How to parse jsp to javascript

JSP (Java Server Pages) is a server-side dynamic page technology based on Java. It can mix Java code and HTML pages and parse them into pure HTML during network transmission, thereby realizing dynamic generation by the server. HTML page functionality. However, in some cases, we need to parse the Java code in the JSP page into JavaScript code so that the client can perform more flexible operations. This article details how to parse JSP into JavaScript.

1. Use JSTL (JSP Standard Tag Library) tag library

JSTL is a tag library that can reference JavaScript script files in JSP pages. To use the JSTL tag library, you need to import the JSTL core tag library file first. The following is an example:

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>

After the introduction is successful, we can use the c:set tag to create a JavaScript global variable:

<c:set var="message" value="Hello, World!" />
<script type="text/javascript">
var message = <c:out value='${message}'/>;
alert(message);
</script>

The above code creates a JavaScript global variable named message and displays the value of "Hello, World!" in the pop-up box. In the code var message = <c:out value='${message}'/>;, we use the <c:out> tag to output the message variable value, this tag will parse the background Java code into JavaScript code and output it to the page.

2. Use EL expression (Expression Language)

EL expression is a language expression used to access properties and variables in JSP. In a JSP page EL expressions can be referenced just like variables. Similar to the JSTL tag library, EL expressions can also parse Java objects into JavaScript objects. Here is an example:

<%
String message = "Hello, World!";
request.setAttribute("message", message);
%>

<script type="text/javascript">
var message = "${message}";
alert(message);
</script>

In the above code, we first define a string variable named message in the Java code and set it to the property of the request object. Then in JavaScript, we used ${message} to reference the message variable in JSP and successfully parsed it into a JavaScript variable.

3. Using AJAX (Asynchronous JavaScript and XML)

AJAX is an asynchronous communication technology that can send requests to the server through JavaScript without reloading the page. and get the response. In JSP, we can use AJAX technology to asynchronously send Java code to the server for processing, and then return the results to the client, thereby parsing the Java code into JavaScript code. The following is an example:

<script type="text/javascript">
function loadMessage() {
    var xmlhttp;
    if (window.XMLHttpRequest) {
        // code for IE7+, Firefox, Chrome, Opera, Safari
        xmlhttp=new XMLHttpRequest();
    } else {
        // code for IE6, IE5
        xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
    }
    xmlhttp.onreadystatechange=function() {
        if (xmlhttp.readyState==4 && xmlhttp.status==200) {
            var message = xmlhttp.responseText;
            alert(message);
        }
    }
    xmlhttp.open("GET","getmessage.jsp",true);
    xmlhttp.send();
}
</script>

The above code uses the XMLHttpRequest object to send a GET request to the server, and after receiving the response, it parses the response content into a message variable, and displays the value of the message in the pop-up box. . Among them, getmessage.jsp is a JSP page that processes Java code and returns results.

Summary:

This article introduces three methods of parsing JSP into JavaScript, using JSTL tag library, EL expressions and AJAX technology. These methods can help us parse Java code into JavaScript code in some special cases, thereby achieving more flexible and dynamic page effects.

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