外文文献
JSP Technology and Servlets
JSP profile
JSP (JavaServer Pages) is initiated by Sun Microsystems Inc with many companies to participate in the establishment of a dynamic web page technical standards JSP technology somewhat similar to ASP technology it is in the traditional HTML web page document (* htm * html) to insert the Java programming paragraph (Scriptlet) and JSP tag (tag) thus JSP documents (* jsp) Using JSP development of the Web application is cross that can run on Linux is also available for other operating systems
JSP technology to use the Java programming language prepared by the category of XML tags and scriptlets to produce dynamic pages package processing logic Page also visit by tags and scriptlets exist in the services side of the resources of logic JSP page logic and web page design and display separation support reusable componentbased design Webbased application development is rapid and easy
Web server in the face of visits JSP page request the first implementation of the procedures of and then together with the results of the implementation of JSP documents in HTML code with the return to the customer Insert the Java programming operation of the database can be reoriented websites in order to achieve the establishment of dynamic pages needed to functionJSP and Java Servlet is in the implementation of the server usually returned to the client is an HTML text as long as the client browser will be able to visit
JSP 10 specification of the final version is launched in September 1999 December has introduced 11 specifications At present relatively new is JSP12 norms JSP20 norms of the draft has also been introducedJSP pages from HTML code and Java code embedded in one of the components
JS script language synopsis
JS is javascrip Javascript is one kind the script language which comes by the Netscape LiveScript development the main purpose is to solve the server terminal language for instance Perl carryover speed question At that time served the end to need to carry on the confirmation to the data because the network speed was quite slow only then 288kbps the confirmation step waste＇s time were too many Therefore Netscape browser Navigator has joined Javascript has provided the data confirmation basic function
The JavaScript official name is ECMAScript This standard by ECMA organization development and maintenance ECMA262 is the official JavaScript standard This standard based on JavaScript (Netscape) and JScript (Microsoft) Netscape (Navigator 20) Brendan Eich has invented this language started from 1996 already appeared in all Netscape and in the Microsoft browser The ECMA262 development began in 1996 in 1997 July the ECMA general meeting has accepted its first edition
The script uses one specific descriptive language rests on certain form compilation to be possible the execution document is also called as great or the batch run document The script usually may transfer temporarily by the application procedure and carry out Each kind of script present widely is applied in the homepage design because the script not only may reduce the homepage the scale and raises the homepage browsing speed moreover may enrich the homepage performance like animation sound and so on Cites a most common example when we click in the homepage the Email address can transfer Outlook Express or the Foxmail this kind of mail software automatically is realizes through the script function Also because of script these characteristics the human who harbors ulterior motives by some are often using For example joins some destruction computer system＇s order in the script like this works as the user browsing homepage once transfers this kind of script will then cause the user the system to come under the attack Therefore the user should act according to visits homepage the trust degree selective security rank specially regarding these itself content on the illegal homepage do not permit the use script easily Through the safe establishment the dialog box the choice the script under option each kind of establishment may with ease realize to script being forbid and begins using
JSP and Servlets
The technology of JSP and Servlet is the most important technology which use Java
technology to exploit request of server and it is also the standard which exploit business application Java developers prefer to use it for a variety of reasons one of which is already familiar with the Java language for the development of this technology are easy to learn Java to the other is a preparation run everywhere to bring the concept of Web applications To achieve a oneprepared everywhere realized And more importantly if followed some of the principles of good design it can be said of separating and content to create highquality reusable easy to maintain and modify the application For example if the document in HTML embedded Java code too much (script) will lead the developed application is extremely complex difficult to read it is not easy reuse but also for future maintenance and modification will also cause difficulties In fact CSDN the JSP Servlet forum can often see some questions the code is very long can logic is not very clear a large number of HTML and Java code mixed together This is the random development of the defects
Early dynamic pages mainly CGI (Common Gateway Interface public Gateway Interface) technology you can use different languages of the CGI programs such as VB C C + + or Delphi and so on Though the technology of CGI is developed and powerful because of difficulties in programming and low efficiency modify complex shortcomings it is gradually being replaced by the trend Of all the new technology JSP Servlet with more efficient and easy to program more powerful more secure and has a good portability they have been many people believe that the future is the most dynamic site of the future development of technology
