<c:forEach items="${sessionScope.cart.cartItem}" var="cartI">
        <div class="cart-con-info">
            <div class="info-top">
            </div>
            <div class="info-mid">
                <input type="checkbox" value="" name="hobby" class="mid-ipt f-l"></input>
                <div class="mid-tu f-l">
                    <a href="#"><img src="${pageContext.request.contextPath}/images/dai1.gif" /></a>
                </div>
                <div class="mid-font f-l">
                    <a href="#">登高阁紫菜肉松鸡蛋卷 海苔蛋卷 糕点<br />江西特产小吃 休闲办公零食</a>
                    <span>满赠</span>
                </div>
                <div class="mid-guige f-l">
                    <p>颜色：蓝色</p>
                    <p>尺码：XL</p>
                    <a href="JavaScript:;" class="xg" xg="xg1">修改</a>
                    <div class="guige-xiugai" xg-g="xg1">
                        <div class="xg-left f-l">
                            <dl>
                                <dt>颜  色</dt>
                                <dd>
                                    <a href="JavaScript:;" class="current">黑色</a>
                                    <a href="JavaScript:;">白色</a>
                                </dd>
                                <div style="clear:both;"></div>
                            </dl>
                            <dl>
                                <dt>尺  码</dt>
                                <dd>
                                    <a href="JavaScript:;" class="current">M</a>
                                    <a href="JavaScript:;">L</a>
                                    <a href="JavaScript:;">XL</a>
                                </dd>
                                <div style="clear:both;"></div>
                            </dl>
                            <a href="JavaScript:;" class="qd">确定</a>
                            <a href="JavaScript:;" class="qx" qx="xg1">取消</a>
                        </div>
                        <div class="xg-right f-l">
                            <a href="#"><img src="${pageContext.request.contextPath}/images/dai2.gif" /></a>
                        </div>
                        <div style="clear:both;"></div>
                    </div>
                </div>
                <div class="mid-sl f-l">
                    <a href="JavaScript:;" class="sl-left">-</a>
                    <input type="text" value="${cartI.count}" />
                    <a href="JavaScript:;" class="sl-right" id="${cartI.productExt.pid}" name="plus">+</a>
                </div>
                <p class="mid-dj f-l">¥ <span>${cartI.price}</span></p>
                <p class="mid-je f-l">¥ <span>${cartI.sum}</span></p>
                <div class="mid-chaozuo f-l">
                    <a href="#">移入收藏夹</a>
                    <a href="#">删除</a>
                </div>
                <div style="clear:both;"></div>
            </div>
        </div>
    </c:forEach>

当上方元素是遍历出来的时候，要定位 <a href="JavaScript:;" class="sl-right" id="${cartI.productExt.pid}" name="plus">+</a>标签时，只需要通过class里的.sl-right属性触发事件即可，如下:

$(".mid-sl .sl-right").click(function(event) {
            var pid = $(this).attr("id");
            var vl = $(this).siblings("input").val();
            $.ajax({
                url : "../cart/updatePro.do",
                type : 'post',
                data :{
                    pid : pid,
                    count : vl
                },
                success : function (data) {
                }
            });
        });

此时已经定位到多行数据中的某一行，要获取此行的数据只需要var pid = $(this).attr("属性名");即可获取属性中的值。