The document discusses the business logic layer in Java EE applications. It covers Enterprise JavaBeans (EJBs), which implement business logic and are deployed in an EJB container. Hands-on exercises are presented for creating EJBs to manage book and lending data, including creating entities, EJB classes with CRUD methods, and a singleton class to initialize test data.

1. Andreas Martin - Page 1
Master of Science in Business Information Systems FHNW
Pre-Master Information Systems
4. Business Logic Layer
Andreas Martin
4. Business Logic Layer
http://www.flickr.com/photos/dirk_hofmann/4200450207

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Business Logic Layer
 Enterprise JavaBeans
 Hands-on:
 Hands-on 3: ENTERPRISE JAVA BEANS I
 Hands-on 4: ENTERPRISE JAVA BEANS II
4. Business Logic Layer

3. The Latte Macchiato «Layering» Principle
http://www.flickr.com/photos/tf28/4367660424
Presentation Layer
Goal: Display of information, processing /
forwarding of user interactions.
Technologies: JavaServer Faces (JSF), JavaServer
Pages (JSP), Servlets, etc.
Business (Logic) Layer
Goal: Reproduction of actions or «verbs» of the
application (buy a book, print an order, deliver a
book, etc.).
Technologies: Enterprise Java Beans (EJBs)
Persistence Layer
Goal: Reproduction of database attributes,
information or «nouns» in object / class attributes
(Object-Relational Mapping, ORM).
Technologies: Java Persistence API (JPA)

4. Enterprise JavaBeans
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From the NOUNS to the VERBS…
 Previously we used the NOUNS on persistence layer, like
Books, Customers, Persons, etc…
 …now we are considering the VERBS, like create a book,
deliver a book, buy a book, etc.
 Now it becomes obvious why we talk about Enterprise Java
Beans…
 …because we are going to implement the business logic.
4. Business Logic Layer

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Enterprise Java Bean (EJB) Container
 An EJB is nothing else as a:
 annotated Java object…
 …, which will be deployed
in a container.
 The EJB Container provides:
 Transaction,
 persistence and
 security- management
 …the engineer can focus on
the development of the
business logic.
4. Business Logic Layer
Source: http://java.sun.com/developer/onlineTraining/EJBIntro/EJBIntro.html

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Business
Layer
Java EE 7 – Typical Layering including injected POJO’s
4. Business Logic Layer
Persistence
Layer
@EntityManager
(JPA)
(JPA)@Entity
(JPA)
Session Bean
(EJB)
@PersistenceContext
Presentation
Layer
Facelets(JSF)@ManagedBean
(JSF)
Facelets
(JSF)
Users
Databases
@EJB / @Inject
POJO
@Inject

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Annotations of an EJB
 @Stateless: A «Stateless Bean» does not have a state between
method calls from outside (e.g. a client) – it does not held
data in-memory.
 @Stateful: A «Stateful Bean» does have a state between
method calls e.g. from a client.
 @Singleton: A «Singleton Bean» (or Single Session Bean) exists
only once as object.
4. Business Logic Layer

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Simple Stateless EJB
4. Business Logic Layer
Listing: A Simple Stateless EJB
@Stateless
public class BookEJB {
@PersistenceContext(unitName = "primary")
private EntityManager em;
public Book findBookById(Long id) {
return em.find(Book.class, id);
}
public Book createBook(Book book) {
em.persist(book);
return book;
}
}

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@Startup and @Singleton Style
Dirty Java EE Testing
4. Business Logic Layer

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@Startup and @Singleton Style - Example
4. Business Logic Layer
@Singleton
@Startup
public class BookStartupSingletonTest {
@EJB
private BookEJBLocal bookEJBLocal;
@PostConstruct
void init() {
try {
shouldCreateABook();
} catch (Exception ex) {
Logger.getLogger(BookTestEJB.class.getName()).log(Level.SEVERE,
null, ex);
}
}
public void shouldCreateABook() throws Exception {
Book book = new Book();
book.setTitle("Hello");
book.setPrice(12.5F);
book.setDescription("Science fiction comedy book");
book.setIsbn("1-84023-742-2");
book.setNbOfPage(354);
book.setIllustrations(false);
book = bookEJBLocal.createBook(book);
assertNotNull("ID should not be null", book.getId());
List<Book> books = bookEJBLocal.findBooks();
assertNotNull(books);
}
}

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Hands-on 3
ENTERPRISE JAVA BEANS I
4. Business Logic Layer
Based on: Goncalves, 2010: Beginning Java™ EE 6 Platform with GlassFish™ 3

