Chapter 86. Basic Session EJB POJO Aspects

EJBs are based on Plain Old Java Objects (POJOs)
Standard POJO rules apply...

86.1. POJO Class

86.1.1. Bean Class

...

public class GreeterEJB implements Greeter {

    private static final Logger logger = LoggerFactory.getLogger(GreeterEJB.class);

...

}

Must not write to static fields. Read-only static fields are allowed (suggests use of final)
Must not use thread synchronization primitives to synchronize execution
Must not manage/manipulate threads, class loaders, or security managers
Must not attempt to become a network server and form a network listen and similar actions
...

86.1.2. Business Method

    @Override

    public String sayHello(String name) throws BadRequestException {

        logger.debug("sayHello({})", name);


        if (name == null || name.isEmpty()) {

            throw new BadRequestException("you must have a name for me to say hello");

        }

        return "hello " + name;

    }

Normal stateless POJO method at this point

86.1.3. Interface

import info.ejava.examples.ejb.basic.dto.Greeting;

import info.ejava.examples.ejb.basic.dto.Name;


public interface Greeter {

    String sayHello(String name) throws BadRequestException;


    Greeting sayHello(Name name) throws BadRequestException;

}

Provides an abstraction of the public class business methods
Some methods use simple/primitive types. Others use complex/custom classes.
All types conveniently defined using Serializable types at this point to permit use of remote interface in future

86.1.4. Serializable DTO

public class Name implements Serializable {

    private String firstName;

    private String lastName;

    ...

public class Greeting implements Serializable {

    private Date date;

    private String message;

    ...

Data abstraction necessary for local and remote interaction
Serializable not necessary until we use this in a remote interface

86.1.5. Business Exceptions

public class BadRequestException extends Exception {

    public BadRequestException(String message) {

        super(message);

    }

}

Checked exceptions used to report business rule failures
Unchecked exceptions used to report infrastructure issues

86.2. POJO Unit Test

86.2.1. JUnit Test Case

import static org.junit.Assert.*;


import info.ejava.examples.ejb.basic.dto.Greeting;

import info.ejava.examples.ejb.basic.dto.Name;

import info.ejava.examples.ejb.basic.ejb.BadRequestException;

import info.ejava.examples.ejb.basic.ejb.Greeter;

import info.ejava.examples.ejb.basic.ejb.GreeterEJB;


import org.junit.Before;

import org.junit.Test;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;


public class GreeterTest {

    private static final Logger logger = LoggerFactory.getLogger(GreeterTest.class);

    private Greeter greeter;


    @Before

    public void setUp() {

        greeter = new GreeterEJB();

    }

    ...

}

Test case used to verify the core functionality of the POJO -- prior to deployment as EJB
Each test case should be independent of another and not depend on a particular order

86.2.2. JUnit Test Method(s)

    @Test

    public void pojoGreeter() throws BadRequestException {

        logger.info("*** pojoGreeter ***");

        String name = "cat inhat";

        String greeting = greeter.sayHello(name);

        assertTrue("greeter did not say my name", greeting.contains(name));

    }

    @Test(expected = BadRequestException.class)

    public void badName() throws BadRequestException {

        logger.info("*** badName ***");

        greeter.sayHello("");

    }

    @Test

    public void dto() throws BadRequestException {

        logger.info("*** dto ***");

        Name name = new Name("thing", "one");

        Greeting greeting = greeter.sayHello(name);

        assertTrue("greeter did not say my name", greeting.getGreeting()

                .contains(name.getFirstName()));

    }

Each test method focused on testing a specific scenario or state
Contains assert statements to verify expected results
Each test method should be independent of another and not depend on a particular order

86.3. POJO Module

86.3.1. Built POJO Archive

Production classes typically deployed in a Java archive (JAR)

$ jar tf target/ejb-basic-ejb-4.0.0-SNAPSHOT.jar 
...
info/ejava/examples/ejb/basic/ejb/BadRequestException.class
info/ejava/examples/ejb/basic/ejb/Greeter.class
info/ejava/examples/ejb/basic/ejb/GreeterEJB.class
info/ejava/examples/ejb/basic/dto/Name.class
info/ejava/examples/ejb/basic/dto/Greeting.class
...

