factors of” n “: “);

In order to compile the servlet source file, you need HttpServlet, HttpServletRequest, and the like, JDK built-in package does not contain these types of documents. In order to compile the servlet servlet source file has been created with the byte code file, you need the environment variable contains servlet.jar , this jar file in TOMCAT installation directory common \ lib File, as shown in Figure 7.1 below (you can download to the sun needed to compile the servlet class). For window2000, right-click “My Computer”, pop-up menu, then select Properties to bring up “System Properties” dialog basket, and then click the Advanced Options dialog box, then click the button “Environment Variables”, edit classpath add new environment variable:
out.println (“ “);
PrintWriter out = response.getWriter ();
throws ServletException, IOException
import javax.servlet .*;
7.5.3 set the HTTP response header
example 4 (results shown in Figure 7.7 shown)
import javax.servlet .*;
click submit button:
the JSP page to submit positive
We already know that, when multiple client requests a servlet, the engine start a thread for each client, then the servlet class member variables are shared by all threads.
}
<% @ page contentType = "text / html; charset = GB2312"%>
the JSP page to submit positive
public class ComputerPI extends HttpServlet
Example7_10 :
else
Example 5 (results shown in Figure 7.8)
This method is the method in the HttpServlet class, we re in a servlet write this way.
{out.print (“

input number letter please! “);
double n = 0;
7.5.1 doGet method and doPost methods

7.5 HttpServlet class
out.println ( method);
Example 10 (results shown in Figure 7.12)
and the servlet byte code file exists in that directory, as shown in Figure 7.4.
catch (NumberFormatException e)
because from the package name, Hello full name is tom.jiafei.Hello (like Dalian full name is: China Liaoning Dalian).
Example 6 (results shown in Figure 7.9)
try {n = Double.parseDouble (number);
7.2.2 compiled servlet
Method Description:
out.println (length);
out.println (““);
out.println (header4); < br /> {/ / get a client to send data to the output stream:
7.2 compile and install the servlet
double n = 0;
public synchronized void service (HttpServletRequest request, HttpServletResponse response)
/ / get client IP address:

public class Sqrt extends HttpServlet
public void doPost (HttpServletRequest request, HttpServletResponse response)
String path = request.getServletPath ();
out.println (i);
/ / the way information is presented by the customer:
public synchronized void doGet (HttpServletRequest request, HttpServletResponse response)
int length = request.getContentLength ();
public void doGet (HttpServletRequest request, HttpServletResponse response)
if (n> = 3)
import java.util. *;
{public void init (ServletConfig config) throws ServletException
public class Hello extends HttpServlet
sum = sum i / j;
out.println (“ < BODY> “);
}
import java.io. *;
Count.java:
response.setContentType (” text / html; charset = GB2312 “); / / set the response MIME type.

}
JSP page
public void init (ServletConfig config) throws ServletException
out.println (“
Parameter Names” );
PrintWriter out = response.getWriter ();
String IP = request.getRemoteAddr ();
int serverPort = request.getServerPort ();
{super.init ( config);
if (person_email == null)
}
describes the response HTTP headers, see Chapter 3.
{out.print (“

input number letter please! “);
{/ / get a client to send data to the output stream:
response.setContentType ( “text / html “);// set the MIME type of the response.
package tom.jiafei;
throws ServletException, IOException
we already know, servlet request is first loaded, the server initializes a servlet, a servlet object is created, this object is called init method to complete the necessary initialization. If your source files to the servlet has been modified, and new bytecode file to the classes, if the server is not closed, then the new servlet will not be created because, when the follow-up customer service servlet requests, we have the beginning of the beginning of the servlet service method is called to respond to customers.
out.println (“
Host:”); String header3 = request.getHeader (“Host”); out.println (header3); / / Get HTTP accept-encoding header value:
7.2.4 run servlet
package gping;
doPost (request, response);
the HTTP request header and forms the introduction, can be found in Chapter 3.
}
String number = request.getParameter (“number”); / / get the customer to submit information.
sevlet source
}
load servlet
out.println (““);
enter a number, submitted to the servlet (Post method):
out.println (header1);
package tom.jiafei;
10 in the following example, servlet set the response header: Refresh header value is 2 , then the servlet refresh automatically after 2 seconds, 2 seconds after the servlet service method is called again to respond to the user.
7.2.3 store servlet directory

