An application client is a client program that runs on a JVM that is different from the server.

An application client calls and executes the main() method and runs until the JVM terminates. Like other Java EE application components, an application client also runs in a client container that provides system services, but the container uses less system resources than other Java EE containers. It provides the environment in which Java EE services offered by JEUS can be provided for a general client application.

The services include scheduler, security, JNDI, and other services with which users can use the application components (EJB) and system resources (JDBC data source, JMS connection factory, etc.) that are bound to JEUS via JNDI.

[Figure 1.1] Application Client Architecture

Like other Java programs, an application client must have the main method that is declared in the public class.

The following example is written in Java EE 7 style, and calls EJB via injection. (refer to the ${JEUSHOME}/samples/client/hello/hello-client).

package helloejb;

import java.io.*;
import javax.ejb.EJB;

public class HelloClient {
    @EJB(mappedName="helloejb.Hello")
    private static Hello hello;
    
    public static void main(String[] args) {
        System.out.println("EJB output : " + hello.sayHello());
    }
}

A deployment descriptor (hereafter, DD) can be created in the following two ways:

If needed for creating a DD, create the jeus-client-dd.xml file before JEUS deploys the client module.

The following example shows an XML file that creates a DD.

Environment variables used by the client, a name to which the EJB application is bound, a name of the bound JDBC datasource, and a JNDI binding name for the JMS queue are specified in the XML file. Except for the environment variables, specify <export-name> as the JNDI name which is actually bound to <ref-name> in the application-client.xml file.

<jeus-client-dd>
    <env>
        <name>year</name>
        <type>java.lang.Integer</type>
        <value>2002</value>
    </env>
    <ejb-ref>
        <jndi-info>
            <ref-name>count</ref-name>
            <export-name>count_bean</export-name>
        </jndi-info>
    </ejb-ref>
    <res-ref>
        <jndi-info>
            <ref-name>datasource</ref-name>
            <export-name>Oracle_DataSource</export-name>
        </jndi-info>
    </res-ref>
    <res-env-ref>
        <jndi-info>
            <ref-name>jms/SalaryInfo</ref-name>
            <export-name>jms/salary_info_queue1</export-name>
        </jndi-info>
    </res-env-ref>
</jeus-client-dd>

To execute an application client module in the console, use appclient. The appclient script is located under the JEUS_HOME\bin directory, and executes an application client module through a client container.

The command line for JEUS client container is as follows: