JSP分页URL查询字符串参数格式异常问题求助

点击分类后，页面显示对应分类的产品列表，此时URL正常：

http://localhost:9999/toyshop/home?category=Đồ%20chơi%20theo%20phim

但点击分页下一页时，URL出现格式错误：

http://localhost:9999/toyshop/home?category{Đồ%20chơi%20theo%20phim}=Đồ%20chơi%20theo%20phim&page=2

期望的正确URL格式应为：

http://localhost:9999/toyshop/home?category=Đồ%20chơi%20theo%20phim&page=2

问题出在手动拼接URL参数的逻辑上：当paramValue包含非ASCII字符（如越南语字符）时，直接通过EL表达式拼接${param}=${paramValue}会触发异常解析，导致参数名被错误替换为category{Đồ%20chơi%20theo%20phim}，而非保持category作为参数名。同时，手动拼接未做标准URL编码，进一步加剧了格式问题。

改用JSTL的<c:url>和<c:param>标签构建URL，它们会自动处理参数编码和格式，避免手动拼接的错误。修改后的代码如下：

<c:remove var="param" scope="session" />
<c:remove var="paramValue" scope="session" />
<c:remove var="href" scope="session" />

<c:remove var="param" scope="request" />
<c:remove var="paramValue" scope="request" />
<c:remove var="href" scope="request" />

<c:choose>
    <c:when test="${not empty sessionScope.productName}">
        <c:set var="servlet" value="search"/>
        <c:set var="param" value="product"/>
        <c:set var="paramValue" value="${sessionScope.productName}"/>
    </c:when>
    <c:when test="${not empty sessionScope.categoryName}">
        <c:set var="servlet" value="home"/>
        <c:set var="param" value="category"/>
        <c:set var="paramValue" value="${sessionScope.categoryName}"/>
    </c:when>
    <c:otherwise>
        <!-- Handle the case where both are empty -->
        <c:set var="servlet" value="home"/>
        <c:set var="param" value=""/>
        <c:set var="paramValue" value=""/>
    </c:otherwise>
</c:choose>

<c:if test="${currentPaginationPage > 1}">
    <c:url var="prevPageHref" value="${servlet}">
        <c:if test="${not empty param and not empty paramValue}">
            <c:param name="${param}" value="${paramValue}"/>
        </c:if>
        <c:param name="page" value="${currentPaginationPage - 1}"/>
    </c:url>
    <a href="${prevPageHref}" class="pagination__item">
        <i class="pagination__icon fas fa-chevron-left"></i>
    </a>
</c:if>

<c:if test="${startPage > 1}">
    <div class="pagination__item pagination__item--none">...</div>
</c:if>

<c:forEach begin="${startPage}" end="${endPage}" var="page">
    <c:url var="pageHref" value="${servlet}">
        <c:if test="${not empty param and not empty paramValue}">
            <c:param name="${param}" value="${paramValue}"/>
        </c:if>
        <c:param name="page" value="${page}"/>
    </c:url>
    <c:choose>
        <c:when test="${page == currentPaginationPage}">
            <a href="${pageHref}" class="pagination__item pagination__item--active">${page}</a>
        </c:when>
        <c:otherwise>
            <a href="${pageHref}" class="pagination__item">${page}</a>
        </c:otherwise>
    </c:choose>
</c:forEach>

<c:if test="${endPage < totalPaginationPage}">
    <div class="pagination__item pagination__item--none">...</div>
</c:if>

<c:if test="${currentPaginationPage < totalPaginationPage}">
    <c:url var="nextPageHref" value="${servlet}">
        <c:if test="${not empty param and not empty paramValue}">
            <c:param name="${param}" value="${paramValue}"/>
        </c:if>
        <c:param name="page" value="${currentPaginationPage + 1}"/>
    </c:url>
    <a href="${nextPageHref}" class="pagination__item">
        <i class="pagination__icon fas fa-chevron-right"></i>
    </a>
</c:if>

• 移除手动拼接URL的逻辑，改用<c:url>标签统一构建链接，<c:param>负责传递参数，自动完成URL编码和格式校验。
• 每个分页链接单独通过<c:url>生成，确保分类参数和分页参数都能正确传递且格式符合HTTP标准。

内容的提问来源于stack exchange，提问作者Vo Hong Thai