openzipkin/zipkin · error · NullPointerException

queue == null

Error message

queue == null

What it means

ActiveMQCollector.Builder.queue(String) throws NullPointerException on null because the queue name must be a concrete string. It is not a format check — empty or blank strings are technically accepted — only null is rejected; the default queue name is "zipkin".

Source

Thrown at zipkin-collector/activemq/src/main/java/zipkin2/collector/activemq/ActiveMQCollector.java:57

      return this;
    }

    @Override public Builder metrics(CollectorMetrics metrics) {
      if (metrics == null) throw new NullPointerException("metrics == null");
      this.metrics = metrics.forTransport("activemq");
      this.delegate.metrics(this.metrics);
      return this;
    }

    public Builder connectionFactory(ActiveMQConnectionFactory connectionFactory) {
      if (connectionFactory == null) throw new NullPointerException("connectionFactory == null");
      this.connectionFactory = connectionFactory;
      return this;
    }

    /** Queue zipkin spans will be consumed from. Defaults to "zipkin". */
    public Builder queue(String queue) {
      if (queue == null) throw new NullPointerException("queue == null");
      this.queue = queue;
      return this;
    }

    /** Count of concurrent message listeners on the queue. Defaults to 1 */
    public Builder concurrency(int concurrency) {
      if (concurrency < 1) throw new IllegalArgumentException("concurrency < 1");
      this.concurrency = concurrency;
      return this;
    }

    @Override public ActiveMQCollector build() {
      if (connectionFactory == null) throw new NullPointerException("connectionFactory == null");
      return new ActiveMQCollector(this);
    }
  }

  final String queue;

View on GitHub (pinned to 878ce2a1fa)

Solutions

1. Only call .queue(...) when you actually have a non-null name, otherwise rely on the default "zipkin".
2. Fix the property source so the queue name resolves (check env var / config key spelling).
3. Coalesce to the default: .queue(name != null ? name : "zipkin").

Example fix

// before
String q = System.getenv("ACTIVEMQ_QUEUE"); // null when unset
builder.queue(q); // NPE

// after
if (System.getenv("ACTIVEMQ_QUEUE") != null) builder.queue(System.getenv("ACTIVEMQ_QUEUE"));

java
String q = System.getenv("ACTIVEMQ_QUEUE");
if (q != null) builder.queue(q); // default "zipkin" otherwise

When it happens

Trigger: Calling .queue(null), most often by forwarding a null configuration property (e.g. ACTIVEMQ_QUEUE not set and the code does .queue(System.getenv("ACTIVEMQ_QUEUE"))).

Common situations: Optional queue-name config treated as mandatory in code; property typo (queue vs destination); tests omitting the queue setting.

Related errors

• metrics == null
• connectionFactory == null
• concurrency < 1
• storage == null
• metrics == null

AI-assisted analysis of openzipkin/zipkin@878ce2a1fa (2026-08-14). Data as JSON: /api/errors/140d6238b0d4b5cf. Report an issue: GitHub.