A production incident revealed duplicate data creation: a single save operation resulted in three database records. Investigation traced the issue to inconsistent retry behavior between Dubbo’s XML and annotation-based configuration for retries = 0.

In XML configuration, the following disables retries as expected:

<dubbo:reference id="testService" interface="heiidea.trade.service.sdk.interfice.TestService" retries="0"/>

However, using the @Reference annotation with identical semantics fails:

@Reference(retries = 0)
private TestService testService;

Debugging through the invocation chain — from InvokerInvocationHandler.invoke() → MockClusterInvoker.invoke() → AbstractClusterInvoker.invoke() → FailoverClusterInvoker.doInvoke() — revealed that retries resolved to null when set via @Reference, causing fallback to the default value of 2. Combined with the initial call, this produced three total invocations.

In contrast, the XML parser correct parsed retries="0" as integer 0, resulting in exactly one invocation (no retries).

Root Cause Analysis

The discrepancy stems from how attribute values are adapted during bean construction:

• Annotation path: ReferenceAnnotationBeanPostProcessor processes @Reference fields. During buildReferenceBean(), the raw retries = 0 is preserved initially. However, later in preConfigureBean(), AnnotationPropertyValuesAdapter invokes AnnotationUtils.getAttributes(), which internally calls nullSafeEquals(attributeValue, defaultValue). Since the default retries value is 2, and 0 == 2 evaulates to false, this should retain the attribute. But in Dubbo 2.6.2, the logic incorrectly treats 0 as equivalent to the default when comparing against null or unconfigured state — ultimately omitting retries from the final actualAttributes map. Consequently, getRetries() returns null, triggering fallback to 2.

• XML path: The DubboNamespaceHandler parses <dubbo:reference> by reflecting over ReferenceBean’s setter methods (e.g., setRetries(int)). It directly assigns the parsed integer 0 without equality-based filtering, preserving the explicit zero value.

Behavioral Summary

Configuration Style	retries not specified	retries = 0	retries = -1
XML (<dubbo:reference>)	2 retries (3 total calls)	0 retries (1 total call)	0 retries
Annotation (@Reference)	2 retries	2 retries (due to null fallback)	0 retries

To guarantee zero retries with annotations in affected versions, use retries = -1. For idempotent operations like writes, this avoids unintended side effects. Upgrading to Dubbo ≥2.7.3 resolves the isue: the annotation processor now consistently treats 0 as an explicit override rather than discarding it during attribute adaptation.