Similar to CGI Servlet support request response model When a customer submit a request to the server the server presented the request Servlet Servlet responsible for handling requests and generate a response and then gave the server and then from the server sent to the customer And the CGI is different Servlet not generate a new process but with HTTP Server at the same process It threads through the use of technology reduce the server costs Servlet handling of the request process is this When received from the client＇s request calling service methods the method of Servlet arrival of the first judgement is what type of request (GET POST HEAD…) then calls the appropriate treatment (DoGet doPost doHead…) and generate a response
Although such a complex in fact simply said to Servlet is a Java class And the general category of the difference is that this type operating in a Servlet container which can provide session management and targeted lifecycle management So that when you use the Servlet you can get all the benefits of the Java platform including the safety of the management use JDBC access the database and crossplatform capability Moreover Servlet using thread and can develop more efficient Web applications
JSP technology is a key J2EE technology it at a higher level of abstraction of a Servlet It allows conventional static and dynamic HTML content generated by combining an HTML page looks like but as a Servlet to run There are many commercial application server support JSP technology such as BEA WebLogic IBM WebSphere JRun and so on JSP and Servlet use more than simple If you have a JSP support for Web servers and a JSP document you can put it Fangdao any static HTML files can be placed do not have to compile do not have to pack do not have to ClassPath settings you can visit as ordinary Web It did visit the server will automatically help you to do other work
JSP document looks like an ordinary static HTML document but inside contains a number of Java code It uses Jsp the suffix used to tell the server this document in need of special treatment When we visit a JSP page the document will first be translated into a JSP engine Java source files is actually a Servlet and compiler and then like other Servlet from Servlet engine to handle Servlet engine of this type loading handling requests from customers and the results returned to the customer
After another visit this page to the customer as long as the paper there have been no changes JSP engine has been loaded directly call the Servlet If you have already been modified it will be once again the implementation of the above process translate compile and load In fact this is the socalled first person to punishment Because when the first visit to the implementation of a series of the above process so will spend some time after such a visit would not
Java servlets offer a powerful API that provides access to all the information about the request the session and the application combining JSP with servlets lets you clearly separate the application logic from the presentation of the application in other words it lets you use the most appropriate component type for the roles of Model View and Controller
Servlets Filters and Listeners
A servlet is a Java class that extends a server with functionality for processing a request and producing a response It＇s implemented using the classes and interfaces defined by the Servlet API The API consists of two packages the javaxservlet package contains classes and interfaces that are protocolindependent while the javaxservlethttp package provides HTTPspecific extensions and utility classes
What makes a servlet a servlet is that the class implements an interface named javaxservletServlet either directly or by extending one of the support classes This interface defines the methods used by the web container to manage and interact with the servlet A servlet for processing HTTP requests typically extends the
javaxservlethttpHttpServlet class This class implements the Servlet interface and provides additional methods suitable for HTTP processing
Servlet Lifecycle
The web container manages all aspects of the servlet＇s lifecycle It creates an instance of the servlet class when needed passes requests to the instance for processing and eventually removes the instance For an HttpServlet the container calls the following methods at the appropriate times in the servlet lifecycle
Besides the doGet( ) and doPost( ) methods there are methods corresponding to the other HTTP methods doDelete( ) doHead( ) doOptions( ) doPut( ) and doTrace( ) Typically you don＇t implement these methods the HttpServlet class already takes care of HEAD OPTIONS and TRACE requests in a way that＇s suitable for most servlets and the DELETE and PUT HTTP methods are rarely used in a web application
It＇s important to realize that the container creates only one instance of each servlet This means that the servlet must be thread safe able to handle multiple requests at the same time each executing as a separate thread through the servlet code Without getting lost in details you satisfy this requirement with regards to instance variables if you modify the referenced objects only in the init( ) and destroy( ) methods and just read them in the request processing methods
Compiling and Installing a Servlet
To compile a servlet you must first ensure that you have the JAR file containing all Servlet API classes in the CLASSPATH environment variable The JAR file is distributed with all web containers Tomcat includes it in a file called servletjar located in the commonlib directory On a Windows platform you include the JAR file in the CLASSPATH
