function getstaffinfo(){
    
     var staffid=$("#staffid").val();
     $.ajax({
            type: "post",
            url: "getInfoById.action?staffid="+$("#staffid").val(),
            contentType:"application/json;charset=utf-8",
            error:function(){
                 alert("err");
                 
             },
            success: function(result) {
             alert("success");
             var json=eval(result);
                 var staffname= json.staffname;
                 var staffcareer = json.staffcareer;
                 document.getElementById("staffname").value=staffname;
                 document.getElementById("staffcareer").value=staffcareer;
         }});
          
     
}

private Map<String, String> result;

//........省略get/set

public String getInfoById(){
        List<Staff> list = this.getSalaryService().findSalaryTableById(this.getStaffid());
        Map<String, String> result2 =new HashMap<String, String>();
        result2.put("staffname", list.get(0).getName());
        result2.put("staffcareer",list.get(0).getCareer());
        this.setResult(result2);
        return SUCCESS;
        
    }

<tr>    
  <td colspan="6"><font color="red">*</font>员工工号</td>
  <td><input type="text" name="salarytable.staffid" id="staffid" onblur="getstaffinfo()"></td>
  <td colspan="6">员工姓名</td>    
  <td><input type="text"  id="staffname" value="" /></td>
  <td colspan="6">员工职位</td>    
  <td><input type="text"  id="staffcareer" value="" /></td>
</tr>

<package name="salary2"  extends="json-default">
    <result-types>    
        <result-type name="json" class="org.apache.struts2.json.JSONResult"/>
    </result-types>
        <action name="getInfoById" class="main.salary.action.SalaryAction" method="getInfoById">
        <result name="json"></result>
    </action>
    </package>
</struts>