Your root node doesn't have a customerSessionId, it has a HotelListResponse. Get that first.

//other methods
public void basicTreeModelRead()
{
    JsonNode innerNode = rootNode.get("HotelListResponse"); // Get the only element in the root node
    // get an element in that node
    JsonNode aField = innerNode.get("customerSessionId");

    //the customerSessionId has a String value
    String myString = aField.asText();

    System.out.println("customerSessionId is:" + myString);
}

This prints

customerSessionId is:0ABAAA7A-90C9-7491-3FF2-7E2C37496CA2

As you said its an Array. Cast the node to an ArrayNode. Select the first element [0] and call the getter. Should be it. Or check out this: https://stackoverflow.com/a/16793133/15565539

You can use elements() method and check if value key exist then add the value to list.

Smaple code

ObjectMapper mapper = new ObjectMapper();
JsonNode jsonNode = mapper.readTree(data);

List<String> values = new ArrayList<>();
jsonNode.forEach(jsonObject -> jsonObject.elements().forEachRemaining(valueNode -> {
    if(valueNode.has("value"))
        values.add(valueNode.get("value").asText());
}));
System.out.println(values);

Output:

[http://www.wikidata.org/entity/Q42442324, http://www.wikidata.org/prop/direct/P21, Kiisu Miisu, http://www.wikidata.org/entity/Q43260736, http://www.wikidata.org/prop/direct/P21, Paddles]

If you want to explicitly traverse through the json and find the value of a , you can do it like this for the json that you specified.

String aValue = jsonNode.get("text").get(0).get("a").asText();

Finding the value of b would be

String bValue = jsonNode.get("text").get(1).get("b").asText();

You can also traverse through the elements within the text array and get the values of a and b as

for (JsonNode node : jsonNode.get("text")) {
    System.out.println(node.fields().next().getValue().asText());
}

And that would print the below on the console

1
2

With Jackson's tree model (JsonNode), you have both "literal" accessor methods (get), which returns null for missing value, and "safe" accessors (path), which allow you to traverse "missing" nodes. So, for example:

JsonNode root = mapper.readTree(inputSource);
int h = root.path("response").path("history").getValueAsInt();

which would return the value at the given path, or, if the path is missing, 0 (default value).

But more conveniently, you can just use JSON pointer expression:

int h = root.at("/response/history").getValueAsInt();

There are other ways too, and often it is more convenient to model your structure as a Plain Old Java Object (POJO). Your content could fit something like:

public class Wrapper {
  public Response response;
} 
public class Response {
  public Map<String,Integer> features; // or maybe Map<String,Object>
  public List<HistoryItem> history;
}
public class HistoryItem {
  public MyDate date; // or just Map<String,String>
  // ... and so forth
}

and if so, you would traverse the resulting objects just like any Java object.

Your node points to the root of the JSON document. To get to id, you have to traverse the path.

ArrayNode docs = node.path("response").path("docs");
for (JsonNode doc: docs) { // this is pseudo-code
  String s = doc.path("id").asText();
}

Or use JsonPath.