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1、中英文资料翻译With thepopularity of theInter NET applications, avarietyofWeb InformationSystemHasbecome a pressing issue. Establish the essence of Web informationsystemsDevelopmentof a Web repository (database asthecoreof avarietyof Web letterInformationstorage) asthecore Web applications. Currently,theWeb
2、 repositorydevelopment technologyOperation of awiderangeof differentcharacteristics. Variousperiods atalllevels, avarietyofpurposesTechnology co-exist, dizzying mirror chaos,itisdifficultto choose. More popularJava ofSer vet Web repository development program amorepracticalOf choice.Servlet is runni
3、ng the applet ontheWebserver, canbecompleted XuMulti-client Applet cannotcomplete thework,whichruns ontheserver and clientsNo end,donot download donot by the client securityrestrictions, the running speedGreatly increasedAndApplet running in a browser and extend the browsers ability similarLike, Ser
4、v thelet run in theWeb server to enable Java Serv thelet engineAnd expand the capacity of the server. Therefore,wecansay Serv thelet is run inApplet onaWebserver, Serv thelet JavaServletAPIAnd Jav a program of classes and packages.1 Servlet access model2 Serv the let, there are three access models:(
5、1) an access model1 browser to Web server to issue a retrieval request.2 the Web server after receipt of the request, the request forwarded to the Servle tengine.3 Serlet engine to perform the requested the Ser vlet and directly through JDBC4Servlet throughJDBC toretrieve searchresults to generate t
6、he html pageandPage backto the Webserver.5 the Web server the page is sent back to the browser.(2)The second access model1 browserto Webserver to issue a retrieval request.2 theWeb serverreceivestherequest afterthe request forwardedto the ofSer v theletengine.3 Serv let engine to perform the request
7、 the the Ser vlet and retrieve sentJa, vabean access to the data.4data access the Javabean searchabledatabase throughJDBC informationAnd fromthesearchresults stored in itself.5Servlet remove searchresults from the data access Javabean generateHtml pageand Ht mlof page backtothe w eb server.6 the Web
8、 server the page is sent back to the browser.(3) The third access model1 A browser issue a retrieval request to the Web server.2 Web server receives the request after the request forwarded to the of Ser v the let engine.Of Ser vlet engine to perform the requested Servlet directly through JDBC inspec
9、tion3 The cable database and search results are stored in the result isstored the Jav abean into.Javabean,4. Ser v the let from the results are stored to remove the search results and JSP files to format the output page.2 Servlet functionality and life cycle2.1 Servlet functions(1) Create andreturn
10、dynamicWebpages based on customerrequests.(2) create canbeembeddedinto existing HTMLpages aspartof HTMLPage(HT fragment) of theML.(3) and other serverresources (includingdatabases and applications based on the Jav aProgram) tocommunicate.(4) to handle multiple client connections,receiving the input
11、of more than one client,andTheresults broadcastto multipleclients. For example,Ser vlet isa multi-participantGameserver.(5) ofMIM E type filter information on the specialhandling,suchas imageConversionand server-side include (SSI).(6) custom processing available to all servers in the standard routin
12、e.2.2Servlet lifecycleServlet lifecycle begins with itinto the WebserversmemoryAnd end in the termination or re-loaded Serv the let.(1) load.Load the servlet at the following times:1.If you have configured automatic load option, and then start the Web server automatically loaded2. After the start of
13、 the Web server, the client Serv the let issued for the first time, please Demand.3. Reload Serv the let.Loaded Servlet,Webservers tocreatea servletServlets initmethod is called. Servlet initialization parameters in the initializationThe number is passed to the Servlet configuration object.instance,
14、 and()phase,(2) terminateWhen the Webserver nolonger needs the servlet, or reload ServletA new instance of the server calls Serv thelets destroy() method, removeitfromtheMemory deleted.3 How to call ServletMethod of Ser vlet is called Total fivekinds: call intheURL in the formTag call, call, in HT t
15、heML page in the JSPfilesCall, call in an ASP file. The following itemized to be introduced.(1) call the servlet in the URL.Simply inputformat inthebrowser as http:yourwebserverthe same the ser vlet name name /servlet path/ servlet theURL toThe site canbe. Ofwhich:your webser ver name is to refer to
