Merge branch '12-relinker' into 'dev'

Android: use ReLinker to load native library

See merge request objectbox/objectbox-java!11

Author: greenrobot

build.gradle

@@ -3,8 +3,9 @@ version = ob_version
 
 buildscript {
     ext {
-        ob_version = '2.4.0-SNAPSHOT'
-        ob_native_version = ob_version // Be careful to diverge here; easy to forget and hard to find JNI problems
+        ob_version = '2.4.0-relinker-SNAPSHOT'
+//        ob_native_version = ob_version // Be careful to diverge here; easy to forget and hard to find JNI problems
+        ob_native_version = '2.4.0-SNAPSHOT' // Be careful to diverge here; easy to forget and hard to find JNI problems
         ob_expected_version = project.hasProperty('expectedVersion') ? project.property('expectedVersion') : 'UNDEFINED'
 
         isLinux = System.getProperty("os.name").contains("Linux")

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

@@ -59,6 +59,12 @@
 @ThreadSafe
 public class BoxStore implements Closeable {
 
+    /** On Android used for native library loading. */
+    @Nullable public static Object context;
+    @Nullable public static Object relinker;
+    /** Change so ReLinker will update native library when using workaround loading. */
+    public static final String JNI_VERSION = "2.4.0";
+
     private static final String VERSION = "2.4.0-2019-01-08";
     private static BoxStore defaultStore;
 
@@ -186,6 +192,8 @@ public static boolean isObjectBrowserAvailable() {
     private final TxCallback failedReadTxAttemptCallback;
 
     BoxStore(BoxStoreBuilder builder) {
+        context = builder.context;
+        relinker = builder.relinker;
         NativeLibraryLoader.ensureLoaded();
 
         directory = builder.directory;

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

@@ -66,6 +66,10 @@ public class BoxStoreBuilder {
     /** BoxStore uses this */
     File directory;
 
+    /** On Android used for native library loading. */
+    @Nullable Object context;
+    @Nullable Object relinker;
+
     /** Ignored by BoxStore */
     private File baseDirectory;
 
@@ -174,6 +178,8 @@ public BoxStoreBuilder androidContext(Object context) {
         if (context == null) {
             throw new NullPointerException("Context may not be null");
         }
+        this.context = getApplicationContext(context);
+
         File baseDir = getAndroidBaseDir(context);
         if (!baseDir.exists()) {
             baseDir.mkdir();
@@ -189,6 +195,29 @@ public BoxStoreBuilder androidContext(Object context) {
         return this;
     }
 
+    private Object getApplicationContext(Object context) {
+        try {
+            return context.getClass().getMethod("getApplicationContext").invoke(context);
+        } catch (ReflectiveOperationException e) {
+            throw new RuntimeException("context must be a valid Android Context", e);
+        }
+    }
+
+    /**
+     * Pass a custom ReLinkerInstance, for example {@code ReLinker.log(logger)} to use for loading the native library
+     * on Android devices. Note that setting {@link #androidContext(Object)} is required for ReLinker to work.
+     */
+    public BoxStoreBuilder androidReLinker(Object reLinkerInstance) {
+        if (context == null) {
+            throw new IllegalArgumentException("Set a Context using androidContext(context) first");
+        }
+        if (reLinkerInstance == null) {
+            throw new NullPointerException("ReLinkerInstance may not be null");
+        }
+        this.relinker = reLinkerInstance;
+        return this;
+    }
+
     static File getAndroidDbDir(Object context, @Nullable String dbName) {
         File baseDir = getAndroidBaseDir(context);
         return new File(baseDir, dbName(dbName));

objectbox-java/src/main/java/io/objectbox/internal/NativeLibraryLoader.java

@@ -25,15 +25,21 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.lang.reflect.Method;
 import java.net.URL;
 import java.net.URLConnection;
 
+import io.objectbox.BoxStore;
+
 /**
  * Separate class, so we can mock BoxStore.
  */
 public class NativeLibraryLoader {
+
+    private static final String OBJECTBOX_JNI = "objectbox-jni";
+
     static {
-        String libname = "objectbox-jni";
+        String libname = OBJECTBOX_JNI;
         String filename = libname + ".so";
         boolean isLinux = false;
         // For Android, os.name is also "Linux", so we need an extra check
@@ -68,11 +74,15 @@ public class NativeLibraryLoader {
                 System.err.println("File not available: " + file.getAbsolutePath());
             }
             try {
-                System.loadLibrary(libname);
+                if (!android || !loadLibraryAndroid(libname)) {
+                    System.loadLibrary(libname);
+                }
             } catch (UnsatisfiedLinkError e) {
                 if (!android && isLinux) {
                     // maybe is Android, but check failed: try loading Android lib
-                    System.loadLibrary("objectbox-jni");
+                    if (!loadLibraryAndroid(OBJECTBOX_JNI)) {
+                        System.loadLibrary(OBJECTBOX_JNI);
+                    }
                 } else {
                     throw e;
                 }
@@ -113,6 +123,32 @@ private static void checkUnpackLib(String filename) {
         }
     }
 
+    @SuppressWarnings("BooleanMethodIsAlwaysInverted") // more readable
+    private static boolean loadLibraryAndroid(String libname) {
+        if (BoxStore.context == null) {
+            return false;
+        }
+
+        try {
+            Class<?> context = Class.forName("android.content.Context");
+            if (BoxStore.relinker == null) {
+                // use default ReLinker
+                Class<?> relinker = Class.forName("com.getkeepsafe.relinker.ReLinker");
+                Method loadLibrary = relinker.getMethod("loadLibrary", context, String.class, String.class);
+                loadLibrary.invoke(null, BoxStore.context, libname, BoxStore.JNI_VERSION);
+            } else {
+                // use custom ReLinkerInstance
+                Method loadLibrary = BoxStore.relinker.getClass().getMethod("loadLibrary", context, String.class, String.class);
+                loadLibrary.invoke(BoxStore.relinker, BoxStore.context, libname, BoxStore.JNI_VERSION);
+            }
+        } catch (ReflectiveOperationException e) {
+            // note: do not catch Exception as it will swallow ReLinker exceptions useful for debugging
+            return false;
+        }
+
+        return true;
+    }
+
     public static void ensureLoaded() {
     }
 }