invoking a Java servlet via JavaScript

Question

invoking a Java servlet via JavaScript

Looking to develop a web application following the MVC design pattern. I am planning to use JavaScript for the GUI and Java Servlets for the controller.

As someone new to JavaScript, I'm struggling to understand how to invoke a Java Servlet from JavaScript and handle the response back from the Servlet.

Any suggestions or guidance on this would be greatly appreciated!

java javascript ajax web-applications servlets

Answer 1

Answer №1

If you are looking to make Ajax calls to a servlet, you will need the XMLHttpRequest object in JavaScript. Here is an example that is compatible with Firefox:

<script>
    var xhr = new XMLHttpRequest();
    xhr.onreadystatechange = function() {
        if (xhr.readyState == 4) {
            var data = xhr.responseText;
            alert(data);
        }
    }
    xhr.open('GET', '${pageContext.request.contextPath}/myservlet', true);
    xhr.send(null);
</script>

However, this method can be verbose and not entirely cross-browser compatible. For a more universally compatible approach to firing ajax requests and navigating the HTML DOM, consider using jQuery. Here is how you can rewrite the above code using jQuery:

<script src="http://code.jquery.com/jquery-latest.min.js"></script>
<script>
    $.get('${pageContext.request.contextPath}/myservlet', function(data) {
        alert(data);
    });
</script>

In either case, ensure that the Servlet on the server is mapped to a URL pattern of /myservlet and implements at least doGet() to write data to the response.

To display the response data on the HTML page, manipulate the HTML DOM as needed. You can use methods like getElementById() or jQuery selectors for this purpose.

For more complex data transfers, consider using formats like XML or JSON. Visit resources like Stack Overflow for detailed examples on utilizing Servlets and Ajax efficiently.

Answer 2

If you are looking to make Ajax calls to a servlet, you will need the XMLHttpRequest object in JavaScript. Here is an example that is compatible with Firefox:

<script>
    var xhr = new XMLHttpRequest();
    xhr.onreadystatechange = function() {
        if (xhr.readyState == 4) {
            var data = xhr.responseText;
            alert(data);
        }
    }
    xhr.open('GET', '${pageContext.request.contextPath}/myservlet', true);
    xhr.send(null);
</script>

However, this method can be verbose and not entirely cross-browser compatible. For a more universally compatible approach to firing ajax requests and navigating the HTML DOM, consider using jQuery. Here is how you can rewrite the above code using jQuery:

<script src="http://code.jquery.com/jquery-latest.min.js"></script>
<script>
    $.get('${pageContext.request.contextPath}/myservlet', function(data) {
        alert(data);
    });
</script>

In either case, ensure that the Servlet on the server is mapped to a URL pattern of /myservlet and implements at least doGet() to write data to the response.

To display the response data on the HTML page, manipulate the HTML DOM as needed. You can use methods like getElementById() or jQuery selectors for this purpose.

For more complex data transfers, consider using formats like XML or JSON. Visit resources like Stack Overflow for detailed examples on utilizing Servlets and Ajax efficiently.

Answer 3

Answer №2

This tutorial demonstrates how to dynamically print text on an HTML5 document using AJAX. The code is inspired by the book "Internet & WWW (Deitel)".

Javascript Implementation:

var asyncRequest;    
function start(){
    try
    {
        asyncRequest = new XMLHttpRequest();
        asyncRequest.addEventListener("readystatechange", stateChange, false);
        asyncRequest.open('GET', '/Test', true);    //   /Test is url to Servlet!
        asyncRequest.send(null);
    }
    catch(exception)
   {
    alert("Request failed");
   }
}

function stateChange(){
if(asyncRequest.readyState == 4 && asyncRequest.status == 200)
    {
    var text = document.getElementById("text");         //  text is an id of a 
    text.innerHTML = asyncRequest.responseText;         //  div in HTML document
    }
}

window.addEventListener("load", start(), false);

Servlet java code:

public class Test extends HttpServlet{
@Override
public void doGet(HttpServletRequest req, HttpServletResponse resp)
    throws IOException{
        resp.setContentType("text/plain");
        resp.getWriter().println("Servlet wrote this! (Test.java)");
    }
}

HTML document

 <div id = "text"></div>

EDIT

When I initially wrote this guide, I was a beginner in web programming. Looking back, the javascript part would be better implemented using jQuery as it offers a more convenient solution compared to raw javascript.

