JSP英文文献和中文翻译(3)

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However, some groups have developed alternative Java-based technologies to try to address these deficiencies. This, in our judgment, is a mistake. Using a third-party tool like Apache Struts that augments JSP and servlet technology is a good idea when that tool adds sufficient benefit to compensate for the additional complexity. But using a nonstandard tool that tries to replace JSP is a bad idea. When choosing a technology, you need to weigh many factors: standardization, portability, integration, industry support, and technical features. The arguments for JSP alternatives have focused almost exclusively on the technical features part. But portability, standardization, and integration are also very important. For example, the servlet and JSP specifications define a standard directory structure for Web applications and provide standard files (.war files) for deploying Web applications. All JSP-compatible servers must support these standards. Filters can be set up to apply to any number of servlets or JSP pages, but not to nonstandard resources. The same goes for Web application security settings.

JSP six built-in objects:

request, response, out, session, application, config, pagecontext, page, exception.

ONE.　Request for:

The object of the package of information submitted by users, by calling the object corresponding way to access the information package, namely the use of the target users can access the information.

TWO.　Response object:

The customer's request dynamic response to the client sent the data.

THREE.　session object

1.　What is the session: session object is a built-in objects JSP, it in the first JSP pages loaded automatically create, complete the conversation of management.

From a customer to open a browser and connect to the server, to close the browser, leaving the end of this server, known as a conversation. When a customer visits a server, the server may be a few pages link between repeatedly, repeatedly refresh a page, the server should be through some kind of way to know this is the same client, which requires session object.

2.　session object ID: When a customer's first visit to a server on the JSP pages, JSP engines produce a session object, and assigned a String type of ID number, JSP engine at the same time, the ID number sent to the client, stored in Cookie, this session objects, and customers on the establishment of a one-to-one relationship. When a customer to connect to the server of the other pages, customers no longer allocated to the new session object, until, close your browser, the client-server object to cancel the session, and the conversation, and customer relationship disappeared. When a customer re-open the browser to connect to the server, the server for the customer to create a new session object.

FORE.　aplication target

1.　What is the application:

Servers have launched after the application object, when a customer to visit the site between the various pages here, this application objects are the same, until the server is down. But with the session difference is that all customers of the application objects are the same, that is, all customers share this built-in application objects.

2.　application objects commonly used methods:

(1)　public void setAttribute (String key, Object obj): Object specified parameters will be the object obj added to the application object, and to add the subject of the designation of a keyword index.

(2)　public Object getAttribute (String key): access to application objects containing keywords for.

FIVE.　out targets

out as a target output flow, used to client output data. out targets for the output data.

SIX.　Cookie

1.　What is Cookie:

Cookie is stored in Web server on the user's hard drive section of the text. Cookie allow a Web site on the user's computer to store information on and then get back to it.