Distributed System reading notes (ix)-----WEB Service Service

First, Introduction

Web Service In a nutshell is that it provides a service interface that enables clients to interact with the server side in a very different way than the normal browser mode. In Web service, it is usually transmitted and communicated in XML format. This also involves the security of XML operations.

1. Web service is an extended form of Web server.

2. The XML data format used by Web service ensures readability.

3, a standard Web service through a URI Uniform Resource Identifier is accessed by the client, the value of the URI can be 2 ways, one is the URL resource Uniform Locator 2, or a URN Uniform Resource name character.

4. A service description language is provided in the Web service, typically represented as WSDL, which contains the definition of the interface and some other information.

Second, Web Services

1. A Web service interface contains a collection of operations that can be invoked by the client, and most Web service services can operate in the form of soap information.

2, an effective agent can be based on each service open interface to coordinate, integration of multiple service services.

3, the characteristics of the WEB service makes the structure in the distributed system become more loosely coupled.

4, the characteristics of the Web service makes him more loosely coupled: 1, the definition and implementation of the program through the form of interface separation. 2. Web service can be accessed through a restful interface. 3, in the transmission of data can be used in the asynchronous message mode.

5, the format of the message using XML is enhanced in terms of readability, but it brings the overhead of occupying space, as well as the cost of parsing language and so on.

6. A reference to a service is distinguished by a unique URL Uniform Resource identifier for each Web service.

7. The most primitive soap is a structure based on the HTTP protocol that makes communication between the client and the server.

8, a standard SOAP message format is also in XML format, including a header, and body message body part. The Body topic section includes parameter information or a reply message.

9. The maximum difference between a remote object reference in a distributed object and a URI in a Web service is that one instance can be created by the client, and the latter cannot be created instance.

10, before the Distributed Object Service CORBA architecture domain The advantage of Web service ratio is that his service coverage is large, in CORBA, for things, security access control and other aspects have corresponding operations.

third, service description and IDL interface Definition language of WEB service

1, in the language of the environment first, is through the service Description language in the XML format to communicate.

2. In the context of a Web service, WSDL is used to do the service description. The WSDL contains a number of components, including definitions, types, messages, bindings, services, and so on.

3. The package in WSDL describes the message that will be used to interact.

Iv. Directory services used in the Web service

1, here the directory as long as the reference is UDDI, through this service, you can use the name or attribute to find the corresponding service, similar to Jndi.

2, the inside of the data is organized into four kinds of structure, each structure can be searched by key to find out, 4 major structures are: 1, businessentity,2, businessservices,3, BindingTemplate4, TModel.

3. In UDDI, there will be a copy storage mechanism after registration.

v. XML data security mechanism

The message format of XML is used extensively in the service of Web service, so the security is not underestimated. Here are some security measures.

1. Transfer data in a secure channel similar to SSL.

2, for the XML Information format of the user's privacy data for partial encryption, but to specify the start label location and end tag location.

3. The algorithm of data signature for XML data.

4, the XML data can be first base64 the plaintext transcoding and then the encryption algorithm processing.

VI. coordination between WEB service services

The main point here is to coordinate the various services through a WSDL-based approach.

vii. Application of WEB service

With the deployment and development of Web services, a SOA-oriented architecture is derived, with examples of grid grid computing and cloud computing cloud computing.

1, first, SOA service-oriented architecture refers to a loosely coupled service group, the specific services can be dynamically discovered and loaded, the services can be mutually coordinated and cooperation.

2. Web service typically applies to cloud computing, such as Amazon's AWS services, with ES2 elastic Deployment Services, and S3 Simple object storage services, which are used in a simple interface open form.

References: <<distributed sysytems Concepts and design>> original version fifth, Author:george Coulouris,jean Dollimore, Tim Kindberg,gordon Blair

Distributed System reading notes (ix)-----WEB Service Service