Hi Chris,
Thanks for your detailed explanation. I understand the issue now.
Thanks!
-Dan
On Mon 09 Dec 2013 02:09:52 AM PST, Chris Hegarty wrote:
On 08/12/13 17:39, Dan Xu wrote:
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?
Yes. Quote from the spec, "All Java objects returned by JNI functions
are local references. "
When shall I call NewGlobalRef()?
I included the NewGlobalRef call in the code above (a modified version
of setNoProxy). Directly after GetStaticObjectField.
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?
Yes. You are adding a new reference to this object, from JNI code.
This reference needs to be registered with the GC so it can be updated
if the referent is relocated.
But why is it not necessary for me to call NewGlobalRef() for
ptype_httpID and ptype_socksID? Thanks!
These are not reference to Java Objects, they are of type jmethodID.
You can think of them as pointers/offsets into particular type, and
are not subject to change.
-Chris.
-Dan