Reading a Request
One of the arguments passed to the doGet( ) and doPost( ) methods is an object that implements the HttpServletRequest interface This interface defines methods that provide access to a wealth of information about the request
Generating a Response
Besides the request object the container passes an object that implements the HttpServletResponse interface as an argument to the doGet( ) and doPost( ) methods This interface defines methods for getting a writer or stream for the response body It also defines methods for setting the response status code and headers
Using Filters and Listeners
The servlet specification defines two component types beside servlets filters and listeners These two types were introduced in the Servlet 23 specification so if you＇re using a container that doesn＇t yet support this version of the specification I＇m afraid you＇re out of luck
Filters
A filter is a component that can intercept a request targeted for a servlet JSP page or static page as well as the response before it＇s sent to the client This makes it easy to centralize tasks that apply to all requests such as access control logging and charging for the content or the services offered by the application A filter has full access to the body and headers of the request and response so it can also perform various transformations One example is compressing the response body if the Acceptlanguage request header indicates that the client can handle a compressed response
A filter can be applied to either a specific servlet or to all requests matching a URL pattern such as URLs starting with the same path elements or having the same extension
Listeners
Listeners allow your application to react to certain events Prior to Servlet 23 you could handle only session attribute binding events (triggered when an object was added or removed from a session) You could do this by letting the object saved as a sessionattributimplement the HttpSessionBindingListener interface With the new interfaces introduced in the 23 version of the specification you can create listeners for servlet context and session lifecycle events as well as session activation and passivation events (used by a container that temporarily saves session state to disk or migrates a session to another server) A newsession attribute event listener also makes it possible to deal with attribute binding events for all sessions in one place instead of placing individual listener objects in each session
The new types of listeners follow the standard Java event model In other words a listener is a class that implements one or more of the listener interfaces The interfaces define methods that correspond to events The listener class is registered with the container when the application starts and the container then calls the event methods at the appropriate times
Initializing Shared Resources Using a Listener
Beans like this typically need to be initialized before they can be used For
instance they may need a reference to a database or some other external data source and may create an initial information cache in memory to provide fast access even to the first request for data You can include code for initialization of the shared resources in the servlet and JSP pages that need them but a more modular approach is to place all this code in one place and let the other parts of the application work on the assumption that the resources are already initialized and available An application lifecycle listener is a perfect tool for this type of resource initialization This type of listener implements the javaxservletServletContextListener interface with methods called by the container when the application starts and when it shuts down
Picking the Right Component Type for Each Task
The Project Billboard application introduced is a fairly complex application Half the pages are pure controller and business logic processing it accesses a database to authenticate users and most pages require access control In real life it would likely contain even more pages for instance pages for access to a shared document archive time schedules and a set of pages for administration As the application evolves it may become hard to maintain as a pure JSP application It＇s easy to forget to include the access control code in new pages
This is clearly an application that can benefit from using a combination of JSP pages and the component types defined by the servlet specification for the MVC roles Let＇s look at the main requirements and see how we can map them to appropriate component types
Database access should be abstracted to avoid knowledge of a specific data
schema or database engine in more than one part of the application beans in the role of Model can be used to accomplish this
The database access beans must be made available to all other parts of the
application when it starts an application lifecycle event listener is the perfect component type for this task
Only authenticated users must be allowed to use the application a filter can
perform access control to satisfy this requirement
Request processing is best done with Java code a servlet acting as the Controller fits the bill
It must be easy to change the presentation this is where JSP shines acting as the View
Adding servlets listeners and filters to the mix minimizes the need for complex logic in the JSP pages Placing all this code in Java classes instead makes it possible to use a regular Java compiler and debugger to fix potential problems
Centralized Request Processing Using a Servlet
