jni_generator: Pass object parameters as JavaParamRef.

base/android/scoped_java_ref.h

 // Copyright (c) 2012 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.
 
 #ifndef BASE_ANDROID_SCOPED_JAVA_REF_H_
 #define BASE_ANDROID_SCOPED_JAVA_REF_H_
 
 #include <jni.h>
 #include <stddef.h>
 
@@ skipping 76 matching lines @@
  protected:
   JavaRef() {}
   ~JavaRef() {}
 
   JavaRef(JNIEnv* env, T obj) : JavaRef<jobject>(env, obj) {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(JavaRef);
 };
 
+// Holds a local reference to a JNI method parameter.
+// Method parameters should not be deleted, and so this class exists purely to
+// wrap them as a JavaRef<T> in the JNI binding generator. Do not create
+// instances manually.
+template<typename T>
+class JavaParamRef : public JavaRef<T> {
+ public:
+  // Assumes that |obj| is a parameter passed to a JNI method from Java.
+  // Does not assume ownership as parameters should not be deleted.
+  JavaParamRef(JNIEnv* env, T obj) : JavaRef<T>(env, obj) {}
+
+  ~JavaParamRef() {}
+
+  // TODO(torne): remove this cast once we're using JavaRef consistently.
+  // http://crbug.com/506850
+  operator T() const { return JavaRef<T>::obj(); }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(JavaParamRef);
+};
+
 // Holds a local reference to a Java object. The local reference is scoped
 // to the lifetime of this object.
 // Instances of this class may hold onto any JNIEnv passed into it until
 // destroyed. Therefore, since a JNIEnv is only suitable for use on a single
 // thread, objects of this class must be created, used, and destroyed, on a
 // single thread.
 // Therefore, this class should only be used as a stack-based object and from a
 // single thread. If you wish to have the reference outlive the current
 // callstack (e.g. as a class member) or you wish to pass it across threads,
 // use a ScopedJavaGlobalRef instead.
@@ skipping 94 matching lines @@
   void Reset() {
     this->ResetGlobalRef();
   }
 
   template<typename U>
   void Reset(const U& other) {
     this->Reset(NULL, other.obj());
   }
 
   template<typename U>
+  void Reset(JNIEnv* env, const JavaParamRef<U>& other) {
+    this->Reset(env, other.obj());
+  }
+
+  template<typename U>
   void Reset(JNIEnv* env, U obj) {
     implicit_cast<T>(obj);  // Ensure U is assignable to T
     this->SetNewGlobalRef(env, obj);
   }
 
   // Releases the global reference to the caller. The caller *must* delete the
   // global reference when it is done with it. Note that calling a Java method
   // is *not* a transfer of ownership and Release() should not be used.
   T Release() {
     return static_cast<T>(this->ReleaseInternal());
   }
 };
 
 }  // namespace android
 }  // namespace base
 
 #endif  // BASE_ANDROID_SCOPED_JAVA_REF_H_