JAVA实现JSON后端向前端传递数据

import java.text.DateFormat;import java.text.ParseException;import java.text.SimpleDateFormat;import java.util.Date;public class ConcurrentDateUtil {  private static ThreadLocal<DateFormat> threadLocal = new ThreadLocal<DateFormat>() {    @Override    protected DateFormat initialValue() {      return new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");    }  };  public static Date parse(String dateStr) throws ParseException {    return threadLocal.get().parse(dateStr);  }  public static String format(Date date) {    return threadLocal.get().format(date);  }}

import com.sf.utils.ConcurrentDateUtil;import java.util.Date;public class JsonResult<T> {  public static int NEED_RE_LOGIN = 1;  public static int NEED_RETRY = 2;  private int errCode;  private String message;  private String timestamp = ConcurrentDateUtil.format(new Date());  private T data;  public String getMessage() {    return message;  }  public void setMessage(String message) {    this.message = message;  }  public String getTimestamp() {    return timestamp;  }  public T getData() {    return data;  }  public void setData(T data) {    this.data = data;  }  public int getErrCode() {    return errCode;  }  public void setErrCode(int errCode) {    this.errCode = errCode;  }}

@ResponseBody@RequestMapping(value = "/user/getUserAmount", method = RequestMethod.POST)public JsonResult<Map<String, Integer>> getUserAmount() {  JsonResult<Map<String, Integer>> result = new JsonResult<>();  try {    //已签到人数    Integer signedAmount = userService.getSignedAmount();    //总人数    Integer totalUserAmount = userService.getTotalUserAmount();    Map<String, Integer> amountMap = new HashMap<>();    amountMap.put("signed", signedAmount);    amountMap.put("sum", totalUserAmount);    result.setData(amountMap);    //这里举个例子，如果觉得setData穿的信息不够，还可以用setMessage方法多传一个字符串过去    result.setMessage("这是签到界面");  } catch (Exception e) {    log.warn(ExceptionUtils.getStackTrace(e));  }  return result;}

function getSignedAmount(){  $.ajax({    type: "post",    url : getContextPath() + "/user/getUserAmount",    dataType:'json',    data: {    },    success: function(data){      var amount = data.data;      //取出总人数      var totalAmount = amount.sum;      //总人数减去已经签到的人数，就是未签到的人      var unsignedNumber = amount.sum-amount.signed;      //取出后端controller中setMessage方法传过来的字符串      var logMessage = data.message;    }  });}