1.判断数组是否为空
<if test="null != queryTradeType and queryTradeType.size > 0"> and B_TRADE_IB.TRADE_TYPE in <foreach collection="queryTradeType" item="item" index="index" open="(" separator="," close=")"> #{item,jdbcType=VARCHAR} </foreach> </if>
原文：http://www.cnblogs.com/wendelhuang/p/6760823.html