SONARJAVA-6539 Create rule S8947: JPA entity classes should not be final

its/autoscan/src/test/resources/autoscan/diffs/diff_S8947.json

@@ -0,0 +1,6 @@
+{
+  "ruleKey": "S8947",
+  "hasTruePositives": false,
+  "falseNegatives": 4,
+  "falsePositives": 0
+}

java-checks-test-sources/default/src/main/java/checks/JpaEntityFinalCheckJakartaSample.java

@@ -0,0 +1,45 @@
+package checks;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+import jakarta.persistence.MappedSuperclass;
+
+@Entity
+final class JpaEntityFinalCheckJakartaFinalEntity { // Noncompliant {{Remove this "final" modifier from this JPA entity class.}}
+//^[sc=1;ec=5]
+  @Id
+  private Long id;
+
+  public Long getId() {
+    return id;
+  }
+}
+
+@MappedSuperclass
+final class JpaEntityFinalCheckJakartaFinalMappedSuperclass { // Noncompliant {{Remove this "final" modifier from this JPA entity class.}}
+//^[sc=1;ec=5]
+  @Id
+  private Long id;
+}
+
+@Entity
+class JpaEntityFinalCheckJakartaCompliantEntity { // Compliant
+  @Id
+  private Long id;
+
+  public Long getId() {
+    return id;
+  }
+}
+
+@MappedSuperclass
+class JpaEntityFinalCheckJakartaCompliantMappedSuperclass { // Compliant
+  @Id
+  private Long id;
+}
+
+class JpaEntityFinalCheckJakartaNotAnEntity { // Compliant - not a JPA entity
+}
+
+final class JpaEntityFinalCheckJakartaFinalNotAnEntity { // Compliant - not a JPA entity
+}

java-checks-test-sources/default/src/main/java/checks/JpaEntityFinalCheckJavaxSample.java

@@ -0,0 +1,33 @@
+package checks;
+
+import javax.persistence.Entity;
+import javax.persistence.Id;
+import javax.persistence.MappedSuperclass;
+
+@Entity
+final class JpaEntityFinalCheckJavaxFinalEntity { // Noncompliant {{Remove this "final" modifier from this JPA entity class.}}
+//^[sc=1;ec=5]
+  @Id
+  private Long id;
+
+  public Long getId() {
+    return id;
+  }
+}
+
+@MappedSuperclass
+final class JpaEntityFinalCheckJavaxFinalMappedSuperclass { // Noncompliant {{Remove this "final" modifier from this JPA entity class.}}
+//^[sc=1;ec=5]
+  @Id
+  private Long id;
+}
+
+@Entity
+class JpaEntityFinalCheckJavaxCompliantEntity { // Compliant
+  @Id
+  private Long id;
+
+  public Long getId() {
+    return id;
+  }
+}

java-checks/src/main/java/org/sonar/java/checks/JpaEntityFinalCheck.java

@@ -0,0 +1,57 @@
+/*
+ * SonarQube Java
+ * Copyright (C) SonarSource Sàrl
+ * mailto:info AT sonarsource DOT com
+ *
+ * You can redistribute and/or modify this program under the terms of
+ * the Sonar Source-Available License Version 1, as published by SonarSource Sàrl.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the Sonar Source-Available License for more details.
+ *
+ * You should have received a copy of the Sonar Source-Available License
+ * along with this program; if not, see https://sonarsource.com/license/ssal/
+ */
+package org.sonar.java.checks;
+
+import java.util.List;
+import org.sonar.check.Rule;
+import org.sonar.java.model.ModifiersUtils;
+import org.sonar.plugins.java.api.IssuableSubscriptionVisitor;
+import org.sonar.plugins.java.api.semantic.SymbolMetadata;
+import org.sonar.plugins.java.api.tree.ClassTree;
+import org.sonar.plugins.java.api.tree.Modifier;
+import org.sonar.plugins.java.api.tree.ModifierKeywordTree;
+import org.sonar.plugins.java.api.tree.Tree;
+
+@Rule(key = "S8947")
+public class JpaEntityFinalCheck extends IssuableSubscriptionVisitor {
+
+  private static final List<String> ENTITY_ANNOTATIONS = List.of(
+    "javax.persistence.Entity",
+    "jakarta.persistence.Entity",
+    "javax.persistence.MappedSuperclass",
+    "jakarta.persistence.MappedSuperclass"
+  );
+
+  @Override
+  public List<Tree.Kind> nodesToVisit() {
+    return List.of(Tree.Kind.CLASS);
+  }
+
+  @Override
+  public void visitNode(Tree tree) {
+    ClassTree classTree = (ClassTree) tree;
+    SymbolMetadata metadata = classTree.symbol().metadata();
+    if (ENTITY_ANNOTATIONS.stream().noneMatch(metadata::isAnnotatedWith)) {
+      return;
+    }
+
+    ModifierKeywordTree finalClassModifier = ModifiersUtils.getModifier(classTree.modifiers(), Modifier.FINAL);
+    if (finalClassModifier != null) {
+      reportIssue(finalClassModifier, "Remove this \"final\" modifier from this JPA entity class.");
+    }
+  }
+}

