Add Transient annotation to private accessor methods

src/main/java/org/openrewrite/java/migrate/javax/AddTransientAnnotationToPrivateAccessor.java

@@ -0,0 +1,126 @@
+/*
+ * Copyright 2024 the original author or authors.
+ * <p>
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * https://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.openrewrite.java.migrate.javax;
+
+import lombok.EqualsAndHashCode;
+import lombok.Value;
+import org.openrewrite.ExecutionContext;
+import org.openrewrite.Preconditions;
+import org.openrewrite.Recipe;
+import org.openrewrite.TreeVisitor;
+import org.openrewrite.java.JavaIsoVisitor;
+import org.openrewrite.java.JavaParser;
+import org.openrewrite.java.JavaTemplate;
+import org.openrewrite.java.search.FindAnnotations;
+import org.openrewrite.java.search.UsesType;
+import org.openrewrite.java.tree.Expression;
+import org.openrewrite.java.tree.J;
+import org.openrewrite.java.tree.JavaType;
+
+import java.util.*;
+import java.util.stream.Collectors;
+
+@Value
+@EqualsAndHashCode(callSuper = false)
+public class AddTransientAnnotationToPrivateAccessor extends Recipe {
+
+    @Override
+    public String getDisplayName() {
+        return "Private accessor methods must have a `@Transient` annotation";
+    }
+
+    @Override
+    public String getDescription() {
+        return "According to the JPA 2.1 specification, when property access is used, the property accessor methods " +
+               "must be public or protected. OpenJPA ignores any private accessor methods, whereas EclipseLink persists " +
+               "those attributes. To ignore private accessor methods in EclipseLink, the methods must have a " +
+               "`@Transient` annotation.";
+    }
+
+
+    @Override
+    public TreeVisitor<?, ExecutionContext> getVisitor() {
+        return Preconditions.check(
+                new UsesType<>("javax.persistence.Entity", true),
+                new JavaIsoVisitor<ExecutionContext>() {
+                    List<JavaType.Variable> classVars = new ArrayList<>();
+                    @Override
+                    public J.ClassDeclaration visitClassDeclaration(J.ClassDeclaration classDecl, ExecutionContext ctx) {
+                        // Collect all class variables
+                        classVars = classDecl.getBody().getStatements().stream()
+                                .filter(J.VariableDeclarations.class::isInstance)
+                                .map(J.VariableDeclarations.class::cast)
+                                .map(J.VariableDeclarations::getVariables)
+                                .flatMap(Collection::stream)
+                                .map(var -> var.getName().getFieldType())
+                                .filter(Objects::nonNull)
+                                .collect(Collectors.toList());
+                        return super.visitClassDeclaration(classDecl, ctx);
+                    }
+
+                    @Override
+                    public J.MethodDeclaration visitMethodDeclaration(J.MethodDeclaration md, ExecutionContext ctx) {
+                        if (isPrivateAccessorMethodWithoutTransientAnnotation(md)) {
+                            // Add @Transient annotation
+                            maybeAddImport("javax.persistence.Transient");
+                            return JavaTemplate.builder("@Transient")
+                                    .contextSensitive()
+                                    .javaParser(JavaParser.fromJavaVersion().classpathFromResources(ctx, "javax.persistence-api-2.2"))
+                                    .imports("javax.persistence.Transient")
+                                    .build()
+                                    .apply(getCursor(), md.getCoordinates().addAnnotation(Comparator.comparing(J.Annotation::getSimpleName)));
+                        }
+                        return md;
+                    }
+
+                    private boolean isPrivateAccessorMethodWithoutTransientAnnotation(J.MethodDeclaration method) {
+                        return method.hasModifier(J.Modifier.Type.Private)
+                               && method.getParameters().get(0) instanceof J.Empty
+                               && method.getReturnTypeExpression().getType() != JavaType.Primitive.Void
+                               && FindAnnotations.find(method, "javax.persistence.Transient").isEmpty()
+                               && methodReturnsFieldFromClass(method);
+                    }
+
+                    /**
+                     * Check if the given method returns a field defined in the parent class
+                     */
+                    private boolean methodReturnsFieldFromClass(J.MethodDeclaration method) {
+                        // Get all return values from method
+                        List<JavaType.Variable> returns = new ArrayList<>();
+                        JavaIsoVisitor<List<JavaType.Variable>> returnValueCollector = new JavaIsoVisitor<List<JavaType.Variable>>() {
+                            @Override
+                            public J.Return visitReturn(J.Return ret, List<JavaType.Variable> returnedVars) {
+                                Expression expression = ret.getExpression();
+                                JavaType.Variable returnedVar;
+                                if (expression instanceof J.FieldAccess) { // ie: return this.field;
+                                    returnedVar = ((J.FieldAccess) expression).getName().getFieldType();
+                                    returnedVars.add(returnedVar);
+                                } else if (expression instanceof J.Identifier) { // ie: return field;
+                                    returnedVar = ((J.Identifier) expression).getFieldType();
+                                    returnedVars.add(returnedVar);
+                                } // last case should be null: do nothing and continue
+                                return super.visitReturn(ret, returnedVars);
+                            }
+                        };
+                        returnValueCollector.visitBlock(method.getBody(), returns);
+
+                        // Check if any return values are a class field
+                        return returns.stream().anyMatch(classVars::contains);
+                    }
+                }
+        );
+    }
+}

src/main/resources/META-INF/rewrite/openjpa-to-eclipselink.yml

@@ -27,6 +27,7 @@ recipeList:
   - org.openrewrite.java.migrate.javax.AddTableGenerator
   - org.openrewrite.java.migrate.javax.AddTransientAnnotationToCollections
   - org.openrewrite.java.migrate.javax.AddTransientAnnotationToEntity
+  - org.openrewrite.java.migrate.javax.AddTransientAnnotationToPrivateAccessor
   - org.openrewrite.java.migrate.javax.RemoveEmbeddableId
   - org.openrewrite.java.migrate.javax.RemoveTemporalAnnotation
   - org.openrewrite.java.migrate.javax.UseJoinColumnForMapping