EL 表达式用法的一些总结

EL 表达式用法的一些总结

    1、是否为空：
            ${empty sessionScope.username}
    2、是否不为空
            ${not empty sessionScope.username}
    3、得到请求参数
            ${param.username}
    4、判断数字
            ${requestScope.age==20}
    5、判断字符串
            ${requestScope.username=='vickzhu'}
            或者${requestScope.username=="vickzhu"}
    6、选中单选、复选、下拉框
            下拉框：<option value="${cityInfo.cityCode }" ${param.cityCode==cityInfo.cityCode? "selected='selected'":"" } >${cityInfo.cityName }</option>
            单选、复选：<input name="gender" type="radio" ${param.gender==1?"checked='checked'":"" } value="1" />男
                                    <input name="gender" type="radio" ${param.gender==2?"checked='checked'":"" } value="2" />女