package pl.edu.icm.saos.common.json;
import java.io.IOException;
import org.springframework.stereotype.Service;
import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonToken;
import com.fasterxml.jackson.databind.MappingJsonFactory;
import com.google.common.base.Preconditions;
/**
* Contains methods facilitating iterating over the json content.
*
* @author Łukasz Dumiszewski
*/
@Service
public class JsonObjectIterator {
/**
* Returns the next token or null if there is no more tokens or the next token is not a json object or array ({@link #isJsonObject(JsonToken)}).
*
*
* @throws IllegalArgumentException if the {@link JsonParser#getCodec()} == null. You can use {@link MappingJsonFactory} for creating
* parser with default codec
* @throws JsonParseException if the nextToken cannot be parsed
* @throws IOException if I/O error occurred
*
* */
public JsonToken nextJsonObject(JsonParser jsonParser) throws JsonParseException, IOException {
Preconditions.checkArgument(jsonParser.getCodec() != null);
JsonToken token = jsonParser.nextToken();
if (isJsonObject(token)) {
return token;
} else {
return null;
}
}
/**
* Returns the next json object as object of the given objectClass.
* <ul>Invokes:
* <li>{@link #nextJsonObject(JsonParser)}</li>
* <li>{@link JsonParser#readValueAs(Class)}</li>
* </ul>
* Returns null if {@link #nextJsonObject(JsonParser)} returns null.
*
*/
public <T> T nextJsonObject(JsonParser jsonParser, Class<T> objectClass) throws IOException {
JsonToken token = nextJsonObject(jsonParser);
if (token == null) {
return null;
}
return jsonParser.readValueAs(objectClass);
}
/**
* Does the given jsonToken indicate the start of json object or array?
*/
public boolean isJsonObject(JsonToken jsonToken) {
if (JsonToken.START_OBJECT.equals(jsonToken) || JsonToken.START_ARRAY.equals(jsonToken)) {
return true;
}
return false;
}
}