Some Java update related changes

Author: mikebroberts

MODERNIZATION.md

@@ -1,76 +1,73 @@
-# Modernization Plan for Programming AWS Lambda Examples
+# Modernization Summary for Programming AWS Lambda Examples
 
-## Completed Work
+## Completed Work (November 2025)
 
-### Test Harness (Done)
+### Test Harness
 - Created `test-harness/` with deploy, test, and teardown scripts
-- Smoke tests for chapters 2, 3, 4, 5-api, 5-event-sources, 7
+- Smoke tests for chapters 2, 3, 4, 5-api, 5-data-pipeline, 5-event-sources, 7
 - Integration tests for chapter 6 (Maven failsafe)
-- GitHub Actions workflow (needs IAM permissions to run)
-- All 9 chapters deploy successfully with `java8.al2` runtime
-
-### Immediate Fixes Applied
-- Updated runtime from `java8` (deprecated) to `java8.al2`
-- Shortened stack prefixes for S3 bucket name limits
-
-### Phase 1 Complete (November 2025)
-- **Java 21 Runtime**: All pom.xml and template.yaml files updated
-- **Security Updates**: Jackson 2.17.2, Log4j 2.23.1
-- **AWS SDK v2 Migration**: All chapters migrated to SDK v2
-  - DynamoDB (chapters 4, 5-api, 7)
-  - S3, SNS (chapters 5-data-pipeline, 6)
-  - CloudFormation, CloudWatch Logs (chapter 6 integration tests)
-  - X-Ray SDK v2 instrumentor (chapter 7)
-
-### Phase 3 Partial (November 2025)
-- **JUnit 5 Migration**: Chapter 6 tests migrated to JUnit Jupiter 5.10.3
-- **system-stubs**: Replaced system-rules with system-stubs-jupiter 2.1.6
-- **Mockito 5.12.0**: Updated for Java 21 compatibility
-- **S3Event tests**: Fixed to build events programmatically (no Jackson deserialization)
-
-### Known Issues (Resolved)
-- **Chapter 6 integration tests**: Fixed stack name passing to Maven failsafe plugin
-  - Root cause: Maven property `${integration.test.stack.name}` resolves at project load time, before `-D` override
-  - Solution: Use shell environment variable `${env.STACK_NAME}` instead of Maven property
-  - Test harness exports `STACK_NAME`, failsafe passes it via `environmentVariables`, test reads `System.getenv()`
+- GitHub Actions workflow (requires IAM permissions - see below)
+
+### Java 21 Runtime
+- All `pom.xml` files updated to Java 21
+- All `template.yaml` files updated to `java21` runtime
+- Applied `var` keyword for cleaner code in chapters 3, 5-api, 6, 7
+
+### Security Updates
+- Jackson 2.17.2 (fixed CVEs from 2.10.1)
+- Log4j 2.23.1
+
+### AWS SDK v2 Migration
+All chapters migrated from AWS SDK v1 to v2:
+- DynamoDB (chapters 4, 5-api, 7)
+- S3, SNS (chapters 5-data-pipeline, 6)
+- CloudFormation, CloudWatch Logs (chapter 6 integration tests)
+- X-Ray SDK v2 instrumentor (chapter 7)
+
+### Testing Modernization
+- JUnit 5 (Jupiter 5.10.3)
+- Mockito 5.12.0
+- system-stubs-jupiter 2.1.6 (replaced system-rules for Java 9+ compatibility)
+- S3Event tests build events programmatically
 
 ---
 
-## Phase 1: Critical Updates (Do First)
+## Current Dependency Versions
 
-### 1. Java 21 Runtime
-**Files to change:**
-- All `pom.xml` files: Update `maven.compiler.source/target` from `1.8` to `21`
-- All `template.yaml` files: Update `Runtime` from `java8.al2` to `java21`
+```xml
+<properties>
+    <!-- Java -->
+    <maven.compiler.source>21</maven.compiler.source>
+    <maven.compiler.target>21</maven.compiler.target>
 
-### 2. Security Updates
-**jackson-databind** (currently 2.10.1 - has CVEs)
-- Update to `2.17.2` in all pom.xml files
-- Locations: chapter5-api, chapter5-data-pipeline, chapter6, chapter7
+    <!-- AWS SDK v2 -->
+    <aws.sdk.version>2.29.6</aws.sdk.version>
 
-**log4j** (currently 2.17.0)
-- Update to `2.23.1` in chapter6, chapter7
+    <!-- Lambda Libraries -->
+    <aws.lambda.java.core.version>1.2.3</aws.lambda.java.core.version>
+    <aws.lambda.java.events.version>3.14.0</aws.lambda.java.events.version>
 
-### 3. AWS SDK v2 Migration (End-of-support Dec 2025)
-**Largest effort - affects all chapters using AWS services**
+    <!-- Logging -->
+    <log4j.version>2.23.1</log4j.version>
 
-Package changes:
-- `com.amazonaws:aws-java-sdk-*` → `software.amazon.awssdk:*`
-- BOM: `1.11.600` → `2.29.x`
+    <!-- JSON -->
+    <jackson.version>2.17.2</jackson.version>
 
-Code changes required:
-- DynamoDB client API changes (chapters 4, 5-api, 7)
-- S3 client API changes (chapters 5-data-pipeline, 6, 8)
-- SNS client API changes (chapters 5-data-pipeline, 6)
-- CloudFormation/Logs client changes (chapter 6 integration tests)
+    <!-- Testing -->
+    <junit.version>5.10.3</junit.version>
+    <mockito.version>5.12.0</mockito.version>
+    <system-stubs.version>2.1.6</system-stubs.version>
 
-**Note:** `aws-lambda-java-core` and `aws-lambda-java-events` are separate artifacts and remain compatible.
+    <!-- X-Ray SDK v2 -->
+    <xray.version>2.18.1</xray.version>
+</properties>
+```
 
 ---
 
-## Phase 2: High Value Improvements
+## Future Improvements
 
-### 4. Lambda SnapStart
+### Lambda SnapStart
 Add to template.yaml for fast cold starts:
 ```yaml
 Globals:
@@ -80,14 +77,14 @@ Globals:
 ```
 Requires `AutoPublishAlias` on each function.
 
-### 5. ARM64 Architecture
+### ARM64 Architecture
 20% better price/performance:
 ```yaml
 Architectures:
   - arm64
 ```
 
-### 6. AWS Lambda Powertools
+### AWS Lambda Powertools
 Replace manual logging/metrics/tracing (chapter 7):
 ```xml
 <dependency>
@@ -97,111 +94,26 @@ Replace manual logging/metrics/tracing (chapter 7):
 </dependency>
 ```
 
----
-
-## Phase 3: Testing & Code Quality
-
-### 7. JUnit 5 Migration
-- `junit:4.12` → `junit-jupiter:5.10.3`
-- `mockito-core:3.0.0` → `mockito-core:5.12.0`
-- Affects chapter 6 test code
-
-### 8. Replace system-rules
-**Critical for Java 9+ compatibility**
-- `system-rules:1.19.0` → `system-stubs-jupiter:2.1.6`
-- Used in chapter 6 bulk-events-stage and single-event-stage tests
-- Currently skipped in test harness due to reflection errors
-
-### 9. Java 21 Language Features
-Modernize code with:
-- Records for DTOs (WeatherEvent, etc.)
-- Pattern matching for instanceof
-- Text blocks for JSON templates
-
----
-
-## Phase 4: Nice to Have
-
-### 10. SAM Template Improvements
+### SAM Template Improvements
 - Use `Globals` section for DRY configuration
-- Consider SAM Connectors syntax
-- Add structured logging config:
-```yaml
-LoggingConfig:
-  LogFormat: JSON
-```
-
-### 11. Build Improvements
-- Consider maven-shade-plugin consistently (simpler than assembly)
-- Update maven plugins to latest versions
-
-### 12. Additional AWS Features
-- Function URLs (alternative to API Gateway for simple cases)
-- Response streaming (for long-running responses)
+- Add structured logging: `LoggingConfig: { LogFormat: JSON }`
 
 ---
 
-## Recommended Dependency Versions
-
-```xml
-<properties>
-    <!-- Java -->
-    <maven.compiler.source>21</maven.compiler.source>
-    <maven.compiler.target>21</maven.compiler.target>
-
-    <!-- AWS SDK v2 -->
-    <aws.sdk.version>2.29.6</aws.sdk.version>
-
-    <!-- Lambda Libraries -->
-    <aws.lambda.java.core.version>1.2.3</aws.lambda.java.core.version>
-    <aws.lambda.java.events.version>3.14.0</aws.lambda.java.events.version>
-
-    <!-- Powertools -->
-    <powertools.version>2.0.0</powertools.version>
-
-    <!-- Logging -->
-    <log4j.version>2.23.1</log4j.version>
+## Test Harness Usage
 
-    <!-- JSON -->
-    <jackson.version>2.17.2</jackson.version>
+### Local Testing
+```bash
+# Deploy all
+./test-harness/deploy/deploy-all.sh
 
-    <!-- Testing -->
-    <junit.version>5.10.3</junit.version>
-    <mockito.version>5.12.0</mockito.version>
-    <system-stubs.version>2.1.6</system-stubs.version>
+# Test all
+./test-harness/test/test-all.sh
 
-    <!-- X-Ray SDK v2 -->
-    <xray.version>2.18.1</xray.version>
-</properties>
+# Cleanup
+./test-harness/teardown/teardown-all.sh
 ```
 
----
-
-## Implementation Order
-
-1. **Start with chapter 2** (simplest - no dependencies)
-   - Update Java version
-   - Update runtime
-   - Test with harness
-
-2. **Then chapter 3** (adds aws-lambda-java-core)
-
-3. **Then chapter 4** (adds DynamoDB - first SDK v2 migration)
-
-4. **Then chapter 5-api** (DynamoDB + Jackson + API Gateway)
-
-5. **Continue with remaining chapters**
-
-6. **Chapter 6 last** (most complex - has tests that need JUnit 5 migration)
-
----
-
-## Test Harness Notes
-
-### Known Issues
-- Chapter 6 integration test uses old CloudWatch logs (may pass when it should fail)
-- Unit tests skipped due to system-rules incompatibility with Java 9+
-
 ### GitHub Actions
 Requires IAM permissions on the GitHub Actions role:
 - `iam:CreateRole`, `iam:DeleteRole`, `iam:GetRole`, `iam:PassRole`
@@ -210,15 +122,3 @@ Requires IAM permissions on the GitHub Actions role:
 - `iam:TagRole`, `iam:UntagRole`
 
 Scope to: `arn:aws:iam::ACCOUNT:role/lb-test-*`
-
-### Local Testing
-```bash
-# Deploy all
-./test-harness/deploy/deploy-all.sh
-
-# Test all
-./test-harness/test/test-all.sh
-
-# Cleanup
-./test-harness/teardown/teardown-all.sh
-```

chapter3/src/main/java/book/ContextLambda.java

@@ -7,7 +7,7 @@
 
 public class ContextLambda {
     public Map<String, Object> handler(Object input, Context context) {
-        Map<String, Object> toReturn = new HashMap<>();
+        var toReturn = new HashMap<String, Object>();
         toReturn.put("getMemoryLimitInMB", context.getMemoryLimitInMB() + "");
         toReturn.put("getFunctionName", context.getFunctionName());
         toReturn.put("getFunctionVersion", context.getFunctionVersion());

chapter3/src/main/java/book/ListMapLambda.java

@@ -8,19 +8,19 @@
 
 public class ListMapLambda {
     public List<Integer> handlerList(List<Integer> input) {
-        List<Integer> newList = new ArrayList<>();
+        var newList = new ArrayList<Integer>();
         input.forEach(x -> newList.add(100 + x));
         return newList;
     }
 
     public Map<String, String> handlerMap(Map<String, String> input) {
-        Map<String, String> newMap = new HashMap<>();
+        var newMap = new HashMap<String, String>();
         input.forEach((k, v) -> newMap.put("New Map -> " + k, v));
         return newMap;
     }
 
     public Map<String, Map<String, Integer>> handlerNestedCollection(List<Map<String, Integer>> input) {
-        Map<String, Map<String, Integer>> newMap = new HashMap<>();
+        var newMap = new HashMap<String, Map<String, Integer>>();
         IntStream.range(0, input.size())
                 .forEach(i -> newMap.put("Nested at position " + i, input.get(i)));
         return newMap;

chapter5-api/src/main/java/book/api/WeatherEventLambda.java

@@ -18,16 +18,16 @@ public class WeatherEventLambda {
     private final String tableName = System.getenv("LOCATIONS_TABLE");
 
     public ApiGatewayResponse handler(ApiGatewayRequest request) throws IOException {
-        final WeatherEvent weatherEvent = objectMapper.readValue(request.body, WeatherEvent.class);
+        var weatherEvent = objectMapper.readValue(request.body, WeatherEvent.class);
 
-        Map<String, AttributeValue> item = new HashMap<>();
+        var item = new HashMap<String, AttributeValue>();
         item.put("locationName", AttributeValue.builder().s(weatherEvent.locationName).build());
         item.put("temperature", AttributeValue.builder().n(String.valueOf(weatherEvent.temperature)).build());
         item.put("timestamp", AttributeValue.builder().n(String.valueOf(weatherEvent.timestamp)).build());
         item.put("longitude", AttributeValue.builder().n(String.valueOf(weatherEvent.longitude)).build());
         item.put("latitude", AttributeValue.builder().n(String.valueOf(weatherEvent.latitude)).build());
 
-        PutItemRequest putItemRequest = PutItemRequest.builder()
+        var putItemRequest = PutItemRequest.builder()
                 .tableName(tableName)
                 .item(item)
                 .build();

chapter6/integration-tests/src/test/java/book/pipeline/PipelineIT.java

@@ -35,9 +35,9 @@ public PipelineIT() {
 
     @Test
     public void endToEndTest() throws InterruptedException {
-        String bucketName = resolvePhysicalId("PipelineStartBucket");
-        String key = UUID.randomUUID().toString();
-        File file = new File(getClass().getResource("/bulk_data.json").getFile());
+        var bucketName = resolvePhysicalId("PipelineStartBucket");
+        var key = UUID.randomUUID().toString();
+        var file = new File(getClass().getResource("/bulk_data.json").getFile());
 
         // 1. Upload bulk_data file to S3
         s3.putObject(PutObjectRequest.builder()
@@ -47,8 +47,8 @@ public void endToEndTest() throws InterruptedException {
 
         // 2. Check for executions of SingleEventLambda
         Thread.sleep(30000);
-        String singleEventLambda = resolvePhysicalId("SingleEventLambda");
-        Set<String> logMessages = getLogMessages(singleEventLambda);
+        var singleEventLambda = resolvePhysicalId("SingleEventLambda");
+        var logMessages = getLogMessages(singleEventLambda);
         assertThat(logMessages, hasItems(
                 "WeatherEvent{locationName='Brooklyn, NY', temperature=91.0, timestamp=1564428897, longitude=-73.99, latitude=40.7}",
                 "WeatherEvent{locationName='Oxford, UK', temperature=64.0, timestamp=1564428898, longitude=-1.25, latitude=51.75}",
@@ -65,23 +65,23 @@ public void endToEndTest() throws InterruptedException {
         logs.deleteLogGroup(DeleteLogGroupRequest.builder()
                 .logGroupName(getLogGroup(singleEventLambda))
                 .build());
-        String bulkEventsLambda = resolvePhysicalId("BulkEventsLambda");
+        var bulkEventsLambda = resolvePhysicalId("BulkEventsLambda");
         logs.deleteLogGroup(DeleteLogGroupRequest.builder()
                 .logGroupName(getLogGroup(bulkEventsLambda))
                 .build());
     }
 
     private String resolvePhysicalId(String logicalId) {
-        DescribeStackResourceRequest request = DescribeStackResourceRequest.builder()
+        var request = DescribeStackResourceRequest.builder()
                 .stackName(stackName)
                 .logicalResourceId(logicalId)
                 .build();
-        DescribeStackResourceResponse response = cfn.describeStackResource(request);
+        var response = cfn.describeStackResource(request);
         return response.stackResourceDetail().physicalResourceId();
     }
 
     private Set<String> getLogMessages(String lambdaName) {
-        String logGroup = getLogGroup(lambdaName);
+        var logGroup = getLogGroup(lambdaName);
 
         return logs.describeLogStreams(DescribeLogStreamsRequest.builder()
                         .logGroupName(logGroup)