Add JavaBoundObject

content/browser/renderer_host/java/java_method.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_method.h"
+
+#include "base/android/jni_android.h"
+#include "base/android/jni_string.h"
+#include "base/memory/singleton.h"
+#include "base/string_util.h"  // For ReplaceSubstringsAfterOffset
+
+using base::android::AttachCurrentThread;
+using base::android::ConvertJavaStringToUTF8;
+using base::android::MethodID;
+using base::android::ScopedJavaLocalRef;
+
+namespace {
+
+// Java's reflection API represents types as a string using an extended 'binary
+// name'. This converts to an enum which we store in place of the binary name
+// for simplicity.
+JavaType::Type BinaryNameToType(const std::string& binary_name) {
+  if (binary_name == "boolean") {
+    return JavaType::TypeBoolean;
+  } else if (binary_name == "byte") {
+    return JavaType::TypeByte;
+  } else if (binary_name == "char") {
+    return JavaType::TypeChar;
+  } else if (binary_name == "short") {
+    return JavaType::TypeShort;
+  } else if (binary_name == "int") {
+    return JavaType::TypeInt;
+  } else if (binary_name == "long") {
+    return JavaType::TypeLong;
+  } else if (binary_name == "float") {
+    return JavaType::TypeFloat;
+  } else if (binary_name == "double") {
+    return JavaType::TypeDouble;
+  } else if (binary_name == "void") {
+    return JavaType::TypeVoid;
+  } else if (binary_name[0] == '[') {
+    return JavaType::TypeArray;
+  } else if (binary_name == "java.lang.String") {
+    return JavaType::TypeString;
+  }
+  return JavaType::TypeObject;
+}
+
+std::string BinaryNameToJNIName(const std::string& binary_name,
+                                JavaType::Type* type) {
+  DCHECK(type);
+  *type = BinaryNameToType(binary_name);
+  switch (*type) {
+    case JavaType::TypeBoolean:
+      return "Z";
+    case JavaType::TypeByte:
+      return "B";
+    case JavaType::TypeChar:
+      return "C";
+    case JavaType::TypeShort:
+      return "S";
+    case JavaType::TypeInt:
+      return "I";
+    case JavaType::TypeLong:
+      return "J";
+    case JavaType::TypeFloat:
+      return "F";
+    case JavaType::TypeDouble:
+      return "D";
+    case JavaType::TypeVoid:
+      return "V";
+    case JavaType::TypeArray:
+      return "[";
+    default:
+      DCHECK (*type == JavaType::TypeString || *type == JavaType::TypeObject);
+      std::string jni_name = "L" + binary_name + ";";
+      ReplaceSubstringsAfterOffset(&jni_name, 0, ".", "/");
+      return jni_name;
+  }
+}
+
+class MethodGetParameterTypesID : public MethodID {
+ public:
+  static MethodGetParameterTypesID* GetInstance() {
+    return Singleton<MethodGetParameterTypesID>::get();
+  }
+ private:
+  friend struct DefaultSingletonTraits<MethodGetParameterTypesID>;
+  MethodGetParameterTypesID()
+      : MethodID(AttachCurrentThread(), "java/lang/reflect/Method",
+                 "getParameterTypes", "()[Ljava/lang/Class;") {
+  }
+  DISALLOW_COPY_AND_ASSIGN(MethodGetParameterTypesID);
+};
+
+class MethodGetNameID : public MethodID {
+ public:
+  static MethodGetNameID* GetInstance() {
+    return Singleton<MethodGetNameID>::get();
+  }
+ private:
+  friend struct DefaultSingletonTraits<MethodGetNameID>;
+  MethodGetNameID()
+      : MethodID(AttachCurrentThread(), "java/lang/reflect/Method",
+                 "getName", "()Ljava/lang/String;") {
+  }
+  DISALLOW_COPY_AND_ASSIGN(MethodGetNameID);
+};
+
+class MethodGetReturnTypeID : public MethodID {
+ public:
+  static MethodGetReturnTypeID* GetInstance() {
+    return Singleton<MethodGetReturnTypeID>::get();
+  }
+ private:
+  friend struct DefaultSingletonTraits<MethodGetReturnTypeID>;
+  MethodGetReturnTypeID()
+      : MethodID(AttachCurrentThread(), "java/lang/reflect/Method",
+                 "getReturnType", "()Ljava/lang/Class;") {
+  }
+  DISALLOW_COPY_AND_ASSIGN(MethodGetReturnTypeID);
+};
+
+class MethodGetDeclaringClassID : public MethodID {
+ public:
+  static MethodGetDeclaringClassID* GetInstance() {
+    return Singleton<MethodGetDeclaringClassID>::get();
+  }
+ private:
+  friend struct DefaultSingletonTraits<MethodGetDeclaringClassID>;
+  MethodGetDeclaringClassID()
+      : MethodID(AttachCurrentThread(), "java/lang/reflect/Method",
+                 "getDeclaringClass", "()Ljava/lang/Class;") {
+  }
+  DISALLOW_COPY_AND_ASSIGN(MethodGetDeclaringClassID);
+};
+
+class ClassGetNameID : public MethodID {
+ public:
+  static ClassGetNameID* GetInstance() {
+    return Singleton<ClassGetNameID>::get();
+  }
+ private:
+  friend struct DefaultSingletonTraits<ClassGetNameID>;
+  ClassGetNameID()
+      : MethodID(AttachCurrentThread(), "java/lang/Class", "getName",
+                 "()Ljava/lang/String;") {
+  }
+  DISALLOW_COPY_AND_ASSIGN(ClassGetNameID);
+};
+
+}  // namespace
+
+JavaMethod::JavaMethod(const base::android::JavaRef<jobject>& method)
+    : java_method_(method),
+      have_calculated_num_parameters_(false),
+      id_(NULL) {
+  JNIEnv* env = java_method_.env();
+  // On construction, we do nothing except get the name. Everything else is
+  // done lazily.
+  ScopedJavaLocalRef<jstring> name(env, static_cast<jstring>(
+      env->CallObjectMethod(java_method_.obj(),
+                            MethodGetNameID::GetInstance()->id())));
+  name_ = ConvertJavaStringToUTF8(env, name.obj());
+}
+
+JavaMethod::~JavaMethod() {
+}
+
+size_t JavaMethod::num_parameters() const {
+  const_cast<JavaMethod*>(this)->EnsureNumParametersIsSetUp();

