com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of TestAcceptanceCriteria out of START_ARRAY token

Question

Given the following JSON file:

 [
      {"name":"test_12345_54321",
              "acceptanceCriteria":
                  [
                    {
                      "given":"I am a developer",
                      "and":"I have some test case to write",
                      "when":"I run my test",
                      "then":"I get a report generated about its details."
                    }
                  ]
       },
       {"name":"test_2",
               "acceptanceCriteria":
                   [
                     {
                      "given":"I am a developer test 2",
                      "and":"I have some test case to write test 2",
                      "when":"I run my test test 2",
                      "then":"I get a report generated about its details.2"
                     }
                   ]
        }
    ]

I am trying to access values within a JSON file using Jackson Object Mapper. As follows:

File jsonFile = new File("results/acceptanceCriteria.json");

        ObjectMapper mapper = new ObjectMapper();
        TestAcceptanceCriteria acceptanceCriteria = null;
        acceptanceCriteria = mapper.readValue(jsonFile, TestAcceptanceCriteria.class);
        System.out.println(acceptanceCriteria.getAcceptanceCriteria());

Each time I try to access any variable I get the following error:

com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of file.readers.TestAcceptanceCriteria out of START_ARRAY token at [Source: results\acceptanceCriteria.json; line: 1, column: 1] at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:270) at com.fasterxml.jackson.databind.DeserializationContext.reportMappingException(DeserializationContext.java:1234) at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1122) at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1075) at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromArray(BeanDeserializerBase.java:1374) at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeOther(BeanDeserializer.java:174) at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:150) at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3798) at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2740) at file.readers.AcceptanceCriteriaJsonReader.main(AcceptanceCriteriaJsonReader.java:51)

My classes are as follows:

 public class AcceptanceCriteria{
    private String given;
    private String and;
    private String when;
    private String then;

    public String getGiven(){
        return given;
    }
    public void setGiven(String given){
        this.given = given;
    }
    public String getAnd(){
        return and;
    }
    public void setAnd(String and){
        this.and = and;
    }
    public String getWhen(){
        return when;
    }
    public void setWhen(String when){
        this.when = when;
    }
    public String getThen(){
        return then;
    }
    public void setThen(String then){
        this.then = then;
    }
}

...

    import java.util.List;
    public class TestAcceptanceCriteria {
    private String name;
    private List<AcceptanceCriteria> acceptanceCriteria;

    public String getName(){
        return name;
    }
    public void setName(String name){
        this.name = name;
    }
    public List<AcceptanceCriteria> getAcceptanceCriteria(){
        return acceptanceCriteria;
    }
    public void setAcceptanceCriteria(List<AcceptanceCriteria> acceptanceCriteria){
        this.acceptanceCriteria = acceptanceCriteria;
    }
}

Łukasz Kuzio Łukasz Kuzio · Accepted Answer · 2017-04-14T16:48:36

You are trying deserialize array of entities to single object, what cause a problem. Let's try:

List<TestAcceptanceCriteria> acceptanceCriteria = null;
acceptanceCriteria = mapper.readValue(json, new TypeReference<List<TestAcceptanceCriteria>>(){});

com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of TestAcceptanceCriteria out of START_ARRAY token

1 Answers