com.datastax.driver.dse.graph.JsonParserConcat Maven / Gradle / Ivy

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/*
 * Copyright DataStax, Inc.
 *
 * This software can be used solely with DataStax Enterprise. Please consult the license at
 * http://www.datastax.com/terms/datastax-dse-driver-license-terms
 */
package com.datastax.driver.dse.graph;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonToken;
import com.fasterxml.jackson.core.util.JsonParserSequence;
import java.io.IOException;

/**
 * Utility class to easily concatenate multiple JsonParsers. This class had to be implemented
 * because the class it is extending, {@link JsonParserSequence}, inevitably skips a token when
 * switching from one empty parser to a new one. I.e. it is automatically calling {@link
 * JsonParser#nextToken()} when switching to the new parser, ignoring the current token.
 *
 * This class is used for better performance in GraphSON when trying to detect types.
 */
class JsonParserConcat extends JsonParserSequence {

  @SuppressWarnings("deprecation")
  JsonParserConcat(final JsonParser[] parsers) {
    super(parsers);
  }

  @Override
  public JsonToken nextToken() throws IOException {
    JsonToken t = this.delegate.nextToken();
    if (t != null) {
      return t;
    } else {
      do {
        if (!this.switchToNext()) {
          return null;
        }
        // call getCurrentToken() instead of nextToken() in JsonParserSequence.
        t = this.delegate.getCurrentToken() == null ? this.nextToken() : this.getCurrentToken();
      } while (t == null);

      return t;
    }
  }
}