import javax. servlet .*;
}
}
out.println (““);
public void doGet (HttpServletRequest request, HttpServletResponse response)
out.print (“
” Math.sqrt (n));
import javax.servlet .*;
}
(1) initialize the servlet. load the servlet is first requested, the server initializes this servlet, a servlet object is created, this object call the init method to complete the necessary initialization.
throws ServletException, IOException

/ / Get HTTP Host header value:
out.println (“
User-Agent:”) ;
int j = 1;
{public void init (ServletConfig config) throws ServletException
try {n = Double.parseDouble (number);
7.1 Servlet works
out.println (“Now Time:”);
enter a number, servlet find the square root of this number:
if (person_name == null)
out.println (““);
(2) friend directory (one of our custom web service catalog)
We will Hello.java the servlet source files saved to F: \ 2000, then compiled bytecode files Hello.class

doPost (request, response);
import javax.servlet.http .*;
< % @ page contentType = "text / html; charset = GB2312"%>
there is a mathematical formula for calculating π:
{for (j = 2; j {super.init (config);
{super.init (config);
/ / in the hash table to find whether there is the name:
{person_name = “”;
servlet source file


{ String person_email = request.getParameter (“address”);
}
7.1.4 destroy method
givenumber.jsp (results shown in Figure 7.5)
sevlet source
http://localhost:8080/examples/servlet/ create a servlet class name
Sqrt.java
{

If you are only examples Service catalog available servelt, so long as the server engine is started, the browser address bar type:
Example7_6.jsp: <% @ page contentType = "text / html; charset = GB2312"%>
enter a number, submitted to the servlet (Post method):
Example7_9.jsp:
D: \ Tomcat \ jakarta-tomcat-4.0 \ common \ lib \ servlet.ja r;
StringTokenizer fenxi = new StringTokenizer (person_email, “@”); < br /> <% @ page contentType = "text / html; charset = GB2312"%>
example, use the following member variables shared by all clients to achieve this feature to help calculate the value of the customer, that is, whenever the customer requests access when they participated in a servlet? calculations.
ComputerFacor.java:
import java.io. *;
String number = request.getParameter (“number”); / / get the customer to submit information.
Note: In dealing with multi-threading issues, we must pay attention to this question: When two or more threads simultaneously access the same variable, and one thread to modify this variable. We should deal with such issues, or confusion may occur, so the above example the service is a synchronized method.

import java.io. *;
out.println (IP);
{/ / get a client to send data to the output Flow:
out.println (str);
{out.println (i);
example 7 (results shown in Figure 7.10)

ComputerFacorandPrimNumber.java:

String clientName = request.getRemoteHost ();
if the user request type is either Post or Get, the server the same process, then we can only write in the doPost method process, and in the doGet method can then call the doPost method, doGet method or just write in the process, and in the doPost method call doGet method again (see Example 6).

out.print (“
” “login success!”);
/ / get users to submit name:

calls the servlet JSP page
{out.print (“

input number letter please! “);
DateServlet.java:
If the type of request for different treatment, they need to write in two different ways in the process (see Example 7).
out.println (“ “);
}

enter a number, submitted to the servlet (Get method): < br />}

{PrintWriter out = response.getWriter ();
(1) can be used for all web services directory location for the servlet

out.println (“

Primnumbers less” n “: “);
(1) Root Service catalog
public void doPost ( HttpServletRequest request, HttpServletResponse response)
throws IOException
out.println (“
client name:”);
import javax.servlet.http .*;
public void service (HttpServletRequest reqest, HttpServletResponse response) throws IOException
throws ServletException, IOException
doPost (request, response);
We are not a genius, but we are professionals! We already know, SUN Java Servlet-based company, launched a Java Server Page. JSP provides almost all the benefits of Java Servlet, when a client requests a JSP page, JSP page the JSP engine generates a Java file that a servlet. This chapter will servlet to do a more detailed description, not only for the deep understanding of the JSP has some help, but by learning servlet, so that we can choose to use JSP javabeans servlet model to develop our Web applications.

then in the classes directory must have the following subdirectories, for example, D: \ Tomcat \ jakarta-tomcat-4.0 \ classes directory under the re-establishment of the following structure.

out.println (clientName);
sevlet source
{String s = (String) enum.nextElement ();
out.println (““);
/ / find all the prime numbers less than n:
public void doGet (HttpServletRequest request, HttpServletResponse response)
public void doGet (HttpServletRequest request, HttpServletResponse response )

}

}
}

program if you use a package statement, such as

public class ComputerFactor extends HttpServlet
engine for the first time when the server received to a servlet request, will use the init method to initialize a servlet, and then later whenever the server receives a servlet request, it will spawn a new thread and call the service method of this thread check the type of HTTP request (Get, Post, etc.), and in the service method based on user request methods, corresponding to the ground and then call the doGet or doPost method. Thus, in the servlet class, we do not have to rewrite the way to respond to customer service, service method can be directly inherited. We can rewrite the servlet class in the doPost or doGet method to respond to user requests, which can increase the flexibility of response and reduce the burden on the server.
examples is the default web service engine TOMCAT one catalog.
If you want a servlet can be used only for the examples directory, then create the servlet byte code file simply stored in the webapps / example / Web-inf / classes directory.
public void init (ServletConfig config) throws ServletException
}
}
<% @ page contentType = "text / html; charset = GB2312"%>
out. println (““);
/ / find all the factor n:
out.println (““);
π / 4 = 1-1/3 1/5-1 / 7 1/9-1 / 11 … …
import javax.servlet.http .*;
}
PrintWriter out = response . getWriter ();
http://localhost:8080/web service catalog / servlet / tom.jiafei.Hello
(3) When the server is closed, call the destroy method to eliminate the servlet object.

Method Description:
}
/ / Get HTTP User-Agent header value:

out.println (““);
out.println (serverName);
public class LoginByServlet extends HttpServlet

String header1 = request. getHeader (“User-Agent”);
can, for example, created for the use of the Hello servlet,
we already know, JavaBeans with JSP support this feature, you can effectively manage the static part of the page and the dynamic part of the page. In addition, we can also call in a JSP page servlet to complete a dynamic data processing, and let the JSP page itself handles static information. Therefore, developing a Web application, there are two modes to choose from:
}

String number = request.getParameter (“number “);// get customers the information submitted.
}
/ / find all the factor n:
7.2.1 simple servlet example < br /> 2011 年 12 月 19 日
http://localhost:8080/web service catalog / servlet / create a servlet class name

eat only a little Flying dreams
import javax.servlet.http .*;

out.println (““);
http://localhost:8080/servlet/Hello
to write a servlet java file, you can use a package statement to the servlet package name. Package name can be a valid identifier, an identifier can also be a number of additional “.” Split is made, such as:
{if (i% j == 0)
try {n = Double . parseDouble (number);
}
response.setContentType (“text / html; charset = GB2312″); / / set the response MIME type.

out.println (“
server name:”);
String person_name = request.getParameter (“name”),


throws ServletException, IOException
import java.io. *;
String header2 = request.getHeader (“accept”);

try {n = Double.parseDouble (number);
public class DateServlet extends HttpServlet
for (int i = 1; i <% @ page contentType = "text / html; charset = GB2312"%>
This method is the method in the HttpServlet class, we can directly inherit the servlet method or override this method.
Enter your name:
example 9 (results shown in Figure 7.11)
public void service (HttpServletRequest request, HttpServletResponse response) throws IOException
}


