Implement remaining methods in JpaTransactionManager (#633)

core/src/main/java/google/registry/persistence/transaction/JpaTransactionManagerImpl.java

@@ -122,32 +122,35 @@ public class JpaTransactionManagerImpl implements JpaTransactionManager {
 
   @Override
   public <T> T transactNew(Supplier<T> work) {
-    // TODO(shicong): Implements the functionality to start a new transaction.
+    return transact(work);
-    throw new UnsupportedOperationException();
   }
 
   @Override
   public void transactNew(Runnable work) {
-    // TODO(shicong): Implements the functionality to start a new transaction.
+    transact(work);
-    throw new UnsupportedOperationException();
   }
 
   @Override
   public <T> T transactNewReadOnly(Supplier<T> work) {
-    // TODO(shicong): Implements read only transaction.
+    return transact(
-    throw new UnsupportedOperationException();
+        () -> {
+          getEntityManager().createNativeQuery("SET TRANSACTION READ ONLY").executeUpdate();
+          return work.get();
+        });
   }
 
   @Override
   public void transactNewReadOnly(Runnable work) {
-    // TODO(shicong): Implements read only transaction.
+    transactNewReadOnly(
-    throw new UnsupportedOperationException();
+        () -> {
+          work.run();
+          return null;
+        });
   }
 
   @Override
   public <T> T doTransactionless(Supplier<T> work) {
-    // TODO(shicong): Implements doTransactionless.
+    return transact(work);
-    throw new UnsupportedOperationException();
   }
 
   @Override

core/src/test/java/google/registry/persistence/transaction/TransactionManagerTest.java

@@ -116,6 +116,30 @@ public class TransactionManagerTest {
     assertEntityExists(theEntity);
   }
 
+  @TestTemplate
+  void transactNew_succeeds() {
+    assertEntityNotExist(theEntity);
+    tm().transactNew(() -> tm().saveNew(theEntity));
+    assertEntityExists(theEntity);
+  }
+
+  @TestTemplate
+  void transactNewReadOnly_succeeds() {
+    assertEntityNotExist(theEntity);
+    tm().transact(() -> tm().saveNew(theEntity));
+    assertEntityExists(theEntity);
+    TestEntity persisted = tm().transactNewReadOnly(() -> tm().load(theEntity.key()));
+    assertThat(persisted).isEqualTo(theEntity);
+  }
+
+  @TestTemplate
+  void transactNewReadOnly_throwsWhenWritingEntity() {
+    assertEntityNotExist(theEntity);
+    assertThrows(
+        RuntimeException.class, () -> tm().transactNewReadOnly(() -> tm().saveNew(theEntity)));
+    assertEntityNotExist(theEntity);
+  }
+
   @TestTemplate
   void saveNew_succeeds() {
     assertEntityNotExist(theEntity);