MyBatis更新话语不成功,为什么这样呢

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try {
			//SUser user= mapper.find(username.toLowerCase());
			//user.setUR_XM(ur_truename_value);
			user.setUR_XM("===================");
			mapper.update(user);//这样不能更新
			//ibatisUtils.getSession().update("com.project.mybaits.SUserMapper.update", user);//这样可以更新
			ibatisUtils.commitSession();
			return true;
			
		} catch (Exception e) {
			e.printStackTrace();
		} finally {    
			ibatisUtils.closeSession();   
		} 
		return false;

<update id="update" parameterType="SUser">
		update S_USER
		<trim prefix="SET" suffixOverrides=",">
			<if test="UR_BM != null">UR_BM = #{UR_BM},</if>
			<if test="UR_XM != null">UR_XM = #{UR_XM},</if>
			<if test="UR_DZ != null">UR_DZ = #{UR_DZ},</if>
			<if test="UR_DH != null">UR_DH = #{UR_DH},</if>
			<if test="UR_MM != null">UR_MM = #{UR_MM},</if>
			<if test="UR_QX != null">UR_QX = #{UR_QX},</if>
			<if test="UR_CJYH != null">UR_CJYH = #{UR_CJYH},</if>
			<if test="UR_MMZHSJ != null">UR_MMZHSJ = #{UR_MMZHSJ},</if>
			<if test="UR_BZ != null">UR_BZ = #{UR_BZ},</if>
		</trim>
		where UR_MC = #{UR_MC}
	</update>

我使用mapper查询是可以,update却不可以, 求高手解答...

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