Servlet implementation methods

Servlet implementation methods

(1) Method 1:

 

// This is the first way to implement servlet, using the time-limit servlet interface method to achieve, use the need to reference servlet-api.jar

Package com. lc; import javax. servlet. *; import java. io. *; import javax. servlet. servletConfig; import javax. servlet. servletException; import javax. servlet. servletRequest; import javax. servlet. servletResponse; import java. io. IOException; public class Hello implements Servlet {// This function is used to initialize the servlet (similar to the class constructor) // This function will only be called once (when the user first accesses the servlet is called) public void init (ServletConfig parm1) throws ServletException {System. ou T. println (init it !);} Public ServletConfig getServletConfig () {return null ;} // This function is used to process the business logic. // The programmer should write the business logic code here. // The Code will be called when the user accesses the servlet. // req is used to obtain the client information // res users want the client to return information (which can be considered as a browser) public void service (ServletRequest req, ServletResponse res) throws ServletException, IOException {// get PrintwriterSystem from res. out. println (service it !); // Display PrintWriter pw = res. getWriter (); pw. println (hello world!) on the console !); // Display in the browser} public String getServletInfo () {return;} // call destroy in three cases: // 1. reload the servlet (webApps) // 2. disable tomcat // 3. shut down public void destroy () {// destroy the servt instance is actually releasing the memory System. out. println (destroy it !);}}

(2) Method 2:

 

 

// The second servlet program is implemented to inherit from GenericServlet. This method is very simple package com. tsinghua; import javax. servlet. genericServlet; import java. io. *; import javax. servlet. *; public class HelloGenericServlet extends GenericServlet {// rewrite the service method to public void service (ServletRequest req, ServletResponse res) {// return hello world! Generictry {PrintWriter pw = res. getWriter (); pw. println (Hello world! Generic !);} Catch (Exception ex) {ex. printStackTrace ();}}}

(3) method 3:

 

 

// The third servlet implementation program inherits HttpServletpackage com. tsinghua; import javax. servlet. http. *; import java. io. *; public class HelloHttp extends HttpServlet {// process get requests // req: used to obtain client (browser) Information // res: used to send to client (browser) public void doGet (HttpServletRequest req, HttpServletResponse res) {// business logic try {PrintWriter pw = res. getWriter (); pw. println (hello http !);} Catch (Exception ex) {ex. printStackTrace () ;}/// process post requests // req: used to obtain client (browser) Information // res: used to send to client (browser) public void doPost (HttpServletRequest req, HttpServletResponse res) {this. doGet (req, res );}}

You need to configure the web. xml file when implementing the above three methods. The Code is as follows:

 

 

 
   
  
   
Welcome to Tomcat
    
  
   
Welcome to Tomcat
    
    
      
       
   
    
Hello
       
       
   
    
Com. tsinghua. Hello
     
     
      
       
   
    
Hello
       
       
   
    
/Helloworld
     
     
      
   
    
HelloGenericServlet
       
   
    
Com. tsinghua. HelloGenericServlet
     
     
      
   
    
HelloGenericServlet
       
   
    
/HelloGeneric
     
     
      
   
    
HelloHttp
       
   
    
Com. tsinghua. HelloHttp
     
     
      
   
    
HelloHttp
       
   
    
/HelloHttp