java-checks/src/test/java/org/sonar/java/checks/JpaEntityFinalCheckTest.java

@@ -0,0 +1,41 @@
+/*
+ * SonarQube Java
+ * Copyright (C) SonarSource Sàrl
+ * mailto:info AT sonarsource DOT com
+ *
+ * You can redistribute and/or modify this program under the terms of
+ * the Sonar Source-Available License Version 1, as published by SonarSource Sàrl.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the Sonar Source-Available License for more details.
+ *
+ * You should have received a copy of the Sonar Source-Available License
+ * along with this program; if not, see https://sonarsource.com/license/ssal/
+ */
+package org.sonar.java.checks;
+
+import org.junit.jupiter.api.Test;
+import org.sonar.java.checks.verifier.CheckVerifier;
+
+import static org.sonar.java.checks.verifier.TestUtils.mainCodeSourcesPath;
+
+class JpaEntityFinalCheckTest {
+
+  @Test
+  void testWithJakarta() {
+    CheckVerifier.newVerifier()
+      .onFile(mainCodeSourcesPath("checks/JpaEntityFinalCheckJakartaSample.java"))
+      .withCheck(new JpaEntityFinalCheck())
+      .verifyIssues();
+  }
+
+  @Test
+  void testWithJavax() {
+    CheckVerifier.newVerifier()
+      .onFile(mainCodeSourcesPath("checks/JpaEntityFinalCheckJavaxSample.java"))
+      .withCheck(new JpaEntityFinalCheck())
+      .verifyIssues();
+  }
+}