16、 the Servlet wheretheWeb server name, theservlet pathis the path referstothe Servlet, theservletThe name refers to the Servlet real name or an alias.(2) call the Servlet tagsCall of Ser the let the the tag allows users to input data on the Webpage, andinputdata submittedtothe vlet ofSer.Serv thelet
17、will be submitted toreceivedata indifferentways.Forexample: place the text input area tags, buttons and other logos(3) in the HTML page to call the servlet.Use mark tags, no need to create a complete HTML page.Instead,the servlet output isonly part of the HTMLpage (HTML fragment)and dynamicallyembed
18、ded into the static text in the original HTML page.All this happened on the server andsent to the user only the resulting HTML page. tag contained in the originalHTML page.Servletwill beinvoked in thesetwomarkers and the Servlet response will cover these two markersbetween all things and mark itself
19、, for example: SERVLET NAME=“my serv let”CODE=“my serv let .class ”CODEBASE=“u r l ”initpar am=“v alue ” PARAM NAME=“parm1 ”VALU E=“v alue1 ” PARAM NAME=“parm2 ”VALU E=“v alue2 ”? /SERVLET (4) call the servlet in the JSP files.Call in the JSPused by the Servlet and HTML page tocall exactlythesame.An
20、dthe principles areidentical. Only reconcile its dynamic JSPnota static HTML page.(5) in an ASPthe servlet.If you Micr oso ft I nt ernet Informatio n-Ser ver (II S) on the legacy of the ASPfile, and cannot be ASPfiles transplanted into a JSPfile, youcanuse the ASPofSer vlet iscalled.Butitmustbe thro
21、ugh a special ActiveX control, anASPonlythrough itcan callthe servlet.4 Servlet Howto use ConnectionManager toefficiently manage the database connection(1) the functionality of the Connection Manager.For non-Web applications, Web-based application access to the database will lead tohigher and unpred
22、ictable overhead, which is due to more frequent Web users connect anddisconnect.Normally connected to the resources used and disconnect from the databasewill farexceed the resources used in the retrieval.Connection Manager function is to minimize the additional occupancy of the users of the database
23、 resources to achieve thebest performance of database access.Connection Manager sharing overhead through the establishment of the connection poolwill connect users Servlet available to multiple users request.In other words, each userrequest only the connect/ disconnect with a small portion of the ov
24、erhead costs.Initialresources to establish the connection of the buffer pool, the rest of the connect/ disconnectoverhead is not big, because this isonly reuse the existing connection.Serv the let in the following manner using the connection pool: When a user throughRequest Web Serv the let the let
25、Serv use an existing connection from the buffer poolNext, this means that the user requests do not cause the connection to the databasesystem overhead. InAfter the termination of serv the let it connect to return to the pool for its Connection ManagerThe Ser vlet. Thus, the user request does not cau
26、se the database is disconnectedOf system overhead.Connection Manager also allows users to be able to control the concurrency of thedatabase products evenThen the number. When the database license agreement limit the number of users, this feature isVery useful. Create a buffer pool for the database,
27、and connection managementBuffering pool maximum number of connections parameter set to the database product license limitGiven maximum number of users. If you use other programs without Connection Managerconnections Database, you can not guarantee that the method is effective.(2) the structure of th
28、e Connection Manager.(3) Connection Manager connection pool to maintain a connection to a specific database is open. Step 1: When the first Serv the let trying to Connection Manager communications is loaded by the Java Application Server Connection Manager. As long as the Java application server run
29、ning the Connection Manager has been loaded. Step 2: The Java application server passes the request to a servlet. Step 3: Servlet Connection Manager requests a connection from the pool. Step four: the buffer pool to Ser vlet allocated a pool of existing idle connection. Step 5: servlet to use to con
