Add JavaBoundObject

content/browser/renderer_host/java/java_bound_object.cc

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "content/browser/renderer_host/java/java_bound_object.h"
+
+#include "base/android/jni_android.h"
+#include "base/android/jni_string.h"
+#include "base/memory/singleton.h"
+#include "base/string_number_conversions.h"
+#include "base/stringprintf.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebBindings.h"
+
+using base::StringPrintf;
+using base::android::AttachCurrentThread;
+using base::android::ConvertUTF8ToJavaString;
+using base::android::JavaRef;
+using base::android::MethodID;
+using base::android::ScopedJavaGlobalRef;
+using base::android::ScopedJavaLocalRef;
+using WebKit::WebBindings;
+
+// The conversion between JavaScript and Java types is based on the Live
+// Connect 2 spec. See
+// http://jdk6.java.net/plugin2/liveconnect/#JS_JAVA_CONVERSIONS.
+
+// Note that in some cases, we differ from from the spec in order to maintain
+// existing behavior. These areas are marked LIVECONNECT_COMPLIANCE. We may
+// revisit this decision in the future.
+
+namespace {
+
+std::string NPIdentifierToString(NPIdentifier identifier) {
+  const NPUTF8* string;
+  int32_t number;
+  bool is_string;
+  WebBindings::extractIdentifierData(identifier, string, number, is_string);
+  DCHECK(is_string);
+  return string;
+}
+
+// Our special NPObject type.  We extend an NPObject with a pointer to a
+// JavaBoundObject.  We also add static methods for each of the NPObject
+// callbacks, which are registered by our NPClass. These methods simply
+// delegate to the private implementation methods of JavaBoundObject.
+struct JavaNPObject : public NPObject {
+  JavaBoundObject* bound_object;
+
+  static const NPClass kNPClass;
+
+  static NPObject* Allocate(NPP npp, NPClass* np_class);
+  static void Deallocate(NPObject* np_object);
+  static bool HasMethod(NPObject* np_object, NPIdentifier np_identifier);
+  static bool Invoke(NPObject* np_object, NPIdentifier np_identifier,
+                     const NPVariant *args, uint32_t arg_count,
+                     NPVariant *result);
+  static bool HasProperty(NPObject* np_object, NPIdentifier np_identifier);
+  static bool GetProperty(NPObject* np_object, NPIdentifier np_identifier,
+                          NPVariant *result);
+};
+
+const NPClass JavaNPObject::kNPClass = {
+  NP_CLASS_STRUCT_VERSION,
+  JavaNPObject::Allocate,
+  JavaNPObject::Deallocate,
+  NULL,  // NPInvalidate
+  JavaNPObject::HasMethod,
+  JavaNPObject::Invoke,
+  NULL,  // NPInvokeDefault
+  JavaNPObject::HasProperty,
+  JavaNPObject::GetProperty,
+  NULL,  // NPSetProperty,
+  NULL,  // NPRemoveProperty
+};
+
+NPObject* JavaNPObject::Allocate(NPP npp, NPClass* np_class) {
+  JavaNPObject* obj = new JavaNPObject;

[M-A Ruel, 2011/11/11 16:22:28]

optional: in general we always put (), e.g. new JavaNPObject();

[Steve Block, 2011/11/11 16:31:34]

Done.

+  return obj;
+}
+
+void JavaNPObject::Deallocate(NPObject* np_object) {
+  JavaNPObject* obj = reinterpret_cast<JavaNPObject*>(np_object);
+  delete obj->bound_object;
+  delete obj;
+}
+
+bool JavaNPObject::HasMethod(NPObject* np_object, NPIdentifier np_identifier) {
+  std::string name = NPIdentifierToString(np_identifier);
+  JavaNPObject* obj = reinterpret_cast<JavaNPObject*>(np_object);
+  return obj->bound_object->HasMethod(name);
+}
+
+bool JavaNPObject::Invoke(NPObject* np_object, NPIdentifier np_identifier,
+                          const NPVariant* args, uint32_t arg_count,
+                          NPVariant* result) {
+  std::string name = NPIdentifierToString(np_identifier);
+  JavaNPObject* obj = reinterpret_cast<JavaNPObject*>(np_object);
+  return obj->bound_object->Invoke(name, args, arg_count, result);
+}
+
+bool JavaNPObject::HasProperty(NPObject* np_object,
+                               NPIdentifier np_identifier) {
+  // LIVECONNECT_COMPLIANCE: Return false to indicate that the property is not
+  // present. We should support this correctly.
