I am using this piece of code to display a TextArea to my JSP page with a button calling two functions after onclick event.
<textarea id="textarea"></textarea>
<button style="float: right;" onclick="jQuery('#reDiv').load(' #reDiv'); doSth();">Get Text</button>
function 1:
<div id="reDiv"><%=new java.util.Date().toString()%></div>
function 2:
<script>
function doSth() {
var text = $("#textarea").val(); //value of textarea
<%=text%> //error
}
</script>
Function 1 works fine.
In function 2 I am trying to pass the value, which I just got from the TextArea, to my Server without reloading the page. My aim later is to call a method and display the data without refreshing the page.
I know the error is that JS is Client-Side and JSP is server side.
But how can I solve this?
It's really bad practice to use scriptlets in your jsp (these things <% %>). It was replaced by EL and JSTL.
But yeah the server runs the java in your jsp page before it gets sent to the client. And the javascript runs on the client side after the java has already been executed. On top of that, you cannot directly access javascript variables with scriptlets. You can however do it the other way round but it won't be useful for you in this case.
You mentioned you want to pass the value from your textarea to the your server without your page reloading. This is what AJAX is for.
<script>
function doSth() {
var text = $("#textarea").val(); //value of textarea
//<%=text%> //error
sendToServer(text);
}
function sendToServer(text){
var params = {
textarea: text
};
$.post("YourServletUrl", $.param(params), function(response) {
// ... handle response here if you have any..
});
}
</script>
Then in the doPost method of your servlet which has a url mapping of YourServletUrl you just do this:
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
String textarea= request.getParameter("textarea");
System.out.println(textarea);
}
I want to call a function of javascript from servlet.
servlet code:
File ff = new File(uploadedFile+"/"+fileName+".mp4");
FileOutputStream fileOutSt = new FileOutputStream( ff );
fileOutSt.write(data);
fileOutSt.close();
request.setAttribute("src", ff);
RequestDispatcher dispatcher=request.getRequestDispatcher("/WEB-INF/jsfunction.js");
dispatcher.include(request, response);
my javascript code:
myfunction(fileInput)
{
var fileUrl = window.URL.createObjectURL(fileInput);
}
The problem is javascript calls but it display the code content but not execute it.
how can i get fileURL.
Several things are wrong here:
First, the inclusion of your javascript source is improper, because the javascript must be included (or referenced) always within an HTML file. In your case, instead, you are serving a MP4 file.
If you must absolutely execute that js code (remember that js is always executed in a browser), I suggest you serve an HTML page instead. In this case, the jsfunction.js script must be referenced within the HTML code:
<html>
<head>
<script type="text/javascript" src="jsfunction.js" />
</head>
<body>
...
</body>
</html>
Second: Even if you include the script, you must then invoke your function. You can call it immediately, from a scriptlet, or as a response to some client event (onclick, onload, etc).
javascript plays on client side and Servlet plays on server side. You cannot execute Javascript on serverside. It should execute by browser.
I suggest you to make a javascript call in window onload.
RequestDispatcher interface provides the facility of dispatching the request to another resource it may be html, servlet or jsp. But not to JS. Since JS always runs in browser itself.
request.setAttribute("filename",filenamehere); //put filename
RequestDispatcher requestDispatcher;
requestDispatcher = request.getRequestDispatcher("/filename.jsp");//dispatch here
requestDispatcher.forward(request, response);
In filename.jsp
String value = (String)request.getAttribute("filename");//getting filename
Do like this. This way we will get the file url.
How to pass response from servlet to html
Call your servlet in same html using ajax with jquery.
In servlet
//getting input from `html` page
String userName = request.getParameter("userName").trim();
//now process your request here
//forward response to `html` page
response.setContentType("text/plain");
response.getWriter().write("your file url");
In html call this servlet using ajax
$.ajax({
url : 'yourservletaction',
data : {
userName : $('#userName').val()//if you want to send any input do like this
},
success : function(responseText) {
$('#ajaxGetUserServletResponse').text(responseText);//getting file url as response. so use this url in you js
}
});
I have a question about getting Javascript Variables from a local PC JS File to a Local C# Program.
I'm writing a C# Program for the PC which needs some Variables from a Webpage which is locally located on my PC with just HTML CSS and JS which is displayed in a webview function in my C# Form.
Now I'm reading a Value from the User in my "Webpage" and want to pass this variables to my C# Code so I can use this variables further.
There are at least two ways to get any variable from a browser to your backend. One is to Post a form that contains the variable. The other is to make an AJAX call to send the variable data to some backend service. The AJAX call would, in most cases, be the way to go since no screen refresh is done and involves no interaction or initiation from the user.
use below code :
HTML and Javascript :
<head runat="server">
<title></title>
<script type="text/javascript">
function HandleIT() {
var name = document.getElementById('<%=txtname.ClientID %>').value;
var address = document.getElementById('<%=txtaddress.ClientID %>').value;
PageMethods.ProcessIT(name, address, onSucess, onError);
function onSucess(result) {
alert(result);
}
function onError(result) {
alert('Something wrong.');
}
}
</script>
Code Behind :
[WebMethod]
public static string ProcessIT(string name, string address)
{
string result = "Welcome Mr. " + name + ". Your address is '" + address + "'.";
return result;
}
More information :
C# functions returns a value and show in webpage
i am developing a website in dotnet.
//function to close SearchSchool.aspx
function CloseSchoolSearch()
{
//storing values
window.close();
//call function in code behind
}
This is a javascript function in an external .js file ,using this function i am storing some values in some hidden controls in an aspx page and closing pop window ,after that i want to execute a function in code behind.and remind one thing,i can't include this function .aspx page contaning that method i want to call.Can anyone guide me how to do this
As i understand the question, you are talking about 2 very different things.
the .ASPX page is rendered on the server and the javascript code is rendered at the client side.
for you to call a function from the aspx page from JS means that you need to make a call to the server to render your page is some other manner with a parameter you mentioned in your call.
only then will the server re-render the page (can be ajax as well) and invoke these methods.
other then that, the server side code is not being sent to the client side.
On the client side:
you can use any framework or implement your own. i'll use jquery for simplicity
/* attach a submit handler to the form */
$("#form_name").submit(function(event) {
/* stop form from submitting normally */
event.preventDefault();
/* get some values from elements on the page: */
url ="<server url>";
var $inputs = $('#form_name :input');
var dataString="";
$inputs.each(function() {
if (this.type != "submit" && this.type != "button")
dataString += (this.name +"="+ $(this).val() +"&").trim();
});
/*Remove the & at the end of the string*/
dataString = dataString.slice(0, -1);
/* Send the data using post and put the results in a div */
$.post( url, dataString,
function( data ) {
}
);
the serialize function will work as well just add its output instead of the dataString.
I understand you want to call a javascript function defined inside the HTML page using <script></script> from an externally loaded .js file.
Just make sure the internal javascript function is available when your external JS is loaded.
If you want to call a function localFoo() defined inside the HTML code, then do this:
// Check for the function availability
if(typeof localFoo != undefined) {
localFoo(arg);
}
I'm writing a web page in ASP.NET. I have some JavaScript code, and I have a submit button with a click event.
Is it possible to call a method I created in ASP with JavaScript's click event?
Well, if you don't want to do it using Ajax or any other way and just want a normal ASP.NET postback to happen, here is how you do it (without using any other libraries):
It is a little tricky though... :)
i. In your code file (assuming you are using C# and .NET 2.0 or later) add the following Interface to your Page class to make it look like
public partial class Default : System.Web.UI.Page, IPostBackEventHandler{}
ii. This should add (using Tab-Tab) this function to your code file:
public void RaisePostBackEvent(string eventArgument) { }
iii. In your onclick event in JavaScript, write the following code:
var pageId = '<%= Page.ClientID %>';
__doPostBack(pageId, argumentString);
This will call the 'RaisePostBackEvent' method in your code file with the 'eventArgument' as the 'argumentString' you passed from the JavaScript. Now, you can call any other event you like.
P.S: That is 'underscore-underscore-doPostBack' ... And, there should be no space in that sequence... Somehow the WMD does not allow me to write to underscores followed by a character!
The __doPostBack() method works well.
Another solution (very hackish) is to simply add an invisible ASP button in your markup and click it with a JavaScript method.
<div style="display: none;">
<asp:Button runat="server" ... OnClick="ButtonClickHandlerMethod" />
</div>
From your JavaScript, retrieve the reference to the button using its ClientID and then call the .click() method on it.
var button = document.getElementById(/* button client id */);
button.click();
The Microsoft AJAX library will accomplish this. You could also create your own solution that involves using AJAX to call your own aspx (as basically) script files to run .NET functions.
I suggest the Microsoft AJAX library. Once installed and referenced, you just add a line in your page load or init:
Ajax.Utility.RegisterTypeForAjax(GetType(YOURPAGECLASSNAME))
Then you can do things like:
<Ajax.AjaxMethod()> _
Public Function Get5() AS Integer
Return 5
End Function
Then, you can call it on your page as:
PageClassName.Get5(javascriptCallbackFunction);
The last parameter of your function call must be the javascript callback function that will be executed when the AJAX request is returned.
You can do it asynchronously using .NET Ajax PageMethods. See here or here.
I think blog post How to fetch & show SQL Server database data in ASP.NET page using Ajax (jQuery) will help you.
