接上:http://guojuanjun.blog.51cto.com/277646/1423392
这一次我们从学习RegistryImpl_Stub.java和RegistryImpl_Skel.java的实现上学习远程方法的调用过程。
RegistryImpl_Stub.bind:
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public
void
bind(java.lang.String $param_String_1, java.rmi.Remote $param_Remote_2)
throws
java.rmi.AccessException, java.rmi.AlreadyBoundException, java.rmi.RemoteException
{
try
{
if
(useNewInvoke) {
ref.invoke(
this
, $method_bind_0,
new
java.lang.Object[] {$param_String_1, $param_Remote_2}, 7583982177005850366L);
}
else
{
java.rmi.server.RemoteCall call = ref.newCall((java.rmi.server.RemoteObject)
this
, operations,
0
, interfaceHash);
try
{
java.io.ObjectOutput out = call.getOutputStream();
out.writeObject($param_String_1);
out.writeObject($param_Remote_2);
}
catch
(java.io.IOException e) {
throw
new
java.rmi.MarshalException(
"error marshalling arguments"
, e);
}
ref.invoke(call);
ref.done(call);
}
}
catch
(java.lang.RuntimeException e) {
throw
e;
}
catch
(java.rmi.RemoteException e) {
throw
e;
}
catch
(java.rmi.AlreadyBoundException e) {
throw
e;
}
catch
(java.lang.Exception e) {
throw
new
java.rmi.UnexpectedException(
"undeclared checked exception"
, e);
}
}
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public
StreamRemoteCall(Connection c, ObjID id,
int
op,
long
hash)
throws
RemoteException
{
try
{
conn = c;
Transport.transportLog.log(Log.VERBOSE,
"write remote call header..."
);
// write out remote call header info...
// call header, part 1 (read by Transport)
conn.getOutputStream().write(TransportConstants.Call);
getOutputStream();
// creates a MarshalOutputStream
id.write(out);
// object id (target of call)
// call header, part 2 (read by Dispatcher)
out.writeInt(op);
// method number (operation index)
out.writeLong(hash);
// stub/skeleton hash
}
catch
(IOException e) {
throw
new
MarshalException(
"Error marshaling call header"
, e);
}
}
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只要传入对象ID，操作号，接口hash值，就可以定位到远程对象及其方法上。
再看服务端：
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public
boolean
serviceCall(
final
RemoteCall call) {
try
{
final
Remote impl;
ObjID id;
try
{
id = ObjID.read(call.getInputStream());
}
catch
(java.io.IOException e) {
throw
new
MarshalException(
"unable to read objID"
, e);
}
/* get the remote object */
Transport transport = id.equals(dgcID) ? null : this;
Target target =
ObjectTable.getTarget(new ObjectEndpoint(id, transport));
if (target == null || (impl = target.getImpl()) == null) {
throw new NoSuchObjectException("no such object in table");
}
final Dispatcher disp = target.getDispatcher();
target.incrementCallCount();
try {
/* call the dispatcher */
transportLog.log(Log.VERBOSE, "call dispatcher");
final AccessControlContext acc =
target.getAccessControlContext();
ClassLoader ccl = target.getContextClassLoader();
Thread t = Thread.currentThread();
ClassLoader savedCcl = t.getContextClassLoader();
try {
t.setContextClassLoader(ccl);
currentTransport.set(this);
try {
java.security.AccessController.doPrivileged(
new java.security.PrivilegedExceptionAction<Void>() {
public Void run() throws IOException {
checkAcceptPermission(acc);
disp.dispatch(impl, call);
return null;
}
}, acc);
} catch (java.security.PrivilegedActionException pae) {
throw (IOException) pae.getException();
}
} finally {
t.setContextClassLoader(savedCcl);
currentTransport.set(null);
}
} catch (IOException ex) {
transportLog.log(Log.BRIEF,
"exception thrown by dispatcher: ", ex);
return false;
} finally {
target.decrementCallCount();
}
} catch (RemoteException e) {
// if calls are being logged, write out exception
if (UnicastServerRef.callLog.isLoggable(Log.BRIEF)) {
// include client host name if possible
String clientHost = "";
try {
clientHost = "[" +
RemoteServer.getClientHost() + "] ";
} catch (ServerNotActiveException ex) {
}
String message = clientHost + "exception: ";
UnicastServerRef.callLog.log(Log.BRIEF, message, e);
}
/* We will get a RemoteException if either a) the objID is
* not readable, b) the target is not in the object table, or
* c) the object is in the midst of being unexported (note:
* NoSuchObjectException is thrown by the incrementCallCount
* method if the object is being unexported). Here it is
* relatively safe to marshal an exception to the client
* since the client will not have seen a return value yet.
*/
try
{
ObjectOutput out = call.getResultStream(
false
);
UnicastServerRef.clearStackTraces(e);
out.writeObject(e);
call.releaseOutputStream();
}
catch
(IOException ie) {
transportLog.log(Log.BRIEF,
"exception thrown marshalling exception: "
, ie);
return
false
;
}
}
return
true
;
}
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id = ObjID.read(call.getInputStream());
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读到ObjId.
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Target target =
ObjectTable.getTarget(
new
ObjectEndpoint(id, transport));
impl = target.getImpl()
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从对象表中找到远程对象的target对象，并获取远程对象。
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disp.dispatch(impl, call);
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分发调用到远程对象上。
RegistryImpl的远程调用是这样实现,但普通对象在JDK1.5之后,已没有显示的stub类.而是用一个代理类代替存根对象,具体参考:http://guojuanjun.blog.51cto.com/277646/1350826
本文转自 anranran 51CTO博客，原文链接:http://blog.51cto.com/guojuanjun/1423511
