= CDI Field Producer
:index-group: CDI
:jbake-type: page
:jbake-status: published

This example shows the usage of the @Produces annotation. @Produces is a CDI mechanism which allows defining a source
 for injection. This example shows one of two ways of declaring a producer. Instead of a producer method (see CDI-produces-disposes example)
a producer field can be used. A producer field can be used instead of a simple getter method. It could be used to
inject resources, such as persistence contexts. One caveat to using producer fields over producer
 methods is that a @Disposes method cannot be used in conjunction with @Produces field.

For the purposes of this example, the type is hard-coded to a specific value.
A Logger implementation shall contain a list of LogHandlers. We shall have three implementations of the LogHandler interface.

* A DatabaseHandler
* A FileHandler
* A ConsoleHandler

The DatabaseHandler would seemingly write the logs to a database. The FileHandler would write the same logs to a file.
The ConsoleHandler would just print the logs to a console (Standard out). This example is just an illustration of how
the concepts within CDI work and is not intended to provide a logging framework design/implementation.

== ConsoleHandler

....
package org.superbiz.cdi.produces.field;

public class ConsoleHandler implements LogHandler {

    private String name;

    public ConsoleHandler(String name) {
        this.name = name;
    }

    @Override
    public String getName() {
        return name;
    }

    @Override
    public void writeLog(String s) {
        System.out.printf("##### Handler: %s, Writing to the console!\n", getName());
    }
}
....

== DatabaseHandler

....
package org.superbiz.cdi.produces.field;

public class DatabaseHandler implements LogHandler {

    private String name;

    public DatabaseHandler(String name) {
        this.name = name;
    }

    @Override
    public String getName() {
        return name;
    }

    @Override
    public void writeLog(String s) {
        System.out.printf("##### Handler: %s, Writing to the database!\n", getName());
        // Use connection to write log to database
    }
}
....

== FileHandler

....
package org.superbiz.cdi.produces.field;

public class FileHandler implements LogHandler {

    private String name;

    public FileHandler(String name) {
        this.name = name;
    }

    @Override
    public String getName() {
        return name;
    }

    @Override
    public void writeLog(String s) {
        System.out.printf("##### Handler: %s, Writing to the file!\n", getName());
        // Write to log file
    }
}
....

== LogFactory

....
package org.superbiz.cdi.produces.field;

import javax.enterprise.inject.Produces;

public class LogFactory {

    private int type = 2;

    @Produces
    LogHandler handler;

    public LogFactory(){
    	handler = getLogHandler();
    }

    public LogHandler getLogHandler() {
        switch (type) {
            case 1:
                return new FileHandler("@Produces created FileHandler!");
            case 2:
                return new DatabaseHandler("@Produces created DatabaseHandler!");
            case 3:
            default:
                return new ConsoleHandler("@Produces created ConsoleHandler!");
        }

    }
}
....

== Logger

....
package org.superbiz.cdi.produces.field;

public interface Logger {

    public void log(String s);

    public LogHandler getHandler();
}
....

== LoggerImpl

....
package org.superbiz.cdi.produces.field;

import javax.inject.Inject;
import javax.inject.Named;

@Named("logger")
public class LoggerImpl implements Logger {

    @Inject
    private LogHandler handler;

    @Override
    public void log(String s) {
        getHandler().writeLog(s);
    }

    public LogHandler getHandler() {
        return handler;
    }
}
....

== LogHandler

....
package org.superbiz.cdi.produces.field;

public interface LogHandler {

    public String getName();

    public void writeLog(String s);
}
....

== beans.xml

....
<beans xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
                            http://java.sun.com/xml/ns/javaee/beans_1_0.xsd">

</beans>
....

