content/browser/android/java/java_method.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "content/browser/android/java/java_method.h"
   6
   7 #include "base/android/jni_android.h"
   8 #include "base/android/jni_string.h"
   9 #include "base/lazy_instance.h"
  10 #include "base/memory/singleton.h"
  11 #include "content/browser/android/java/jni_helper.h"
  12
  13 using base::android::AttachCurrentThread;
  14 using base::android::ConvertJavaStringToUTF8;
  15 using base::android::GetClass;
  16 using base::android::MethodID;
  17 using base::android::ScopedJavaGlobalRef;
  18 using base::android::ScopedJavaLocalRef;
  19
  20 namespace content {
  21 namespace {
  22
  23 const char kGetName[] = "getName";
  24 const char kGetDeclaringClass[] = "getDeclaringClass";
  25 const char kGetModifiers[] = "getModifiers";
  26 const char kGetParameterTypes[] = "getParameterTypes";
  27 const char kGetReturnType[] = "getReturnType";
  28 const char kIntegerReturningBoolean[] = "(I)Z";
  29 const char kIsStatic[] = "isStatic";
  30 const char kJavaLangClass[] = "java/lang/Class";
  31 const char kJavaLangReflectMethod[] = "java/lang/reflect/Method";
  32 const char kJavaLangReflectModifier[] = "java/lang/reflect/Modifier";
  33 const char kReturningInteger[] = "()I";
  34 const char kReturningJavaLangClass[] = "()Ljava/lang/Class;";
  35 const char kReturningJavaLangClassArray[] = "()[Ljava/lang/Class;";
  36 const char kReturningJavaLangString[] = "()Ljava/lang/String;";
  37
  38 struct ModifierClassTraits :
  39       public base::internal::LeakyLazyInstanceTraits<ScopedJavaGlobalRef<
  40                                                          jclass> > {
  41   static ScopedJavaGlobalRef<jclass>* New(void* instance) {
  42     JNIEnv* env = AttachCurrentThread();
  43     // Use placement new to initialize our instance in our preallocated space.
  44     return new (instance) ScopedJavaGlobalRef<jclass>(
  45         GetClass(env, kJavaLangReflectModifier));
  46   }
  47 };
  48
  49 base::LazyInstance<ScopedJavaGlobalRef<jclass>, ModifierClassTraits>
  50     g_java_lang_reflect_modifier_class = LAZY_INSTANCE_INITIALIZER;
  51
  52 std::string BinaryNameToJNISignature(const std::string& binary_name,
  53                                      JavaType* type) {
  54   DCHECK(type);
  55   *type = JavaType::CreateFromBinaryName(binary_name);
  56   return type->JNISignature();
  57 }
  58
  59 }  // namespace
  60
  61 JavaMethod::JavaMethod(const base::android::JavaRef<jobject>& method)
  62     : java_method_(method),
  63       have_calculated_num_parameters_(false),
  64       id_(NULL) {
  65   JNIEnv* env = AttachCurrentThread();
  66   // On construction, we do nothing except get the name. Everything else is
  67   // done lazily.
  68   ScopedJavaLocalRef<jstring> name(env, static_cast<jstring>(
  69       env->CallObjectMethod(java_method_.obj(), GetMethodIDFromClassName(
  70           env,
  71           kJavaLangReflectMethod,
  72           kGetName,
  73           kReturningJavaLangString))));
  74   name_ = ConvertJavaStringToUTF8(name);
  75 }
  76
  77 JavaMethod::~JavaMethod() {
  78 }
  79
  80 size_t JavaMethod::num_parameters() const {
  81   EnsureNumParametersIsSetUp();
  82   return num_parameters_;
  83 }
  84
  85 bool JavaMethod::is_static() const {
  86   EnsureTypesAndIDAreSetUp();
  87   return is_static_;
  88 }
  89
  90 const JavaType& JavaMethod::parameter_type(size_t index) const {
  91   EnsureTypesAndIDAreSetUp();
  92   return parameter_types_[index];
  93 }
  94
  95 const JavaType& JavaMethod::return_type() const {
  96   EnsureTypesAndIDAreSetUp();
  97   return return_type_;
  98 }
  99
 100 jmethodID JavaMethod::id() const {
 101   EnsureTypesAndIDAreSetUp();
 102   return id_;
 103 }
 104
 105 void JavaMethod::EnsureNumParametersIsSetUp() const {
 106   if (have_calculated_num_parameters_) {
 107     return;
 108   }
 109   have_calculated_num_parameters_ = true;
 110
 111   // The number of parameters will be used frequently when determining
 112   // whether to call this method. We don't get the ID etc until actually
 113   // required.
