基于JＳＰ技术的ＷｅｂＧＩＳ

《基于JＳＰ技术的ＷｅｂＧＩＳ》由会员分享，可在线阅读，更多相关《基于JＳＰ技术的ＷｅｂＧＩＳ（10页珍藏版）》请在装配图网上搜索。

1、附录1 外文参考文献（译文）基于技术的1 Web GIS概述Web GIS是利用互联网技术，完善和扩展传统的地理信息系统功能的一门新技术。通过网络，GIS的功能得以扩展，真正成为一种大众使用的工具。用户可以浏览Web GIS站点中的空间数据、制作专题地图，进行各种空间检索和分析。与传统的GIS相比，Web GIS体系结构发生了根本性的转变，它基于浏览器/服务器体系(浏览器、中间件服务器、数据库服务器)，三层客户机/服务器模型(用户界面层、中间件服务器、GIS数据层)，以及Web环境，采用TCP/IP通信协议来扩大空间数据共享范围。采用客户端/服务器多层体系结构提高系统的安全性，可重用性。在应用

2、层采用HTTP议增强GIS的开放性。Web GIS的发展为GIS数据与信息的获取、发布、共享与操作开辟了广阔的前景，和传统的GIS相比，具有以下优点：（1）更广泛的访问范围。（2）平台独立。（3）系统成本降低。（4）操作简单。2 Web GIS的实现技术随着网络技术的发展，出现了多种实现Web GIS方法，如CGI，ISAPI，Java，ASP等。2.1基于CGI和Web API的被动式Web GISCGI(Common Gateway Interface)是最早用来建立动态Web资源的技术，它是外部应用程序和Web服务器之间的接口标准，可让浏览器与服务器之间产生互动的关系。基于CGI技术的W

3、eb GIS系统在用户发出一个请求时，服务器把请求通过CGI转发给后端GIS应用程序，应用程序生成的结果又通过服务器传回客户端。基于CGI技术实现Web GIS的优势在于服务器软件之间的可移植性，缺陷是其浏览器的请求与生成的进程一一对应，它的进程通常都不在常驻系统内，只要有客户需求送置，服务器就要建立一个新的进程，致使多个用户同时访问时，系统资源占用过多，执行效率低。Web API是建立在CGI技术之上的另一类应用程序接口，实际应用中主要有Microsoft的ISAPI。它用动态链接库取代CGI程序，不会在系统中产生新的进程，资源共用，因而响应速度比CGI要高。但基于Web API的Web G

4、IS与服务器联系较紧，用户发出的所有请求都在服务器端完成，客户端仅起了一个图形终端的作用，对服务器性能要求较高，程序移植难度大，也容易使服务器瘫痪，并且其没有统一标准，通用性差。2.2基于ASP和Java的主动式WebGISASP是微软公司推出的动态网页技术，可以在HTML程序码中内嵌VBScript或JavaScript，服务器端还需安装适当的编译程序引擎。客户端请求ASP网页时，ASP文件由服务器端的ASP Engine解释执行，源程序不会传到浏览器，但它的安全性仍不是很好，必需随时注意微软公司的新补丁，以便更新系统。基于ASP的Web GIS还必须和IIS(Internet Inform

5、ation Server)，ActiveX紧密相连，ADO(ActiveX Data Object)作为数据库访问控件，用它使客户端的程序通过BC和OLE DB来操纵GIS数据。并且ASP执行环境仅限于Microsoft Internet Information Server，Microsoft Site Server和Personal Web Server，缺乏跨平台的特性。另一方面，每当客户端请求ASP网页时，服务器端都必须重新编译一次，在执行效率上略显不足。Java语言正是针对Internet应用而开发的编程语言，也是一种面向对象、支持多线程、体系结构独立的解释型动态语言，具有高度的安全

6、性、可移植性和代码重用性，它具有“一次编译，处处运行”的效果，支持Web计算模式，能实现Web的数据分布和操作分布。Java的特殊性质使它成为开发Web GIS的主流技术。它利用URL对象可以分布式访问具有URL的数据对象，通过在客户端下载Java Applet小程序完成GIS功能，实现对分布式数据的操作，但在实现大型GIS任务时能力受限制。3 基于JSP技术实现Web GIS3.1JSP简介JSP(Java Server Pages)是由Sun微系统公司于1999年6月推出的一种建构在Servlet技术之上的Web技术，JSP将Servlet中的HTML代码脱离了出来，从而可以加速Web应用

