Question

我正在尝试使用JSON。我有一些可以很好地序列化对象的代码，但是尝试反序列化时出现了MismatchedInputException异常，无法从START_ARRAY令牌中反序列化com.john.irrigator3.irrigation.WateringSchedule实例

我猜杰克逊在我的WateringScheduleCollection中反序列化数组时遇到了麻烦，并且我尝试过更改要添加到数组中的方法的名称，没有创建任何参数构造函数，但是我遇到了麻烦。有人可以告诉我我要去哪里拧吗？

WaterScheduleCollection：

public class WateringScheduleCollection {

    Map<String, WateringSchedule> schedules = new LinkedHashMap<>();

    public void removeSchedule(String name) {
        schedules.remove(name);
    }

    public void addSchedule(WateringSchedule wateringSchedule) {
        schedules.put(wateringSchedule.getName(), wateringSchedule);
    }

    public Map<String, WateringSchedule> getSchedules() {
        return schedules;
    }
}

WateringSchedule：

public class WateringSchedule {
    String name;
    ArrayList<WateringRoutine> wateringRoutines;
    SeasonLimits seasonLimits = null;
    int sprinkleDuration = 30;

    public WateringSchedule() {
        wateringRoutines = new ArrayList<WateringRoutine>();
    }

    public WateringSchedule(List<WateringRoutine> wateringRoutines) {
        this();
        for (WateringRoutine wateringRoutine : wateringRoutines) {
            addWateringRoutine(wateringRoutine);
        }
    }

    public void addWateringRoutine(WateringRoutine wateringRoutine) {
        wateringRoutines.add(wateringRoutine);
    }

    public ArrayList<WateringRoutine> getWateringRoutines() {
        return wateringRoutines;
    }

序列化可以很好地解决此问题：

 public void writeFile(){
        WateringRoutine wr1 = new WateringRoutine(0,1,10);
        WateringRoutine wr2 = new WateringRoutine(1,2,100);
        WateringRoutine wr3 = new WateringRoutine(2,3,1000);
        SeasonLimits seasonLimits = new SeasonLimits(4, 1, 6, 7);

        WateringSchedule wateringSchedule1 = new WateringSchedule();
        wateringSchedule1.setName("wateringSchedule1");
        wateringSchedule1.addWateringRoutine(wr1);
        wateringSchedule1.addWateringRoutine(wr2);

        WateringSchedule wateringSchedule2 = new WateringSchedule();
        wateringSchedule2.setName("wateringSchedule2");
        wateringSchedule2.addWateringRoutine(wr2);
        wateringSchedule2.addWateringRoutine(wr3);

        WateringSchedule wateringSchedule3 = new WateringSchedule();
        wateringSchedule3.setName("wateringSchedule3");
        wateringSchedule3.addWateringRoutine(wr1);
        wateringSchedule3.addWateringRoutine(wr2);
        wateringSchedule3.addWateringRoutine(wr3);
        wateringSchedule3.setSeasonLimits(seasonLimits);

        WateringScheduleCollection wateringScheduleCollection = new WateringScheduleCollection();
        wateringScheduleCollection.addSchedule(wateringSchedule1);
        wateringScheduleCollection.addSchedule(wateringSchedule2);
        wateringScheduleCollection.addSchedule(wateringSchedule3);

        ObjectMapper mapper = new ObjectMapper();
        mapper.getSerializerProvider().setNullKeySerializer(new MyDtoNullKeySerializer());
        mapper.enable(SerializationFeature.INDENT_OUTPUT);

        String json = null;
        try {
            json = mapper.writeValueAsString(wateringScheduleCollection);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        System.out.println(json);
    }

给出以下输出：

{
  "schedules" : {
    "wateringSchedule1" : {
      "name" : "wateringSchedule1",
      "wateringRoutines" : [ {
        "secsWatering" : 1,
        "hoursAllowedWithoutWater" : 10.0,
        "scheduleSprinkle" : false,
        "age" : 0
      }, {
        "secsWatering" : 2,
        "hoursAllowedWithoutWater" : 100.0,
        "scheduleSprinkle" : false,
        "age" : 1
      } ],
      "seasonLimits" : null,
      "sprinkleDuration" : 30
    },
    "wateringSchedule2" : {
      "name" : "wateringSchedule2",
      "wateringRoutines" : [ {
        "secsWatering" : 2,
        "hoursAllowedWithoutWater" : 100.0,
        "scheduleSprinkle" : false,
        "age" : 1
      }, {
        "secsWatering" : 3,
        "hoursAllowedWithoutWater" : 1000.0,
        "scheduleSprinkle" : false,
        "age" : 2
      } ],
      "seasonLimits" : null,
      "sprinkleDuration" : 30
    },
    "wateringSchedule3" : {
      "name" : "wateringSchedule3",
      "wateringRoutines" : [ {
        "secsWatering" : 1,
        "hoursAllowedWithoutWater" : 10.0,
        "scheduleSprinkle" : false,
        "age" : 0
      }, {
        "secsWatering" : 2,
        "hoursAllowedWithoutWater" : 100.0,
        "scheduleSprinkle" : false,
        "age" : 1
      }, {
        "secsWatering" : 3,
        "hoursAllowedWithoutWater" : 1000.0,
        "scheduleSprinkle" : false,
        "age" : 2
      } ],
      "seasonLimits" : {
        "startOfSeason" : 1554098900367,
        "endOfSeason" : 1559887700367,
        "monthStart" : 4,
        "dayStart" : 1,
        "monthEnd" : 6,
        "dayEnd" : 7
      },
      "sprinkleDuration" : 30
    }
  }
}

但尝试使用以下代码反序列化：

public void readFile() {
        ObjectMapper objectMapper = new ObjectMapper();
        try {
            WateringScheduleCollection wsc = objectMapper.readValue(new File(testPath+fileName), WateringScheduleCollection.class);
            System.out.println(wsc.toString());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

导致：

com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `com.john.irrigator3.irrigation.WateringSchedule` out of START_ARRAY token
 at [Source: (File); line: 3, column: 15] (through reference chain: com.john.irrigator3.irrigation.WateringScheduleCollection["schedules"]->java.util.LinkedHashMap["schedule"])
    at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:63)

Answer 1

我认为Jackson在选择Collection实现（LinkedHashMap，ArrayList）而不是接口（Map，List）时遇到问题。通常，杰克逊会选择一些默认值（例如，我猜的是ArrayList的{{1}}）。

请参考此答案以指定预期的接口实现：

Jackson - How to specify a single implementation for interface-referenced deserialization?

Answer 2

我刚刚发现我做错了什么。我正在将JSON写入文件，然后读取文件进行反序列化。好吧，那是我以为我在做的事情。原来，我正在写一个文件，而在读另一个文件。看到了这个愚蠢的错误之后，JSON就可以正常工作了，可以毫无问题地进行序列化和反序列化。

感谢您的回答，但我真正需要的是解决愚蠢问题的方法。

可以序列化好，反序列化给出MismatchedInputException

2 个答案: