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[Java教程]获取表中字段最大值,并且保存在前台页面中


//获取Useridfunction getUserId(){   $.getJSON('<%=basePath %>user/getUserId.do',    function(data){	      alert(eval(data).userId);	      document.getElementById("userId").value=data.userId;  });	}    


<input id="userId" name="userId"  value=""  type="text"  readonly="readonly"/><input  value="获取最大的Userid"  onclick="javascript:getUserId();" type="button" />

  UserSlaveController 获取参数

	@ResponseBody                          //@ResponseBody 返回的是数据,不加 @ResponseBody 返回的是页面。 	@RequestMapping(value="/user/getUserId.do")//method=RequestMethod.POST	public JSONObject getUserId(HttpServletRequest request, HttpServletResponse response)throws Exception {	  response.setContentType("text/html");	  request.setCharacterEncoding("utf-8");	  response.setCharacterEncoding("utf-8");	  JSONObject jsonObject = new JSONObject();	  	  Integer userId = 0;	    try	    {	     	      userId = userSlaveService.getUserId();	      	    }	    catch (Exception e)	    {	      Loger.logtxt("user", "获取id异常:" + e.toString());	    }	    	    jsonObject.accumulate("userId", userId);	    System.out.println(jsonObject.toString());   //输出: {"userId":182888}	    System.out.println(jsonObject.values());    //输出: [182888]	    return jsonObject;               //返回json,在上面的jsp页面中接收,并且保存值到input中。	}

  UserSlaveService.java 接口声明方法 :  public Integer getUserId()throws Exception;

 

  UserSlaveServiceImpl.java 实现UserSlaveService接口:

  @Override
  public Integer getUserId() throws Exception {
    return userDAO.getUserId();
  }

 

  IUserDAO.java 接口声明方法:  public Integer getUserId()throws Exception;   

 

  user.

  <select id="getUserId" resultType="java.lang.Integer">

  <![CDATA[
    SELECT (MAX(userid)+1) AS userid FROM userinfo
  ]]>