1、是否為空：
${empty sessionScope.username}
2、是否不為空
${not empty sessionScope.username}
3、得到請求參數
${param.username}
4、判斷數字
${requestScope.age==20}
5、判斷字符串
${requestScope.username=='vickzhu'}
或者${requestScope.username=="vickzhu"}
6、選中單選、復選、下拉框
下拉框：<option value="${cityInfo.cityCode }" ${param.cityCode==cityInfo.cityCode? "selected='selected'":"" } >${cityInfo.cityName }</option>
單選、復選：<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