ApiKey.java

package com.nicusa.util;

import com.google.common.util.concurrent.RateLimiter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
import org.springframework.web.util.UriComponentsBuilder;

@Component
public class ApiKey {
  private static final Logger log = LoggerFactory.getLogger(ApiKey.class);

  // 4 requests per second per key
  private static RateLimiter rateLimiter = null;

  private static int totalRequests = 0;

  @Autowired
  @Value("${api.fda.keys:}")
  String[] fdaApiKeys;

  @Autowired
  @Value("${api.fda.limiterEnabled:false}")
  boolean fdaLimiterEnabled;

  public boolean hasKeys() {
    return (fdaApiKeys != null && fdaApiKeys.length > 0 && fdaApiKeys[0] != null && fdaApiKeys[0]
        .trim().length() > 1);
  }

  String getFdaApiKey() {
    if (this.hasKeys()) {
      limit();
      String rv = this.fdaApiKeys[totalRequests++ % this.fdaApiKeys.length];
      return rv;
    } else {
      return null;
    }
  }

  private void limit() {
    if (rateLimiter == null) {
      rateLimiter = RateLimiter.create(this.fdaApiKeys.length * 3.5);
    }
    if (fdaLimiterEnabled){
      log.info("Rate limiter enabled");
      rateLimiter.acquire(); // may wait
    }
  }

  public String getFdaApiKeyName() {
    return "api_key";
  }

  public String getFdaApiKeyQuery() {
    if (this.hasKeys()) {
      return "&" + this.getFdaApiKeyName() + "=" + this.getFdaApiKey();
    } else {
      return "";
    }
  }

  public void addToUriComponentsBuilder(UriComponentsBuilder builder) {
    if (this.hasKeys()) {
      builder.queryParam(this.getFdaApiKeyName(), this.getFdaApiKey());
    }
  }
}