With a servlet as the common entry point for all application requests you gain control over the page flow of the application The servlet can decide which type of response to generate depending on the outcome of the requested action such as returning a common error page for all requests that fail or different responses depending on the type of client making the request With the help from some utility classes it can also provide services such as input validation I18N preparations and in general encourage a more streamlined approach to request handling
Mapping Application Requests to the Servlet
The first requirement for using a Controller servlet is that all requests must pass through it This can be satisfied in many ways If you have played around a bit with servlets previously you＇re probably used to invoking a servlet with a URI that starts with myAppservlet This is a convention introduced by Suns Java Web Server (JWS) the first product to support servlets before the API was standardized Most servlet containers support this convention today even though it＇s not formally defined in the servlet specification
中文翻译
JSP技术Servlets
JSP简介
JSP(JavaServer Pages)Sun Microsystems公司倡导许公司参起建立种动态网页技术标准JSP技术点类似ASP技术传统网页HTML文件(*htm*html)中插入Java程序段(Scriptlet)JSP标记(tag)形成JSP文件(*jsp)JSP开发Web应跨台Linux运行操作系统运行
JSP技术Java编程语言编写类XMLtagsscriptlets封装产生动态网页处理逻辑网页通tagsscriptlets访问存服务端资源应逻辑JSP网页逻辑网页设计显示分离支持重基组 件设计基Web应程序开发变迅速容易
Web服务器遇访问JSP网页请求时首先执行中程序段然执行结果连JSP文件中HTML代码起返回客户插入Java程序段操作数库重新定网页等实现建立动态网页需功JSPJava Servlet样服务器端进行执行通常返回该客户端HTML文客户端浏览器浏览
JSP10规范版1999年9月推出12月推出11规范目前较新JSP12规范JSP20规范征求意见稿已出台JSP页面HTML代码嵌入中Java代码组成
JS脚语言简介
JSjavascripJavascript种NetscapeLiveScript发展脚语言目解决服务器终端语言Perl遗留速度问题时服务端需数进行验证网络速度相缓慢288kbps验证步骤浪费时间太Netscape浏览器Navigator加入Javascript提供数验证基功
JavaScript 正式名称 ECMAScript标准 ECMA 组织发展维护ECMA262 正式 JavaScript 标准标准基JavaScript JScriptNetscape (Navigator 20) Brendan Eich 发明门语言 1996 年开始已出现 Netscape Microsoft 浏览器中ECMA262 开发始 1996 年 1997 年 7 月ECMA 会员会采纳首版
脚script种特定描述性语言定格式编写执行文件称作宏批处理文件脚通常应程序时调执行类脚目前广泛应网页设计中脚仅减网页规模提高网页浏览速度丰富网页表现动画声音等举常见例子点击网页E－mail址时动调Outlook ExpressFoxmail类邮件软件通脚功实现正脚特点心利例脚中加入破坏计算机系统命令样户浏览网页时旦调类脚便会户系统受攻击户应根访问网页信程度选择安全等级特身容非法网页更轻易允许脚通安全设置话框选择脚选项种设置轻松实现脚禁启
ServletJSP
ServletJSP技术Java开发服务器端应技术开发商务应表示端标准Java开发者喜欢种原已熟悉Java语言开发者说技术容易学二Java次编写处运行理念带入Web应中实现次编写处实现更重果遵循良设计原话表示容相分离创造出高质量复易维护修改应程序方说HTML文档中果嵌入Java代码（scriptlet）会导致开发出应非常复杂难阅读容易复维护修改会造成困难事实CSDNJSPServlet坛中常提问代码长逻辑清晰量HTMLJava代码混杂起头雾水意开发弊端
早期动态网页采CGI（Common Gateway Interface公网关接口）技术语言编写CGI程序VBCC++Delphi等然CGI技术发展成熟功强编程困难效率低修改复杂等缺点逐渐取代趋势新技术中JSPServlet具备更高效更容易编程功更强更安全具良移植性许认未发展前途动态网站技术
CGI相似Servlet支持请求响应模型客户服务器递交请求时服务器请求送ServletServlet负责处理请求生成响应然送服务器服务器发送客户CGIServlet没生成新进程HTTP Server处进程中通线程技术减服务器开销Servlet处理请求程样：收客户端请求调service方法该方法中Servlet先判断请求什类型（GETPOSTHEAD„）然调相应处理方法（doGetdoPostdoHead„）生成响应
复杂实简单说ServletJava类般类处类运行Servlet容器提供session理象生命周期理Servlet时候Java台处包括安全性理JDBC访问数库跨台力Servlet线程开发出效率更高Web应
JSP技术J2EE关键技术更高级层次抽象Servlet常规静态HTML动态产生容相结合起HTML网页作Servlet运行现许商业应服务器支持JSP技术BEA WebLogicIBM WebSphere JRun等等JSPServlet更简单果支持JSPWeb服务器JSP文件放倒静态HTML文件放置位置编译包进行ClassPath设置访问普通网页样访问服务器会动帮做工作
JSP 文件起普通静态HTML文件里面包含Java代码jsp缀告诉服务器文件需特殊处理访问JSP页面时候文件首先会JSP引擎翻译Java源文件实Servlet进行编译然Servlet样Servlet引擎处理Servlet引擎装载类处理客户请求结果返回客户
客户访问页面时候该文件没发生更改JSP引擎直接调已装载Servlet果已做修改话会次执行程翻译编译装载实谓第惩罚首次访问时候执行系列程会耗费时间访问会样
Java servlet提供种强力APIAPI访问关请求会话应程序信息servletJSP页面组合起应程序逻辑部分外观呈现部分清楚分开换句话利方式模型视图控制器三种角色分合适组件类型
Servlet滤器监听器
Servlet种Java类服务器功扩展处理请求生成应答Servlet API定义类接口实现API两程序包组成：jvavaxservlet程序包包含独立协议类接口javaxservlethttp程序包提供HTTP特定扩展实程序类
Servlet实质实现接口javaxservletServlet类实现直接完成通扩展某支持类完成该接口定义Web容器理servlet交互方法处理HTTP请求servlet般情况会扩展javaxservlethttpHttpServlet类该类实现Servlet接口提供HTTP处理附加方法
Servlet生命周期
Web容器理servlet生命周期方面根需创建servlet类实例请求传递实例进行处理终删实例HttpServlet说容器会servlet生命周期适时间调方法
doGet（）doPost（）方法外应HTTP方法方法：doDelete（）doHead（）doOptiongs（）doPut（）doTrace（）般情况实现方法HttpServlet类已适数servlet方法考虑HEADOPTIONSTRACE请求DELETEPUT两种HTTP方法少Web应程序中
容器Servlet创建实例非常重意味着servlet必须线程安全—够时处理请求处理通servlet代码作单独线程执行果init（）destroy（）方法中修改参考象请求处理方法中读取丧失细节满足关实例变量求
编译安装servlet
编译servlet必须首先确保JAR文件包含着CLASSPATH环境变量中Servlet API类该JAR文件Web容器起发布Tomcat中包含名servletjarJAR文件位commonlib目录中Windows台中应CLASSPATH中包含JAR文件
读取请求
传递doGet（）doPost（）方法参数实现HttpServletRequest接口象该接口定义方法提供关请求许信息访问
生成应答
应答象外容器实现HttpServletRequest接口象作icanshu传递doGet（）doPost（）方法该接口定义应答行体获取数序程序流方法定义设置应答状态代码首部方法
滤器监听器
Servlet规范servlet定义两种组件类型：滤器监听器两种类型Servlet 23规范中引入果支持该版规范容器恐怕继续学
滤器
滤器种组件解释servletJSP页面静态页面请求发送客户端前应答样容易应请求务集中起例访问控制登录容开销应提供服务等滤器请求应答行体首部具完全访问权限执行种转换例果AcceptLanguage请求首部指出客户端处理压缩应答滤器压缩应答行体
滤器应特定servlet匹配某种URL模式请求例相路径元素开头具相扩展名URL
监听器
监听器允许应程序特定事件做出回应Servlet 23前处理会话属性绑定事件（添加象会话中删象时）实现监听器方式保存会话属性（HttpSessionsetAttribute()方法）象实现HttpSessionBindingListener接口着Servlet规范23版中新接口引入servlet环境会话生命周期事件激活钝化事件（容器暂时会话状态保存磁盘会话移植服务器）创建监听器新会话属性事件监听器位置处理会话属性绑定事件会话中防止单独监听器象
新类型监听器遵循标准Java事件模型换句话说监听器实现监听器接口类接口定义事件相应方法应程序启动容易会注册监听器类然该容器会合适事件调事件方法
监听器初始化享资源
Bean般需前进行初始化例需数库某外部数源引存中创建初始消息缓存便第请求数提供更快访问需享资源servletJSP页面中包含初始化享资源代码更标准方法位置放置代码假设资源已初始化情况应程序部分正常工作应程序生命周期监听器类资源初始化绝工具类监听器实现javaxservletServletContextListener接口应程序启动关闭时会容器调该接口方法
务选择正确组件类型
前介绍项目公告牌应程序相复杂应程序页面般纯粹控制器商务逻辑处理访问数库户进行身份验证数页面需访问控制现实生活中会包含更页面例访问享文档档案事件表页面理组页面等应程序断发展变化变难作纯JSP应程序维护例容易忘记新页面中包含访问控制代码
明显种应程序JSP页面组件类型组合中受益中组件类型MVC角色servlet规范定义面求解映射适组件类型：
(1) 数库访问应该抽象避免连接应程序中部分特定数模式数库引擎：模型角色中bean完成种认知
(2) 数库访问bean必须应程序启动时部分：应程序生命周期时间监听器该务完美组件类型
(3) 通验证户允许应程序：滤器完成访问控制满足该求
(4) Java代码进行请求处理效果佳：servlet作控制器正符合需
(5) 必须容易改编外观呈现：正JSP反光点作视图
servlet监听器滤器混合起JSP页面复杂逻辑需求降低代码放置Java类中普通Java编译程序调试程序修复潜问题
servlet集中处理请求
servlet作应程序请求公入口时获应程序页面流整体控制Servlet根请求行结果决定生成应答类型例失败请求返回公错误页面者根发出请求客户端返回应答等某程序类帮助servlet提供诸输入验证J18N准备类服务通常会鼓励更效率方法请求处理
应程序请求映射servlet
控制器servlet第求请求必须该servlet该求通种方式满足果前servlet惯myAppservlet开头URI调servletSun公司Java Web Server（JWS）引入约定JWS推出标准API前第支持servlet产品天部分servlet容器支持约定servlet规范中没正式定义
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JSP Technology and Servlets
