JSP嵌入EL表达式？

Question

我想在jsp页面里使用EL表达式的值做一个减法运算， ${tmp.id.rainDate}-${cropPlant}，其中rainDate，cropPlant都是java.util.Date型，
例如rainDate是2012-05-06，cropPlant是2012-05-05，想在单元格里显示 1 ，可是得到的确是2012-05-06 - 2012-05-05，各位帮忙看看
怎么解决？
<table width="960" border="1" bordercolor="#999999" cellpadding="0" cellspacing="0">

                            <colgroup span="17" style="FONT-WEIGHT:bold; FONT-SIZE:12px; COLOR:#003366">
                            </colgroup>

                            <logic:iterate name="ls" indexId="index" id="tmp">
                                <tr>
                                    <TD width="212" style="WIDTH: 100px">
                                        ${tmp.id.rainDate }
                                    </TD>
                                    <TD width="190" style="WIDTH: 50px">
                                        ${tmp.id.rainDate}-${cropPlant}
                                    </TD>
                                    <TD width="135" style="WIDTH: 50px">
                                        ${tmp.id.rainValid }
                                    </TD>
                                    <TD width="135" style="WIDTH: 50px">
                                        ${tmp.id.irrigationData }
                                    </TD>
                                    <TD width="135" style="WIDTH: 50px">
                                        ${tmp.id.etData }
                                    </TD>
                                    <TD width="139" style="WIDTH: 50px">
                                        ${tmp.id.humidityData }
                                    </TD>
                                </tr>
                            </logic:iterate>
                        </table>

Answer 1

${(tmp.id.rainDate-cropPlant)}
这样试试