Javaweb Easy-to-start case based on Java servlet login

Project Flow

First step: Create a Java webproject
Step Two: Create three interfaces, 1,login.jsp 2 success.jsp 3 fail.jsp
The third step: Change the new Interface encoding format, Utf-8 silent encoding format will be garbled in Chinese.
Fourth step: Add the current new project to the Tomcat server and start the server to see the interface effect
Fifth Step: Browser access http://127.0.0.1:8080/HelloServlet/login.jsp 127.0.0.1 local IP 8080 port number, the Tomcat default port number is the project name plus the specified interface name
The interface has been built.
Start Focus servlet
What is a servlet?
A servlet is a class of the Java programming language that is used to extend the performance of the server, responding to any type of request, specifically www.baidu.com HHA

Servlet has two request mode get and post, our interface uses POST request way

Sixth step: The whole case has been completed, try to run it again, see the effect
The sign-in button should use the Submit
The specific reason is unclear, we debug the code ...

Java Inside string judgment equality error case username== "sa" correctly with Username.equals ("sa")

1 New Project HelloServlet

Click OK to finish

2 new Interface login.jsp success.jsp fail.jsp

Click Finish

Click Finish

Click Finish

3 Adjusting the interface

A. Since the interface default encoding format only supports English, input Chinese will be garbled, we change to Utf-8

The modified effect

PS: The three new interfaces that were just created are

4: A: Modify the login.jsp code

Add the following code inside the body

<!--   by post-      <form action= "logins" method= "POST" >    username: <input type= "text" Name= " Username "><br>    password: <input type=" password "name=" password "><br>    <input type=" Submit ">    </form>

B:success.jsp interface

<div style= "size:25px;" > Log In Success </div>

C:fail.jsp interface

<div style= "size:25px;" > Log in Failure </div>

5, adding a servlet class

A, create a new package first

B New Servlet

Note: We just have to choose the Doget Dopost method.

Note: Red box code

Create a new servlet class and replace it with the following code.

 PackageCom.wilson.servlet;Importjava.io.IOException;ImportJava.io.PrintWriter;Importjavax.servlet.ServletException;ImportJavax.servlet.http.HttpServlet;Importjavax.servlet.http.HttpServletRequest;ImportJavax.servlet.http.HttpServletResponse; Public classLoginsextendsHttpServlet {/*** The Doget method of the servlet. <br> * * This method was called when a form have its tag value met     Hod equals to get. *      * @paramrequest the request send by the client to the server *@paramresponse The response send by the server to the client *@throwsservletexception If an error occurred *@throwsIOException If an error occurred*/     Public voiddoget (httpservletrequest request, httpservletresponse response)throwsservletexception, IOException {doPost (request,response); }    /*** The DoPost method of the servlet. <br> * * This method was called when a form have its tag value me     Thod equals to post. *      * @paramrequest the request send by the client to the server *@paramresponse The response send by the server to the client *@throwsservletexception If an error occurred *@throwsIOException If an error occurred*/     Public voidDoPost (httpservletrequest request, httpservletresponse response)throwsservletexception, IOException {String username= Request.getparameter ("username"); String Password= Request.getparameter ("Password"); //because there is no database connection, write a dead judge of the user name password        if(Username.equals ("sa") &&password.equals ("123")) {System.out.println ("Log In Success"); //Jump Login Success ScreenResponse.sendredirect ("success.jsp"); }Else{            //Otherwise, jump to our defined failure interface System.out.println like a log to print a bitSystem.out.println ("Log in Failed"); Response.sendredirect ("Fail.jsp"); }    }}

Logins

Add to Tomcat and run Tomcat

Then the browser enters the URL: http://127.0.0.1:8080/HelloServlet/login.jsp

Enter user name password: SA 123

We're trying to enter an incorrect user name.

OK, all allowed through.

Javaweb Easy-to-start case based on Java servlet login