将Servlet和JSP组合使-毕业论文外文翻译xWord下载.docx

1、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 effic

2、iency, modify complex shortcomings,11it 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 th

3、e 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

4、 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 clients request, calling service m

5、ethods, 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 d

6、ifference is that this type operating in a Servlet container, which can provide session management and targeted life-cycle 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 cross-p

7、latform 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 aServlet. It allows conventional static and dynamic HTML content generated by combining an HTML page looks like, but as

8、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

9、, 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

10、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 ty

11、pe loading, handling requests from customers, and the results returned to the customer, as shown below:Figure 1: Calling the process of JSP pagesAfter 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 yo

12、u have already been modified, it will be once again the implementation of the above process, translate, compile and load. In fact, this is the so-called 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

13、 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

14、 the most appropriate component type for the roles of Model, View and Controller.Servlets, Filters, and ListenersA servlet is a Java class that extends a server with functionality for processing a request and producing a response. Its implemented using the classes and interfaces defined by the Servl

15、et API. The API consists of two packages: the javax.servlet package contains classes and interfaces that are protocol-independent, while the javax.servlet.http package provides HTTP-specific extensions and utility classes.What makes a servlet a servlet is that the class implements an interface named

16、 javax.servlet.Servlet, 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 theservlet. A servlet for processing HTTP requests typically extends the javax.servlet.http.HttpServlet class. This class imple

17、ments the Servlet interface and provides additional methods suitable for HTTP processing.Servlet LifecycleThe web container manages all aspects of the servlets lifecycle. It creates an instance of the servlet class when needed, passes requests to the instance for processing, and eventually removes t

18、he 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（ ）. Typicall

19、y you dont implement these methods; the HttpServlet class already takes care of HEAD, OPTIONS, and TRACE requests in a way thats suitable for most servlets, and the DELETE and PUT HTTP methods are rarely used in a web application.Its important to realize that the container creates only one instance

20、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 refer

21、enced objects only in the init（ ） and destroy（ ） methods, and just read them in the request processing methods.Compiling and Installing a ServletTo 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 fi

22、le is distributed with all web containers. Tomcat includes it in a file called servlet.jar, located in the common/lib directory. On a Windows platform, you include the JAR file in the CLASSPATH. Reading a RequestOne of the arguments passed to the doGet（ ） and doPost（ ） methods is an object that impl

23、ements the HttpServletRequest interface. This interface defines methods that provide access to a wealth of information about the request.Generating a ResponseBesides the request object, the container passes an object that implements the HttpServletResponse interface as an argument to the doGet（ ） an

24、d 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 ListenersThe servlet specification defines two component types beside servlets: filters and listeners.

25、These two types were introduced in the Servlet 2.3 specification, so if youre using a container that doesnt yet support this version of the specification, Im afraid youreout of luck.FiltersA filter is a component that can intercept a request targeted for a servlet, JSP page, or static page, as well

26、as the response before its 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

27、 it can also perform various transformations. One example is compressing the response body if the Accept-Language 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 sta

28、rting with the same path elements or having the same extension.ListenersListeners allow your application to react to certain events. Prior to Servlet 2.3, 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 sessionattribute（using the HttpSession.setAttribute（） method）implement the HttpSessionBindingListener interface. With the new interfaces introduced in the 2.3 version of the specification, you can