86.3.2. Source POJO Module

|-- pom.xml
`-- src
    |-- main
    |   `-- java
    |       `-- info
    |           `-- ejava
    |               `-- examples
    |                   `-- ejb
    |                       `-- basic
    |                           |-- dto
    |                           |   |-- Greeting.java
    |                           |   `-- Name.java
    |                           `-- ejb
    |                               |-- BadRequestException.java
    |                               |-- GreeterEJB.java
    |                               `-- Greeter.java
    `-- test
        |-- java
        |   `-- info
        |       `-- ejava
        |           `-- examples
        |               `-- ejb
        |                   `-- basic
        |                       `-- pojo
        |                           `-- GreeterTest.java
        `-- resources
            `-- log4j.xml

Module contains separate source trees for production and unit test code

86.4. Unit Test Execution

Unit tests should run with every module build
Unit tests should auto-evaluate themselves so that no human analysis is required

$ mvn clean test                        
...
[INFO] Deleting .../ejb-basic-ejb/target
[INFO] 
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ ejb-basic-ejb ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory .../ejb-basic-ejb/src/main/resources
[INFO] 
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ ejb-basic-ejb ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 5 source files to .../ejb-basic-ejb/target/classes
[INFO] 
[INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ ejb-basic-ejb ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 1 resource
[INFO] 
[INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ ejb-basic-ejb ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 1 source file to .../ejb-basic-ejb/target/test-classes
[INFO] 
[INFO] --- maven-surefire-plugin:2.17:test (default-test) @ ejb-basic-ejb ---
[INFO] Surefire report directory: .../ejb-basic-ejb/target/surefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running info.ejava.examples.ejb.basic.pojo.GreeterTest
16:57:12,237 INFO  (GreeterTest.java:41) -*** dto ***
16:57:12,243 DEBUG (GreeterEJB.java:41) -sayHello(Name [firstName=thing, lastName=one])
16:57:12,249 INFO  (GreeterTest.java:27) -*** pojoGreeter ***
16:57:12,250 DEBUG (GreeterEJB.java:27) -sayHello(cat inhat)
16:57:12,252 INFO  (GreeterTest.java:35) -*** badName ***
16:57:12,255 DEBUG (GreeterEJB.java:27) -sayHello()
Tests run: 3, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.239 sec - in info.ejava.examples.ejb.basic.pojo.GreeterTest

Results :

Tests run: 3, Failures: 0, Errors: 0, Skipped: 0

[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 3.815 s
...

86.5. Maven Aspects: POJO

Basic POJO/JAR pom thus far


<project>

    <modelVersion>4.0.0</modelVersion>



    <groupId>info.ejava.examples.ejb.basicejb</groupId>

    <artifactId>ejb-basic-ejb</artifactId>

    <packaging>jar</packaging>



    <dependencies>

        <!-- core implementation dependencies -->

        <dependency>

            <groupId>org.slf4j</groupId>

            <artifactId>slf4j-api</artifactId>

            <scope>provided</scope>

        </dependency>



        <!-- test dependencies -->

        <dependency>

            <groupId>junit</groupId>

            <artifactId>junit</artifactId>

            <scope>test</scope>

        </dependency>

        <dependency>

            <groupId>org.slf4j</groupId>

            <artifactId>slf4j-log4j12</artifactId>

            <scope>test</scope>

        </dependency>

        <dependency>

            <groupId>log4j</groupId>

            <artifactId>log4j</artifactId>

            <scope>test</scope>

        </dependency>

    </dependencies>

</project>

86.6. Summary

Created module to house POJO bean
Defined a standard POJO bean elements (bean class, interface, exception(s), data class(es))
Defined unit test for POJO bean
Built and tested POJO bean