ognl.OgnlException: target is null for setProperty(null, "taskStatus"

ognl.OgnlException: target is null for setProperty(null, “taskStatus”, [Ljava.lang.String;@4a5a5f)
点击查询，调用js中的query方法，报错。不知道如何解决

      <tr>
	                 <td width="90" align="right" >任务类型</td>
	                  <td width="232" align="center" height="36"><select class="text w_2" id="taskType">
                  			<option value="" selected="selected"></option>
                  				 <c:forEach items="${requestScope.listMCode }" var="mcode" >
                  					<option value="${mcode.id.codeCode }">${mcode.codeCName }</option>
                  				</c:forEach>
              
                  		</select>
 </td>
</tr>

function pageLoadIni(){
	params = {
	        "domian.taskStatus" : $("#taskStatus").val()
        	};
} 

	  function query(){
	        pageLoadIni();
	    	var url = contextRootPath + ""/statements/dispatchTaskCount.do?"";
}

action

private DispatchTaskCountDoMain domain;
	public DispatchTaskCountDoMain getDomain() {
		return domain;
	}

	public void setDomain(DispatchTaskCountDoMain domain) {
		this.domain = domain;
	}

bean

public class DispatchTaskCountDoMain implements java.io.Serializable{
	private String taskStatus;
        public String getTaskStatus() {
		return taskStatus;
	}

	public void setTaskStatus(String taskStatus) {
		this.taskStatus = taskStatus;
	}
}