 114   JNIEnv* env = AttachCurrentThread();
 115   ScopedJavaLocalRef<jarray> parameters(env, static_cast<jarray>(
 116       env->CallObjectMethod(java_method_.obj(), GetMethodIDFromClassName(
 117           env,
 118           kJavaLangReflectMethod,
 119           kGetParameterTypes,
 120           kReturningJavaLangClassArray))));
 121   num_parameters_ = env->GetArrayLength(parameters.obj());
 122 }
 123
 124 void JavaMethod::EnsureTypesAndIDAreSetUp() const {
 125   if (id_) {
 126     return;
 127   }
 128
 129   // Get the parameters
 130   JNIEnv* env = AttachCurrentThread();
 131   ScopedJavaLocalRef<jobjectArray> parameters(env, static_cast<jobjectArray>(
 132       env->CallObjectMethod(java_method_.obj(), GetMethodIDFromClassName(
 133           env,
 134           kJavaLangReflectMethod,
 135           kGetParameterTypes,
 136           kReturningJavaLangClassArray))));
 137   // Usually, this will already have been called.
 138   EnsureNumParametersIsSetUp();
 139   DCHECK_EQ(num_parameters_,
 140             static_cast<size_t>(env->GetArrayLength(parameters.obj())));
 141
 142   // Java gives us the argument type using an extended version of the 'binary
 143   // name'. See
 144   // http://download.oracle.com/javase/1.4.2/docs/api/java/lang/Class.html#getName().
 145   // If we build the signature now, there's no need to store the binary name
 146   // of the arguments. We just store the simple type.
 147   std::string signature("(");
 148
 149   // Form the signature and record the parameter types.
 150   parameter_types_.resize(num_parameters_);
 151   for (size_t i = 0; i < num_parameters_; ++i) {
 152     ScopedJavaLocalRef<jobject> parameter(env, env->GetObjectArrayElement(
 153         parameters.obj(), i));
 154     ScopedJavaLocalRef<jstring> name(env, static_cast<jstring>(
 155         env->CallObjectMethod(parameter.obj(), GetMethodIDFromClassName(
 156             env,
 157             kJavaLangClass,
 158             kGetName,
 159             kReturningJavaLangString))));
 160     std::string name_utf8 = ConvertJavaStringToUTF8(name);
 161     signature += BinaryNameToJNISignature(name_utf8, &parameter_types_[i]);
 162   }
 163   signature += ")";
 164
 165   // Get the return type
 166   ScopedJavaLocalRef<jclass> clazz(env, static_cast<jclass>(
 167       env->CallObjectMethod(java_method_.obj(), GetMethodIDFromClassName(
 168           env,
 169           kJavaLangReflectMethod,
 170           kGetReturnType,
 171           kReturningJavaLangClass))));
 172   ScopedJavaLocalRef<jstring> name(env, static_cast<jstring>(
 173       env->CallObjectMethod(clazz.obj(), GetMethodIDFromClassName(
 174           env,
 175           kJavaLangClass,
 176           kGetName,
 177           kReturningJavaLangString))));
 178   signature += BinaryNameToJNISignature(ConvertJavaStringToUTF8(name),
 179                                         &return_type_);
 180
 181   // Determine whether the method is static.
 182   jint modifiers = env->CallIntMethod(
 183       java_method_.obj(), GetMethodIDFromClassName(env,
 184                                                    kJavaLangReflectMethod,
 185                                                    kGetModifiers,
 186                                                    kReturningInteger));
 187   is_static_ = env->CallStaticBooleanMethod(
 188       g_java_lang_reflect_modifier_class.Get().obj(),
 189       MethodID::Get<MethodID::TYPE_STATIC>(
 190           env, g_java_lang_reflect_modifier_class.Get().obj(), kIsStatic,
 191           kIntegerReturningBoolean),
 192       modifiers);
 193
 194   // Get the ID for this method.
 195   ScopedJavaLocalRef<jclass> declaring_class(env, static_cast<jclass>(
 196       env->CallObjectMethod(java_method_.obj(), GetMethodIDFromClassName(
 197           env,
 198           kJavaLangReflectMethod,
 199           kGetDeclaringClass,
 200           kReturningJavaLangClass))));
 201   id_ = is_static_ ?
 202       MethodID::Get<MethodID::TYPE_STATIC>(
 203           env, declaring_class.obj(), name_.c_str(), signature.c_str()) :
 204       MethodID::Get<MethodID::TYPE_INSTANCE>(
 205           env, declaring_class.obj(), name_.c_str(), signature.c_str());
 206   java_method_.Reset();
 207 }
 208
 209 }  // namespace content