== LoggerTest

....
package org.superbiz.cdi.produces.field;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import javax.ejb.embeddable.EJBContainer;
import javax.inject.Inject;
import javax.naming.Context;

import static junit.framework.Assert.assertNotNull;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;

public class LoggerTest {

    @Inject
    Logger logger;

    private Context ctxt;

    @Before
    public void setUp() {
        try {
            ctxt = EJBContainer.createEJBContainer().getContext();
            ctxt.bind("inject", this);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @After
    public void cleanUp() {
        try {
            ctxt.unbind("inject");
            ctxt.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Test
    public void testLogHandler() {
        assertNotNull(logger);
        assertFalse("Handler should not be a ConsoleHandler", logger.getHandler() instanceof ConsoleHandler);
        assertFalse("Handler should not be a FileHandler", logger.getHandler() instanceof FileHandler);
        assertTrue("Handler should be a DatabaseHandler", logger.getHandler() instanceof DatabaseHandler);
        logger.log("##### Testing write\n");
        logger = null;
    }

}
....

= Running

....
-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running org.superbiz.cdi.produces.field.LoggerTest
INFO - ********************************************************************************
INFO - OpenEJB http://tomee.apache.org/
INFO - Startup: Thu May 10 01:28:19 CDT 2012
INFO - Copyright 1999-2012 (C) Apache OpenEJB Project, All Rights Reserved.
INFO - Version: 7.0.0-SNAPSHOT
INFO - Build date: 20120510
INFO - Build time: 04:06
INFO - ********************************************************************************
INFO - openejb.home = /home/daniel/projects/openejb/source/openejb/examples/cdi-produces-field
INFO - openejb.base = /home/daniel/projects/openejb/source/openejb/examples/cdi-produces-field
INFO - Created new singletonService org.apache.openejb.cdi.ThreadSingletonServiceImpl@a81b1fb
INFO - succeeded in installing singleton service
INFO - Using 'javax.ejb.embeddable.EJBContainer=true'
INFO - Cannot find the configuration file [conf/openejb.xml].  Will attempt to create one for the beans deployed.
INFO - Configuring Service(id=Default Security Service, type=SecurityService, provider-id=Default Security Service)
INFO - Configuring Service(id=Default Transaction Manager, type=TransactionManager, provider-id=Default Transaction Manager)
INFO - Creating TransactionManager(id=Default Transaction Manager)
INFO - Creating SecurityService(id=Default Security Service)
INFO - Inspecting classpath for applications: 26 urls. Consider adjusting your exclude/include.  Current settings: openejb.deployments.classpath.exclude='', openejb.deployments.classpath.include='.*'
INFO - Searched 26 classpath urls in 2015 milliseconds.  Average 77 milliseconds per url.
INFO - Beginning load: /home/daniel/projects/openejb/source/openejb/examples/cdi-produces-field/target/classes
INFO - Configuring enterprise application: /home/daniel/projects/openejb/source/openejb/examples/cdi-produces-field
INFO - Auto-deploying ejb cdi-produces-field.Comp: EjbDeployment(deployment-id=cdi-produces-field.Comp)
INFO - Configuring Service(id=Default Managed Container, type=Container, provider-id=Default Managed Container)
INFO - Auto-creating a container for bean cdi-produces-field.Comp: Container(type=MANAGED, id=Default Managed Container)
INFO - Creating Container(id=Default Managed Container)
INFO - Using directory /tmp for stateful session passivation
INFO - Enterprise application "/home/daniel/projects/openejb/source/openejb/examples/cdi-produces-field" loaded.
INFO - Assembling app: /home/daniel/projects/openejb/source/openejb/examples/cdi-produces-field
INFO - ignoreXmlConfiguration == true
INFO - ignoreXmlConfiguration == true
INFO - existing thread singleton service in SystemInstance() org.apache.openejb.cdi.ThreadSingletonServiceImpl@a81b1fb
INFO - OpenWebBeans Container is starting...
INFO - Adding OpenWebBeansPlugin : [CdiPlugin]
INFO - All injection points were validated successfully.
INFO - OpenWebBeans Container has started, it took [69] ms.
INFO - Deployed Application(path=/home/daniel/projects/openejb/source/openejb/examples/cdi-produces-field)
##### Handler: @Produces created DatabaseHandler!, Writing to the database!
INFO - Undeploying app: /home/daniel/projects/openejb/source/openejb/examples/cdi-produces-field
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 3.79 sec

Results :

Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
....