+  return false;
+}
+
+bool JavaNPObject::GetProperty(NPObject* np_object,
+                               NPIdentifier np_identifier,
+                               NPVariant* result) {
+  // LIVECONNECT_COMPLIANCE: Return false to indicate that the property is
+  // undefined. We should support this correctly.
+  return false;
+}
+
+// Calls a Java method through JNI and returns the result as an NPVariant. Note
+// that this method does not do any type coercion. The Java return value is
+// simply converted to the corresponding NPAPI type.
+NPVariant CallJNIMethod(jobject object, JavaType::Type return_type,
+                        jmethodID id, jvalue* parameters) {
+  JNIEnv* env = AttachCurrentThread();
+  NPVariant result;
+  switch (return_type) {
+    case JavaType::TypeBoolean:
+      BOOLEAN_TO_NPVARIANT(env->CallBooleanMethodA(object, id, parameters),
+                           result);
+      break;
+    case JavaType::TypeByte:
+      INT32_TO_NPVARIANT(env->CallByteMethodA(object, id, parameters), result);
+      break;
+    case JavaType::TypeChar:
+      INT32_TO_NPVARIANT(env->CallCharMethodA(object, id, parameters), result);
+      break;
+    case JavaType::TypeShort:
+      INT32_TO_NPVARIANT(env->CallShortMethodA(object, id, parameters), result);
+      break;
+    case JavaType::TypeInt:
+      INT32_TO_NPVARIANT(env->CallIntMethodA(object, id, parameters), result);
+      break;
+    case JavaType::TypeLong:
+      DOUBLE_TO_NPVARIANT(env->CallLongMethodA(object, id, parameters), result);
+      break;
+    case JavaType::TypeFloat:
+      DOUBLE_TO_NPVARIANT(env->CallFloatMethodA(object, id, parameters),
+                          result);
+      break;
+    case JavaType::TypeDouble:
+      DOUBLE_TO_NPVARIANT(env->CallDoubleMethodA(object, id, parameters),
+                          result);
+      break;
+    case JavaType::TypeVoid:
+      env->CallVoidMethodA(object, id, parameters);
+      VOID_TO_NPVARIANT(result);
+      break;
+    case JavaType::TypeArray:
+      // TODO(steveblock): Handle arrays
+      VOID_TO_NPVARIANT(result);
+      break;
+    case JavaType::TypeString: {
+      ScopedJavaLocalRef<jstring> java_string(env, static_cast<jstring>(
+          env->CallObjectMethodA(object, id, parameters)));
+      if (!java_string.obj()) {
+        // LIVECONNECT_COMPLIANCE: Return undefined to maintain existing
+        // behavior. We should return a null string.
+        VOID_TO_NPVARIANT(result);
+        break;
+      }
+      std::string str =
+          base::android::ConvertJavaStringToUTF8(env, java_string.obj());
+      // Take a copy and pass ownership to the variant. We must allocate using
+      // NPN_MemAlloc, to match NPN_ReleaseVariant, which uses NPN_MemFree.
+      size_t length = str.length();
+      char* buffer = static_cast<char*>(NPN_MemAlloc(length));
+      str.copy(buffer, length, 0);
+      STRINGN_TO_NPVARIANT(buffer, length, result);
+      break;
+    }
+    case JavaType::TypeObject: {
+      ScopedJavaLocalRef<jobject> java_object(
+          env,
+          env->CallObjectMethodA(object, id, parameters));
+      if (!java_object.obj()) {
+        NULL_TO_NPVARIANT(result);
+        break;
+      }
+      OBJECT_TO_NPVARIANT(JavaBoundObject::Create(java_object), result);
+      break;
+    }
+  }
+  return result;
+}
+
+jvalue CoerceJavaScriptNumberToJavaValue(const NPVariant& variant,
+                                         JavaType::Type target_type) {
+  // See http://jdk6.java.net/plugin2/liveconnect/#JS_NUMBER_VALUES.
+  jvalue result;
+  DCHECK(variant.type == NPVariantType_Int32 ||
+         variant.type == NPVariantType_Double);
+  bool is_double = variant.type == NPVariantType_Double;
+  switch (target_type) {
+    case JavaType::TypeByte:
+      result.b = is_double ? static_cast<jbyte>(NPVARIANT_TO_DOUBLE(variant)) :
+                             static_cast<jbyte>(NPVARIANT_TO_INT32(variant));
+      break;
+    case JavaType::TypeChar:
+      // LIVECONNECT_COMPLIANCE: Convert double to 0 to maintain existing
+      // behavior.
+      result.c = is_double ? 0 :
+                             static_cast<jchar>(NPVARIANT_TO_INT32(variant));
+      break;
+    case JavaType::TypeShort:
+      result.s = is_double ? static_cast<jshort>(NPVARIANT_TO_DOUBLE(variant)) :
+                             static_cast<jshort>(NPVARIANT_TO_INT32(variant));
+      break;
+    case JavaType::TypeInt:
+      result.i = is_double ? static_cast<jint>(NPVARIANT_TO_DOUBLE(variant)) :
+                             NPVARIANT_TO_INT32(variant);
+      break;
+    case JavaType::TypeLong:
+      result.j = is_double ? static_cast<jlong>(NPVARIANT_TO_DOUBLE(variant)) :
+                             NPVARIANT_TO_INT32(variant);
+      break;
+    case JavaType::TypeFloat:
+      result.f = is_double ? static_cast<jfloat>(NPVARIANT_TO_DOUBLE(variant)) :
+                             NPVARIANT_TO_INT32(variant);
+      break;
+    case JavaType::TypeDouble:
+      result.d = is_double ? NPVARIANT_TO_DOUBLE(variant) :
+                             NPVARIANT_TO_INT32(variant);
+      break;
+    case JavaType::TypeObject:
+      // LIVECONNECT_COMPLIANCE: Convert to null to maintain existing behavior.
+      // We should handle object equivalents of primitive types.
+      result.l = NULL;
+      break;
+    case JavaType::TypeString:
+      result.l = ConvertUTF8ToJavaString(
+          AttachCurrentThread(),
+          is_double ?  StringPrintf("%.6lg", NPVARIANT_TO_DOUBLE(variant)) :
+                       base::IntToString(NPVARIANT_TO_INT32(variant)));
+      break;
+    case JavaType::TypeBoolean:
+      // LIVECONNECT_COMPLIANCE: Convert to false to maintain existing behavior.
+      // We should convert to false for o or NaN, true otherwise.
+      result.z = JNI_FALSE;
+      break;
+    case JavaType::TypeArray:
+      // LIVECONNECT_COMPLIANCE: Convert to null to maintain existing behavior.
+      // We should raise a JavaScript exception.
+      result.l = NULL;
+      break;
+    case JavaType::TypeVoid:
+      // Conversion to void must never happen.
+      NOTREACHED();
+      break;
+  }
+  return result;
+}
+
+jvalue CoerceJavaScriptBooleanToJavaValue(const NPVariant& variant,
+                                          JavaType::Type target_type) {
+  // See http://jdk6.java.net/plugin2/liveconnect/#JS_BOOLEAN_VALUES.
+  DCHECK_EQ(NPVariantType_Bool, variant.type);
+  bool boolean_value = NPVARIANT_TO_BOOLEAN(variant);
+  jvalue result;
+  switch (target_type) {
+    case JavaType::TypeBoolean:
+      result.z = boolean_value ? JNI_TRUE : JNI_FALSE;
+      break;
+    case JavaType::TypeObject:
+      // LIVECONNECT_COMPLIANCE: Convert to NULL to maintain existing behavior.
+      // We should handle java.lang.Boolean and java.lang.Object.
+      result.l = NULL;
+      break;
+    case JavaType::TypeString:
+      result.l = ConvertUTF8ToJavaString(AttachCurrentThread(),
+                                         boolean_value ? "true" : "false");
+      break;
+    case JavaType::TypeByte:
+    case JavaType::TypeChar:
+    case JavaType::TypeShort:
+    case JavaType::TypeInt:
+    case JavaType::TypeLong:
+    case JavaType::TypeFloat:
+    case JavaType::TypeDouble: {
+      // LIVECONNECT_COMPLIANCE: Convert to 0 to maintain existing behavior. We
+      // should convert to 0 or 1.
+      jvalue null_value = {0};
+      result = null_value;
+      break;
+    }
+    case JavaType::TypeArray:
+      // LIVECONNECT_COMPLIANCE: Convert to NULL to maintain existing behavior.
+      // We should raise a JavaScript exception.
+      result.l = NULL;
+      break;
+    case JavaType::TypeVoid:
+      // Conversion to void must never happen.
+      NOTREACHED();
+      break;
+  }
+  return result;
+}
+
+jvalue CoerceJavaScriptStringToJavaValue(const NPVariant& variant,
+                                         JavaType::Type target_type) {
+  // See http://jdk6.java.net/plugin2/liveconnect/#JS_STRING_VALUES.
+  DCHECK_EQ(NPVariantType_String, variant.type);
+  jvalue result;
+  switch (target_type) {
+    case JavaType::TypeString:
+      result.l = ConvertUTF8ToJavaString(
+          AttachCurrentThread(),
+          base::StringPiece(NPVARIANT_TO_STRING(variant).UTF8Characters,
+                            NPVARIANT_TO_STRING(variant).UTF8Length));
+      break;
+    case JavaType::TypeObject:
+      // LIVECONNECT_COMPLIANCE: Convert to NULL to maintain existing behavior.
+      // We should handle java.lang.Object.
+      result.l = NULL;
+      break;
+    case JavaType::TypeByte:
+    case JavaType::TypeShort:
+    case JavaType::TypeInt:
+    case JavaType::TypeLong:
+    case JavaType::TypeFloat:
+    case JavaType::TypeDouble: {
+      // LIVECONNECT_COMPLIANCE: Convert to 0 to maintain existing behavior. we
+      // should use valueOf() method of corresponding object type.
+      jvalue null_value = {0};
+      result = null_value;
+      break;
+    }
+    case JavaType::TypeChar:
+      // LIVECONNECT_COMPLIANCE: Convert to 0 to maintain existing behavior. we
+      // should use java.lang.Short.decode().
+      result.c = 0;
+      break;
+    case JavaType::TypeBoolean:
+      // LIVECONNECT_COMPLIANCE: Convert to false to maintain existing behavior.
+      // We should convert the empty string to false, otherwise true.
+      result.z = JNI_FALSE;
+      break;
+    case JavaType::TypeArray:
+      // LIVECONNECT_COMPLIANCE: Convert to NULL to maintain existing behavior.
+      // We should raise a JavaScript exception.
+      result.l = NULL;
+      break;
+    case JavaType::TypeVoid:
+      // Conversion to void must never happen.
+      NOTREACHED();
+      break;
+  }
+  return result;
+}
+
+jvalue CoerceJavaScriptObjectToJavaValue(const NPVariant& variant,
+                                         JavaType::Type target_type) {
+  // We only handle Java objects. See
+  // http://jdk6.java.net/plugin2/liveconnect/#JS_JAVA_OBJECTS.
+  // TODO(steveblock): Handle arrays.
+  // TODO(steveblock): Handle JavaScript objects.
+  DCHECK_EQ(NPVariantType_Object, variant.type);
+
+  // The only type of object we should encounter is a Java object, as
+  // other objects should have been converted to NULL in the renderer.
+  // See CreateNPVariantParam().
+  // TODO(steveblock): This will have to change once we support arrays and
+  // JavaScript objects.
+  NPObject* object = NPVARIANT_TO_OBJECT(variant);
+  DCHECK_EQ(&JavaNPObject::kNPClass, object->_class);
+
+  jvalue result;
+  switch (target_type) {
+    case JavaType::TypeObject:
+      // LIVECONNECT_COMPLIANCE: Pass all Java objects to maintain existing
+      // behavior. We should pass only Java objects which are
+      // assignment-compatibile.
+      result.l = AttachCurrentThread()->NewLocalRef(
+          JavaBoundObject::GetJavaObject(object));
+      break;
+    case JavaType::TypeString:
+      // LIVECONNECT_COMPLIANCE: Convert to "undefined" to maintain existing
+      // behavior. We should call toString() on the Java object.
+      result.l = ConvertUTF8ToJavaString(AttachCurrentThread(), "undefined");
+      break;
+    case JavaType::TypeByte:
+    case JavaType::TypeShort:
+    case JavaType::TypeInt:
+    case JavaType::TypeLong:
+    case JavaType::TypeFloat:
+    case JavaType::TypeDouble:
+    case JavaType::TypeChar: {
+      // LIVECONNECT_COMPLIANCE: Convert to 0 to maintain existing behavior. We
+      // should raise a JavaScript exception.