JavaScript Code
<script src="http://code.jquery.com/jquery-3.3.1.js" />
<script language="javascript" type="text/javascript">
function GetCompanies() {
$("#UpdatePanel").html("<div style='text-align:center; background-color:yellow; border:1px solid red; padding:3px; width:200px'>Please Wait...</div>");
$.ajax({
type: "POST",
url: "Default.aspx/GetCompanies",
data: "{}",
dataType: "json",
contentType: "application/json; charset=utf-8",
success: OnSuccess,
error: OnError
});
}
function OnSuccess(data) {
var TableContent = "<table border='0'>" +
"<tr>" +
"<td>Rank</td>" +
"<td>Company Name</td>" +
"<td>Revenue</td>" +
"<td>Industry</td>" +
"</tr>";
for (var i = 0; i < data.d.length; i++) {
TableContent += "<tr>" +
"<td>"+ data.d[i].Rank +"</td>" +
"<td>"+data.d[i].CompanyName+"</td>" +
"<td>"+data.d[i].Revenue+"</td>" +
"<td>"+data.d[i].Industry+"</td>" +
"</tr>";
}
TableContent += "</table>";
$("#UpdatePanel").html(TableContent);
}
function OnError(data) {
}
</script>
ASP.NET Server Side Function
[WebMethod]
[ScriptMethod(ResponseFormat= ResponseFormat.Json)]
public static List<TopCompany> GetCompanies()
{
System.Threading.Thread.Sleep(5000);
List<TopCompany> allCompany = new List<TopCompany>();
using (MyDatabaseEntities dc = new MyDatabaseEntities())
{
allCompany = dc.TopCompanies.ToList();
}
return allCompany;
}
Static, strongly-typed programming has always felt very natural to me, so at first I resisted learning JavaScript (not to mention HTML and CSS) when I had to build web-based front-ends for my applications. I would do anything to work around this like redirecting to a page just to perform and action on the OnLoad event, as long as I could code pure C#.
You will find however that if you are going to be working with websites, you must have an open mind and start thinking more web-oriented (that is, don't try to do client-side things on the server and vice-versa). I love ASP.NET webforms and still use it (as well as MVC), but I will say that by trying to make things simpler and hiding the separation of client and server it can confuse newcomers and actually end up making things more difficult at times.
My advice is to learn some basic JavaScript (how to register events, retrieve DOM objects, manipulate CSS, etc.) and you will find web programming much more enjoyable (not to mention easier). A lot of people mentioned different Ajax libraries, but I didn't see any actual Ajax examples, so here it goes. (If you are not familiar with Ajax, all it is, is making an asynchronous HTTP request to refresh content (or perhaps perform a server-side action in your scenario) without reloading the entire page or doing a full postback.
Client-Side:
<script type="text/javascript">
var xmlhttp = new XMLHttpRequest(); // Create object that will make the request
xmlhttp.open("GET", "http://example.org/api/service", "true"); // configure object (method, URL, async)
xmlhttp.send(); // Send request
xmlhttp.onstatereadychange = function() { // Register a function to run when the state changes, if the request has finished and the stats code is 200 (OK). Write result to <p>
if (xmlhttp.readyState == 4 && xmlhttp.statsCode == 200) {
document.getElementById("resultText").innerHTML = xmlhttp.responseText;
}
};
</script>
That's it. Although the name can be misleading the result can be in plain text or JSON as well, you are not limited to XML. jQuery provides an even simpler interface for making Ajax calls (among simplifying other JavaScript tasks).
The request can be an HTTP-POST or HTTP-GET and does not have to be to a webpage, but you can post to any service that listens for HTTP requests such as a RESTful API. The ASP.NET MVC 4 Web API makes setting up the server-side web service to handle the request a breeze as well. But many people do not know that you can also add API controllers to web forms project and use them to handle Ajax calls like this.
Server-Side:
public class DataController : ApiController
{
public HttpResponseMessage<string[]> Get()
{
HttpResponseMessage<string[]> response = new HttpResponseMessage<string[]>(
Repository.Get(true),
new MediaTypeHeaderValue("application/json")
);
return response;
}
}
Global.asax
Then just register the HTTP route in your Global.asax file, so ASP.NET will know how to direct the request.
void Application_Start(object sender, EventArgs e)
{
RouteTable.Routes.MapHttpRoute("Service", "api/{controller}/{id}");
}
With AJAX and Controllers, you can post back to the server at any time asynchronously to perform any server side operation. This one-two punch provides both the flexibility of JavaScript and the power the C# / ASP.NET, giving the people visiting your site a better overall experience. Without sacrificing anything, you get the best of both worlds.
References
Ajax,
jQuery Ajax,
Controller in Webforms
The Microsoft AJAX library will accomplish this. You could also create your own solution that involves using AJAX to call your own aspx (as basically) script files to run .NET functions.
This is the library called AjaxPro which was written an MVP named Michael Schwarz. This was library was not written by Microsoft.
