ebean-test: Add PersistenceContextAccess.clear() for tests that need to clear the Persistence Context

To support tests that use a transaction that wraps test setup and running the test logic. The need for this case is to clear the persistence context after the test setup phase.

ebean-spring-txn/src/test/java/org/example/EbeanSpringModuleTest.java

@@ -2,15 +2,19 @@ package org.example;
 
 import io.ebean.DB;
 import io.ebean.Transaction;
+import io.ebean.test.PersistenceContextAccess;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.test.annotation.Rollback;
 import org.springframework.test.context.ContextConfiguration;
 import org.springframework.test.context.junit.jupiter.SpringExtension;
+import org.springframework.transaction.annotation.Transactional;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.in;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
@@ -42,6 +46,24 @@ public class EbeanSpringModuleTest {
     super();
   }
 
+  @Transactional
+  @Rollback
+  @Test
+  public void testWithRollback() {
+    // setup
+    User user = new User();
+    user.setName("rollback1");
+    DB.save(user);
+
+    // this loads the user into the [transaction scoped] persistence context
+    User found = DB.find(User.class, user.getOid());
+    found.setName("mutated");
+
+    PersistenceContextAccess.clear();
+
+    userService.insideTestRollback(user.getOid());
+  }
+
   /**
    * Test app.
    */

ebean-spring-txn/src/test/java/org/example/UserService.java

@@ -16,4 +16,6 @@ public interface UserService {
 	void batchInsert();
 
 	void requiresNew();
+
+  void insideTestRollback(long oid);
 }

ebean-spring-txn/src/test/java/org/example/UserServiceImpl.java

@@ -12,6 +12,8 @@ import org.springframework.transaction.annotation.Transactional;
 import java.util.ArrayList;
 import java.util.List;
 
+import static org.assertj.core.api.Assertions.assertThat;
+
 /**
  * The Class UserServiceImpl.
  *
@@ -28,6 +30,13 @@ public class UserServiceImpl implements UserService, ApplicationContextAware {
     @Autowired
     private Database ebeanServer;
 
+    @Override
+    @Transactional(propagation = Propagation.REQUIRED, rollbackFor = Throwable.class)
+    public void insideTestRollback(long oid) {
+      User found = ebeanServer.find(User.class, oid);
+      assertThat(found.getName()).isEqualTo("rollback1");
+    }
+
     @Transactional(propagation = Propagation.REQUIRED, rollbackFor = Throwable.class)
     public void save(User user) {
         ebeanServer.save(user);

ebean-test/src/main/java/io/ebean/test/PersistenceContextAccess.java

@@ -0,0 +1,59 @@
+package io.ebean.test;
+
+import io.ebean.Transaction;
+import io.ebean.bean.PersistenceContext;
+import io.ebeaninternal.api.SpiTransaction;
+
+/**
+ * Provides tests access to the persistence context.
+ * <p>
+ * Expected to be used with tests that use Spring test {@code @Rollback} {@code @Transactional}.
+ * These tests have an outer transaction that will rollback. The issue is that test setup code
+ * is now running in the SAME TRANSACTION as the code under test (main code we are testing) and
+ * that the Ebean Persistence Context is transaction scoped - so the test setup code can load
+ * entities into the ebean persistence context during the test setup phase - we SHOULD clear the
+ * persistence context AFTER the setup phase of the test and BEFORE we run the code under test.
+ *
+ * <pre>{@code
+ *
+ * @Test
+ * @Transactional   // spring transactional
+ * @Rollback        // spring test rollback
+ * void myTestWithSpringRollback() {
+ *
+ *   // Test Setup: this MIGHT load entities into the persistence context
+ *   performTestSetup();
+ *
+ *   // clear out the persistence context
+ *   PersistenceContextAccess.clear();
+ *
+ *   // Act
+ *   performActionsWeAreTestingHere();
+ *
+ *   // Assert
+ *   assertThat(...)
+ *
+ * }
+ *
+ * }</pre>
+ */
+public class PersistenceContextAccess {
+
+  /**
+   * Clear the persistence context of the current transaction.
+   * <p>
+   * This is expected to be called after test setup phase and before
+   * the test executes the code we are looking to test - so
+   * AFTER "setup" and BEFORE "act".
+   */
+  public static void clear() {
+    Transaction current = Transaction.current();
+    if (current != null) {
+      SpiTransaction spiTransaction = (SpiTransaction) current;
+      PersistenceContext pc = spiTransaction.persistenceContext();
+      if (pc != null) {
+        pc.clear();
+      }
+    }
+  }
+}