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Composing URL in JSP

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既然无缘
既然无缘 2021-01-02 14:39

Lets say my current URL is: /app.jsp?filter=10&sort=name.

I have a pagination component in JSP which should contain links like:
/app.

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  • 盖世英雄少女心
    2021-01-02 14:52

    To construct a new URL based on the current URL, you first need to get the current URL from the request object. To access the request object in a JSP use pageContext implicit object defined by the JSP expression language:

    ${pageContext.request.requestURL}

    Here is the simple example of constructing URL in a JSP page:

    test.jsp 

    <%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<!DOCTYPE html>
<html>
<head>
    <title>Test Page</title>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
    <h1>Testing URL construction</h1>
    <c:choose>
        <c:when test="${pageContext.request.queryString != null}">
            <a href="${pageContext.request.requestURL}?${pageContext.request.queryString}&page=xxx">Go to page xxx</a>
        </c:when>
        <c:otherwise>
            <a href="${pageContext.request.requestURL}?page=xxx">Go to page xxx</a>
        </c:otherwise>
    </c:choose>
</body>
</html>


    This solution allows you to construct URLs depending on whether the current URL already contains some query string or not. So you respectively append either

    ?${pageContext.request.queryString}&page=xxx

    or just

    ?page=xxx

    to the current URL.

    JSTL and the Expression Language were used to implement checking for a query string. And we used getRequestURL() method to obtain the current URL.

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  • 名媛妹妹
    2021-01-02 14:54

    Ok, I found answer. First problem is that I have to preserve all current parameters in URL and change only page parameter. To do this I have to iterate over all current parameters and add those I don't want to change to URL. Then I added parameters I want to either change or add. So I ended up with solution like this:

    <c:url var="nextUrl" value="">
    <c:forEach items="${param}" var="entry">
        <c:if test="${entry.key != 'page'}">
            <c:param name="${entry.key}" value="${entry.value}" />
        </c:if>
    </c:forEach>
    <c:param name="page" value="${some calculation}" />
</c:url>

    This will create nice and clean URL independent of page parameter in request. Bonus to this approach is that URL can be just anything.

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  • 夕颜
    2021-01-02 15:07 
    <c:url var="myURL" value="/app.jsp">
   <c:param name="filter" value="10"/>
   <c:param name="sort" value="name"/>
</c:url>

    To show the url you can do something like this

    <a href="${myURL}">Your URL Text</a>
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