Add classloader test for Java Logger.

java/CMakeLists.txt

@@ -352,6 +352,7 @@ set(JAVA_TEST_CLASSES
   src/test/java/org/rocksdb/KeyExistsTest.java
   src/test/java/org/rocksdb/KeyMayExistTest.java
   src/test/java/org/rocksdb/LRUCacheTest.java
+  src/test/java/org/rocksdb/LoggerClassloaderTest.java
   src/test/java/org/rocksdb/LoggerTest.java
   src/test/java/org/rocksdb/MemTableTest.java
   src/test/java/org/rocksdb/MemoryUtilTest.java
@@ -895,6 +896,9 @@ add_custom_command(
         COMMAND ${CMAKE_COMMAND} -E copy
         ${ROCKSDBJNI_CLASSES_TEST_DIR}/org/rocksdb/EventListenerClassloaderTest.class
         ${PROJECT_BINARY_DIR}/java/cl-test/org/rocksdb/EventListenerClassloaderTest.class
+        COMMAND ${CMAKE_COMMAND} -E copy
+        ${ROCKSDBJNI_CLASSES_TEST_DIR}/org/rocksdb/LoggerClassloaderTest.class
+        ${PROJECT_BINARY_DIR}/java/cl-test/org/rocksdb/LoggerClassloaderTest.class
         VERBATIM
 )
 
@@ -925,5 +929,9 @@ else()
         NAME jtest_org.rocksdb.EventListenerClassloaderTest
         COMMAND ${Java_JAVA_EXECUTABLE} -ea -Xcheck:jni -Drocks-jar=${CMAKE_CURRENT_BINARY_DIR}/${ROCKSDB_JAR}  -classpath ${JAVA_RUN_TESTCLASSPATH}:${PROJECT_BINARY_DIR}/java/cl-test org.junit.runner.JUnitCore org.rocksdb.EventListenerClassloaderTest
     )
+    add_test(
+            NAME jtest_org.rocksdb.LoggerClassloaderTest
+            COMMAND ${Java_JAVA_EXECUTABLE} -ea -Xcheck:jni -Drocks-jar=${CMAKE_CURRENT_BINARY_DIR}/${ROCKSDB_JAR}  -classpath ${JAVA_RUN_TESTCLASSPATH}:${PROJECT_BINARY_DIR}/java/cl-test org.junit.runner.JUnitCore org.rocksdb.EventListenerClassloaderTest
+    )
 endif()
 

java/src/test/java/org/rocksdb/LoggerClassloaderTest.java

@@ -0,0 +1,55 @@
+package org.rocksdb;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.fail;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+/**
+ * Only this class can be on default classpath.
+ * It loads rocksDB code with custom classloader and then test that all
+ * log levels for log events can be instantiated.
+ */
+public class LoggerClassloaderTest {
+  @Rule public TemporaryFolder dbFolder = new TemporaryFolder();
+
+  @Test
+  public void testWithCustomClassLoader() throws Exception {
+    try {
+      this.getClass().getClassLoader().loadClass("org.rocksdb.RocksDB");
+      fail("It looks like RocksDB is on classpath. This test must load RocksDB via custom "
+          + "classLoader"
+          + " to verify that callback cache all class instances.");
+    } catch (ClassNotFoundException e) {
+      ;
+    }
+
+    String jarPath = System.getProperty("rocks-jar");
+    assertThat(jarPath).isNotNull().as("Java property 'rocks-jar' was not setup properly");
+
+    Path classesDir = Paths.get(jarPath);
+    ClassLoader cl = new URLClassLoader(new URL[] {classesDir.toAbsolutePath().toUri().toURL()});
+
+    Class rocksDBclazz = cl.loadClass("org.rocksdb.RocksDB");
+    Method loadLibrary = rocksDBclazz.getMethod("loadLibrary");
+    loadLibrary.invoke(null);
+
+    Class classUnderTest = cl.loadClass("org.rocksdb.LoggerTest");
+    Method customLogger = classUnderTest.getMethod("customLogger");
+    Field dbFolderField = classUnderTest.getDeclaredField("dbFolder");
+
+    Object testInstance = classUnderTest.getDeclaredConstructor().newInstance();
+
+    dbFolderField.set(testInstance, dbFolder);
+
+    customLogger.invoke(testInstance);
+  }
+}