feat: Support CRaC priming of powertools validation

docs/utilities/validation.md

@@ -292,3 +292,31 @@ If you need to configure the Jackson ObjectMapper, you can use the `ValidationCo
        }
     }
     ```
+
+## Advanced
+
+### SnapStart priming
+To enable priming with AWS Lambda SnapStart, you need an explicit reference to `ValidationConfig` to allow the library to register before SnapStart takes a memory snapshot.
+
+The `@Validation` annotation uses AspectJ compile-time weaving, which means there may be no runtime reference that triggers `ValidationConfig` to load during the INIT phase. 
+Hence without explicit reference, the priming logic will not execute.
+
+So to ensure `ValidationConfig` is loaded, you need to add an explicit reference in your handler class. This can be done by adding one of the following to your handler class:
+
+=== "Constructor"
+
+    ```java hl_lines="3"
+    ... 
+    public MyHandler() {
+        ValidationConfig.get(); // Ensure ValidationConfig is loaded for SnapStart
+    }
+    ```
+
+=== "Static Initializer"
+
+    ```java hl_lines="3"
+    ...
+    static {
+        ValidationConfig.get(); // Ensure ValidationConfig is loaded for SnapStart
+    }
+    ```

powertools-validation/pom.xml

@@ -71,6 +71,10 @@
             <groupId>com.amazonaws</groupId>
             <artifactId>aws-lambda-java-serialization</artifactId>
         </dependency>
+        <dependency>
+            <groupId>org.crac</groupId>
+            <artifactId>crac</artifactId>
+        </dependency>
 
         <!-- Test dependencies -->
         <dependency>
@@ -119,4 +123,25 @@
             <scope>test</scope>
         </dependency>
     </dependencies>
+
+    <profiles>
+        <profile>
+            <id>generate-classesloaded-file</id>
+            <build>
+                <plugins>
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-surefire-plugin</artifactId>
+                        <configuration>
+                            <argLine>
+                                -Xlog:class+load=info:classesloaded.txt
+                                --add-opens java.base/java.util=ALL-UNNAMED
+                                --add-opens java.base/java.lang=ALL-UNNAMED
+                            </argLine>
+                        </configuration>
+                    </plugin>
+                </plugins>
+            </build>
+        </profile>
+    </profiles>
 </project>

powertools-validation/src/main/java/software/amazon/lambda/powertools/validation/ValidationConfig.java

@@ -16,10 +16,15 @@
 
 import com.fasterxml.jackson.databind.JsonNode;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.networknt.schema.JsonSchema;
 import com.networknt.schema.JsonSchemaFactory;
 import com.networknt.schema.SpecVersion;
 import io.burt.jmespath.JmesPath;
 import io.burt.jmespath.function.BaseFunction;
+import org.crac.Context;
+import org.crac.Core;
+import org.crac.Resource;
+import software.amazon.lambda.powertools.common.internal.ClassPreLoader;
 import software.amazon.lambda.powertools.utilities.JsonConfig;
 import software.amazon.lambda.powertools.utilities.jmespath.Base64Function;
 import software.amazon.lambda.powertools.utilities.jmespath.Base64GZipFunction;
@@ -31,10 +36,15 @@
  * For everything but the validation features (factory, schemaVersion), {@link ValidationConfig}
  * is just a wrapper of {@link JsonConfig}.
  */
-public class ValidationConfig {
+public class ValidationConfig implements Resource {
     private SpecVersion.VersionFlag jsonSchemaVersion = SpecVersion.VersionFlag.V7;
     private JsonSchemaFactory factory = JsonSchemaFactory.getInstance(jsonSchemaVersion);
 
+    // Static block to ensure CRaC registration happens at class loading time
+    static {
+        Core.getGlobalContext().register(get());
+    }
+
     private ValidationConfig() {
     }
 
@@ -102,7 +112,27 @@
         return JsonConfig.get().getObjectMapper();
     }
 
+    @Override
+    public void beforeCheckpoint(Context<? extends Resource> context) throws Exception {
+        // Initialize key components
+        getObjectMapper();
+        getJmesPath();
+        getFactory();
+
+        // Dummy validation
+        String sampleSchema = "{\"type\":\"object\"}";
+        JsonSchema schema = ValidationUtils.getJsonSchema(sampleSchema);
+        ValidationUtils.validate("{\"test\":\"dummy\"}", schema);
+
+        ClassPreLoader.preloadClasses();
+    }
+
+    @Override
+    public void afterRestore(Context<? extends Resource> context) throws Exception {
+        // No action needed after restore
+    }
+
     private static class ConfigHolder {
         private static final ValidationConfig instance = new ValidationConfig();
     }
 }