JSP profile
JSP (JavaServer Pages) is initiated by Sun Microsystems Inc with many companies to participate in the establishment of a dynamic web page technical standards JSP technology somewhat similar to ASP technology it is in the traditional HTML web page document (* htm * html) to insert the Java programming paragraph (Scriptlet) and JSP tag (tag) thus JSP documents (* jsp) Using JSP development of the Web application is cross that can run on Linux is also available for other operating systems
JSP technology to use the Java programming language prepared by the category of XML tags and scriptlets to produce dynamic pages package processing logic Page also visit by tags and scriptlets exist in the services side of the resources of logic JSP page logic and web page design and display separation support reusable componentbased design Webbased application development is rapid and easy
Web server in the face of visits JSP page request the first implementation of the procedures of and then together with the results of the implementation of JSP documents in HTML code with the return to the customer Insert the Java programming operation of the database can be reoriented websites in order to achieve the establishment of dynamic pages needed to functionJSP and Java Servlet is in the implementation of the server usually returned to the client is an HTML text as long as the client browser will be able to visit
JSP 10 specification of the final version is launched in September 1999 December has introduced 11 specifications At present relatively new is JSP12 norms JSP20 norms of the draft has also been introducedJSP pages from HTML code and Java code embedded in one of the components
JS script language synopsis
JS is javascrip Javascript is one kind the script language which comes by the Netscape LiveScript development the main purpose is to solve the server terminal language for instance Perl carryover speed question At that time served the end to need to carry on the confirmation to the data because the network speed was quite slow only then 288kbps the confirmation step waste＇s time were too many Therefore Netscape browser Navigator has joined Javascript has provided the data confirmation basic function
The JavaScript official name is ECMAScript This standard by ECMA organization development and maintenance ECMA262 is the official JavaScript standard This standard based on JavaScript (Netscape) and JScript (Microsoft) Netscape (Navigator 20) Brendan Eich has invented this language started from 1996 already appeared in all Netscape and in the Microsoft browser The ECMA262 development began in 1996 in 1997 July the ECMA general meeting has accepted its first edition
The script uses one specific descriptive language rests on certain form compilation to be possible the execution document is also called as great or the batch run document The script usually may transfer temporarily by the application procedure and carry out Each kind of script present widely is applied in the homepage design because the script not only may reduce the homepage the scale and raises the homepage browsing speed moreover may enrich the homepage performance like animation sound and so on Cites a most common example when we click in the homepage the Email address can transfer Outlook Express or the Foxmail this kind of mail software automatically is realizes through the script function Also because of script these characteristics the human who harbors ulterior motives by some are often using For example joins some destruction computer system＇s order in the script like this works as the user browsing homepage once transfers this kind of script will then cause the user the system to come under the attack Therefore the user should act according to visits homepage the trust degree selective security rank specially regarding these itself content on the illegal homepage do not permit the use script easily Through the safe establishment the dialog box the choice the script under option each kind of establishment may with ease realize to script being forbid and begins using
JSP and Servlets
The technology of JSP and Servlet is the most important technology which use Java
technology to exploit request of server and it is also the standard which exploit business application Java developers prefer to use it for a variety of reasons one of which is already familiar with the Java language for the development of this technology are easy to learn Java to the other is a preparation run everywhere to bring the concept of Web applications To achieve a oneprepared everywhere realized And more importantly if followed some of the principles of good design it can be said of separating and content to create highquality reusable easy to maintain and modify the application For example if the document in HTML embedded Java code too much (script) will lead the developed application is extremely complex difficult to read it is not easy reuse but also for future maintenance and modification will also cause difficulties In fact CSDN the JSP Servlet forum can often see some questions the code is very long can logic is not very clear a large number of HTML and Java code mixed together This is the random development of the defects
Early dynamic pages mainly CGI (Common Gateway Interface public Gateway Interface) technology you can use different languages of the CGI programs such as VB C C + + or Delphi and so on Though the technology of CGI is developed and powerful because of difficulties in programming and low efficiency modify complex shortcomings it is gradually being replaced by the trend Of all the new technology JSP Servlet with more efficient and easy to program more powerful more secure and has a good portability they have been many people believe that the future is the most dynamic site of the future development of technology
