JSON后端向前端传递数据 JAVA

1 后端两个辅助类

ConcurrentDateUtil.java，用于生成我们需要格式的时间

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);
}
}

JsonResult.java，JsonResult封装，用于后端向前端传递数据

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;
}
}

上面这两个类完成之后，我们就可以在web层的controller中使用JsonResult封装数据并传递到前端。

接下来介绍两种情况，看看前端怎么取数据出来

2 前端JS怎么取出数据

如果后端传给前端的JsonResult封装的是一个Map，例如

@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;
}

现在想在前端JS把已签到人数和总人数两个数据取出来，要怎么做呢？只需要在”.”后面跟着Map的Key就好了，如下所示：

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;
}
});
}

说明：

如有转载，请务必在文章开头注明出处：

http://blog.csdn.net/antony9118/article/details/54411284