Initial commit

skills/recipe-writer/examples/example-say-hello-recipe.java

@@ -0,0 +1,186 @@
+package com.yourorg;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import lombok.EqualsAndHashCode;
+import lombok.Value;
+import org.jspecify.annotations.NonNull;
+import org.openrewrite.*;
+import org.openrewrite.java.JavaIsoVisitor;
+import org.openrewrite.java.JavaTemplate;
+import org.openrewrite.java.tree.J;
+
+/**
+ * A simple recipe that adds a hello() method to a specified class.
+ *
+ * This example demonstrates:
+ * - Basic recipe structure with @Value and @EqualsAndHashCode
+ * - Using @Option for configurable parameters
+ * - Using JavaTemplate for code generation
+ * - Checking preconditions before making changes
+ * - Following the "do no harm" principle
+ *
+ * Based on the official OpenRewrite tutorial:
+ * https://docs.openrewrite.org/authoring-recipes/writing-a-java-refactoring-recipe
+ */
+@Value
+@EqualsAndHashCode(callSuper = false)
+public class SayHelloRecipe extends Recipe {
+
+    @Option(
+        displayName = "Fully Qualified Class Name",
+        description = "A fully qualified class name indicating which class to add a hello() method to.",
+        example = "com.yourorg.FooBar"
+    )
+    @NonNull
+    String fullyQualifiedClassName;
+
+    @JsonCreator
+    public SayHelloRecipe(@NonNull @JsonProperty("fullyQualifiedClassName") String fullyQualifiedClassName) {
+        this.fullyQualifiedClassName = fullyQualifiedClassName;
+    }
+
+    @Override
+    public String getDisplayName() {
+        return "Say 'Hello'";
+    }
+
+    @Override
+    public String getDescription() {
+        return "Adds a \"hello\" method to the specified class.";
+    }
+
+    @Override
+    public TreeVisitor<?, ExecutionContext> getVisitor() {
+        // Always return a new instance - never cache visitors
+        return new JavaIsoVisitor<ExecutionContext>() {
+
+            @Override
+            public J.ClassDeclaration visitClassDeclaration(J.ClassDeclaration classDecl, ExecutionContext ctx) {
+                // Step 1: Traverse the subtree first
+                J.ClassDeclaration cd = super.visitClassDeclaration(classDecl, ctx);
+
+                // Step 2: Check if this is the class we're looking for
+                // Do no harm: return unchanged if this isn't the target class
+                if (cd.getType() == null || !cd.getType().getFullyQualifiedName().equals(fullyQualifiedClassName)) {
+                    return cd;
+                }
+
+                // Step 3: Check if the class already has a hello() method
+                // Do no harm: don't add if it already exists
+                boolean helloMethodExists = cd.getBody().getStatements().stream()
+                    .filter(statement -> statement instanceof J.MethodDeclaration)
+                    .map(J.MethodDeclaration.class::cast)
+                    .anyMatch(methodDeclaration -> "hello".equals(methodDeclaration.getName().getSimpleName()));
+
+                if (helloMethodExists) {
+                    return cd;
+                }
+
+                // Step 4: Add the hello() method using JavaTemplate
+                // The template uses #{} for parameter substitution
+                J.Block body = JavaTemplate.apply(
+                    "public String hello() { return \"Hello from #{}!\"; }",
+                    new Cursor(getCursor(), cd.getBody()),
+                    cd.getBody().getCoordinates().lastStatement(),
+                    fullyQualifiedClassName
+                );
+
+                return cd.withBody(body);
+            }
+        };
+    }
+}
+
+// ============================================================
+// TEST CLASS
+// ============================================================
+
+/*
+package com.yourorg;
+
+import org.junit.jupiter.api.Test;
+import org.openrewrite.DocumentExample;
+import org.openrewrite.test.RecipeSpec;
+import org.openrewrite.test.RewriteTest;
+
+import static org.openrewrite.java.Assertions.java;
+
+class SayHelloRecipeTest implements RewriteTest {
+
+    @Override
+    public void defaults(RecipeSpec spec) {
+        spec.recipe(new SayHelloRecipe("com.yourorg.FooBar"));
+    }
+
+    @DocumentExample
+    @Test
+    void addsHelloToFooBar() {
+        rewriteRun(
+            java(
+                """
+                package com.yourorg;
+
+                class FooBar {
+                }
+                """,
+                """
+                package com.yourorg;
+
+                class FooBar {
+                    public String hello() {
+                        return "Hello from com.yourorg.FooBar!";
+                    }
+                }
+                """
+            )
+        );
+    }
+
+    @Test
+    void doesNotChangeExistingHello() {
+        rewriteRun(
+            java(
+                """
+                package com.yourorg;
+
+                class FooBar {
+                    public String hello() { return ""; }
+                }
+                """
+            )
+        );
+    }
+
+    @Test
+    void doesNotChangeOtherClasses() {
+        rewriteRun(
+            java(
+                """
+                package com.yourorg;
+
+                class OtherClass {
+                }
+                """
+            )
+        );
+    }
+}
+*/
+
+// ============================================================
+// YAML USAGE
+// ============================================================
+
+/*
+Save this in src/main/resources/META-INF/rewrite/say-hello.yml:
+
+---
+type: specs.openrewrite.org/v1beta/recipe
+name: com.yourorg.SayHelloToFooBar
+displayName: Say Hello to FooBar
+description: Adds a hello() method to the FooBar class.
+recipeList:
+  - com.yourorg.SayHelloRecipe:
+      fullyQualifiedClassName: com.yourorg.FooBar
+*/