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

Why make the member function const if it isn't?

I'd vote for removing the const_cast<>.

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

I think that conceptually, the method is const - we just happen to do stuff
lazily. Isn't there value in leaving it const to signal that?

[M-A Ruel, 2011/11/11 16:43:29]

Then you would probably better to put your member a mutable. I prefer
correctness over false advertisement. :) That said, I don't mind enough to block
the CL.

[Steve Block, 2011/11/11 17:05:43]

The reason I preferred the const_cast to using mutable was that it made clear
where the members need to be modified. But I guess you're right about false
advertising. Changed

+  return num_parameters_;
+}
+
+JavaType::Type JavaMethod::parameter_type(size_t index) const {
+  const_cast<JavaMethod*>(this)->EnsureTypesAndIDAreSetUp();
+  return parameter_types_[index];
+}
+
+JavaType::Type JavaMethod::return_type() const {
+  const_cast<JavaMethod*>(this)->EnsureTypesAndIDAreSetUp();
+  return return_type_;
+}
+
+jmethodID JavaMethod::id() const {
+  const_cast<JavaMethod*>(this)->EnsureTypesAndIDAreSetUp();
+  return id_;
+}
+
+void JavaMethod::EnsureNumParametersIsSetUp() {
+  if (have_calculated_num_parameters_) {
+    return;
+  }
+  have_calculated_num_parameters_ = true;
+
+  // The number of parameters will be used frequently when determining
+  // whether to call this method. We don't get the ID etc until actually
+  // required.
+  JNIEnv* env = java_method_.env();
+  ScopedJavaLocalRef<jarray> parameters(env, static_cast<jarray>(
+      env->CallObjectMethod(java_method_.obj(),
+                            MethodGetParameterTypesID::GetInstance()->id())));
+  num_parameters_ = env->GetArrayLength(parameters.obj());
+}
+
+void JavaMethod::EnsureTypesAndIDAreSetUp() {
+  if (id_) {
+    return;
+  }
+
+  // Get the parameters
+  JNIEnv* env = java_method_.env();
+  ScopedJavaLocalRef<jobjectArray> parameters(env, static_cast<jobjectArray>(
+      env->CallObjectMethod(java_method_.obj(),
+                            MethodGetParameterTypesID::GetInstance()->id())));
+  // Usually, this will already have been called.
+  EnsureNumParametersIsSetUp();
+  DCHECK_EQ(num_parameters_,
+            static_cast<size_t>(env->GetArrayLength(parameters.obj())));
+
+  // Java gives us the argument type using an extended version of the 'binary
+  // name'. See
+  // http://download.oracle.com/javase/1.4.2/docs/api/java/lang/Class.html#getName().
+  // If we build the signature now, there's no need to store the binary name
+  // of the arguments. We just store the simple type.
+  std::string signature("(");
+
+  // Form the signature and record the parameter types.
+  parameter_types_.resize(num_parameters_);
+  for (size_t i = 0; i < num_parameters_; ++i) {
+    ScopedJavaLocalRef<jobject> parameter(env, env->GetObjectArrayElement(
+        parameters.obj(), i));
+    ScopedJavaLocalRef<jstring> name(env, static_cast<jstring>(
+        env->CallObjectMethod(parameter.obj(),
+                              ClassGetNameID::GetInstance()->id())));
+    std::string name_utf8 = ConvertJavaStringToUTF8(env, name.obj());
+    signature += BinaryNameToJNIName(name_utf8, &parameter_types_[i]);
+  }
+  signature += ")";
+
+  // Get the return type
+  ScopedJavaLocalRef<jclass> clazz(env, static_cast<jclass>(
+      env->CallObjectMethod(java_method_.obj(),
+                            MethodGetReturnTypeID::GetInstance()->id())));
+  ScopedJavaLocalRef<jstring> name(env, static_cast<jstring>(
+      env->CallObjectMethod(clazz.obj(), ClassGetNameID::GetInstance()->id())));
+  signature += BinaryNameToJNIName(ConvertJavaStringToUTF8(env, name.obj()),
+                                   &return_type_);
+
+  // Get the ID for this method.
+  ScopedJavaLocalRef<jclass> declaring_class(env, static_cast<jclass>(
+      env->CallObjectMethod(java_method_.obj(),
+                            MethodGetDeclaringClassID::GetInstance()->id())));
+  id_ = base::android::GetMethodID(env, declaring_class.obj(), name_.c_str(),
+                                   signature.c_str());
+
+  java_method_.Reset();
+}