7、开发和页面维护。在这种技术中你可以将Java代码嵌入到HTML文件，服务器将自动为页面创建一个Servlet。利用JSP可以建立跨平台的、更加先进和安全的动态网站。JSP的最大特点是将内容的生成与显示分离。使用JSP技术，Web页面开发人员可以使用JSP标记或小脚本来生成Web页面上的动态内容。生成内容的逻辑被封装在JSP标记和JavaBean组件中并运行于服务器端，由JSP引擎解释执行。在JSP中大量的Java程序代码可以封装于与平台无关的JavaBean中，而只留下极少的标记用于调用Bean，这样就避免了代码的混乱性。除了JavaBean外，Enterprise Java Bean (EJ

8、B)和Remote MethodInvocation (RMI)等对象都可以很容易在JSP中访问到。JSP使用JDBC(Java DataBase Connectivity)/JDO技术访问数据库，对于只有ODBC的数据库，使用SUN公司的JDBC-ODBC桥程序来连接访问。服务器端生成的结果以HTML或XML页面的形式返回，保护了代码的安全性。JSP属于服务器端程序设计语言，基于Web层(三层)客户机/服务器应用模型，将用户界面层、事物逻辑层和数据层分开来，利用Java的跨平台性，具有一次编写，处处运行的优点。以服务器端调用JSP的方式来分，它的基本模型一般情况下可分两种：一是服务器请求JS

9、P，由JSP调用可重用的JavaBean组件来执行任务，譬如访问数据库、设置属性等。另一种是不用JavaBean，服务器只请求一个Servlet，它生成响应所要包含的动态内容，再激活一个JSP用来表示生成的内容。3.2基于JSP的Web GIS基于JSP的Web GIS由于与数据库联系较紧，一般采用JavaBean组件技术。JSP用Java组件JavaBean执行确定任务和封装对象数据，JSP与JavaBean的关系就像ASP与COM的关系，COM对象常用于帮助从ASP网页中分离出逻辑或计算的代码，可以在任何允许标准对象模型的语言中引用，而JavaBean仅限于Java程序设计语言，比COM更

10、易于开发，只要通晓Java，就很容易掌握JavaBean的结构。在ASP中使用COM对象必须在服务器上注册，对象改变时，服务器需重新启动，而JavaBean不需在服务器上注册，对象改变时，只需重新启动对象即可。用JSP技术实现的Web GIS， JSP应用程序置于Web服务器端，当用户请求JSP网页时，JSP程序将自动送给JSP引擎(JSP Engine)处理，它将程序中的Java代码分离出来，生成Servlet，若无语法错误，则编译成class文件后，载入Java VM(Java Virtual Machine)执行(这是JSP程序的惟一一次执行)。当客户端有请求时，JSPEngine会同时

11、为每一个请求产生一个请求对象(Request)和回应对象(Response)传入Servlet的_JSPService ( )方法，JSP调用封装了访问GIS数据库、撷取和提供内部属性功能的JavaBean，将请求参数传给Bean组件，由Bean动态计算处理结果，JSP获取相关信息后传回HTML形式表现结果。这样客户端看到的只是转换过的HTML文件，有效地隐藏了JSP源代码，保证了安全性，由于JSP不需要每次请求都编译，速度有所提高。4 实际应用Web GIS用JSP从Oracle数据库中读取数据与用户进行交互，在客户端下载Java Applet，实现地图的发布、比例放缩、信息查询功能。系统采

12、用浏览器/服务器结构模式，由浏览器发出请求给Web服务器(Apache/Tomcat等等)，Web服务器将请求送给相应的由JSP中的Java代码生成的Servlet，Servlet负责激活设定了相关属性的JavaBean，由JavaBean与数据库相连接，在服务器端进行数据的各种查询、分析、检索等操作，这样每次JSP询问JavaBean组件属性时，JavaBean动态处理并将结果传给浏览器，由浏览器显示结果给用户。5 结束语本文对JSP技术与Web GIS其他实现技术进行了介绍，由于JSP使用Java作为脚本语言，具有跨平台性，JSP与JavaBean技术相结合，为Web GIS的开发带来了极

13、大的便利。实践证明，使用JSP技术开发Web GIS优越于以前的CGI，ASP等等技术。相信在不久的将来，JSP技术会日益成熟，并将有力推动Web GIS的发展。附录2 外文参考文献（原文）Web GIS on the basis of JSP technology1 Web GIS summary Web GIS utilizes Internet technologyimproves and expands a new technology of the traditional geographical function of information system. Through the

