. Distributed systems are also prone to changes. This is the application of UDDI. It is intended for two purposes. It was initially considered as a "general business registration center ". The idea is that enterprises can use one of the following three methods to search partners:

• "White Pages": similar to the white pages used to find company information in the phone book. For example, if you know the company name, you can find the company address, how to contact the company, or even determine which person in the organization to contact.

• "Yellow Pages": similar to the yellow pages in the phone book, you can search for a company by category. UDDI specifies various classifications for companies to classify themselves. For example, if you are looking for sports equipment, you can find the company whose North American Industrial Classification System (NAICS) code is 339920.

• "Green page": There is no green page in the phone book, but the idea here is that companies can use this search method to find trade partners that implement specific services. For example, you can search for companies that use the zip code distance calculation function.

UDDI is also considered to be a way to keep distributed applications running for a long time. The idea is that the application can cache information about access to a specific service. If the client crashes, the application will automatically return to the Registration Center and check whether the information has been changed. If the change has been made, you can make the change directly within the application (the change will be made automatically in ideal cases) and retry your request.

After reading it, I understand it. UDDI is actually the Business Registration logic and registration, allowing users to quickly search.