Jsp + ajax Method for sending GET requests

Jsp + ajax Method for sending GET requests

The example in this article describes how ajax sends a GET request and then receives the processing through the jsp page. Share it with you for your reference. The specific implementation method is as follows:

Ajax sends a GET request

Here, we use an instance to demonstrate how Ajax sends a get request. The instance must be a registration page. When the user fills in the user name, the input box will send verification information to the background through Ajax if the focus is lost, if the user name is not admin, it is verified; otherwise, it is not verified.

The following describes the details of the JSP page:

The Code is as follows:

<Form action = "servlet/LoginServlet" method = "post">
<Table>
<Tr>
<Td> User Account: </td>
<Td> <input type = "text" name = "username" onblur = "checkUser (this)"/> </td>
</Tr>
<Tr>
<Td> User Password: </td>
<Td> <input type = "password" name = "password"/> </td>
</Tr>
<Tr>
<Td> <input type = "submit" value = "register"/> </td>
<Td> <input type = "reset" value = "reset"> </td>
</Tr>
</Table>
</Form>

 

The backend processing information is processed using Servlet.

First, check the web. xml configuration information.

The Code is as follows:

<Servlet>
<Servlet-name> LoginServlet </servlet-name>
<Servlet-class> login. LoginServlet </servlet-class>
</Servlet>

 

<Servlet-mapping>
<Servlet-name> LoginServlet </servlet-name>
<Url-pattern>/servlet/LoginServlet </url-pattern>
</Servlet-mapping>

 

Then, let's look at the specific servlet class's doGet method.

The Code is as follows:

Public void doGet (HttpServletRequest request, HttpServletResponse response)
Throws ServletException, IOException {

 

Response. setContentType ("text/html; charaet = UTF-8 ");
PrintWriter out = response. getWriter ();
String name = request. getParameter ("username ");
System. out. println (name );
If (name. equals ("admin "))
Out. print (false );
Else
Out. print (true );
Out. flush ();
Out. close ();
}

 

Perform a simple verification in the Servlet class.

In the JSP form, a focus loss event is set for the input box of the user name, that is, the onblur event. The following describes the javascript code.

The Code is as follows:

<Script type = "text/javascript">
// Create XMLHttpRequest
Function createXmlHttpRequest (){
If (window. XMLHttpRequest ){
Return new XMLHttpRequest ();
} Else {
Return new ActiveXObject ("Microsoft. XMLHTTP ");
}
}
// Call this method when the user account input box loses focus
Function checkUser (obj ){
// Obtain the value entered in the input box
Var user = obj. value;
// If the value in the input box is empty, a prompt is displayed, and the focus of the input box is obtained.
If (! User ){
Alert ("the user name cannot be blank! ");
Obj. focus ();
Return;
}
// If it is not empty, use Ajax requests to send information to the background to verify whether the user name is available
// Get request string
Var url = "servlet/LoginServlet? Username = "+ user;
// Call a method to create an XMLHttpRequest object
XmlHttpRequest = createXmlHttpRequest ();
// Set the callback function
XmlHttpRequest. onreadystatechange = finish;
// Initialize xmlhttprequest
XmlHttpRequest. open ("GET", url, true );
// Send the request
XmlHttpRequest. send (null );
}
// Callback function
Function finish (){
If (XmlHttpRequest. readyState = 4 & XmlHttpRequest. status = 200 ){
Var result = XmlHttpRequest. responseText;
If (result = "true "){
Alert ("the user name is available! ");
} Else {
Alert ("the user name is unavailable! ");
}
}
}
</Script>

 

I hope this article will help you with jsp + Ajax programming.