14、 network, the function of GIS can be expanded, really becomes a tool which a kind of masses used with. Users can be in order to have a look around the space data in Web GIS website, make thematic map, search and analyze various space. Compared with traditional GIS, last fundamental one transition We

15、b GIS system structure,last browser / server system (browser it, in the middle of pieces of server, database server), three layers of client / server model (user interface layer, the middle a server, GIS data layer), and Web environment, adopt TCP/IP communication protocol come, expand space datum s

16、hare the range. Adopt the customer end / multi-layer system structure of server to improve systematic security, reusable. Employing layer to adopt HTTP to discuss and strengthen the opening of GIS.To develop into GIS data with obtain, issue, sharing and operating and opening vast vistas of informati

17、on Web GIS, compared with traditional GIS, have the following advantages: (1)More extensive visit range. (2)Independence of the platform. (3)The systematic cost is reduced.(4)Easy to operate. Implementation technique of 2 Web GIS With the development of network technology present, realize Web GIS me

18、thod while being many kinds of, for instance CGI, ISAPI, Java, ASP,etc.2.1 passive form Web GIS based on CGI and Web API CGI (Common Gateway Interface) is the technology used for setting up dynamic Web resources initially, it is a interface standard between application program of outside and Web ser

19、ver, can let browser and server produce the interdynamic relation. When users send out a request, server transmit through CGI to back GIS application program asking on the basis of CGI Web GIS system of technology, result that application program turn into pass the customer end back through the serv

20、er. The advantage based on CGI technology Web GIS lies in the portability between the server software, Defect request and process one-to-one correspondence that produce of browser their, usually in resident system process of it, have customer demand give, put, server establish a new process, while c

21、ausing a lot of users to visit at the same time, systematic resources are taken up too much, it is low to carry out efficiency.Web API is another kind of application program interface based on CGI technology, mainly there is ISAPI of Microsoft in practical application. It can not produce the new pro

22、cess in the system by chaining the storehouse and replacing CGI procedure dynamically, resources share, therefore the response speed is higher than CGI. But based on Web API Web GIS and server get in touch relatively urgent, all that user send out ask end finish in server, the customer end is only g

23、iven the terminal function of a figure, have relatively high expectations for server performance, the procedure transplants the difficulty heavily, aptly to make the server paralysed too, and it has not sought unity of standard, the commonability is bad.2.2 active WebGIS ASP based on ASP and Java is

24、 the dynamic webpage technology that Microsoft puts out, can inlay VBScript or JavaScript inside in HTML procedure yard, server end need to install the appropriate compiler engine yet. Customer end ask for ASP when the webpage, ASP , carry out by ASP Engine of end by server, source program can pass

25、browser to, but its security is not still very good, must pay attention to the new patches of Microsoft at any time, in order to upgrade the system. Web GIS on the basis of ASP must also be with IIS (Internet Information Server), ActiveX links up closely, ADO (ActiveX Data Object) visit controlling

26、part as database, make procedure of customer end handle GIS data with it by BC and OLE DB.And ASP carries out the environment and is only limited to Microsoft Internet Information Server, Microsoft Site Server and Personal Web Server, lacks the characteristic of stepping the platform. On the other h

27、and, customer end ask for ASP when the webpage, server end must recompilate once, slightly show insufficiently in carrying out efficiency.Just to programming language that Internet employ and develop Java, it is a kind of explanation type dynamic language facing the target, supporting many thread, s

28、ystem to be with independent structure too, have high-level security, portability and code, it compiles once, if operate everywhere , support Web to calculate the mode, can realize the data of Web are distributed and operated and distributed. The special properties of Java make it become major techn

29、ology of developing Web GIS. It utilizes URL target to visit the data target with URL distributedly, through downloading Java Applet little procedure to finish GIS function on the customer end, realize the operation of the distributed data, but ability is restricted while realizing large-scale GIS t

30、ask.3because of JSP technology Web GIS 3.1JSP pro buildconstruct in Servlet Web technology on the technology on one that will it be June 1999 put out by Sun little system Company, JSP break away HTML code of Servlet, can accelerate Web application and development and page maintain. You can imbed Jav

31、a code to HTML this kind of technology, the server will establish one Servlet automatically for the page. Utilizing JSP can be set up and stepped the platform, more advanced and more safe dynamic website.Most great characteristic of JSP formulation of content with reveal, separate. Using JSP technol

32、ogy, Web page developer can use JSP mark or bound foot to actually produced the dynamic content on Web page. The logic of producing the content is encapsulated in the package of JSP mark and JavaBean and operated in the end of the server, explained that carries out by JSP engine. A large number of J

