BoxStore: assert native Entity instances are not leaked (#825)

Author: greenrobot-team

objectbox-java/src/main/java/io/objectbox/BoxStore.java

@@ -148,6 +148,15 @@ public static String getVersionNative() {
 
     static native void nativeDropAllData(long store);
 
+    /**
+     * A static counter for the alive entity types (entity schema instances); this can be useful to test against leaks.
+     * This number depends on the number of currently opened stores; no matter how often stores were closed and
+     * (re-)opened. E.g. when stores are regularly opened, but not closed by the user, the number should increase. When
+     * all stores are properly closed, this value should be 0.
+     */
+    @Internal
+    static native long nativeGloballyActiveEntityTypes();
+
     static native long nativeBeginTx(long store);
 
     static native long nativeBeginReadTx(long store);

tests/objectbox-java-test/src/test/java/io/objectbox/BoxStoreTest.java

@@ -77,10 +77,16 @@ public void testCloseThreadResources() {
 
     @Test
     public void testClose() {
+        // This test suite uses a single entity (TestEntity) by default
+        // and all other tests close the store after being done. So should be 1.
+        assertEquals(1, BoxStore.nativeGloballyActiveEntityTypes());
+
         BoxStore store = this.store;
         assertFalse(store.isClosed());
         store.close();
         assertTrue(store.isClosed());
+        // Assert native Entity instances are not leaked.
+        assertEquals(0, BoxStore.nativeGloballyActiveEntityTypes());
 
         // Double close should be fine
         store.close();
@@ -154,8 +160,13 @@ public void openSamePath_fails() {
     @Test
     public void openSamePath_afterClose_works() {
         store.close();
+        // Assert native Entity instances are not leaked.
+        assertEquals(0, BoxStore.nativeGloballyActiveEntityTypes());
+
         BoxStore store2 = createBoxStore();
         store2.close();
+        // Assert native Entity instances are not leaked.
+        assertEquals(0, BoxStore.nativeGloballyActiveEntityTypes());
     }
 
     @Test

tests/objectbox-java-test/src/test/java/io/objectbox/query/QueryTest.java

@@ -160,6 +160,7 @@ public void useAfterStoreClose_failsIfUsingStore() {
         ).build();
         store.close();
 
+        // All methods accessing the store throw.
         assertThrowsStoreIsClosed(query::count);
         assertThrowsStoreIsClosed(query::find);
         assertThrowsStoreIsClosed(() -> query.find(0, 1));
@@ -171,9 +172,14 @@ public void useAfterStoreClose_failsIfUsingStore() {
         assertThrowsStoreIsClosed(query::findUnique);
         assertThrowsStoreIsClosed(query::remove);
 
-        // describe and setParameter continue to work as store is not accessed.
-        assertFalse(query.describe().isEmpty());
-        assertFalse(query.describeParameters().isEmpty());
+        // describe works, but returns no property info.
+        assertEquals("Query for entity <deleted entity type> with 15 conditions", query.describe());
+
+        // describeParameters does not work.
+        IllegalStateException exc = assertThrows(IllegalStateException.class, query::describeParameters);
+        assertEquals("Query cannot be used after entity type was deleted (e.g. store was closed)", exc.getMessage());
+
+        // setParameter continues to work.
         query.setParameter(simpleString, "value");
         query.setParameters(stringObjectMap, "a", "b");
         query.setParameter(simpleInt, 1);