parse recursively unknown json input structure in java

Question

I'm trying to parse recursively unknown json input structure in java like the format below and trying to rewrite the same structure in another json.

Meanwhile I need to validate each & every json key/values while parsing.

{"Verbs":[{
    "aaaa":"30d", "type":"ed", "rel":1.0, "id":"80", "spoken":"en", "ct":"on", "sps":null
},{
    "aaaa":"31", "type":"cc", "rel":3.0, "id":"10", "spoken":"en", "ct":"off", "sps":null
},{
    "aaaa":"81", "type":"nn", "rel":3.0, "id":"60", "spoken":"en", "ct":"on", "sps":null
}]}

Please advice which json parser I can use for reading and writing unknown json content.

How to parse each json element and reassemble it as same as input — erdarun, Mar 01 '14 at 08:09
I want to validate each & every json token key/value for special chars. Then I will replace the values and reframe json again back to old structure — erdarun, Mar 01 '14 at 09:08
I submitted sample that you can reuse as template. Just set value instead of printing. And once you are finished, just print the tree with method on parent object. Nevertheless I wonder if it is neccessary, JSON library shall escape neccessary characters for you. — Leos Literak, Mar 01 '14 at 09:27
Use a JSON parser to parse it, update what you want to in the resulting structures, and then use the companion JSON serializer to produce a new JSON string. You can use any of a dozen different parser/serializer kits, and probably the simpler the better. — Hot Licks, Mar 01 '14 at 19:21
(Don't use Jackson, or any other "we'll build your POJOs for you" tool, unless the structure is fairly regular and repeatable. Unless you really understand them they cause more confusion than they're worth.) — Hot Licks, Mar 01 '14 at 19:26

score 4 · Answer 1 · answered Mar 01 '14 at 09:13

This way you can recursively parse JSON object:

import com.eclipsesource.json.JsonArray;
import com.eclipsesource.json.JsonObject;
import com.eclipsesource.json.JsonValue;

public class JsonQuestion {

    public static void main(String[] args) {
        String input =  "{\"Verbs\":[{\n" +
                "    \"aaaa\":\"30d\", \"type\":\"ed\", \"rel\":1.0, \"id\":\"80\", \"spoken\":\"en\", \"ct\":\"on\", \"sps\":null\n" +
                "},{\n" +
                "    \"aaaa\":\"31\", \"type\":\"cc\", \"rel\":3.0, \"id\":\"10\", \"spoken\":\"en\", \"ct\":\"off\", \"sps\":null\n" +
                "},{\n" +
                "    \"aaaa\":\"81\", \"type\":\"nn\", \"rel\":3.0, \"id\":\"60\", \"spoken\":\"en\", \"ct\":\"on\", \"sps\":null\n" +
                "}]}";

        JsonObject jsonObject = JsonObject.readFrom(input);
        handleObject(jsonObject);
    }

    private static void handleValue(JsonObject.Member member, JsonValue value) {
        if (value.isArray()) {
            if (member != null) {
                System.out.print("name = " + member.getName());
            }
            System.out.println("array value ");
            recurseArray(value.asArray());
        } else if (value.isBoolean()) {
            if (member != null) {
                System.out.print("name = " + member.getName());
            }
            System.out.println(", boolean value = " + value.asBoolean());
        } else if (value.isNull()) {
            if (member != null) {
                System.out.print("name = " + member.getName());
            }
            System.out.println(", null value");
        } else if (value.isNumber()) {
            if (member != null) {
                System.out.print("name = " + member.getName());
            }
            System.out.println(", number value = " + value.asDouble());
        } else if (value.isObject()) {
            if (member != null) {
                System.out.print("name = " + member.getName());
            }
            System.out.println(", object value ");
            handleObject(value.asObject());
        } else if (value.isString()) {
            if (member != null) {
                System.out.print("name = " + member.getName());
            }
            System.out.println(", string value = " + value.asString());
        }
    }

    private static void handleObject(JsonObject object) {
        for (JsonObject.Member next : object) {
            JsonValue value = next.getValue();
            handleValue(next, value);
        }
    }

    private static void recurseArray(JsonArray array) {
        for (JsonValue value : array) {
            handleValue(null, value);
        }
    }
}

Thanks for your reply, Parallely can we frame json response while parsing each & every values. — erdarun, Mar 01 '14 at 09:29
yes can we achieve the same parsing logic in gson/jackson library? Because we are using gson/jackson libs only in my project, — erdarun, Mar 01 '14 at 09:46
It would be better if you specify COMPLETE requirements in advance before somebody spent some time trying to help you. — Leos Literak, Mar 01 '14 at 13:49
@LeosLiterak can you check http://stackoverflow.com/questions/41360172/modify-jsonnode-of-unknown-json-dynamically-in-java — InCh, Dec 28 '16 at 10:45

score 2 · Answer 2 · edited Jan 17 '20 at 12:02

Using gson library https://sites.google.com/site/gson/gson-user-guide

public void parseJson() {
     String jsonStr = "";//input json String.
     JsonParser parser = new JsonParser();
     JsonElement jsonElement = parser.parse(jsonStr);
     processJsonElement(jsonElement);
}


private void processJsonElement(JsonElement e) {
    if (e.isJsonArray()) {
        processJsonArray(e.getAsJsonArray());
    } else if (e.isJsonNull()) {
        processJsonNull(e.getAsJsonNull());
    } else if (e.isJsonObject()) {
        processJsonObject(e.getAsJsonObject());
    } else if (e.isJsonPrimitive()) {
        processJsonPrimitive(e.getAsJsonPrimitive());
    }
}

private void processJsonArray(JsonArray a) {
    for (JsonElement e : a) {
        processJsonElement(e);
    }
}

private void processJsonNull(JsonNull n) {
    System.out.println("null || : " + n);
}

private void processJsonObject(JsonObject o) {
    Set<Map.Entry<String, JsonElement>> members= o.entrySet();
    for (Map.Entry<String, JsonElement> e : members) {
        System.out.println("Processing object member: " + e.getKey());
        processJsonElement(e.getValue());
    }
}

private void processJsonPrimitive(JsonPrimitive p) {
    System.out.println("Primitive || :" + p);
}

Or Jackson

public void processJson() {
    ObjectMapper objectMapper = new ObjectMapper();
    try {
        JsonNode node = objectMapper.readTree(jsonStr);
        System.out.println(node);
        processNode(node);
    } catch (IOException e) {
        throw new RuntimeException(e);
    }

}

private void processNode(JsonNode n) {
    if (n.isContainerNode()) {
        processJsonContainer(n.iterator());
    } else if (n.isNull()) {
        System.out.println("Null || :" + n);
    } else if (n.isNumber()) {
        System.out.println("Number || :" + n.asDouble());
    } else if (n.isBoolean()) {
        System.out.println("Boolean || :" + n.asBoolean());
    } else if (n.isTextual()) {
        System.out.println("Text || :" + n.asText());
    }
}

private void processJsonContainer(Iterator<JsonNode> iterator) {
   while (iterator.hasNext()) {
       processNode(iterator.next());
   }
}

parse recursively unknown json input structure in java

2 Answers2

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