Temporal Training Exercise - Java Solution

Complete Java implementation for progressive Temporal training exercises.

Prerequisites

• Java 17+
• Temporal CLI

Setup

1. Start Temporal dev server with AccountId search attribute:

temporal server start-dev --search-attribute AccountId=Text

2. Build project:

./gradlew build

Exercise Progression

Exercise 1: Hello Temporal (30 min)

• Basic Workflow and Activity setup
• Worker registration and execution

Exercise 2: Money Transfer Basics (45 min)

• Multiple activities (withdraw, deposit, refund)
• Signal-based approval mechanism
• Workflow.await() for conditional waiting
• Basic error handling and compensation

Exercise 3: Query Handlers (35 min)

• Query methods for workflow state inspection
• Status tracking throughout execution
• External workflow monitoring
• Signal vs Query differences

Exercise 4: Visibility & Monitoring (30 min)

• Custom Search Attributes (AccountId)
• Upsert Search Attributes from workflows
• Workflow filtering and discovery

Exercise 5: User Metadata & Activity Summaries (30 min)

• Activity summaries for better observability
• Static workflow summaries
• Enhanced monitoring in Temporal Web UI

Exercise 6: Testing Strategy (45 min)

• Unit tests with TestWorkflowRule
• Time skipping for fast tests
• Activity mocking with Mockito
• Search attribute registration in tests

Exercise 7: Manual Activity Retry (40 min)

• Manual retry pattern using signals
• Invalid data handling scenarios
• Disabling automatic retries
• Interactive retry commands

Running Exercises

Exercise 1 (Hello Temporal)

# Start worker
./gradlew execute -PmainClass=com.temporal.training.exercise1.StartWorker
# Run workflow (in another terminal)
./gradlew execute -PmainClass=com.temporal.training.exercise1.StartWorkflow

Exercise 2 (Money Transfer Basics)

# Start worker
./gradlew execute -PmainClass=com.temporal.training.exercise2.StartWorker
# Run workflow (in another terminal)
./gradlew execute -PmainClass=com.temporal.training.exercise2.StartWorkflow

Exercise 3 (Query Handlers)

# Start worker
./gradlew execute -PmainClass=com.temporal.training.exercise3.StartWorker
# Run workflow (in another terminal)
./gradlew execute -PmainClass=com.temporal.training.exercise3.StartWorkflow

Exercise 4 (Visibility & Monitoring)

# Start worker
./gradlew execute -PmainClass=com.temporal.training.exercise4.StartWorker
# Run workflow (in another terminal)
./gradlew execute -PmainClass=com.temporal.training.exercise4.StartWorkflow

Exercise 5 (User Metadata & Activity Summaries)

# Start worker
./gradlew execute -PmainClass=com.temporal.training.exercise5.StartWorker
# Run workflow (in another terminal)
./gradlew execute -PmainClass=com.temporal.training.exercise5.StartWorkflow

Exercise 6 (Testing Strategy)

# Run tests
./gradlew test --tests "com.temporal.training.exercise6.MoneyTransferWorkflowTest"

Exercise 7 (Manual Activity Retry)

# Start worker
./gradlew execute -PmainClass=com.temporal.training.exercise7.StartWorker
# Run workflow (in another terminal)
./gradlew execute -PmainClass=com.temporal.training.exercise7.StartWorkflow
# Send retry signal with corrected data
temporal workflow signal \
  --workflow-id money-transfer-workflow \
  --name retry \
  --input '{"key":"fromAccount","value":"account-123"}'

Running Solutions

Replace exercise with solution in the class names above to run complete implementations.

Key Features Implemented

• Java 17 Records: Modern data classes
• Activity Retry: Configurable retry policies
• Signal/Query: Workflow interaction patterns
• Search Attributes: Custom filtering
• User Metadata: Activity context
• Compensation: Saga pattern for rollbacks
• Testing: Time-skipping unit tests
• Error Handling: Distinguishes activity vs workflow failures
• Manual Retry: Signal-based retry for failed activities