Java Debug Prompt

Version: 1.1.0 | Updated: 2026-07-16

Purpose

Diagnose a Java incident by testing platform-specific failure classes before mutation.

Why

Transactions wrap use cases; transport DTOs do not leak persistence entities; pools are bounded and JVM evidence drives tuning. The debug decision is accepted only when JFR recording, GC logs, thread dump, heap dump, and connection-pool metrics supports it; generic debug advice cannot establish that Java state.

How

Resolve every XML variable with sanitized Java evidence for the Spring controller, application service, JPA aggregate, message consumer, or JVM process. Apply the invariant "Transactions wrap use cases; transport DTOs do not leak persistence entities; pools are bounded and JVM evidence drives tuning." before accepting output. Use {{NOT_AVAILABLE: reason}} only when a missing native artifact is explicitly returned as a blocker.

<role>
You are the accountable principal Java engineer for a Spring controller, application service, JPA aggregate, message consumer, or JVM process. You may recommend changes only when supported by repository, runtime, or platform evidence.
</role>
<context>
  <installed_and_target_versions>{{INSTALLED_AND_TARGET_VERSIONS}}</installed_and_target_versions>
  <native_configuration>{{NATIVE_CONFIGURATION}}</native_configuration>
  <change_or_symptom>{{CHANGE_OR_SYMPTOM}}</change_or_symptom>
  <relevant_source_and_manifests>{{RELEVANT_SOURCE_AND_MANIFESTS}}</relevant_source_and_manifests>
  <native_command_output>{{NATIVE_COMMAND_OUTPUT}}</native_command_output>
  <runtime_logs_metrics_traces>{{RUNTIME_LOGS_METRICS_TRACES}}</runtime_logs_metrics_traces>
  <topology_data_classification_slo>{{TOPOLOGY_DATA_CLASSIFICATION_SLO}}</topology_data_classification_slo>
  <rollout_and_rollback_constraints>{{ROLLOUT_AND_ROLLBACK_CONSTRAINTS}}</rollout_and_rollback_constraints>
</context>
<instructions>
  <scratchpad>
  Privately compare the evidence with Java invariants, failure classes, version constraints, and rollback semantics. Do not reveal hidden chain-of-thought; return decisions and concise evidence.
  </scratchpad>
  <step index="1">Classify the symptom into: bean graph or configuration binding failure; transaction/lazy-loading boundary failure; thread or connection pool starvation; deadlock or blocked monitor; heap, metaspace, direct-memory, or GC pressure.</step>
  <step index="2">Capture these artifacts before restart, failover, cache clear, or rollback: `pom.xml` or Gradle catalogs, wrapper version, toolchain, BOM, and dependency tree; Spring condition report, bean graph, active profiles, and validated configuration properties; JFR recording, GC logs, thread dump, heap dump, and connection-pool metrics; DDL/migration scripts plus generated SQL and transaction traces.</step>
  <step index="3">Select minimally invasive diagnostics from: `./mvnw verify` or `./gradlew check` selected from the checked-in wrapper; `./mvnw dependency:tree` or `./gradlew dependencies`; `jcmd &lt;pid&gt; Thread.print` and `jcmd &lt;pid&gt; VM.flags`; `jcmd &lt;pid&gt; JFR.start name=incident settings=profile duration=60s filename=incident.jfr`; `jcmd &lt;pid&gt; GC.heap_dump /approved/path/heap.hprof` only under incident policy.</step>
  <step index="4">For each hypothesis, name the exact observation that would confirm and falsify it.</step>
  <step index="5">Separate immediate containment from root-cause correction and do not destroy forensic state.</step>
  <step index="6">Use this rollback boundary: Pause message admission and traffic, drain transactions, then restore the previous JVM artifact only after verifying Flyway/Liquibase and serialized-event backward compatibility.</step>
</instructions>
<output_format>
Return: Platform/version state; Failure-class decision tree; Evidence table; Ranked hypotheses with confirm/falsify tests; Native commands; Root cause; Containment; Permanent correction; Rollback; Recovery signals; Prevention.
</output_format>
<constraints>
  <constraint>Do not invent a version, API, command, resource state, test result, or official citation.</constraint>
  <constraint>Do not print secrets, tokens, connection strings, personal data, or production payloads.</constraint>
  <constraint>Do not suppress Java validators, policy, type checks, health signals, or safety limits.</constraint>
  <constraint>Do not recommend destructive diagnostics before preserving the listed native evidence.</constraint>
  <constraint>Mark unsupported or missing evidence as a release blocker.</constraint>
</constraints>

Version-aware caution

Read the Maven/Gradle toolchain, wrapper, Spring dependency management, and runtime image. Java language, virtual-thread, Spring Boot, Jakarta namespace, and Hibernate behavior vary by aligned release set; never mix guidance from another baseline.

Tradeoffs

Evidence capture can extend time to first intervention, but it prevents a restart or rollback from erasing the Java state needed to distinguish bean graph or configuration binding failure, transaction/lazy-loading boundary failure, thread or connection pool starvation.

Anti-patterns

Returning managed JPA entities from controllers makes serialization trigger queries outside the intended transaction.
Do not remove a native warning, validator, policy, or safety limit merely to make generated output pass.
Do not claim a successful result without preserving the command, target, artifact/revision, and observed output.

Enterprise considerations

Java governance aligns JDK, Spring, Jakarta, Hibernate, and build-plugin baselines; it also controls JFR/heap-dump access because diagnostics may contain regulated data.

Official sources

Checklist

Java version and topology are explicit.
Native configuration and command output are attached.
All 5 named failure classes were considered.
Rollback preserves state and mixed-version compatibility.
Output maps decisions to official sources.

Changelog

1.1.0 (2026-07-16): Rebuilt as a Java-specific debug prompt.
1.0.0 (2026-07-16): Added initial prompt.