jsp cannot use jquery

It is a common problem that JSP cannot use jQuery. Many beginners often encounter this problem when using JSP. Because JSP is a dynamic web page technology written in Java language, and jQuery is a library based on JavaScript, there are certain differences between the two. This article will explore why JSP cannot use jQuery and how to solve this problem.

1. Reasons why JSP cannot use jQuery

You can use JavaScript to write scripts in JSP, but you cannot use jQuery directly. This is because JSP will generate a Servlet program after compilation, and jQuery is a JavaScript library that needs to be interpreted and executed in the browser. Therefore, if you place a jQuery reference in a JSP page, it will cause a compilation error because jQuery's syntax cannot be recognized on the server side.

2. Solution

1. Reference the jQuery library in the JSP page

In order to use jQuery in the JSP page, we need to introduce the jQuery library into the JSP. This can be achieved in the following two ways:

(1) Online reference to the jQuery library

You can add the following code to the JSP page:

<script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.6.0/jquery.min.js"></script>

This code will be downloaded from jQuery official Download the jQuery library from the website and introduce it into the JSP page. This method is very simple, but it requires downloading the jQuery library from the remote server every time the page is loaded, which may affect the page loading speed.

(2) Local reference jQuery library

You can download the jQuery library locally and reference it in the JSP page. This can be achieved through the following steps:

①Access jQuery Official website (https://jquery.com) and download the latest version of jQuery library.

②Put the downloaded jQuery file into a specified directory of the project (such as the "js" directory).

③Reference the local jQuery library in the JSP page. The sample code is as follows:

<script src="${pageContext.request.contextPath}/js/jquery-3.6.0.min.js"></script>

This code introduces the local jQuery library into the JSP page. Among them, ${pageContext.request.contextPath} represents the root directory path of the current web application.

2. Use JSTL tag library

JSTL (JavaServer Pages Standard Tag Library) is a type of JSP tag library that can easily call Java objects, execute conditional judgments, and loop structures in JSP wait. JSTL also provides some tags that can be used to implement functions similar to jQuery. For example: you can use the tag to implement conditional judgment, tag to traverse the collection, etc. These tags can be used with JavaScript to achieve jQuery-like effects.

For example, we can implement an event delegation function similar to jQuery through the following code:

<c:forEach items="${persons}" var="p">
    <tr>
        <td>${p.id}</td>
        <td>${p.name}</td>
        <td>${p.age}</td>
        <td><button id="delBtn-${p.id}" class="delBtn">删除</button></td>
    </tr>
</c:forEach>

<script>
  $(".delBtn").on("click", function() {
      var btnId = $(this).attr("id");
      var id = btnId.split("-")[1];
      if (confirm("确定删除该条记录？")) {
          window.location.href = "deletePerson.jsp?id=" + id;
      }
  });
</script>

The above code uses the tag to traverse the persons collection and generate a table , and added a delete button. When the user clicks the delete button, JavaScript is used to obtain the button ID, extract the ID of the record to be deleted, and jump to the deletePerson.jsp page for the delete operation. The click event and attr method similar to jQuery are used here.

Since JSP cannot use jQuery directly, we need to implement functions similar to jQuery by introducing the jQuery library or using the JSTL tag library. When using it, you need to fully understand the differences and connections between JSP and JavaScript in order to successfully complete the development work.

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