Add Hibernate 7 batches 2-6: mapping styles, JPA annotations, natural IDs, @Immutable, stored procedures, in-memory test databases, JNDI mocking, proxies, associations, temporal mapping, named queries, HQL, Criteria API and EntityManager bootstrapping (Hibernate 7.4.5.Final + Spring Boot 4.1.1 + JDK 25)

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01EQNA6DJ9VgCtW6zhCE8Xud

src/test/java/com/ankurm/hibernatedemo/testdb/DbCloseDelayTest.java

@@ -0,0 +1,61 @@
+package com.ankurm.hibernatedemo.testdb;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.SQLException;
+import java.sql.Statement;
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Backs docs/09-testing-in-memory-databases.md, chapter "What DB_CLOSE_DELAY=-1 actually does". Raw JDBC, no
+ * Hibernate, to isolate exactly the H2-specific behaviour rather than anything the ORM layer
+ * might paper over.
+ */
+class DbCloseDelayTest {
+
+    private static final Logger DEMO = LoggerFactory.getLogger("DEMO");
+
+    @Test
+    void withoutCloseDelay_dataDisappearsWhenTheLastConnectionCloses() throws Exception {
+        String url = "jdbc:h2:mem:no-close-delay-demo"; // no DB_CLOSE_DELAY at all
+        try (Connection c1 = DriverManager.getConnection(url, "sa", "")) {
+            try (Statement st = c1.createStatement()) {
+                st.execute("create table t (id integer)");
+                st.execute("insert into t values (1)");
+            }
+        } // c1 closes here -- this is H2's LAST open connection to this in-memory DB
+
+        // A brand new connection to the SAME url now gets a BRAND NEW, EMPTY database --
+        // querying the table we just created throws, because it no longer exists.
+        try (Connection c2 = DriverManager.getConnection(url, "sa", "");
+             Statement st = c2.createStatement()) {
+            SQLException ex = assertThrows(SQLException.class, () -> st.execute("select * from t"));
+            DEMO.info("without DB_CLOSE_DELAY=-1, reconnecting after the last close throws: {}: {}",
+                    ex.getClass().getSimpleName(), ex.getMessage());
+        }
+    }
+
+    @Test
+    void withCloseDelayMinusOne_dataSurvivesAcrossConnectionCloses() throws Exception {
+        String url = "jdbc:h2:mem:with-close-delay-demo;DB_CLOSE_DELAY=-1";
+        try (Connection c1 = DriverManager.getConnection(url, "sa", "")) {
+            try (Statement st = c1.createStatement()) {
+                st.execute("create table t (id integer)");
+                st.execute("insert into t values (1)");
+            }
+        } // c1 closes -- but DB_CLOSE_DELAY=-1 tells H2 to keep the in-memory DB alive anyway
+
+        try (Connection c2 = DriverManager.getConnection(url, "sa", "");
+             Statement st = c2.createStatement()) {
+            var rs = st.executeQuery("select id from t");
+            assertThat(rs.next()).isTrue();
+            assertThat(rs.getInt(1)).isEqualTo(1);
+            DEMO.info("with DB_CLOSE_DELAY=-1, reconnecting after the last close still sees the row inserted earlier");
+        }
+    }
+}