Which protocol to use for sending JMS messages?

Question

I need some advise to implement the best protocol (not http, tcp, ...) te send messages.

• Should I send Serialized Objects? (POJO's)
• Should I send technology independent XML messages?
• What would be recommended? Both will work, but what is best practice. Sharing a library is not what I prefer, but is it easy to work with XML? Are there better alternatives? Thanks in advance!

I have one server, with a 1000 clients connected. The server delivers task to the clients. The clients send information back after executing different tasks.

How should I send a task to a JMS client with some parameters?

A task is nothing more than an action and some parameters.

• Example: "action=measure; parameters: duration=100sec; samples=100" --> collect 100 samples during 100 seconds.
• Example: "action=config; parameters: set of configuration parameters" --> to change the client configuration
• Example: "action=stop" --> Stop the client (the system wil restart after a daily reboot)

A report is nothing more than data.

• Example: "list of 100 values from measurement"
• Example: "the content of a log-file"

I have read many articles, but couldn't find an answer for this question. Thanks in advance.

Answer 1

This is our current implementation.

We define a protocol with an XSD and let this generate classes (POJO's). This allows us to marshal/unmarshal the objects and send them as XML objects.

Our XSD:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:jaxb="http://java.sun.com/xml/ns/jaxb"
           jaxb:version="2.0">

    <!-- Ping
        The server will send a ping to a client and waits for a pong.
    ****************************************************************** -->
    <xs:element name="Ping">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="client" type="xs:string"/>
                <xs:element name="message" type="xs:string"/>
            </xs:sequence>
        </xs:complexType>
    </xs:element>

    <!-- Pong
        The client will send a pong back to the server.
    ****************************************************************** -->
    <xs:element name="Pong">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="client" type="xs:string"/>
                <xs:element name="message" type="xs:string"/>
            </xs:sequence>
        </xs:complexType>
    </xs:element>

    <!-- Alive
        The client will send an alive message when it starts up.
        The time is local client time.
    ****************************************************************** -->
    <xs:element name="Alive">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="client" type="xs:string"/>
                <xs:element name="time" type="xs:string"/>
            </xs:sequence>
        </xs:complexType>
    </xs:element>

    <!-- ... Many more message definitions ...
    ****************************************************************** -->

</xs:schema>

Our test class:

public class JaxbFacadeTest {

    @Test
    public void testPing() throws JAXBException, SAXException, UnsupportedEncodingException {
        System.out.println("testPing");
        Ping ping = new Ping();
        ping.setClient("guid-client");
        ping.setMessage("Ping Message");
        String marshalToString = JaxbFacade.getInstance().marshalToString(ping);
        System.out.println(marshalToString);
    }

    @Test
    public void testPong() throws JAXBException, SAXException, UnsupportedEncodingException {
        System.out.println("testPong");
        Pong pong = new Pong();
        pong.setClient("guid-client");
        pong.setMessage("Ping Message");
        String marshalToString = JaxbFacade.getInstance().marshalToString(pong);
        System.out.println(marshalToString);
    }

    @Test
    public void testAlive() throws JAXBException, SAXException, UnsupportedEncodingException {
        System.out.println("testAlive");
        Date now = new Date();
        Alive alive = new Alive();
        alive.setClient("guid-client");
        alive.setTime(now.toString());
        String marshalToString = JaxbFacade.getInstance().marshalToString(alive);
        System.out.println(marshalToString);
    }

    //Many more
}

The classes are generated with maven:

<build>
    <resources>
        <resource>
            <directory>${project.basedir}/src/main/xsd</directory>
            <targetPath>com/test/package/client/jaxb</targetPath>
        </resource>
    </resources>
    <plugins>
        <plugin>
            <groupId>org.jvnet.jaxb2.maven2</groupId>
            <artifactId>maven-jaxb2-plugin</artifactId>
            <executions>
                <execution>
                    <id>jaxb</id>
                    <goals>
                        <goal>generate</goal>
                    </goals>
                </execution>
            </executions>
            <configuration>
                <generatePackage>com.test.package.client.jaxb</generatePackage>
                <schemaDirectory>${project.basedir}/src/main/xsd</schemaDirectory>
            </configuration>
        </plugin>
    </plugins>
</build>