MINA Component

The mina: component is a transport for working with Apache MINA

Maven users will need to add the following dependency to their pom.xml for this component:

<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-mina</artifactId>
    <version>x.x.x</version>
    <!-- use the same version as your Camel core version -->
</dependency>

URI format

mina:tcp://hostname[:port][?options]
mina:udp://hostname[:port][?options]
mina:vm://hostname[:port][?options]

From Camel 1.3 onwards you can specify a codec in the Registry using the codec option. If you are using TCP and no codec is specified then the textline flag is used to determine if text line based codec or object serialization should be used instead. By default the object serialization is used.

For UDP if no codec is specified the default uses a basic ByteBuffer based codec.

The VM protocol is used as a direct forwarding mechanism in the same JVM. See the MINA VM-Pipe API documentation for details.

A Mina producer has a default timeout value of 30 seconds, while it waits for a response from the remote server.

In normal use, camel-mina only supports marshalling the body content—message headers and exchange properties are not sent.
However, the option, transferExchange, does allow you to transfer the exchange itself over the wire. See options below.

You can append query options to the URI in the following format, ?option=value&option=value&...

Options

Option Default Value Description
codec null As of 1.3, you can refer to a named ProtocolCodecFactory instance in your Registry such as your Spring ApplicationContext, which is then used for the marshalling.
codec null Camel 2.0: You must use the # notation to look up your codec in the Registry. For example, use #myCodec to look up a bean with the id value, myCodec.
disconnect false Camel 2.3: Whether or not to disconnect(close) from Mina session right after use. Can be used for both consumer and producer.
textline false Only used for TCP. If no codec is specified, you can use this flag in 1.3 or later to indicate a text line based codec; if not specified or the value is false, then Object Serialization is assumed over TCP.
textlineDelimiter DEFAULT Camel 1.6.0/2.0 Only used for TCP and if textline=true. Sets the text line delimiter to use. Possible values are: DEFAULT, AUTO, WINDOWS, UNIX or MAC. If none provided, Camel will use DEFAULT. This delimiter is used to mark the end of text.
sync false/true As of 1.3, you can configure the exchange pattern to be either InOnly (default) or InOut. Setting sync=true means a synchronous exchange (InOut), where the client can read the response from MINA (the exchange Out message). The default value has changed in Camel 1.5 to true. In older releases, the default value is false.
lazySessionCreation See description As of 1.3, sessions can be lazily created to avoid exceptions, if the remote server is not up and running when the Camel producer is started. From Camel 2.0 onwards, the default is true. In Camel 1.x, the default is false.
timeout 3000 As of 1.3, you can configure the timeout that specifies how long to wait for a response from a remote server. The timeout unit is in milliseconds, so 60000 is 60 seconds. The timeout is only used for Mina producer.
encoding JVM Default As of 1.3, you can configure the encoding (a charset name) to use for the TCP textline codec and the UDP protocol. If not provided, Camel will use the JVM default Charset.
transferExchange false Only used for TCP. As of 1.3, you can transfer the exchange over the wire instead of just the body. The following fields are transferred: In body, Out body, fault body, In headers, Out headers, fault headers, exchange properties, exchange exception. This requires that the objects are serializable. Camel will exclude any non-serializable objects and log it at WARN level.
minaLogger false As of 1.3, you can enable the Apache MINA logging filter. Apache MINA uses slf4j logging at INFO level to log all input and output.
filters null As of 2.0, you can set a list of Mina IoFilters to register. The filters value must be one of the following:
  • Camel 2.2: comma-separated list of bean references (e.g. #filterBean1,#filterBean2) where each bean must be of type org.apache.mina.common.IoFilter.
  • Camel 2.0: a reference to a bean of type List<org.apache.mina.common.IoFilter>.
encoderMaxLineLength -1 As of 2.1, you can set the textline protocol encoder max line length. By default the default value of Mina itself is used which are Integer.MAX_VALUE.
decoderMaxLineLength -1 As of 2.1, you can set the textline protocol decoder max line length. By default the default value of Mina itself is used which are 1024.
producerPoolSize 16 1.6.2 (only in 1.6.x): The TCP producer is now thread safe and supports concurrency much better. This option allows you to configure the number of threads in its thread pool for concurrent producers. Note: Camel 2.0 have a pooled service which ensured it was already thread safe and supported concurrency already. So this is a special patch for 1.6.x.
allowDefaultCodec true The mina component installs a default codec if both, codec is null and textline is false. Setting allowDefaultCodec to false prevents the mina component from installing a default codec as the first element in the filter chain. This is useful in scenarios where another filter must be the first in the filter chain, like the SSL filter.
disconnectOnNoReply true Camel 2.3: If sync is enabled then this option dictates MinaConsumer if it should disconnect where there is no reply to send back.
noReplyLogLevel WARN Camel 2.3: If sync is enabled this option dictates MinaConsumer which logging level to use when logging a there is no reply to send back. Values are: FATAL, ERROR, INFO, DEBUG, OFF.

