servlet interview summary

2010-09-21  来源:本站原创  分类:Java  人气:154 

ndex:
1 What is Servlet
2, Servlet What is the role of
3, Servlet life cycle
4, Servlet how to handle a request
5, Servlet and JSP What is the difference
6, Servlet technology in the cookie
7, Servlet filters in
8, Servlet in the listener

I. What is Servlet?

Servlet is a program written in Java, this procedure is based on the Http protocol, running on the server side (such as tomcat),

Prepared in accordance with a Java Servlet specification class.

Second, Servlet for?

Mainly dealing with client requests and send the results to the client.

3, Servlet life cycle?

Servlet life cycle is controlled by the Servlet container, which can be divided into three stages; initialization, operation, destruction.

Initialization phase:

1, Servlet container load servlet class, the servlet class. Class files in the data read in memory.

2, and then Servlet container creates a ServletConfig object. Servlet ServletConfig object contains initialization configuration information.

3, Servlet container creates a servlet object.

4, Servlet servlet container calls the init method to initialize the object.

Operational phase:

When the servlet container receives a request, servlet container will create servletRequest for the request and servletResponse object.

Then call the service method. And these two parameters passed to the service method. Service Methods servletRequest object access request

Information. And process the request. Then the object generated by servletResponse response to this request the results. And then destroyed servletRequest

servletResponse object. We both submitted the request is post or get submitted by the end of this request will be handled by the service method.

Destruction stages:

When the Web application is terminated, servlet container will first call the servlet object destrory method, and then destroy servlet object

Will also destroy the object associated with the servlet servletConfig object. We can destroy method implementation, the release of

servlet that takes up resources, such as closing database connections, close the file input and output streams.

Where the pay attention to:

In the servlet life cycle, servlet initialization and destruction phases, and occurs only once, while the number of service methods of implementation will depend on servlet by the customer

Client visits

4, Servlet how to handle a request?

When a user sends a request to a Servlet when, Servlet container creates a ServletResponse object and ServletRequst.

In ServletRequst object encapsulates the user's request information, and Servlet containers to ServletRequst and ServletResponse objects

Passed to the user the requested Servlet, Servlet to deal with good results written in ServletResponse, and then to respond to the results of the Servlet container

To the user.

5, Servlet and JSP What is the difference?

1, jsp is compiled by the servlet, it can be said jsp equivalent servlet.

2, jsp pages also good (performance). servlet better at logic editor. (The core of the difference).

3, in practical applications to control the business process using Servlet, and JSP to generate dynamic web pages using. In the struts framework,

JSP MVC design pattern in the view layer, while the Servlet in the control layer.

6, Servlet in the cookie technology?

cookies is a WEB server through the browser the visitor's hard disk to store information means is developed by Netscape Corporation.

cookie technology benefits:

1, Cookie expiration date not yet reached the time, Cookie does not allow users to type a password and user name, entered a number of sites have been visited.

2, Cookie tracking specific visitors make site visits, last access time and the path of visitors into the site.

Create a cookie
Java code

1. / / Inside of the two parameters are the cookie name and cookie value
2.
3. Response.addCookie (new Cookie ("abc", "10000000"));

/ / Inside the two parameters are the cookie name and cookie value

response.addCookie (new Cookie ("abc", "10000000"));

Use cookie
Java code

1. Cookie [] cook = request.getCookies ();// array receiver with a Cookie
2.
3. For (int j = 0; j <cook.length; j ++){// Cookie through the loop to print
4.
5. Cook [j]. GetName ():// take the name of cookie
6. Cook [j]. GetValue ():// to the cookie's value
7.
8.)

Cookie [] cook = request.getCookies ();// array receiver with a Cookie

for (int j = 0; j <cook.length; j ++){// Cookie through the loop to print

cook [j]. getName ():// take the name of cookie
cook [j]. getValue ():// to the cookie's value

)

7, Servlet filters inside?

The main function of the filter

1, any system or site must determine whether the user login.

2, network chat system or forum, the text function is to filter the illegal

3, unified coding

(2) how to create a filter:

1, generates a normal class and realizes Filter Interface (javax.servlet.Filter;).

2, rewrite the interfaces inside the three methods: init, doFilter, destroy.

3, and then configure the filter in the web.xml.

8, Servlet in the listener?

The role of listener: automate some operations.

Three types of servlet listeners:

On the request of the monitor. Listening to the session. On the application of the monitor.

How to create a session listener:

1, generates an ordinary class type, if the session is listening, then realized HttpSessionListener.

2, and then rewrite the inside of the five methods:

Java code

1. Public void sessionCreated (HttpSessionEvent arg0) () / / create
2.
3. Public void sessionDestroyed (HttpSessionEvent arg0) () / / destruction
4.
5. Public void attributeAdded (HttpSessionEvent arg0) () / / increase
6.
7. Public void attributeRemoved (HttpSessionEvent arg0) () / / Remove
8.
9. Public void attributeReplaced (HttpSessionEvent arg0) () / / Replacement

public void sessionCreated (HttpSessionEvent arg0) () / / create

public void sessionDestroyed (HttpSessionEvent arg0) () / / destruction

public void attributeAdded (HttpSessionEvent arg0) () / / increase

public void attributeRemoved (HttpSessionEvent arg0) () / / Remove

public void attributeReplaced (HttpSessionEvent arg0) () / / Replacement

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