Similar to CGI Servlet support request response model When a customer submit a request to the server the server presented the request Servlet Servlet responsible for handling requests and generate a response and then gave the server and then from the server sent to the customer And the CGI is different Servlet not generate a new process but with HTTP Server at the same process It threads through the use of technology reduce the server costs Servlet handling of the request process is this When received from the client＇s request calling service methods the method of Servlet arrival of the first judgement is what type of request (GET POST HEAD…) then calls the appropriate treatment (DoGet doPost doHead…) and generate a response
Although such a complex in fact simply said to Servlet is a Java class And the general category of the difference is that this type operating in a Servlet container which can provide session management and targeted lifecycle management So that when you use the Servlet you can get all the benefits of the Java platform including the safety of the management use JDBC access the database and crossplatform capability Moreover Servlet using thread and can develop more efficient Web applications
JSP technology is a key J2EE technology it at a higher level of abstraction of a Servlet It allows conventional static and dynamic HTML content generated by combining an HTML page looks like but as a Servlet to run There are many commercial application server support JSP technology such as BEA WebLogic IBM WebSphere JRun and so on JSP and Servlet use more than simple If you have a JSP support for Web servers and a JSP document you can put it Fangdao any static HTML files can be placed do not have to compile do not have to pack do not have to ClassPath settings you can visit as ordinary Web It did visit the server will automatically help you to do other work
JSP document looks like an ordinary static HTML document but inside contains a number of Java code It uses Jsp the suffix used to tell the server this document in need of special treatment When we visit a JSP page the document will first be translated into a JSP engine Java source files is actually a Servlet and compiler and then like other Servlet from Servlet engine to handle Servlet engine of this type loading handling requests from customers and the results returned to the customer
After another visit this page to the customer as long as the paper there have been no changes JSP engine has been loaded directly call the Servlet If you have already been modified it will be once again the implementation of the above process translate compile and load In fact this is the socalled first person to punishment Because when the first visit to the implementation of a series of the above process so will spend some time after such a visit would not
Java servlets offer a powerful API that provides access to all the information about the request the session and the application combining JSP with servlets lets you clearly separate the application logic from the presentation of the application in other words it lets you use the most appropriate component type for the roles of Model View and Controller
Servlets Filters and Listeners
A servlet is a Java class that extends a server with functionality for processing a request and producing a response It＇s implemented using the classes and interfaces defined by the Servlet API The API consists of two packages the javaxservlet package contains classes and interfaces that are protocolindependent while the javaxservlethttp package provides HTTPspecific extensions and utility classes
What makes a servlet a servlet is that the class implements an interface named javaxservletServlet either directly or by extending one of the support classes This interface defines the methods used by the web container to manage and interact with the servlet A servlet for processing HTTP requests typically extends the
javaxservlethttpHttpServlet class This class implements the Servlet interface and provides additional methods suitable for HTTP processing
Servlet Lifecycle
The web container manages all aspects of the servlet＇s lifecycle It creates an instance of the servlet class when needed passes requests to the instance for processing and eventually removes the instance For an HttpServlet the container calls the following methods at the appropriate times in the servlet lifecycle
Besides the doGet( ) and doPost( ) methods there are methods corresponding to the other HTTP methods doDelete( ) doHead( ) doOptions( ) doPut( ) and doTrace( ) Typically you don＇t implement these methods the HttpServlet class already takes care of HEAD OPTIONS and TRACE requests in a way that＇s suitable for most servlets and the DELETE and PUT HTTP methods are rarely used in a web application
It＇s important to realize that the container creates only one instance of each servlet This means that the servlet must be thread safe able to handle multiple requests at the same time each executing as a separate thread through the servlet code Without getting lost in details you satisfy this requirement with regards to instance variables if you modify the referenced objects only in the init( ) and destroy( ) methods and just read them in the request processing methods
Compiling and Installing a Servlet
To compile a servlet you must first ensure that you have the JAR file containing all Servlet API classes in the CLASSPATH environment variable The JAR file is distributed with all web containers Tomcat includes it in a file called servletjar located in the commonlib directory On a Windows platform you include the JAR file in the CLASSPATH