sonar-java-plugin/src/main/resources/org/sonar/l10n/java/rules/java/S8947.html

@@ -0,0 +1,76 @@
+<p>This issue arises when Java classes annotated with <code>@Entity</code> or <code>@MappedSuperclass</code> are declared <code>final</code>, or when
+methods within these classes are declared <code>final</code>. JPA providers require the ability to create proxy subclasses for lazy loading and other
+runtime optimizations, which is prevented by the <code>final</code> modifier.</p>
+<h2>Why is this an issue?</h2>
+<p>JPA (Java Persistence API) providers like Hibernate rely on runtime proxy generation to implement several key features:</p>
+<ul>
+  <li><strong>Lazy loading</strong>: Loading associated entities only when they are actually accessed, rather than eagerly fetching everything
+  upfront</li>
+  <li><strong>Dirty checking</strong>: Tracking which fields have changed to optimize database updates</li>
+  <li><strong>Performance optimizations</strong>: Creating lightweight proxies that defer expensive operations</li>
+</ul>
+<p>To create these proxies, the JPA provider needs to generate a subclass of your entity class at runtime. This subclass overrides methods to add the
+lazy loading and tracking behavior.</p>
+<p>When you declare a class or method as <code>final</code>, you prevent inheritance and method overriding. This breaks the proxy mechanism:</p>
+<ul>
+  <li>A <code>final</code> class cannot be subclassed, so no proxy can be created</li>
+  <li>A <code>final</code> method cannot be overridden, so the JPA provider cannot intercept calls to implement lazy loading</li>
+</ul>
+<p>Without working proxies, lazy loading fails. Instead of loading data on demand, the JPA provider may fall back to eager loading, which can cause
+significant performance problems. In some cases, it may even cause runtime exceptions.</p>
+<h3>What is the potential impact?</h3>
+<p>When JPA entities or their methods are marked as <code>final</code>, the application can experience:</p>
+<ul>
+  <li><strong>Performance degradation</strong>: Lazy loading fails, forcing the application to eagerly load entire object graphs. This can result in
+  loading hundreds or thousands of unnecessary records from the database, significantly slowing down queries.</li>
+  <li><strong>Increased memory consumption</strong>: Eagerly loading large object graphs consumes excessive memory, potentially leading to
+  OutOfMemoryErrors in production.</li>
+  <li><strong>Runtime exceptions</strong>: Some JPA providers throw exceptions when they cannot create required proxies, causing application
+  failures.</li>
+  <li><strong>Unpredictable behavior</strong>: The application may work correctly in development or testing (with small datasets) but fail or perform
+  poorly in production (with realistic data volumes).</li>
+</ul>
+<h2>How to fix it</h2>
+<p>Remove the <code>final</code> modifier from the entity class declaration. This allows the JPA provider to create proxy subclasses for lazy loading
+and other optimizations.</p>
+<h3>Code examples</h3>
+<h4>Noncompliant code example</h4>
+<pre data-diff-id="1" data-diff-type="noncompliant">
+@Entity
+public final class User { // Noncompliant
+    @Id
+    private Long id;
+
+    private String username;
+
+    @OneToMany(fetch = FetchType.LAZY)
+    private List&lt;Order&gt; orders;
+
+    // getters and setters
+}
+</pre>
+<h4>Compliant solution</h4>
+<pre data-diff-id="1" data-diff-type="compliant">
+@Entity
+public class User {
+    @Id
+    private Long id;
+
+    private String username;
+
+    @OneToMany(fetch = FetchType.LAZY)
+    private List&lt;Order&gt; orders;
+
+    // getters and setters
+}
+</pre>
+<h2>Resources</h2>
+<h3>Documentation</h3>
+<ul>
+  <li>JPA Specification - Entity Classes - <a href="https://jakarta.ee/specifications/persistence/3.0/jakarta-persistence-spec-3.0.html#a121">Official
+  JPA specification section on entity class requirements</a></li>
+  <li>Hibernate User Guide - Proxies - <a
+  href="https://docs.jboss.org/hibernate/orm/current/userguide/html_single/Hibernate_User_Guide.html#BytecodeEnhancement">Hibernate documentation
+  explaining proxy generation and bytecode enhancement</a></li>
+</ul>
+

sonar-java-plugin/src/main/resources/org/sonar/l10n/java/rules/java/S8947.json

@@ -0,0 +1,26 @@
+{
+  "title": "JPA entity classes should not be final",
+  "type": "BUG",
+  "status": "ready",
+  "remediation": {
+    "func": "Constant\/Issue",
+    "constantCost": "5min"
+  },
+  "tags": [
+    "jpa",
+    "hibernate",
+    "pitfall"
+  ],
+  "defaultSeverity": "Critical",
+  "ruleSpecification": "RSPEC-8947",
+  "sqKey": "S8947",
+  "scope": "Main",
+  "quickfix": "unknown",
+  "code": {
+    "impacts": {
+      "RELIABILITY": "HIGH",
+      "MAINTAINABILITY": "MEDIUM"
+    },
+    "attribute": "LOGICAL"
+  }
+}

sonar-java-plugin/src/main/resources/org/sonar/l10n/java/rules/java/Sonar_way_profile.json

@@ -534,6 +534,7 @@
     "S8745",
     "S8786",
     "S8911",
-    "S8924"
+    "S8924",
+    "S8947"
   ]
 }