将JSON文件中的日期值读取到Java HashMap中

如何解决将JSON文件中的日期值读取到Java HashMap中

我有一个如下所示的JSON文件：

{
    "calendar": {
        "dateToDayId": {
            "2016-07-14": 290356,"2016-08-26": 380486,"2016-09-07": 417244,"2016-08-15": 354271,"2016-07-25": 311762
        },"dishIdToMealId": {
            "1228578": 474602,"1228585": 474602,"1228586": 474602,...... // more fields
}

我试图将Java中<date,number>下的dateToDayId对读入HashMap<Date,Long>中。首先，我创建了一个JsonInfo类，其中包含一个Calendar类对象。 Calendar类对象又包含所有类，包括DateToDayId，DishToMealId等。我的DateToDayId类看起来像这样（我正在使用Jackson来解析JSON文件）：

package jsonfields;

import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import deserializers.CustomDateDeserializer;

import java.util.Date;
import java.util.TreeMap;

public class DateToDayId {
    @JsonDeserialize(using = CustomDateDeserializer.class)
    private TreeMap <Date,Long> dateToDayMappings;

    public TreeMap<Date,Long> getDateToDayMappings() {
        return dateToDayMappings;
    }

    public void setDateToDayMappings(TreeMap<Date,Long> dateToDayMappings) {
        this.dateToDayMappings = dateToDayMappings;
    }

    @Override
    public String toString() {
        return "DateToDayId{" +
                "dateToDayMappings=" + dateToDayMappings +
                '}';
    }
}

我的Main类看起来像这样：

import java.io.*;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class Main {
    public static void main(String[] args) {
        ObjectMapper objectMapper = new ObjectMapper();
        try {
            InputStreamReader inputStreamReader = new InputStreamReader(new FileInputStream("path\\to\\file\\test.json"));
            JsonInfo jsonInfo = objectMapper.readValue(inputStreamReader,JsonInfo.class);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

运行它时，出现以下异常：

com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "2016-07-14" (class jsonfields.DateToDayId),not marked as ignorable (one known property: "dateToDayMappings"])
 at [Source: (InputStreamReader); line: 1,column: 48] (through reference chain: JsonInfo["calendar"]->jsonfields.Calendar["dateToDayId"]->jsonfields.DateToDayId["2016-07-14"])

我该如何解决？

解决方法

您的类映射是错误的。您需要在dateToDayId中使用变量名称为Calendar的映射。下面的修改后的代码应该可以满足您的需求。

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Date;
import java.util.TreeMap;

public class JSONMapTest {
    public static void main(String[] args) {
        ObjectMapper objectMapper = new ObjectMapper();
        try {
            InputStreamReader inputStreamReader = new InputStreamReader(new FileInputStream("C:\\ws\\test\\test.json"));
            JsonInfo jsonInfo = objectMapper.readValue(inputStreamReader,JsonInfo.class);
            System.out.println(jsonInfo);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

class JsonInfo{
    Calendar calendar;

    public Calendar getCalendar() {
        return calendar;
    }

    public void setCalendar(Calendar calendar) {
        this.calendar = calendar;
    }
}

class Calendar {
    private TreeMap <Date,Long> dateToDayId;

    public TreeMap<Date,Long> getDateToDayId() {
        return dateToDayId;
    }

    public void setDateToDayId(TreeMap<Date,Long> dateToDayId) {
        this.dateToDayId = dateToDayId;
    }

    @Override
    public String toString() {
        return "DateToDayId{" +
                "dateToDayMappings=" + dateToDayId +
                '}';
    }
}