Reading a Request
One of the arguments passed to the doGet( ) and doPost( ) methods is an object that implements the HttpServletRequest interface This interface defines methods that provide access to a wealth of information about the request
Generating a Response
Besides the request object the container passes an object that implements the HttpServletResponse interface as an argument to the doGet( ) and doPost( ) methods This interface defines methods for getting a writer or stream for the response body It also defines methods for setting the response status code and headers
Using Filters and Listeners
The servlet specification defines two component types beside servlets filters and listeners These two types were introduced in the Servlet 23 specification so if you＇re using a container that doesn＇t yet support this version of the specification I＇m afraid you＇re out of luck
Filters
A filter is a component that can intercept a request targeted for a servlet JSP page or static page as well as the response before it＇s sent to the client This makes it easy to centralize tasks that apply to all requests such as access control logging and charging for the content or the services offered by the application A filter has full access to the body and headers of the request and response so it can also perform various transformations One example is compressing the response body if the Acceptlanguage request header indicates that the client can handle a compressed response
A filter can be applied to either a specific servlet or to all requests matching a URL pattern such as URLs starting with the same path elements or having the same extension
Listeners
Listeners allow your application to react to certain events Prior to Servlet 23 you could handle only session attribute binding events (triggered when an object was added or removed from a session) You could do this by letting the object saved as a sessionattributimplement the HttpSessionBindingListener interface With the new interfaces introduced in the 23 version of the specification you can create listeners for servlet context and session lifecycle events as well as session activation and passivation events (used by a container that temporarily saves session state to disk or migrates a session to another server) A newsession attribute event listener also makes it possible to deal with attribute binding events for all sessions in one place instead of placing individual listener objects in each session
The new types of listeners follow the standard Java event model In other words a listener is a class that implements one or more of the listener interfaces The interfaces define methods that correspond to events The listener class is registered with the container when the application starts and the container then calls the event methods at the appropriate times
Initializing Shared Resources Using a Listener
Beans like this typically need to be initialized before they can be used For
instance they may need a reference to a database or some other external data source and may create an initial information cache in memory to provide fast access even to the first request for data You can include code for initialization of the shared resources in the servlet and JSP pages that need them but a more modular approach is to place all this code in one place and let the other parts of the application work on the assumption that the resources are already initialized and available An application lifecycle listener is a perfect tool for this type of resource initialization This type of listener implements the javaxservletServletContextListener interface with methods called by the container when the application starts and when it shuts down
Picking the Right Component Type for Each Task
The Project Billboard application introduced is a fairly complex application Half the pages are pure controller and business logic processing it accesses a database to authenticate users and most pages require access control In real life it would likely contain even more pages for instance pages for access to a shared document archive time schedules and a set of pages for administration As the application evolves it may become hard to maintain as a pure JSP application It＇s easy to forget to include the access control code in new pages
This is clearly an application that can benefit from using a combination of JSP pages and the component types defined by the servlet specification for the MVC roles Let＇s look at the main requirements and see how we can map them to appropriate component types
Database access should be abstracted to avoid knowledge of a specific data
schema or database engine in more than one part of the application beans in the role of Model can be used to accomplish this
The database access beans must be made available to all other parts of the
application when it starts an application lifecycle event listener is the perfect component type for this task
Only authenticated users must be allowed to use the application a filter can
perform access control to satisfy this requirement
Request processing is best done with Java code a servlet acting as the Controller fits the bill
It must be easy to change the presentation this is where JSP shines acting as the View
Adding servlets listeners and filters to the mix minimizes the need for complex logic in the JSP pages Placing all this code in Java classes instead makes it possible to use a regular Java compiler and debugger to fix potential problems
Centralized Request Processing Using a Servlet
