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<p> This package provides support for communication with Erlang and
representation of Erlang datatypes.
<p><em>Note:</em> By default, <code>jinterface</code> is only guaranteed
to be compatible with other Erlang/OTP components from the same release as
<code>jinterface</code> itself. For example, <code>jinterface</code>
from the OTP R10 release is not compatible with an Erlang emulator from
the OTP R9 release by default. <code>jinterface</code> can be set in
compatibility mode of an earlier release (not earlier that R7), though.
The compatibility mode is set by usage of the <code>OtpCompatRel</code>
property. By starting the jvm with the command-line argument
<code>-DOtpCompatRel=9</code>, <code>jinterface</code> will be compatible
with the R9 release of OTP. <em>Warning!</em> You may run into trouble if
this feature is used carelessly. Always make sure that all communicating
components are either from the same Erlang/OTP release, or from release
X and release Y where all components from release Y are in compatibility
mode of release X.
<p> The classes
{@link com.ericsson.otp.erlang.OtpErlangList},
{@link com.ericsson.otp.erlang.OtpErlangTuple},
{@link com.ericsson.otp.erlang.OtpErlangBinary},
{@link com.ericsson.otp.erlang.OtpErlangAtom},
{@link com.ericsson.otp.erlang.OtpErlangBoolean},
{@link com.ericsson.otp.erlang.OtpErlangByte},
{@link com.ericsson.otp.erlang.OtpErlangChar},
{@link com.ericsson.otp.erlang.OtpErlangDouble},
{@link com.ericsson.otp.erlang.OtpErlangFloat},
{@link com.ericsson.otp.erlang.OtpErlangLong},
{@link com.ericsson.otp.erlang.OtpErlangInt},
{@link com.ericsson.otp.erlang.OtpErlangUInt},
{@link com.ericsson.otp.erlang.OtpErlangShort},
{@link com.ericsson.otp.erlang.OtpErlangUShort},
{@link com.ericsson.otp.erlang.OtpErlangString},
{@link com.ericsson.otp.erlang.OtpErlangObject},
{@link com.ericsson.otp.erlang.OtpErlangPid},
{@link com.ericsson.otp.erlang.OtpErlangPort},
and {@link com.ericsson.otp.erlang.OtpErlangRef}
represent the various Erlang datatypes.
<p> There are two basic mechanisms for communicating with Erlang,
described briefly here. Note that the two mechanisms are not intended
to be used together. Which mechanism you choose depends on your
application and the level of control it needs. </p>
<p> You can use {@link com.ericsson.otp.erlang.OtpNode}, which can
manage incoming and outgoing connections for you. With {@link
com.ericsson.otp.erlang.OtpNode} a thread is automatically started to
listen for incoming connections, make necessary outgoing connections,
and dispatch messages to their recipients. {@link
com.ericsson.otp.erlang.OtpNode} supports the concept of {@link
com.ericsson.otp.erlang.OtpMbox mailboxes}, allowing you to have
several Java components communicating independently with Erlang.
</p>
<pre>
OtpNode node = new OtpNode("bingo");
OtpMbox mbox = node.createMbox();
mbox.send("foo@localhost",new OtpErlangAtom("hej"));
</pre>
<p> If you need more control (but less support from the library), you
can manage connections yourself using the {@link
com.ericsson.otp.erlang.OtpSelf} and {@link
com.ericsson.otp.erlang.OtpConnection} classes, in which case you can
control explicitly which connections are made and which messages are
sent. Received messages are not dispatched by {@link
com.ericsson.otp.erlang.OtpConnection}. </p>
<p> The classes {@link com.ericsson.otp.erlang.OtpPeer}, {@link
com.ericsson.otp.erlang.OtpSelf} and {@link
com.ericsson.otp.erlang.OtpServer} are used to represent OTP nodes and
are neccessary in order to set up communication between the Java
thread and a remote node. Once a connection has been established, it
is represented by an {@link com.ericsson.otp.erlang.OtpConnection},
through which all communication goes.
<p> Setting up a connection with a remote node is straightforward. You
create objects representing the local and remote nodes, then call the
local node's {@link
com.ericsson.otp.erlang.OtpSelf#connect(com.ericsson.otp.erlang.OtpPeer)
connect()} method:
<pre>
OtpSelf self = new OtpSelf("client","cookie");
OtpPeer other = new OtpPeer("server");
OtpConnection conn = self.connect(other);
</pre>
<p>If you wish to be able to accept incoming connections as well as
make outgoing ones, you first must register the listen port with EPMD
(described in the Erlang documentation). Once that is done, you can
accept incoming connections:
<pre>
OtpServer self = new OtpSelf("server","cookie");
self.publishPort();
OtpConnection conn = self.accept();
</pre>
<p>Once the connection is established by one of the above methods ({@link
com.ericsson.otp.erlang.OtpSelf#connect(com.ericsson.otp.erlang.OtpPeer)
connect()} or {@link com.ericsson.otp.erlang.OtpSelf#accept()
accept()}), you can use the resulting {@link
com.ericsson.otp.erlang.OtpConnection OtpConnection} to send and
receive messages:
<pre>
OtpErlangAtom msg = new ErlangOtpAtom("hello");
conn.send("echoserver", msg);
OtpErlangObject reply = conn.receive();
System.out.println("Received " + reply);
</pre>
<p> Finally, you can get an even greater level of control (and even
less support from the library) by subclassing {@link
com.ericsson.otp.erlang.AbstractConnection} and implementing the
communication primitives needed by your application. </p>
</body>
</html>
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