+      jvalue null_value = {0};
+      result = null_value;
+      break;
+    }
+    case JavaType::TypeBoolean:
+      // LIVECONNECT_COMPLIANCE: Convert to false to maintain existing behavior.
+      // We should raise a JavaScript exception.
+      result.z = JNI_FALSE;
+      break;
+    case JavaType::TypeArray:
+      // LIVECONNECT_COMPLIANCE: Convert to NULL to maintain existing behavior.
+      // We should raise a JavaScript exception.
+      result.l = NULL;
+      break;
+    case JavaType::TypeVoid:
+      // Conversion to void must never happen.
+      NOTREACHED();
+      break;
+  }
+  return result;
+}
+
+jvalue CoerceJavaScriptNullOrUndefinedToJavaValue(const NPVariant& variant,
+                                                  JavaType::Type target_type) {
+  // See http://jdk6.java.net/plugin2/liveconnect/#JS_NULL.
+  DCHECK(variant.type == NPVariantType_Null ||
+         variant.type == NPVariantType_Void);
+  jvalue result;
+  switch (target_type) {
+    case JavaType::TypeObject:
+      result.l = NULL;
+      break;
+    case JavaType::TypeString:
+      if (variant.type == NPVariantType_Void) {
+        // LIVECONNECT_COMPLIANCE: Convert undefined to "undefined" to maintain
+        // existing behavior. We should convert undefined to NULL.
+        result.l =  ConvertUTF8ToJavaString(AttachCurrentThread(), "undefined");
+      } else {
+        result.l = NULL;
+      }
+      break;
+    case JavaType::TypeByte:
+    case JavaType::TypeChar:
+    case JavaType::TypeShort:
+    case JavaType::TypeInt:
+    case JavaType::TypeLong:
+    case JavaType::TypeFloat:
+    case JavaType::TypeDouble: {
+      jvalue null_value = {0};
+      result = null_value;
+      break;
+    }
+    case JavaType::TypeBoolean:
+      result.z = JNI_FALSE;
+      break;
+    case JavaType::TypeArray:
+      // LIVECONNECT_COMPLIANCE: Convert to NULL to maintain existing behavior.
+      // We should raise a JavaScript exception.
+      result.l = NULL;
+      break;
+    case JavaType::TypeVoid:
+      // Conversion to void must never happen.
+      NOTREACHED();
+      break;
+  }
+  return result;
+}
+
+jvalue CoerceJavaScriptValueToJavaValue(const NPVariant& variant,
+                                        JavaType::Type target_type) {
+  // Note that in all these conversions, the relevant field of the jvalue must
+  // always be explicitly set, as jvalue does not initialize its fields.
+
+  // Some of these methods create new Java Strings. Note that we don't
+  // explicitly release the local ref to these new objects, as there's no simple
+  // way to do so.
+  switch (variant.type) {
+    case NPVariantType_Int32:
+    case NPVariantType_Double:
+      return CoerceJavaScriptNumberToJavaValue(variant, target_type);
+    case NPVariantType_Bool:
+      return CoerceJavaScriptBooleanToJavaValue(variant, target_type);
+    case NPVariantType_String:
+      return CoerceJavaScriptStringToJavaValue(variant, target_type);
+    case NPVariantType_Object:
+      return CoerceJavaScriptObjectToJavaValue(variant, target_type);
+    case NPVariantType_Null:
+    case NPVariantType_Void:
+      return CoerceJavaScriptNullOrUndefinedToJavaValue(variant, target_type);
+  }
+  NOTREACHED();
+  return jvalue();
+}
+
+class ObjectGetClassID : public MethodID {
+ public:
+  static ObjectGetClassID* GetInstance() {
+    return Singleton<ObjectGetClassID>::get();
+  }
+ private:
+  friend struct DefaultSingletonTraits<ObjectGetClassID>;
+  ObjectGetClassID()
+      : MethodID(AttachCurrentThread(), "java/lang/Object", "getClass",
+                 "()Ljava/lang/Class;") {
+  }
+  DISALLOW_COPY_AND_ASSIGN(ObjectGetClassID);
+};
+
+class ClassGetMethodsID : public MethodID {
+ public:
+  static ClassGetMethodsID* GetInstance() {
+    return Singleton<ClassGetMethodsID>::get();
+  }
+ private:
+  friend struct DefaultSingletonTraits<ClassGetMethodsID>;
+  ClassGetMethodsID()
+      : MethodID(AttachCurrentThread(), "java/lang/Class", "getMethods",
+                 "()[Ljava/lang/reflect/Method;") {
+  }
+  DISALLOW_COPY_AND_ASSIGN(ClassGetMethodsID);
+};
+
+}  // namespace
+
+
+NPObject* JavaBoundObject::Create(const JavaRef<jobject>& object) {
+  // The first argument (a plugin's instance handle) is passed through to the
+  // allocate function directly, and we don't use it, so it's ok to be 0.