Answer 4

This tutorial demonstrates how to dynamically print text on an HTML5 document using AJAX. The code is inspired by the book "Internet & WWW (Deitel)".

Javascript Implementation:

var asyncRequest;    
function start(){
    try
    {
        asyncRequest = new XMLHttpRequest();
        asyncRequest.addEventListener("readystatechange", stateChange, false);
        asyncRequest.open('GET', '/Test', true);    //   /Test is url to Servlet!
        asyncRequest.send(null);
    }
    catch(exception)
   {
    alert("Request failed");
   }
}

function stateChange(){
if(asyncRequest.readyState == 4 && asyncRequest.status == 200)
    {
    var text = document.getElementById("text");         //  text is an id of a 
    text.innerHTML = asyncRequest.responseText;         //  div in HTML document
    }
}

window.addEventListener("load", start(), false);

Servlet java code:

public class Test extends HttpServlet{
@Override
public void doGet(HttpServletRequest req, HttpServletResponse resp)
    throws IOException{
        resp.setContentType("text/plain");
        resp.getWriter().println("Servlet wrote this! (Test.java)");
    }
}

HTML document

 <div id = "text"></div>

EDIT

When I initially wrote this guide, I was a beginner in web programming. Looking back, the javascript part would be better implemented using jQuery as it offers a more convenient solution compared to raw javascript.

Answer 5

Answer №3

If you're looking to improve your javascript calls, I highly recommend using jquery and implementing JSR311, such as jersey, for the service layer. This approach will allow your controllers to delegate efficiently.

By utilizing these tools, you can streamline handling HTTP calls and data serialization, providing significant assistance in managing underlying logic.

Answer 6

If you're looking to improve your javascript calls, I highly recommend using jquery and implementing JSR311, such as jersey, for the service layer. This approach will allow your controllers to delegate efficiently.

By utilizing these tools, you can streamline handling HTTP calls and data serialization, providing significant assistance in managing underlying logic.

Answer 7

Answer №4

Apologies, I was focusing on jsp rather than javascript. In order to achieve the desired outcome, you will need to implement something similar to the following code snippet (please note that this is a relative URL and may vary depending on the document's URL where this javascript is located):

document.location = 'path/to/servlet';

Your servlet-mapping configuration in web.xml should resemble the following structure:

<servlet-mapping>
    <servlet-name>someServlet</servlet-name>
    <url-pattern>/path/to/servlet*</url-pattern>
</servlet-mapping>

Answer 8

Apologies, I was focusing on jsp rather than javascript. In order to achieve the desired outcome, you will need to implement something similar to the following code snippet (please note that this is a relative URL and may vary depending on the document's URL where this javascript is located):

document.location = 'path/to/servlet';

Your servlet-mapping configuration in web.xml should resemble the following structure:

<servlet-mapping>
    <servlet-name>someServlet</servlet-name>
    <url-pattern>/path/to/servlet*</url-pattern>
</servlet-mapping>

Answer 9

Answer №5

   function initiateServletRequest() {
 document.getElementById("adminForm").action = "./Administrator";
 document.getElementById("adminForm").method = "GET";
 document.getElementById("adminForm").submit();

}

<button type="submit" onclick="initiateServletRequest()" align="center"> Register</button>

Answer 10

   function initiateServletRequest() {
 document.getElementById("adminForm").action = "./Administrator";
 document.getElementById("adminForm").method = "GET";
 document.getElementById("adminForm").submit();

}

<button type="submit" onclick="initiateServletRequest()" align="center"> Register</button>

Answer 11

Answer №6

let btn = document.getElementById("<<button-id>>");
btn.addEventListener("click", function() {
  window.location.href= "<<full-servlet-path>>" (example: http://localhost:8086/xyz/servlet)
});

Answer 12

let btn = document.getElementById("<<button-id>>");
btn.addEventListener("click", function() {
  window.location.href= "<<full-servlet-path>>" (example: http://localhost:8086/xyz/servlet)
});

invoking a Java servlet via JavaScript

Answer №1

Answer №2

Javascript Implementation:

Servlet java code:

HTML document

EDIT

Answer №3

Answer №4

Answer №5

Answer №6

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