With a servlet as the common entry point for all application requests you gain control over the page flow of the application The servlet can decide which type of response to generate depending on the outcome of the requested action such as returning a common error page for all requests that fail or different responses depending on the type of client making the request With the help from some utility classes it can also provide services such as input validation I18N preparations and in general encourage a more streamlined approach to request handling
Mapping Application Requests to the Servlet
The first requirement for using a Controller servlet is that all requests must pass through it This can be satisfied in many ways If you have played around a bit with servlets previously you＇re probably used to invoking a servlet with a URI that starts with myAppservlet This is a convention introduced by Suns Java Web Server (JWS) the first product to support servlets before the API was standardized Most servlet containers support this convention today even though it＇s not formally defined in the servlet specification
中文翻译
JSP技术Servlets
JSP简介
JSP(JavaServer Pages)Sun Microsystems公司倡导许公司参起建立种动态网页技术标准JSP技术点类似ASP技术传统网页HTML文件(*htm*html)中插入Java程序段(Scriptlet)JSP标记(tag)形成JSP文件(*jsp)JSP开发Web应跨台Linux运行操作系统运行
JSP技术Java编程语言编写类XMLtagsscriptlets封装产生动态网页处理逻辑网页通tagsscriptlets访问存服务端资源应逻辑JSP网页逻辑网页设计显示分离支持重基组 件设计基Web应程序开发变迅速容易
Web服务器遇访问JSP网页请求时首先执行中程序段然执行结果连JSP文件中HTML代码起返回客户插入Java程序段操作数库重新定网页等实现建立动态网页需功JSPJava Servlet样服务器端进行执行通常返回该客户端HTML文客户端浏览器浏览
JSP10规范版1999年9月推出12月推出11规范目前较新JSP12规范JSP20规范征求意见稿已出台JSP页面HTML代码嵌入中Java代码组成
JS脚语言简介
JSjavascripJavascript种NetscapeLiveScript发展脚语言目解决服务器终端语言Perl遗留速度问题时服务端需数进行验证网络速度相缓慢288kbps验证步骤浪费时间太Netscape浏览器Navigator加入Javascript提供数验证基功
JavaScript 正式名称 ECMAScript标准 ECMA 组织发展维护ECMA262 正式 JavaScript 标准标准基JavaScript JScriptNetscape (Navigator 20) Brendan Eich 发明门语言 1996 年开始已出现 Netscape Microsoft 浏览器中ECMA262 开发始 1996 年 1997 年 7 月ECMA 会员会采纳首版
脚script种特定描述性语言定格式编写执行文件称作宏批处理文件脚通常应程序时调执行类脚目前广泛应网页设计中脚仅减网页规模提高网页浏览速度丰富网页表现动画声音等举常见例子点击网页E－mail址时动调Outlook ExpressFoxmail类邮件软件通脚功实现正脚特点心利例脚中加入破坏计算机系统命令样户浏览网页时旦调类脚便会户系统受攻击户应根访问网页信程度选择安全等级特身容非法网页更轻易允许脚通安全设置话框选择脚选项种设置轻松实现脚禁启
ServletJSP
ServletJSP技术Java开发服务器端应技术开发商务应表示端标准Java开发者喜欢种原已熟悉Java语言开发者说技术容易学二Java次编写处运行理念带入Web应中实现次编写处实现更重果遵循良设计原话表示容相分离创造出高质量复易维护修改应程序方说HTML文档中果嵌入Java代码（scriptlet）会导致开发出应非常复杂难阅读容易复维护修改会造成困难事实CSDNJSPServlet坛中常提问代码长逻辑清晰量HTMLJava代码混杂起头雾水意开发弊端
早期动态网页采CGI（Common Gateway Interface公网关接口）技术语言编写CGI程序VBCC++Delphi等然CGI技术发展成熟功强编程困难效率低修改复杂等缺点逐渐取代趋势新技术中JSPServlet具备更高效更容易编程功更强更安全具良移植性许认未发展前途动态网站技术
CGI相似Servlet支持请求响应模型客户服务器递交请求时服务器请求送ServletServlet负责处理请求生成响应然送服务器服务器发送客户CGIServlet没生成新进程HTTP Server处进程中通线程技术减服务器开销Servlet处理请求程样：收客户端请求调service方法该方法中Servlet先判断请求什类型（GETPOSTHEAD„）然调相应处理方法（doGetdoPostdoHead„）生成响应
复杂实简单说ServletJava类般类处类运行Servlet容器提供session理象生命周期理Servlet时候Java台处包括安全性理JDBC访问数库跨台力Servlet线程开发出效率更高Web应
JSP技术J2EE关键技术更高级层次抽象Servlet常规静态HTML动态产生容相结合起HTML网页作Servlet运行现许商业应服务器支持JSP技术BEA WebLogicIBM WebSphere JRun等等JSPServlet更简单果支持JSPWeb服务器JSP文件放倒静态HTML文件放置位置编译包进行ClassPath设置访问普通网页样访问服务器会动帮做工作
JSP 文件起普通静态HTML文件里面包含Java代码jsp缀告诉服务器文件需特殊处理访问JSP页面时候文件首先会JSP引擎翻译Java源文件实Servlet进行编译然Servlet样Servlet引擎处理Servlet引擎装载类处理客户请求结果返回客户
客户访问页面时候该文件没发生更改JSP引擎直接调已装载Servlet果已做修改话会次执行程翻译编译装载实谓第惩罚首次访问时候执行系列程会耗费时间访问会样
Java servlet提供种强力APIAPI访问关请求会话应程序信息servletJSP页面组合起应程序逻辑部分外观呈现部分清楚分开换句话利方式模型视图控制器三种角色分合适组件类型
Servlet滤器监听器
Servlet种Java类服务器功扩展处理请求生成应答Servlet API定义类接口实现API两程序包组成：jvavaxservlet程序包包含独立协议类接口javaxservlethttp程序包提供HTTP特定扩展实程序类
Servlet实质实现接口javaxservletServlet类实现直接完成通扩展某支持类完成该接口定义Web容器理servlet交互方法处理HTTP请求servlet般情况会扩展javaxservlethttpHttpServlet类该类实现Servlet接口提供HTTP处理附加方法
Servlet生命周期
Web容器理servlet生命周期方面根需创建servlet类实例请求传递实例进行处理终删实例HttpServlet说容器会servlet生命周期适时间调方法
doGet（）doPost（）方法外应HTTP方法方法：doDelete（）doHead（）doOptiongs（）doPut（）doTrace（）般情况实现方法HttpServlet类已适数servlet方法考虑HEADOPTIONSTRACE请求DELETEPUT两种HTTP方法少Web应程序中
容器Servlet创建实例非常重意味着servlet必须线程安全—够时处理请求处理通servlet代码作单独线程执行果init（）destroy（）方法中修改参考象请求处理方法中读取丧失细节满足关实例变量求
编译安装servlet
编译servlet必须首先确保JAR文件包含着CLASSPATH环境变量中Servlet API类该JAR文件Web容器起发布Tomcat中包含名servletjarJAR文件位commonlib目录中Windows台中应CLASSPATH中包含JAR文件
读取请求
传递doGet（）doPost（）方法参数实现HttpServletRequest接口象该接口定义方法提供关请求许信息访问
生成应答
应答象外容器实现HttpServletRequest接口象作icanshu传递doGet（）doPost（）方法该接口定义应答行体获取数序程序流方法定义设置应答状态代码首部方法
滤器监听器
Servlet规范servlet定义两种组件类型：滤器监听器两种类型Servlet 23规范中引入果支持该版规范容器恐怕继续学
滤器
滤器种组件解释servletJSP页面静态页面请求发送客户端前应答样容易应请求务集中起例访问控制登录容开销应提供服务等滤器请求应答行体首部具完全访问权限执行种转换例果AcceptLanguage请求首部指出客户端处理压缩应答滤器压缩应答行体
滤器应特定servlet匹配某种URL模式请求例相路径元素开头具相扩展名URL
监听器
监听器允许应程序特定事件做出回应Servlet 23前处理会话属性绑定事件（添加象会话中删象时）实现监听器方式保存会话属性（HttpSessionsetAttribute()方法）象实现HttpSessionBindingListener接口着Servlet规范23版中新接口引入servlet环境会话生命周期事件激活钝化事件（容器暂时会话状态保存磁盘会话移植服务器）创建监听器新会话属性事件监听器位置处理会话属性绑定事件会话中防止单独监听器象
新类型监听器遵循标准Java事件模型换句话说监听器实现监听器接口类接口定义事件相应方法应程序启动容易会注册监听器类然该容器会合适事件调事件方法
监听器初始化享资源
Bean般需前进行初始化例需数库某外部数源引存中创建初始消息缓存便第请求数提供更快访问需享资源servletJSP页面中包含初始化享资源代码更标准方法位置放置代码假设资源已初始化情况应程序部分正常工作应程序生命周期监听器类资源初始化绝工具类监听器实现javaxservletServletContextListener接口应程序启动关闭时会容器调该接口方法
务选择正确组件类型
前介绍项目公告牌应程序相复杂应程序页面般纯粹控制器商务逻辑处理访问数库户进行身份验证数页面需访问控制现实生活中会包含更页面例访问享文档档案事件表页面理组页面等应程序断发展变化变难作纯JSP应程序维护例容易忘记新页面中包含访问控制代码
明显种应程序JSP页面组件类型组合中受益中组件类型MVC角色servlet规范定义面求解映射适组件类型：
(1) 数库访问应该抽象避免连接应程序中部分特定数模式数库引擎：模型角色中bean完成种认知
(2) 数库访问bean必须应程序启动时部分：应程序生命周期时间监听器该务完美组件类型
(3) 通验证户允许应程序：滤器完成访问控制满足该求
(4) Java代码进行请求处理效果佳：servlet作控制器正符合需
(5) 必须容易改编外观呈现：正JSP反光点作视图
servlet监听器滤器混合起JSP页面复杂逻辑需求降低代码放置Java类中普通Java编译程序调试程序修复潜问题
servlet集中处理请求
servlet作应程序请求公入口时获应程序页面流整体控制Servlet根请求行结果决定生成应答类型例失败请求返回公错误页面者根发出请求客户端返回应答等某程序类帮助servlet提供诸输入验证J18N准备类服务通常会鼓励更效率方法请求处理
应程序请求映射servlet
控制器servlet第求请求必须该servlet该求通种方式满足果前servlet惯myAppservlet开头URI调servletSun公司Java Web Server（JWS）引入约定JWS推出标准API前第支持servlet产品天部分servlet容器支持约定servlet规范中没正式定义
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