Default behavior changed

In Camel 2.0 the codec option must use # notation for lookup of the codec bean in the Registry.
In Camel 2.0 the lazySessionCreation option now defaults to true.

In Camel 1.5 the sync option has changed its default value from false to true, as we felt it was confusing for end-users when they used MINA to call remote servers and Camel wouldn't wait for the response.

In Camel 1.4 or later codec=textline is no longer supported. Use the textline=true option instead.

Using a custom codec

See the Mina documentation how to write your own codec. To use your custom codec with camel-mina, you should register your codec in the Registry; for example, by creating a bean in the Spring XML file. Then use the codec option to specify the bean ID of your codec. See HL7 that has a custom codec.

Sample with sync=false

In this sample, Camel exposes a service that listens for TCP connections on port 6200. We use the textline codec. In our route, we create a Mina consumer endpoint that listens on port 6200:

from("mina:tcp://localhost:" + port1 + "?textline=true&sync=false").to("mock:result");

As the sample is part of a unit test, we test it by sending some data to it on port 6200.

MockEndpoint mock = getMockEndpoint("mock:result");
mock.expectedBodiesReceived("Hello World");

template.sendBody("mina:tcp://localhost:" + port1 + "?textline=true&sync=false", "Hello World");

assertMockEndpointsSatisfied();

Sample with sync=true

In the next sample, we have a more common use case where we expose a TCP service on port 6201 also use the textline codec. However, this time we want to return a response, so we set the sync option to true on the consumer.

from("mina:tcp://localhost:" + port2 + "?textline=true&sync=true").process(new Processor() {
    public void process(Exchange exchange) throws Exception {
        String body = exchange.getIn().getBody(String.class);
        exchange.getOut().setBody("Bye " + body);
    }
});

Then we test the sample by sending some data and retrieving the response using the template.requestBody() method. As we know the response is a String, we cast it to String and can assert that the response is, in fact, something we have dynamically set in our processor code logic.

String response = (String)template.requestBody("mina:tcp://localhost:" + port2 + "?textline=true&sync=true", "World");
assertEquals("Bye World", response);

Sample with Spring DSL

Spring DSL can, of course, also be used for MINA. In the sample below we expose a TCP server on port 5555:

   <route>
     <from uri="mina:tcp://localhost:5555?textline=true"/>
     <to uri="bean:myTCPOrderHandler"/>
  </route>

In the route above, we expose a TCP server on port 5555 using the textline codec. We let the Spring bean with ID, myTCPOrderHandler, handle the request and return a reply. For instance, the handler bean could be implemented as follows:

    public String handleOrder(String payload) {
        ...
        return "Order: OK"
   }

Configuring Mina endpoints using Spring bean style

Available as of Camel 2.0

Configuration of Mina endpoints is now possible using regular Spring bean style configuration in the Spring DSL.

However, in the underlying Apache Mina toolkit, it is relatively difficult to set up the acceptor and the connector, because you can not use simple setters. To resolve this difficulty, we leverage the MinaComponent as a Spring factory bean to configure this for us. If you really need to configure this yourself, there are setters on the MinaEndpoint to set these when needed.

The sample below shows the factory approach:

<!-- Creating mina endpoints is a bit complex so we reuse MinaComponnet
     as a factory bean to create our endpoint, this is the easiest to do -->
<bean id="myMinaFactory" class="org.apache.camel.component.mina.MinaComponent">
    <!-- we must provide a camel context so we refer to it by its id -->
    <constructor-arg index="0" ref="myCamel"/>
</bean>

<!-- This is our mina endpoint configured with spring, we will use the factory above
     to create it for us. The goal is to invoke the createEndpoint method with the
     mina configuration parameter we defined using the constructor-arg option -->
<bean id="myMinaEndpoint"
      factory-bean="myMinaFactory"
      factory-method="createEndpoint">
    <!-- and here we can pass it our configuration -->
    <constructor-arg index="0" ref="myMinaConfig"/>
</bean>

