Use JoinColumn annotation for relationship mappings (#416)

* Use JoinColumn annotation for relationship mappings

* Add failing test where other Column annotations are modified when it shouldn't be

* Apply changes only to current variable declaration

* Fix test case imports to wildcard

* Move test to javax package

* Minor polish

* Remove comment

Co-authored-by: Tim te Beek <[email protected]>

* Update wording and names

* Add test cases, add Entity check, cleanup

* Add test case and fix for inner classes

* Show that type is only changed for affected field

* Add trailing newline

---------

Co-authored-by: Tim te Beek <[email protected]>

Author: evie-lau

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

@@ -0,0 +1,83 @@
+/*
+ * 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 org.openrewrite.ExecutionContext;
+import org.openrewrite.Preconditions;
+import org.openrewrite.Recipe;
+import org.openrewrite.TreeVisitor;
+import org.openrewrite.java.ChangeType;
+import org.openrewrite.java.JavaIsoVisitor;
+import org.openrewrite.java.RemoveAnnotationAttribute;
+import org.openrewrite.java.search.FindAnnotations;
+import org.openrewrite.java.search.UsesType;
+import org.openrewrite.java.tree.J;
+
+@EqualsAndHashCode(callSuper = false)
+public class UseJoinColumnForMapping extends Recipe {
+    private final String JOIN_COLUMN = "javax.persistence.JoinColumn";
+    private final String COLUMN = "javax.persistence.Column";
+
+    @Override
+    public String getDisplayName() {
+        return "`@JoinColumn` annotations must be used with relationship mappings";
+    }
+
+    @Override
+    public String getDescription() {
+        return "In OpenJPA, when a relationship attribute has either a `@OneToOne` or a `@ManyToOne` annotation with a " +
+               "`@Column` annotation, the `@Column` annotation is treated as a `@JoinColumn` annotation. EclipseLink " +
+               "throws an exception that indicates that the entity class must use `@JoinColumn` instead of `@Column` " +
+               "to map a relationship attribute.";
+    }
+
+    @Override
+    public TreeVisitor<?, ExecutionContext> getVisitor() {
+        return Preconditions.check(
+                Preconditions.and(
+                        new UsesType<>("javax.persistence.Entity", true),
+                        new UsesType<>(COLUMN, true),
+                        Preconditions.or(
+                                new UsesType<>("javax.persistence.OneToOne", true),
+                                new UsesType<>("javax.persistence.ManyToOne", true)
+                        )
+                ),
+                new JavaIsoVisitor<ExecutionContext>() {
+                    @Override
+                    public J.VariableDeclarations visitVariableDeclarations(J.VariableDeclarations multiVariable, ExecutionContext ctx) {
+                        // Exit if not annotated with @Column and a relationship mapping annotation
+                        if (FindAnnotations.find(multiVariable, COLUMN).isEmpty()
+                            || (FindAnnotations.find(multiVariable, "javax.persistence.OneToOne").isEmpty()
+                                && FindAnnotations.find(multiVariable, "javax.persistence.ManyToOne").isEmpty())) {
+                            return multiVariable;
+                        }
+
+                        // Change @Column to @JoinColumn
+                        // The javax.persistence.Column attributes length, precision, and scale are not kept.
+                        maybeRemoveImport(COLUMN);
+                        maybeAddImport(JOIN_COLUMN);
+                        J.VariableDeclarations joinColumn = (J.VariableDeclarations) new ChangeType(COLUMN, JOIN_COLUMN, false).getVisitor().visit(multiVariable, ctx);
+                        joinColumn = (J.VariableDeclarations) new RemoveAnnotationAttribute(JOIN_COLUMN, "length").getVisitor().visit(joinColumn, ctx);
+                        joinColumn = (J.VariableDeclarations) new RemoveAnnotationAttribute(JOIN_COLUMN, "precision").getVisitor().visit(joinColumn, ctx);
+                        joinColumn = (J.VariableDeclarations) new RemoveAnnotationAttribute(JOIN_COLUMN, "scale").getVisitor().visit(joinColumn, ctx);
+
+                        return joinColumn;
+                    }
+                }
+        );
+    }
+}

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

@@ -26,3 +26,4 @@ recipeList:
   - org.openrewrite.java.migrate.javax.AddColumnAnnotation
   - org.openrewrite.java.migrate.javax.AddDefaultConstructorToEntityClass
   - org.openrewrite.java.migrate.javax.RemoveEmbeddableId
+  - org.openrewrite.java.migrate.javax.UseJoinColumnForMapping