33、ava procedure code can be encapsulated in JavaBean having nothing to do with the platform in JSP, leave few mark use for transferring Bean, avoid the confusion of the code in this way only. Besides JavaBean, targets such as Enterprise Java Bean (EJB) and Remote MethodInvocation (RMI),etc. can all be

34、 very easy to visit to in JSP.JSP uses JDBC (Java DataBase Connectivity) / JDO technology to visit the database, for database to have only ODBC, use SUN JDBC-ODBC bridge procedure of Company join visiting. The result that the server turns into end returns in the form of HTML or XML page, protect the

35、 security of the code.JSP server end programming language, (three F), client / server employ models on the basis of Web layer, come user interface layer, thing logic layer separately with data layer, utilize stepping the platform of Java, once is written, the advantage operated everywhere. Adjust, d

36、ivide with way of JSP by end by server, basic model of it can divide two kinds into generally speaking:First, server ask JSP, is transfer, execute the task by JSP with reusable JavaBean package, for example visiting database, setting up attribute,etc. Another kind does not use JavaBean, the server o

37、nly asks one Servlet, it produces and responds dynamic contents included, activate another JSP used for content turned into to show.Web GIS based on JSP Because based on JSP Web GIS contact database relatively urgent, generally adopt JavaBean package technology. JSP carry out task of confirming and

38、encapsulate target data by package JavaBean with Java, JSP and just like ASP and relation of COM relation of JavaBean, COM target use for, help, isolate logic or code of calculation in the webpage from ASP often, can quote in the languages of the standard targets model of any permission, and JavaBea

39、n is only limited to Java programming language, develop more readily than COM, understand thoroughly Java is very structure to know JavaBean more. Use COM target to register on the server in ASP, when the target changes, the server needs to restart, JavaBean does not need to register on the server,

40、when the target changes, only need to restart the target.Use JSP Web GIS of technology, JSP application program put to Web server end, when users asks for JSP webpage, JSP procedure will deal with for JSP engine (JSP Engine) automatically, it separates Java code in the procedure out, produce Servlet

41、, except for grammar mistake, compile class behind the file, write into Java VM (Java Virtual Machine) carry out (whether this carry out JSP an only once of procedure). When the customer end is asked, JSPEngine will produce a request target (Request) and respond the target (Response) to spread into

42、Servlet for every request at the same time _ JSPService () method,it transfer JSP it encapsulate it last GIS database, it pick fetch and attribute the JavaBeans of the functionses internal will be offered, ask for parameter pass Bean package to, calculate result dynamically by Bean, JSP obtain behin

43、d the relevant information passing back HTML form display result. In this way what the customer end is seen is only HTML conversion, hide JSP source code effectively, guarantee security, because JSP does not need each request to translate and edit, the pace is improved to some extent.4 employs Web G

44、IS to read data and user to carry on mutually from Oracle database with JSP actually, download Java Applet on the customer end, realize contracting, information inquiry function is put in the issue, proportion of the map. System adopt browser / server structural mode, send out, ask, give Web server

45、(Apache/Tomcat,etc.) by browser, Web server ask, give a corresponding one by Java Servlet that code turn into of JSP, Servlet responsible for, activate, establish relevant JavaBean of attribute, linked with database by JavaBean, carry on the various inquiry, analysis of the data, search etc. to oper

46、ate in the end of the server, so each time when JSP inquires JavaBean package attribute, JavaBean deals with dynamically and passes the result to the browser, the browser reveals the result is given to users.5 conclusion this text realize to JSP technology and Web GIS technology make an introduction

47、, because JSP uses Java as the script language while being other, step platform nature, JSP and JavaBean technology combines together, has brought the great facility to the development of Web GIS. Practice has proved, have used JSP technological development Web GIS to be superior to CGI in the past,

48、 technology such as ASP. It is believed that in the near future, JSP technology will be ripe day by day, and will promote the development of Web GIS effectively.References: 1Chen JunJie, Chen CanZhang. Web GIS technology and implementation method J. The journal of institute of technology of Taiyuan,

49、 2000, 31 (4): 394-396.2Zhou YanKun, Li ManChun. Web GIS development approach comparative study J. Application study of the computer. 3Qi MingYao, the Milky Way of the pool, Huo Liang. Enterprise layer solution discussion of Web GIS C. The journal of South China Normal University (natural science edition), 2001, 7:50-55. Ext. stick on Chinese thesis download center 10 / 10