30、nect a direct dialogue with the database, this process is the standard API for a particular database. Step 6: the database through Ser vlet the connection returns data. Step 7: When the Servlet end to communicate with the database, servlet connections returned to the connection manager pool for othe
31、r servlet uses. Step 8: Servlet Jav a application server to the user sends back response.Servlet requests a connection, if the buffer pool, there is no idle connection, then the connection manager directly communicate with the database. Connection Manager will: Step 9: to the database requests a new
32、 connection. Step 10: Add connections to the buffer pool. If the buffer pool is connected to the prescribed ceiling, connect to the serverWill not be a new connection to join the buffer pool(3) the performance characteristics of the Connection Manager. Buffer pool to create a new connection is a hig
33、h overhead tasks, new connections will use the resources on the database. Therefore, theConnection Manager the best use of existing connections of the buffer pool to meet the request of the Servlet. Meanwhile, the connecting tubeThe processor must be as much as possible to minimize the buffer pool i
34、dle connections, because this is a great waste of systemresources. Connection Manager Serv the let with the implementation of these minimize and maximize task. Connection Manager to maintain each connection verification time stamp, and recently used tags and use the logo. When the a Ser vlet first t
35、he connection, connection verification time stamp, and most recent time stamp is set to the current time, the connection is being used flag is set to true.Connection Manager can be removed from a Serv the let a long-unused connections, this length of timespecified by the Connection Manager, the long
36、est cycle parameters.Connection Manager can view recently used mark is being used to connect. If the time between the most recently used time and time difference is greater than the longest cycle configuration parameters, the connection will be considered to be a residual connection, which indicates
37、 Serv the let take its discontinued or no response. Residual connection will be returned to the pool for other Ser vlet, it is being used flag is set to false, authentication and time stamp is set to the current time.If Ser vlet is ready within a longer period of time to use the connection with the
38、database several timesCommunications, you must code to the Serv the let, so that each time you use to connectConfirm that it still occupies this connection.Connection Manager can be removed from the buffer pool idle connections, because theyWould be a waste of resources. In order to determine which
39、connection is idle, Connection Manager will checkInvestigation connected the sign and time stamp, this operation is connected by periodic access toBuffer pool information. Connection Manager checks have not been any Ser vlet makeWith the connections (these connections is to use the logo is false). I
40、f you have recently usedBetween time and the current time difference exceeds a maximum idle time configuration parameters, theThat the connection is idle. Idle connection will be removed from the buffer pool, down toMinimum number of connections configuration parameter specifies the lower limit valu
41、e.翻译： 随着 Inter net的普及应用 ,各种 Web 信息系统的建立已成为一个迫在眉睫的问题。建立 Web 信息系统的实质就是开发一个以 Web 信息库 ( 以数据库为核心的多种 Web 信息存储 ) 为核心的 Web 应用系统。目前 ,Web 信息库开发技术的种类繁多 , 特点各异。各个时期、各个层面、 各种用途的技术并存 , 令人眼花镜乱 , 难以选择。而目前较为流行的基于 Java Ser vet 技术就是 Web 信息库开发方案的一种比较实用的的选择。Serv let是运行在 Web 服务器上的 Applet,可以完成许多客户 Applet不能完成的工作 ,它运行在服务器上
42、,与客户端无任何关系 ,不用下载不用受到客户端安全限制,运行速度大大提高。与 Applet运行在浏览器上并扩展浏览器的能力相类似, Serv let运行在启用Java Serv let引擎的 Web 服务器上并扩展该服务器的能力。因此,可以说 Servlet就是运行在 Web 服务器上的 Applet,Serv let就是使用 Jav a Ser vletAPI及相关类和软件包的 Jav a程序。 1Servlet的访问模型Serv let有三种访问模型 :( 1)第一种访问模型。1 浏览器向 Web 服务器发出检索请求。2Web 服务器收到请求后将请求转交给Ser vlet引擎。3Serv
43、let引擎执行所请求的 Ser vlet并通过 JDBC 直接检索数据库中的信息。4Ser vlet通过 JDBC 取回检索结果生成 html 页面并将页面送回 Web 服务器。5Web 服务器将页面发送回浏览器。( 2) 第二种访问模型1浏览器向 Web 服务器发出检索请求。2Web 服务器收到请求后将请求转交给Ser v let引擎。3Serv let引擎执行所请求的 Ser vlet并将检索式发送给数据访问 Ja vabean 。4数据访问 Ja vabean通过 JDBC 检索数据库中的信息并将从检索结果存储在自身之中。5 Ser vlet从数据访问 Javabean 中取出检索结果生
44、成 Html 页面并将 Ht ml页面返回给 w eb 服务器。6Web 服务器将页面发送回浏览器。( 3)第三种访问模型 ( 见图 3) 。1浏览器向 Web 服务器发出检索请求。2Web 服务器收到请求后将请求转交给Ser v let 引擎。3Ser vlet引擎执行所请求的 Serv let直接通过 JDBC 检索数据库并将检索结果存储在结果存储 Jav abean 之中。4Ser v let从结果存储 Jav abea n 中取出检索结果并用 JSP 文件格式化输出页面。5将格式化后的输出页面发送给 Web 服务器。6 Web 服务器将页面发送回浏览器。2Servlet的功能与生命周期2. 1Ser vlet 的功能( 1)创建并返回一个基于客户请求的动态Web 页面。( 2)创建可嵌入到现有 H