Why does Jackson 2 not recognize the first capital letter if the leading camel case word is only a single letter long?

The problem you are seeing is due to the fact that Jackson uses Java Bean naming conventions to figure out the the Json properties in a Java class.

Here is a reference of the specific problem you see, the recommendation is not to capitalize either of the first two letters in your field. If you use an IDE like IntelliJ or eclipse and let the IDE generate the setters for you, you will notice the same “behavior” occurs, you will end up with the following methods:

public void setaLogId(String aLogId) {
    this.aLogId = aLogId;
}

public String getaLogId() {
    return aLogId;
}

Hence, when you change the “L” to lower case Jackson was able to figure it out the field you wanted to map.

Having said the above, you still have the alternative to use the “aLogId” field name and make Jackson work all you have to do is use the @JsonProperty annotation with the aLogId in it.

@JsonProperty("aLogId")
private String aLogId;

The following test code is to show how this will work:

import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.databind.ObjectMapper;

public class Test {

    @JsonProperty("aLogId")
    private String aLogId;

    public void setaLogId(String aLogId) {
        this.aLogId = aLogId;
    }

    public String getaLogId() {
        return aLogId;
    }

    public static void main(String[] args) {

        ObjectMapper objectMapper = new ObjectMapper();

        Test test = new Test();

        test.setaLogId("anId");

        try {
            System.out.println("Serialization test: " + objectMapper.writeValueAsString(test));


            String json = "{\"aLogId\":\"anotherId\"}";

            Test anotherTest = objectMapper.readValue(json, Test.class);

            System.out.println("Deserialization test: " +anotherTest.getaLogId());

        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}

The output of the test is:

Serialization test: {"aLogId":"anId"}

Deserialization test: anotherId