Strange Issue With Static Global Variable in Native

[Dan Xu]

On 12/08/2013 01:34 AM, Chris Hegarty wrote:
>
> On 07/12/2013 18:12, Dan Xu wrote:
>> ...
>>> Just so I understand, did you use a JNI global when caching the 
>>> reference?
>>>
>>> -Alan
>> Hi Alan,
>>
>> What is a JNI global?
>
> http://docs.oracle.com/javase/7/docs/technotes/guides/jni/spec/design.html#wp1242 
>
>
> > What I use here is a static global variable. I
>> have uploaded this file to
>> http://cr.openjdk.java.net/~dxu/8025437/DefaultProxySelector1.c. You can
>> search for "no_proxy". I have declared this variable as "static jobject'
>> at the beginning, and initialized it in function initJavaClass().
>
> You can only store global, not local, refs across multiple 
> calls/contexts.
>
> In your case it would look something like:
>
> static jobject setNoProxy(JNIEnv *env) {
>               jobject empty_proxy = NULL;
>               jfieldID pr_no_proxyID = NULL;
>                 pr_no_proxyID = (*env)->GetStaticFieldID(env, 
> proxy_class,
>                         "NO_PROXY", "Ljava/net/Proxy;");
>                 if (proxy_class && pr_no_proxyID) {
>                     printf("create NO_PROXY\n");
>                     empty_proxy = (*env)->GetStaticObjectField(env, 
> proxy_class, pr_no_proxyID);
>
>                     empty_proxy = (*env)->NewGlobalRef(env, empty_proxy);
>                 }
>                 return empty_proxy;
> }
>
> -Chris.

Do you mean (*env)->GetStaticObjectField() return me a local reference? 
When shall I call NewGlobalRef()? In Proxy.java, this static field has 
already been created by "public final static Proxy NO_PROXY = new 
Proxy();" And I still need call NewGlobalRef() to make it global, right?

But why is it not necessary for me to call NewGlobalRef() for 
ptype_httpID and ptype_socksID? Thanks!

-Dan
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