将复杂的 JSON 反序列化为 Java，类嵌套多层

Question

我正在尝试将 Cucumber 的 Json 输出变成单个 Java 对象。这包含嵌套了四层深的对象，我在反序列化时遇到了麻烦。我目前正在使用 Jackson，但愿意接受建议。这是我的 Json 代码：

{
"line": 1,
"elements": [
  {
    "line": 3,
    "name": "Converteren centimeters naar voeten/inches",
    "description": "",
    "id": "applicatie-neemt-maten-in-cm-en-converteert-ze-naar-voet/inch,-en-vice-versa;converteren-centimeters-naar-voeten/inches",
    "type": "scenario",
    "keyword": "Scenario",
    "steps": [
      {
        "result": {
          "duration": 476796588,
          "status": "passed"
        },
        "line": 4,
        "name": "maak Maten-object aan met invoer in \"centimeters\"",
        "match": {
          "arguments": [
            {
              "val": "centimeters",
              "offset": 37
            }
          ],
          "location": "StepDefinition.maakMatenObjectAanMetInvoerIn(String)"
        },
        "keyword": "Given "
      },
      {
        "result": {
          "duration": 36319,
          "status": "passed"
        },
        "line": 5,
        "name": "ik converteer",
        "match": {
          "location": "StepDefinition.converteerMaten()"
        },
        "keyword": "When "
      },
      {
        "result": {
          "duration": 49138,
          "status": "passed"
        },
        "line": 6,
        "name": "uitvoer bevat maat in \"voeten/inches\"",
        "match": {
          "arguments": [
            {
              "val": "voeten/inches",
              "offset": 23
            }
          ],
          "location": "StepDefinition.uitvoerBevatMaatIn(String)"
        },
        "keyword": "Then "
      }
    ]
  },
  {
    "line": 8,
    "name": "Converteren voeten/inches naar centimeters",
    "description": "",
    "id": "applicatie-neemt-maten-in-cm-en-converteert-ze-naar-voet/inch,-en-vice-versa;converteren-voeten/inches-naar-centimeters",
    "type": "scenario",
    "keyword": "Scenario",
    "steps": [
      {
        "result": {
          "duration": 84175,
          "status": "passed"
        },
        "line": 9,
        "name": "maak Maten-object aan met invoer in \"voeten/inches\"",
        "match": {
          "arguments": [
            {
              "val": "voeten/inches",
              "offset": 37
            }
          ],
          "location": "StepDefinition.maakMatenObjectAanMetInvoerIn(String)"
        },
        "keyword": "Given "
      },
      {
        "result": {
          "duration": 23928,
          "status": "passed"
        },
        "line": 10,
        "name": "ik converteer",
        "match": {
          "location": "StepDefinition.converteerMaten()"
        },
        "keyword": "When "
      },
      {
        "result": {
          "duration": 55547,
          "status": "passed"
        },
        "line": 11,
        "name": "uitvoer bevat maat in \"centimeters\"",
        "match": {
          "arguments": [
            {
              "val": "centimeters",
              "offset": 23
            }
          ],
          "location": "StepDefinition.uitvoerBevatMaatIn(String)"
        },
        "keyword": "Then "
      }
    ]
  }
],
"name": "Applicatie neemt maten in cm en converteert ze naar voet/inch, en vice versa",
"description": "",
"id": "applicatie-neemt-maten-in-cm-en-converteert-ze-naar-voet/inch,-en-vice-versa",
"keyword": "Feature",
"uri": "sample.feature"
}

我尝试了多种不同的方法。首先，我使用了嵌套内部 classes，但看起来你必须将它们设为静态，我担心这不会起作用，因为我在一个对象中有多个相同对象的实例（多个 "element"-objects in the根，例如）。然后我尝试将它们放在单独的 classes 中，并带有 Json 注释。这就是我的灵感所在（省略二传手）：

public class CucumberUitvoer {
    private String name;
    private String description;
    private String id;
    private String keyword;
    private String uri;
    private int line;
    @JsonProperty("elements")
    private List<FeatureObject> elements;

    public CucumberUitvoer(){}
}

public class FeatureObject {
    private String name;
    private String description;
    private String id;
    private String type;
    private String keyword;
    private int line;
    @JsonProperty("steps")
    private List<StepObject> steps;

    public FeatureObject() {
    }
}

public class StepObject {
    @JsonProperty("result")
    private ResultObject result;
    private String name;
    private String given;
    private String location;
    private String keyword;
    private int line;
    @JsonProperty("match")
    private MatchObject match;

    public StepObject(){}
}

public class ResultObject {
    private int duration;
    private String status;

    public ResultObject(){}
}

public class MatchObject {
    @JsonProperty("arguments")
    private List<ArgumentObject> arguments;
    private String location;

    public MatchObject(){}
}

public class ArgumentObject {
    private String val;
    private String offset;

    public ArgumentObject(){}
}

为了清楚起见，here 提供了一个 class 嵌套工作原理图。

此解决方案出现以下错误：

com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of nl.icaprojecten.TestIntegratieQuintor.JSONInterpreter.CucumberUitvoer out of START_ARRAY token

下面是执行实际映射的代码：

ObjectMapper mapper = new ObjectMapper();
    mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

    CucumberUitvoer obj1 = null;
    try {
        obj1 = mapper.readValue(json, CucumberUitvoer.class);
    } catch (IOException e) {
        e.printStackTrace();
    }

是否有快速修复此方法以使其工作的方法，或者我应该尝试一些完全不同的方法？

Answer 1

你可以从这段代码中得到反序列化的想法，

public class testCustomDeSerializer extends JsonDeserializer<test> {

public testCustomDeSerializer() {
    this(null);
}

public TestCustomDeSerializer(Class t) {
   // super(t);
}

@Override
public Test deserialize(JsonParser p, DeserializationContext ctx) throws IOException, JsonProcessingException {
    ObjectCodec objectCodec = p.getCodec();
    JsonNode node = objectCodec.readTree(p);

    ObjectMapper objectMapper =  new ObjectMapper();
    Test test= new Test();


    test.setId(node.get("line").asText());

    List<elements> elementList = new ArrayList<>();
    JsonNode elementsNode = node.get("elements");
    Iterator<JsonNode> slaidsIterator = elementsNode.elements();
    while (slaidsIterator.hasNext()) {
        Steps steps= new Steps();
        JsonNode slaidNode = slaidsIterator.next();
        JsonNode stepNode= (JsonNode) slaidNode.get("Steps");
        BoundingPoly in = objectMapper.readValue(stepNode.toString(), Steps.class);
        elementsNode.setSteps(in);
        /// continue

 return
        }

希望对您有所帮助

Answer 2

我刚刚尝试了您的示例代码，奇怪的是，它有效。

请仔细检查您的导入，如果 JSON 按照提供的方式进入并且 getter、setter 和构造函数确实存在？

Answer 3

好吧，我花了一些时间调试并试图找出问题所在，最后发现了一些非常明显的问题。

implements Serializable

这就是我添加到 MatchObject 并起作用的行。

当我们首先尝试反序列化某些对象时，我们必须让那些类实现接口 Serializable

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