<!-- this is our mina configuration with plain properties -->
<bean id="myMinaConfig" class="org.apache.camel.component.mina.MinaConfiguration">
    <property name="protocol" value="tcp"/>
    <property name="host" value="localhost"/>
    <property name="port" value="1234"/>
    <property name="sync" value="false"/>
</bean>

And then we can refer to our endpoint directly in the route, as follows:

<route>
    <!-- here we route from or mina endpoint we have defined above -->
    <from ref="myMinaEndpoint"/>
    <to uri="mock:result"/>
</route>

Closing Session When Complete

Available as of Camel 1.6.1

When acting as a server you sometimes want to close the session when, for example, a client conversion is finished. To instruct Camel to close the session, you should add a header with the key CamelMinaCloseSessionWhenComplete set to a boolean true value.

For instance, the example below will close the session after it has written the bye message back to the client:

        from("mina:tcp://localhost:8080?sync=true&textline=true").process(new Processor() {
            public void process(Exchange exchange) throws Exception {
                String body = exchange.getIn().getBody(String.class);
                exchange.getOut().setBody("Bye " + body);
                exchange.getOut().setHeader(MinaConstants.MINA_CLOSE_SESSION_WHEN_COMPLETE, true);
            }
        });

Get the IoSession for message

Available since Camel 2.1
You can get the IoSession from the message header with this key MinaEndpoint.HEADER_MINA_IOSESSION, and also get the local host address with the key MinaEndpoint.HEADER_LOCAL_ADDRESS and remote host address with the key MinaEndpoint.HEADER_REMOTE_ADDRESS.

Configuring Mina filters

Available since Camel 2.0

Filters permit you to use some Mina Filters, such as SslFilter. You can also implement some customized filters. Please note that codec and logger are also implemented as Mina filters of type, IoFilter. Any filters you may define are appended to the end of the filter chain; that is, after codec and logger.

For instance, the example below will send a keep-alive message after 10 seconds of inactivity:

public class KeepAliveFilter extends IoFilterAdapter {
    @Override
    public void sessionCreated(NextFilter nextFilter, IoSession session)
            throws Exception {
        session.setIdleTime(IdleStatus.BOTH_IDLE, 10);

        nextFilter.sessionCreated(session);
    }

    @Override
    public void sessionIdle(NextFilter nextFilter, IoSession session,
            IdleStatus status) throws Exception {
        session.write("NOOP"); // NOOP is a FTP command for keep alive
        nextFilter.sessionIdle(session, status);
    }
}

As Camel Mina may use a request-reply scheme, the endpoint as a client would like to drop some message, such as greeting when the connection is established. For example, when you connect to an FTP server, you will get a 220 message with a greeting (220 Welcome to Pure-FTPd). If you don't drop the message, your request-reply scheme will be broken.

public class DropGreetingFilter extends IoFilterAdapter {

    @Override
    public void messageReceived(NextFilter nextFilter, IoSession session,
            Object message) throws Exception {
        if (message instanceof String) {
            String ftpMessage = (String) message;
            // "220" is given as greeting. "200 Zzz" is given as a response to "NOOP" (keep alive)
            if (ftpMessage.startsWith("220") || or ftpMessage.startsWith("200 Zzz")) {
                // Dropping greeting
                return;
            }
        }
        nextFilter.messageReceived(session, message);
    }
}

Then, you can configure your endpoint using Spring DSL:

<bean id="myMinaFactory" class="org.apache.camel.component.mina.MinaComponent">
    <constructor-arg index="0" ref="camelContext" />
</bean>

<bean id="myMinaEndpoint"
      factory-bean="myMinaFactory"
      factory-method="createEndpoint">
    <constructor-arg index="0" ref="myMinaConfig"/>
</bean>

<bean id="myMinaConfig" class="org.apache.camel.component.mina.MinaConfiguration">
    <property name="protocol" value="tcp" />
    <property name="host" value="localhost" />
    <property name="port" value="2121" />
    <property name="sync" value="true" />
    <property name="minaLogger" value="true" />
    <property name="filters" ref="listFilters"/>
</bean>

<bean id="listFilters" class="java.util.ArrayList" >
    <constructor-arg>
        <list value-type="org.apache.mina.common.IoFilter">
            <bean class="com.example.KeepAliveFilter"/>
            <bean class="com.example.DropGreetingFilter"/>
        </list>
    </constructor-arg>
</bean>

See Also

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