{/ / get a client to send data to the output Flow:
import java.io. *;

import javax.servlet .*;


int n = fenxi.countTokens ();
7.2.5 with package name servle < strong> t
for (int i = 1; i <= n; i )
import javax.servlet .*;
http://localhost:8080/friend/servlet/Hello < br />}
double n = 0;

}
XMLNAMESPACE PREFIX = “ST1″ /> 7.1.1 Servlet
view the life cycle of the time
}
}
{
7.4 servlet of shared variables
out.println (protocol);
enter a number, submitted to the servlet (Get method):
{super.init (config);
catch (NumberFormatException e)
{/ / get a client to send data to the output stream:
PrintWriter out = response.getWriter ();
7.3 invoke the servlet by the JSP page

{if (n% i == 0)
stored in the directory of the servlet and stored in the above (1 ) as described in the servlet directory is different, the server engine first checks webapps / example / Web-inf / classes directory to create the servlet byte code file has been modified, if the re-modified, will be used to eliminate servlet, with the new bytecode re-initialization servlet.
}
handle the HTTP request header sevlet source
Example7_8.jsp:
When the servlet successfully created and initialized, servlet service method is invoked to handle the user request and return a response. Servlet engine two parameters passed to the method, a type HttpServletRequest object that encapsulates the user request for information, call the appropriate method of this object can get the information package that you can use this object to obtain user-submitted information. Another object is a parameter of type HttpServletResponse object used to respond to user requests. And the difference is that the init method, init method is called only once, and service methods may be invoked many times, we already know, when the follow-up customer service request servlet, Servlet engine will start a new thread in the thread , servlet service method is called to respond to customer requests, that is, each customer every request led to the implementation of service method is invoked, the calling process is running in a different thread, without disturbing each other.
response.setContentType (“text / html; charset = GB2312″); / / set the response MIME type.
response.setContentType (“text / html; charset = GB2312″); / / set the response MIME type.
else
}
{Hashtable hashtable = new Hashtable ();

Example 3

String header4 = request.getHeader (” accept-encoding “);

out.println (” “);
/ / client protocol used is:
throws ServletException, IOException
ServletException, IOException
PrintWriter out = response.getWriter ();
if (j> = i )
public class ComputerFactorandPrimNumber extends HttpServlet
{super.init (config);
calls the servlet page (the page is stored in the root directory of web services in Root)

public destroy ()
see PI values ??
import java.io. *;
servlet first When a load is requested, the server initializes a servlet, a servlet that creates the object, call the init method of this object to complete the necessary initialization. This method is executed, servlet engine will a SevletConfig type of object passed to init () method, this object is stored in the servlet object, until the servlet object is eliminated, the ServletConfig object passed to the servlet responsible for service settings, if delivery failure occurs ServeletException, servlet will not work properly.
out.println (“
accept:”);
out.println (“
text:”);
out.println (“
” new Date ());

}
name_found = null;
{/ / get a client to send data to the output stream:
throws ServletException , IOException
PrintWriter out = response.getWriter ();
name_found = (String) hashtable.get (person_name);
import java.io. *;
out.println ( “ “);
String protocol = request.getProtocol ();
JSP page to submit information
In the following example 1 , Hello extends HttpServlet.

servlet from the server supports servlet: servlet engine, responsible for managing the operation. When multiple client requests a servlet engine to start a thread for each client, rather than start a process, these threads to manage the server from the servlet engine, and the traditional start a CGI process for each customer, compared to high efficiency and more.
When the Servlet engine termination of service, such as shutting down the server, etc., destroy () method is executed, the eradication of the servlet object.
}
import javax.servlet.http .*; public class Count extends HttpServlet {int count; public void init (ServletConfig config) throws ServletException {super.init (config); count = 0;} public synchronized void service (HttpServletRequest request, HttpServletResponse response) throws IOException {/ / get a client to send data to the output stream:
Example7_7.jsp:
(2) only for the examples directory service storage available seclet