+  // The object is created with a ref count of one.
+  NPObject* np_object = WebBindings::createObject(0, const_cast<NPClass*>(
+      &JavaNPObject::kNPClass));
+  // The NPObject takes ownership of the JavaBoundObject.
+  reinterpret_cast<JavaNPObject*>(np_object)->bound_object =
+      new JavaBoundObject(object);
+  return np_object;
+}
+
+JavaBoundObject::JavaBoundObject(const JavaRef<jobject>& object)
+    : java_object_(object.env()->NewGlobalRef(object.obj())) {
+  // We don't do anything with our Java object when first created. We do it all
+  // lazily when a method is first invoked.
+}
+
+JavaBoundObject::~JavaBoundObject() {
+  // Use the current thread's JNI env to release our global ref to the Java
+  // object.
+  AttachCurrentThread()->DeleteGlobalRef(java_object_);
+}
+
+jobject JavaBoundObject::GetJavaObject(NPObject* object) {
+  DCHECK_EQ(&JavaNPObject::kNPClass, object->_class);
+  JavaBoundObject* jbo = reinterpret_cast<JavaNPObject*>(object)->bound_object;
+  return jbo->java_object_;
+}
+
+bool JavaBoundObject::HasMethod(const std::string& name) const {
+  const_cast<JavaBoundObject*>(this)->EnsureMethodsAreSetUp();
+  return methods_.find(name) != methods_.end();
+}
+
+bool JavaBoundObject::Invoke(const std::string& name, const NPVariant* args,
+                             size_t arg_count, NPVariant* result) {
+  EnsureMethodsAreSetUp();
+
+  // Get all methods with the correct name.
+  std::pair<JavaMethodMap::const_iterator, JavaMethodMap::const_iterator>
+      iters = methods_.equal_range(name);
+  if (iters.first == iters.second) {
+    return false;
+  }
+
+  // Take the first method with the correct number of arguments.
+  JavaMethod* method = NULL;
+  for (JavaMethodMap::const_iterator iter = iters.first; iter != iters.second;
+       ++iter) {
+    if (iter->second->num_parameters() == arg_count) {
+      method = iter->second.get();
+      break;
+    }
+  }
+  if (!method) {
+    return false;
+  }
+
+  // Coerce
+  std::vector<jvalue> parameters(arg_count);
+  for (size_t i = 0; i < arg_count; ++i) {
+    parameters[i] = CoerceJavaScriptValueToJavaValue(args[i],
+                                                     method->parameter_type(i));
+  }
+
+  // Call
+  *result = CallJNIMethod(java_object_, method->return_type(), method->id(),
+                          &parameters[0]);
+  return true;
+}
+
+void JavaBoundObject::EnsureMethodsAreSetUp() {
+  if (!methods_.empty()) {
+    return;
+  }
+
+  JNIEnv* env = AttachCurrentThread();
+  ScopedJavaLocalRef<jclass> clazz(env, static_cast<jclass>(
+      env->CallObjectMethod(java_object_,
+                            ObjectGetClassID::GetInstance()->id())));
+  ScopedJavaLocalRef<jobjectArray> methods(env, static_cast<jobjectArray>(
+      env->CallObjectMethod(clazz.obj(),
+                            ClassGetMethodsID::GetInstance()->id())));
+  size_t num_methods = env->GetArrayLength(methods.obj());
+  DCHECK(num_methods) << "Java objects always have public methods";
+  for (size_t i = 0; i < num_methods; ++i) {
+    ScopedJavaLocalRef<jobject> java_method(
+        env,
+        env->GetObjectArrayElement(methods.obj(), i));
+    JavaMethod* method = new JavaMethod(java_method);
+    methods_.insert(std::make_pair(method->name(), method));
+  }
+}