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<head>
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<title>RMI connector</title>
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</head>
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<body bgcolor="white">
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<p>The RMI connector is a connector for the JMX Remote API that
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uses RMI to transmit client requests to a remote MBean server.
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This package defines the classes that the user of an RMI
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connector needs to reference directly, for both the client and
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server sides. It also defines certain classes that the user
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will not usually reference directly, but that must be defined so
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that different implementations of the RMI connector can
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interoperate.</p>
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<p>The RMI connector supports both the JRMP and the IIOP transports
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for RMI.</p>
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<p>Like most connectors in the JMX Remote API, an RMI connector
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usually has an address, which
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is a {@link javax.management.remote.JMXServiceURL
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JMXServiceURL}. The protocol part of this address is
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<code>rmi</code> for a connector that uses the default RMI
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transport (JRMP), or <code>iiop</code> for a connector that
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uses RMI/IIOP.</p>
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<p>There are two forms for RMI connector addresses:</p>
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<ul>
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<li>
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In the <em>JNDI form</em>, the URL indicates <em>where to find
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an RMI stub for the connector</em>. This RMI stub is a Java
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object of type {@link javax.management.remote.rmi.RMIServer
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RMIServer} that gives remote access to the connector server.
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With this address form, the RMI stub is obtained from an
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external directory entry included in the URL. An external
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directory is any directory recognized by {@link javax.naming
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JNDI}, typically the RMI registry, LDAP, or COS Naming.
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<li>
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In the <em>encoded form</em>, the URL directly includes the
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information needed to connect to the connector server. When
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using RMI/JRMP, the encoded form is the serialized RMI stub
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for the server object, encoded using BASE64 without embedded
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newlines. When using RMI/IIOP, the encoded form is the CORBA
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IOR for the server object.
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</ul>
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<p>Addresses are covered in more detail below.</p>
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<h3>Creating an RMI connector server</h3>
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<p>The usual way to create an RMI connector server is to supply an
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RMI connector address to the method {@link
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javax.management.remote.JMXConnectorServerFactory#newJMXConnectorServer
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JMXConnectorServerFactory.newJMXConnectorServer}. The MBean
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server to which the connector server is attached can be
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specified as a parameter to that method. Alternatively, the
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connector server can be registered as an MBean in that MBean
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server.</p>
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<p>An RMI connector server can also be created by constructing an
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instance of {@link
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javax.management.remote.rmi.RMIConnectorServer
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RMIConnectorServer}, explicitly or through the MBean server's
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<code>createMBean</code> method.</p>
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<h4>Choosing the RMI transport</h4>
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<p>You can choose the RMI transport (JRMP or IIOP) by specifying
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<code>rmi</code> or <code>iiop</code> in the
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<code><em>protocol</em></code> part of the
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<code>serviceURL</code> when creating the connector server. You
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can also create specialised connector servers by instantiating
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an appropriate subclass of {@link
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javax.management.remote.rmi.RMIServerImpl RMIServerImpl} and
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supplying it to the <code>RMIConnectorServer</code>
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constructor.</p>
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<h4><a name="servergen">Connector addresses generated by the
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server</a></h4>
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<p>If the <code>serviceURL</code> you specify has an empty URL
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path (after the optional host and port), or if you do not
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specify a <code>serviceURL</code>, then the connector server
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will fabricate a new <code>JMXServiceURL</code> that clients can
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use to connect:</p>
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<ul>
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<li><p>If the <code>serviceURL</code> looks like:</p>
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<pre>
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<code>service:jmx:rmi://<em>host</em>:<em>port</em></code>
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</pre>
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<p>then the connector server will generate an {@link
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javax.management.remote.rmi.RMIJRMPServerImpl
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RMIJRMPServerImpl} and the returned <code>JMXServiceURL</code>
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looks like:</p>
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<pre>
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<code>service:jmx:rmi://<em>host</em>:<em>port</em>/stub/<em>XXXX</em></code>
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</pre>
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<p>where <code><em>XXXX</em></code> is the serialized form of the
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stub for the generated object, encoded in BASE64 without
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newlines.</p>
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<li><p>If the <code>serviceURL</code> looks like:</p>
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<pre>
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<code>service:jmx:iiop://<em>host</em>:<em>port</em></code>
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</pre>
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<p>then the connector server will generate an {@link
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javax.management.remote.rmi.RMIIIOPServerImpl
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RMIIIOPServerImpl} and the returned
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<code>JMXServiceURL</code> looks like:</p>
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<pre>
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<code>service:jmx:iiop://<em>host</em>:<em>port</em>/ior/IOR:<em>XXXX</em></code>
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</pre>
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<p>where <code>IOR:<em>XXXX</em></code> is the standard CORBA
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encoding of the Interoperable Object Reference for the
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generated object.</p>
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<li><p>If there is no <code>serviceURL</code>, there must be a
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user-provided <code>RMIServerImpl</code>. If the {@link
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javax.management.remote.rmi.RMIServerImpl#toStub toStub}
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method on this object returns an instance of {@link
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javax.rmi.CORBA.Stub}, then the connector server will generate
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a <code>JMXServiceURL</code> using the <code>iiop</code>
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form above. Otherwise, it will generate a
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<code>JMXServiceURL</code> using the <code>rmi</code>
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form.</p>
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</ul>
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<p>The <code><em>host</em></code> in a user-provided
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<code>serviceURL</code> is optional. If present, it is copied
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into the generated <code>JMXServiceURL</code> but otherwise
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ignored. If absent, the generated <code>JXMServiceURL</code>
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will have the local host name.</p>
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<p>The <code><em>port</em></code> in a user-provided
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<code>serviceURL</code> is also optional. If present, it is
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also copied into the generated <code>JMXServiceURL</code>;
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otherwise, the generated <code>JMXServiceURL</code> has no port.
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For an <code>serviceURL</code> using the <code>rmi</code>
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protocol, the <code><em>port</em></code>, if present, indicates
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what port the generated remote object should be exported on. It
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has no other effect.</p>
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<p>If the user provides an <code>RMIServerImpl</code> rather than a
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<code>JMXServiceURL</code>, then the generated
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<code>JMXServiceURL</code> will have the local host name in its
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<code><em>host</em></code> part and no
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<code><em>port</em></code>.</p>
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<h4><a name="directory">Connector addresses based on directory
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entries</a></h4>
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<p>As an alternative to the generated addresses just described,
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the <code>serviceURL</code> address supplied when creating a
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connector server can specify a <em>directory address</em> in
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which to store the provided or generated <code>RMIServer</code>
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stub. This directory address is then used by both client and
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server.</p>
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<p>In this case, the <code>serviceURL</code> has one of these two
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forms:</p>
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<pre>
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<code>service:jmx:rmi://<em>host</em>:<em>port</em>/jndi/<em>jndi-name</em></code>
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<code>service:jmx:iiop://<em>host</em>:<em>port</em>/jndi/<em>jndi-name</em></code>
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</pre>
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<p>Here, <code><em>jndi-name</em></code> is a string that can be
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supplied to {@link javax.naming.InitialContext#bind
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javax.naming.InitialContext.bind}.</p>
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<p>As usual, the <code><em>host</em></code> and
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<code>:<em>port</em></code> can be omitted.</p>
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<p>The connector server will generate an
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<code>RMIServerImpl</code> based on the protocol
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(<code>rmi</code> or <code>iiop</code>) and, for
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<code>rmi</code>, the <code><em>port</em></code> if any. When
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the connector server is started, it will derive a stub from this
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object using its {@link
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javax.management.remote.rmi.RMIServerImpl#toStub toStub} method
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and store the object using the given
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<code><em>jndi-name</em></code>. The properties defined by the
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JNDI API are consulted as usual.</p>
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<p>For example, if the <code>JMXServiceURL</code> is:
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<pre>
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<code>service:jmx:rmi://ignoredhost/jndi/rmi://myhost/myname</code>
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</pre>
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then the connector server will generate an
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<code>RMIJRMPServerImpl</code> and store its stub using the JNDI
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name
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<pre>
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<code>rmi://myhost/myname</code>
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</pre>
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which means entry <code>myname</code> in the RMI registry
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running on the default port of host <code>myhost</code>. Note
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that the RMI registry only allows registration from the local
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host. So, in this case, <code>myhost</code> must be the name
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(or a name) of the host that the connector server is running
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on.</p>
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<p>In this <code>JMXServiceURL</code>, the first <code>rmi:</code>
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specifies the RMI
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connector, while the second <code>rmi:</code> specifies the RMI
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registry.</p>
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<p>As another example, if the <code>JMXServiceURL</code> is:
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<pre>
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<code>service:jmx:iiop://ignoredhost/jndi/ldap://dirhost:9999/cn=this,ou=that</code>
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</pre>
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then the connector server will generate an
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<code>RMIIIOPServerImpl</code> and store its stub using the JNDI
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name
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<pre>
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<code>ldap://dirhost:9999/cn=this,ou=that</code>
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</pre>
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which means entry <code>cn=this,ou=that</code> in the LDAP
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directory running on port 9999 of host <code>dirhost</code>.</p>
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<p>If the <code>JMXServiceURL</code> is:
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<pre>
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<code>service:jmx:iiop://ignoredhost/jndi/cn=this,ou=that</code>
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</pre>
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then the connector server will generate an
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<code>RMIIIOPServerImpl</code> and store its stub using the JNDI
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name
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<pre>
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<code>cn=this,ou=that</code>
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</pre>
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For this case to work, the JNDI API must have been configured
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appropriately to supply the information about what directory to
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use.</p>
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<p>In these examples, the host name <code>ignoredhost</code> is
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not used by the connector server or its clients. It can be
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omitted, for example:</p>
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<pre>
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<code>service:jmx:iiop:///jndi/cn=this,ou=that</code>
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</pre>
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<p>However, it is good practice to use the name of the host
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where the connector server is running. This is often different
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from the name of the directory host.</p>
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<h4>Connector server attributes</h4>
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<p>When using the default JRMP transport, RMI socket factories can
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be specified using the attributes
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<code>jmx.remote.rmi.client.socket.factory</code> and
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<code>jmx.remote.rmi.server.socket.factory</code> in the
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<code>environment</code> given to the
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<code>RMIConnectorServer</code> constructor. The values of these
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attributes must be of type {@link
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java.rmi.server.RMIClientSocketFactory} and {@link
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java.rmi.server.RMIServerSocketFactory}, respectively. These
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factories are used when creating the RMI objects associated with
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the connector.</p>
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<h3>Creating an RMI connector client</h3>
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<p>An RMI connector client is usually constructed using {@link
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javax.management.remote.JMXConnectorFactory}, with a
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<code>JMXServiceURL</code> that has <code>rmi</code> or
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<code>iiop</code> as its protocol.</p>
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<p>If the <code>JMXServiceURL</code> was generated by the server,
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as described above under <a href="#servergen">"connector
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addresses generated by the server"</a>, then the client will
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need to obtain it directly or indirectly from the server.
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Typically, the server makes the <code>JMXServiceURL</code>
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available by storing it in a file or a lookup service.</p>
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<p>If the <code>JMXServiceURL</code> uses the directory syntax, as
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described above under <a href="#directory">"connector addresses
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based on directory entries"</a>, then the client may obtain it
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as just explained, or client and server may both know the
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appropriate directory entry to use. For example, if the
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connector server for the Whatsit agent uses the entry
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<code>whatsit-agent-connector</code> in the RMI registry on host
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<code>myhost</code>, then client and server can both know
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that the appropriate <code>JMXServiceURL</code> is:</p>
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<pre>
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<code>service:jmx:rmi:///jndi/rmi://myhost/whatsit-agent-connector</code>
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</pre>
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<p>If you have an RMI stub of type {@link
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javax.management.remote.rmi.RMIServer RMIServer}, you can
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construct an RMI connection directly by using the appropriate
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constructor of {@link javax.management.remote.rmi.RMIConnector
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RMIConnector}.</p>
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<h3>Specifying an ORB for the RMI/IIOP connector</h3>
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<p>When using the IIOP transport, the client and server can
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specify what ORB to use
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with the attribute <code>java.naming.corba.orb</code>.
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Connection to the ORB happens at {@link
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javax.management.remote.rmi.RMIConnectorServer#start() start} time
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for the connector server, and at {@link
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javax.management.remote.rmi.RMIConnector#connect(java.util.Map)
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connect} time for the connector client.
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If the <code>java.naming.corba.orb</code> attribute is contained
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in the environment Map, then its value (an {@link
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org.omg.CORBA.ORB ORB}), is used to connect the IIOP Stubs.
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Otherwise, a new org.omg.CORBA.ORB is created by calling {@link
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org.omg.CORBA.ORB
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org.omg.CORBA.ORB.init((String[])null,(Properties)null)}. A
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later RMI connector client or server in the same JVM can reuse
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|
364 |
this ORB, or it can create another one in the same way.</p>
|
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|
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<p>If the <code>java.naming.corba.orb</code> attribute is
|
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|
367 |
specified and does not point to an {@link org.omg.CORBA.ORB ORB},
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|
368 |
then an <code>{@link java.lang.IllegalArgumentException}</code>
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|
369 |
will be thrown.</p>
|
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|
370 |
|
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|
371 |
<p>The mechanism described here does not apply when the IIOP
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Remote objects (Stubs or Servers) are created and connected to
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|
373 |
an ORB manually before being passed to the RMIConnector and
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|
374 |
RMIConnectorServer.</p>
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|
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<h3>Dynamic code downloading</h3>
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|
378 |
|
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|
379 |
<p>If an RMI connector client or server receives from its peer an
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instance of a class that it does not know, and if dynamic code
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|
381 |
downloading is active for the RMI connection, then the class can
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|
382 |
be downloaded from a codebase specified by the peer. The
|
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383 |
article <a
|
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|
384 |
href="{@docRoot}/../technotes/guides/rmi/codebase.html"><em>Dynamic
|
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|
385 |
code downloading using Java RMI</em></a> explains this in more
|
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|
386 |
detail.</p>
|
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|
387 |
|
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|
388 |
|
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|
389 |
@see <a href="{@docRoot}/../technotes/guides/rmi/index.html">
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|
390 |
Java<sup><font size="-1">TM</font></sup> Remote Method
|
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|
391 |
Invocation (RMI)</a>
|
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|
392 |
|
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|
393 |
@see <a href="{@docRoot}/../technotes/guides/jndi/index.html">
|
|
|
394 |
Java Naming and Directory Interface<sup><font
|
|
|
395 |
size="-1">TM</font></sup> (JNDI)</a>
|
|
|
396 |
|
|
|
397 |
@see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045,
|
|
|
398 |
section 6.8, "Base64 Content-Transfer-Encoding"</a>
|
|
|
399 |
|
|
|
400 |
|
|
|
401 |
@since 1.5
|
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|
402 |
|
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|
403 |
</body>
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|
404 |
</html>
|