Servlet overview

---

Preface

A simple learning Servlet The record of

---

One 、Servlet (Java EE 6 )

1. What is? Servlet

    Servlet Is in Web Small running in the server Java Program .Servlet Receive and respond from Web Client requests , Usually by HTTP, Hypertext transmission ​​ agreement .
     It can be understood as Servlet Yes, it is Java Language implementation of an interface , yes Web Browser or something HTTP Client and HTTP The database on the server or the intermediate layer between applications .

2.Servlet The process of

     The client initiates a http request
    Servlet The container received a request , Read the client （ browser ） Data sent , And call the corresponding... According to the request information Servlet.
    Servlet To deal with specific business logic , That's what we wrote Servlet The code in .
    Servlet Process data and generate results , Return to Servlet Containers .
    Servlet The container returns the final result to the client .

3.Servlet Life cycle of

    Servlet By calling init () Method initialization Servlet object ,init Methods are called only once .
    Servlet call service() Method to handle client requests ,service() The corresponding doGet perhaps doPost And so on .
    Servlet By calling destroy() Method termination （ end ）, This method will only be implemented once .