Introduction to J2EE-based Web Services and j2eeweb services

Introduction to J2EE-based Web Services and j2eeweb services

Introduction to Web Services Based on J2EE

1,What is Web service?

In people's daily life, weather information of a city on the webpage is often queried, which is dynamic and real-time. It is a service provided by professional meteorological stations. For example, online payment is usually used for online shopping, which is achieved through a third-party payment tool. Providing such a service on the network is called a Web service.

From the perspective of software developers, Web services are a set of standards. This specification defines how different application systems interact, including information transfer content, formats, information transfer protocols, and related security, policies, and interoperability.

From the perspective of programming users, Web services are a type of applications that can implement a certain function through Web calls through programming methods.

 

2,Web service features

(1) Encapsulation:

For Web service users, only the list of functions provided by the Web service can be seen. The specific implementation and running platform of the Web service is invisible to users.

(2) loose coupling

For Web service users, as long as the Web service call interface remains unchanged, any changes to the implementation of Web services cannot be felt by them.

(3) Use of standard protocols

All public protocols of Web services use standard protocol descriptions, transmission, and exchange.

(4) highly integrated capabilities

Because Web services use simple and easy-to-understand standard protocols, the differences between different platforms are completely shielded. Both CORBA, DCOM, and ejbs can use this standard protocol for interoperability, achieve high system integration.

(5) Interoperability

Implement mutual calls between different systems, with language independence, supports multiple component standards such as CORBA, DCOM, and EJB, and supports communication protocols such as HTTP and SMTP.

 

3. Web Service Architecture

There are three roles in the Web Service Architecture: Service Provider (server), service requestor (client), and Service Registration Center (optional roles ), the interaction between them forms the architecture of Web Services. See Figure 1 (Web Service Architecture ):

 

Figure 1: Web Service Architecture

4,Web Service technical standards

A Web Service is a piece of code that can be found, described, and accessed in XML. Web service specifications are a set of protocol specifications. They can be divided into two parts: Web service specifications and extended Web service specifications. These specifications include the following technical standards:

(1) Web service-based specifications

1) XML

XML is the basic format for data representation in Web services and a standard method for describing Web Service data. In addition to ease of creation and analysis, XML has the main advantages of language independence and platform independence, thus realizing the language independence of Web Services and platform independence.

2) SOAP

Simple Object Access Protocol (SOAP) is a Simple Protocol used to exchange Web service information and exchange information in a distributed environment, is based on XML. It details the Message format for transmitting Web services, including four parts: SOAP encapsulation, SOAP encoding rules, SOAP remote representation, and SOAP binding.

3) WSDL

Web Service Description Language (WSDL) is a standard specification used to describe Web Services. It uses XML format to describe all the information required to call Web Services. The application can extract the detailed information from the WSDL file and generate the programming interface file required to call the Web service.

4) UDDI

Universal Description, Discovery and Integration (UDDI) is a standard that defines how to publish and discover Web services. With it, applications can provide their functions to other applications or find and use services provided by other applications. By using UDDI to discover Web services, enterprises can register Web services and allow other enterprises to substitute their own Web Services.

(2) extended Web service specifications

1) WS-Security

It is used to process encryption and digital signatures. It allows you to create specific types of applications to prevent eavesdropping on messages and implement undeniable functions.

2) WS-Policy

It is used to expand WS-Security and define which users can use the Web service by formulating complex policies.

3) WS-I

The WS-I provides a set of standards and practices that can be used to prevent various issues and provides standardized testing to check possible issues.

4) WS-BPEL

A single Web service is difficult to meet complex enterprise application requirements under most conditions. It is often necessary to combine multiple Web services into a complete system, and the WS-BPEL provides the interaction required to specify the creation of such systems.

 

5. Simple Web Service Application Instances

Here I recommend a blog, explain the instance super detailed, very love oh: http://www.cnblogs.com/yisheng163/p/4524808.html? Utm_source = tuicool