Mybatis 遍历 map

在做mybatis物理端分页的过程中遇到通过遍历page对象中的参数map来拼写动态SQL，而传入的paramType类型是page对象，这个map中的key是数据库中的字段SQL的where条件是key=value

<select id="getEmployeePage" resultType="Employee" parameterType="Page"  >  
   		
   		SELECT  * FROM t_employee 
   		
   		<if test="null != params and  params.size()> 0"> WHERE  '1'='1'  </if> 
   		 
   		<foreach collection="params" index="key" item="item" open=""  close="" >
          
            <choose>
   				<when test="key =='RealName' and item !=null and item !=''">
  					
  					and ${key}  LIKE  CONCAT(CONCAT('%', #{params.${key}}), '%')
  					
  				</when>
  				<when test=" item != null and item!=''">
  					
  					and  ${key} =  #{params.${key}}
  					
  				</when>
  				
  				<otherwise>
 					
  				</otherwise>
  			</choose>
      	</foreach> 
   		
	</select>