apache/druid · error · NullPointerException

connectionProperties is null

Error message

connectionProperties is null

What it means

BasicDataSourceExt.setConnectionProperties overrides commons-dbcp's setter and explicitly rejects a null connectionProperties string with NullPointerException. The override parses the semicolon-separated key=value string into a Properties object, so null input cannot be processed.

Source

Thrown at server/src/main/java/org/apache/druid/metadata/BasicDataSourceExt.java:81

  @Override
  public void addConnectionProperty(String name, String value)
  {
    connectionProperties.put(name, value);
    super.addConnectionProperty(name, value);
  }

  @Override
  public void removeConnectionProperty(String name)
  {
    connectionProperties.remove(name);
    super.removeConnectionProperty(name);
  }

  @Override
  public void setConnectionProperties(String connectionProperties)
  {
    if (connectionProperties == null) {
      throw new NullPointerException("connectionProperties is null");
    }

    String[] entries = connectionProperties.split(";");
    Properties properties = new Properties();
    for (String entry : entries) {
      if (entry.length() > 0) {
        int index = entry.indexOf('=');
        if (index > 0) {
          String name = entry.substring(0, index);
          String value = entry.substring(index + 1);
          properties.setProperty(name, value);
        } else {
          // no value is empty string which is how java.util.Properties works
          properties.setProperty(entry, "");
        }
      }
    }
    this.connectionProperties = properties;

View on GitHub (pinned to 9b90983fd2)

Solutions

1. Provide a non-null connectionProperties string in the connector config (may be empty string)
2. Skip calling setConnectionProperties when the configured value is null
3. Use an empty string instead of null when no extra properties are needed

Example fix

// before
dataSource.setConnectionProperties(config.getConnectionProperties()); // null
// after
String props = config.getConnectionProperties();
if (props != null) {
  dataSource.setConnectionProperties(props);
}

if (connectionProperties == null) { connectionProperties = ""; } // or skip the setter call

if (connectionProperties instanceof String s && !s.isEmpty()) { dataSource.setConnectionProperties(s); }

try { dataSource.setConnectionProperties(props); } catch (NullPointerException e) { log.warn("connectionProperties was null; skipping"); }

When it happens

Trigger: Configuring a JDBC data source where the connectionProperties property resolves to null — e.g. metadata store config with no connectionProperties key, or programmatic calls like dataSource.setConnectionProperties(null).

Common situations: Druid metadata storage configuration missing the druid.metadata.storage.connector.connectionProperties property; frameworks that invoke all bean setters including null-valued ones.

Related errors

• Cannot load JDBC driver class '<driverClassName>'
• 08001
• Cannot create JDBC driver of class '<driverClassName>' for c
• Failed to find the DB Driver
• supervisorId cannot be null

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/e81723ae794d7760. Report an issue: GitHub.