I have used AjaxPro extensively, and it is a very nice library, that I would recommend for simple callbacks to the server. It does function well with the Microsoft version of Ajax with no issues. However, I would note, with how easy Microsoft has made Ajax, I would only use it if really necessary. It takes a lot of JavaScript to do some really complicated functionality that you get from Microsoft by just dropping it into an update panel.
It is so easy for both scenarios (that is, synchronous/asynchronous) if you want to trigger a server-side event handler, for example, Button's click event.
For triggering an event handler of a control:
If you added a ScriptManager on your page already then skip step 1.
Add the following in your page client script section
//<![CDATA[
var theForm = document.forms['form1'];
if (!theForm) {
theForm = document.form1;
}
function __doPostBack(eventTarget, eventArgument) {
if (!theForm.onsubmit || (theForm.onsubmit() != false)) {
theForm.__EVENTTARGET.value = eventTarget;
theForm.__EVENTARGUMENT.value = eventArgument;
theForm.submit();
}
}
//]]>
Write you server side event handler for your control
protected void btnSayHello_Click(object sender, EventArgs e)
{
Label1.Text = "Hello World...";
}
Add a client function to call the server side event handler
function SayHello() {
__doPostBack("btnSayHello", "");
}
Replace the "btnSayHello" in code above with your control's client id.
By doing so, if your control is inside an update panel, the page will not refresh. That is so easy.
One other thing to say is that: Be careful with client id, because it depends on you ID-generation policy defined with the ClientIDMode property.
I'm trying to implement this but it's not working right. The page is
posting back, but my code isn't getting executed. When i debug the
page, the RaisePostBackEvent never gets fired. One thing i did
differently is I'm doing this in a user control instead of an aspx
page.
If anyone else is like Merk, and having trouble over coming this, I have a solution:
When you have a user control, it seems you must also create the PostBackEventHandler in the parent page. And then you can invoke the user control's PostBackEventHandler by calling it directly. See below:
public void RaisePostBackEvent(string _arg)
{
UserControlID.RaisePostBackEvent(_arg);
}
Where UserControlID is the ID you gave the user control on the parent page when you nested it in the mark up.
Note: You can also simply just call methods belonging to that user control directly (in which case, you would only need the RaisePostBackEvent handler in the parent page):
public void RaisePostBackEvent(string _arg)
{
UserControlID.method1();
UserControlID.method2();
}
You might want to create a web service for your common methods.
Just add a WebMethodAttribute over the functions you want to call, and that's about it.
Having a web service with all your common stuff also makes the system easier to maintain.
If the __doPostBack function is not generated on the page you need to insert a control to force it like this:
<asp:Button ID="btnJavascript" runat="server" UseSubmitBehavior="false" />
Regarding:
var button = document.getElementById(/* Button client id */);
button.click();
It should be like:
var button = document.getElementById('<%=formID.ClientID%>');
Where formID is the ASP.NET control ID in the .aspx file.
Add this line to page load if you are getting object expected error.
ClientScript.GetPostBackEventReference(this, "");
You can use PageMethods.Your C# method Name in order to access C# methods or VB.NET methods into JavaScript.
Try this:
if(!ClientScript.IsStartupScriptRegistered("window"))
{
Page.ClientScript.RegisterStartupScript(this.GetType(), "window", "pop();", true);
}
Or this
Response.Write("<script>alert('Hello World');</script>");
Use the OnClientClick property of the button to call JavaScript functions...
You can also get it by just adding this line in your JavaScript code:
document.getElementById('<%=btnName.ClientID%>').click()
I think this one is very much easy!
Please try this:
<%= Page.ClientScript.GetPostBackEventReference(ddlVoucherType, String.Empty) %>;
ddlVoucherType is a control which the selected index change will call... And you can put any function on the selected index change of this control.
The simplest and best way to achieve this is to use the onmouseup() JavaScript event rather than onclick()
That way you will fire JavaScript after you click and it won't interfere with the ASP OnClick() event.
I try this and so I could run an Asp.Net method while using jQuery.
Do a page redirect in your jQuery code
window.location = "Page.aspx?key=1";
Then use a Query String in Page Load
protected void Page_Load(object sender, EventArgs e)
{
if (Request.QueryString["key"] != null)
{
string key= Request.QueryString["key"];
if (key=="1")
{
// Some code
}
}
}
So no need to run an extra code
This reply works like a breeze for me thanks cross browser:
The __doPostBack() method works well.
Another solution (very hackish) is to simply add an invisible ASP button in your markup and click it with a JavaScript method.
<div style="display: none;">
<asp:Button runat="server" ... OnClick="ButtonClickHandlerMethod" />
</div>
From your JavaScript, retrieve the reference to the button using its ClientID and then call the .Click() method on it:
var button = document.getElementByID(/* button client id */);
button.Click();
Blockquote