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Database Connection
…will be used for the next hands-on’s
 Modify the MySQL_premscis-ds.xml file:
 When using a Web Project in Eclipse, it is possible to deploy a datasource using a JBoss
datasource file (…-ds.xml)
 This file must be placed under:
Project
+---srcmainwebappWEB-INF
¦ faces-config.xml
¦ jboss-web.xml
¦ MySQL_premscis-ds.xml
 Choose another student ‘number’ (DatabaseName) to avoid overwriting.
4. Business Logic Layer
<?xml version="1.0" encoding="UTF-8"?>
<datasources xmlns="http://www.jboss.org/ironjacamar/schema">
<datasource jta="true" jndi-name="java:jboss/datasources/MySQL_premscis" enabled="true"
use-java-context="true" pool-name="MySQL_premscis">
<connection-url>jdbc:mysql://mature.iwi.wirtschaft.fhnw.ch:80/premscis</connection-url>
<driver>mysql-connector-java-5.1.32-bin.jarcom.mysql.jdbc.Driver_5_1</driver>
<pool></pool>
<security>
<user-name>premscis</user-name>
<password>premscis</password>
</security>
</datasource>
</datasources>

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Hands-on 3
1. Import project «Hands-on-3» and…
2. …create a «Book» entity with the following attributes (id,
title, price, description, isbn, numberOfPages und
illustrations)
3. Extend the «Book» entity with the following two
NamedQueries: findAllBooks und findAllBooksById
4. Business Logic Layer

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Hands-on 3
4. Create a «BookEJB».
5. …and implement the following methods: findBooks, findBookById,
createBook, deleteBook und updateBook.
6. Write a @Startup - @Singleton, which creates and retrieves a book
from database.
4. Business Logic Layer
@Singleton
@Startup
public class BookStartupSingletonTest {
@EJB
private BookEJB bookEJBLocal;
@PostConstruct
void init() {
try { shouldCreateABook();
} catch (Exception ex) { ex.printStackTrace();
}
}
public void shouldCreateABook() throws Exception {
Book book = new Book();
book.setTitle("HelloNew");
book.setPrice(12.5F);
book.setDescription("Science fiction comedy book");
book.setIsbn("1-84023-742-2");
book.setNbOfPage(354);
book.setIllustrations(false);
book = bookEJBLocal.createBook(book);
assertNotNull("ID should not be null", book.getId());
List<Book> books = bookEJBLocal.findBooks();
assertNotNull(books);
}}

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Hands-on 4
ENTERPRISE JAVA BEANS II
4. Business Logic Layer

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Book EJBCustomer EJB
Business cases:
• Create a customer including address
• …CRUD…
Book Lending EJB
Hands-on 4
 Now in «Hands-on-4» we create an EJB based application for
lending books.
 Primary we represent the following business use cases: the
lending, retrieval and returning of books.
4. Business Logic Layer
<Entity>
Address
<Entity>
Customer
<Entity>
Book Lending
<Entity>
Book
n 1 0..1 0..1 1
Business cases:
• Lend a book
• Return a book
• Show all lendings
Business cases:
• Create a book
• …CRUD..
1

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Hands-on 4
1. Import the «Hands-on-4» project.
2. Create the following entities Customer, Address and Book.
Can you read the cardinalities? What does that mean?
3. Create a BookLending entity with the following attributes:
Customer, Book, LendingDate, ReturnDate,
nbOfDaysToReturn and bookIsLended.
4. Business Logic Layer
Book EJBCustomer EJB
Business cases:
• Create a customer including address
• …CRUD…
Book Lending EJB
<Entity>
Address
<Entity>
Customer
<Entity>
Book Lending
<Entity>
Book
n 1 0..1 0..1 1
Business cases:
• Lend a book
• Return a book
• Show all lendings
Business cases:
• Create a book
• …CRUD..
1

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Hands-on 4
4. Write for the Customer and Book entity a corresponding EJB.
5. Write a Lending EJB that convers the use cases.
6. And finally write a @Startup - @Singleton and create test
data.
4. Business Logic Layer
Book EJBCustomer EJB
Business cases:
• Create a customer including address
• …CRUD…
Book Lending EJB
<Entity>
Address
<Entity>
Customer
<Entity>
Book Lending
<Entity>
Book
n 1 0..1 0..1 1
Business cases:
• Lend a book
• Return a book
• Show all lendings
Business cases:
• Create a book
• …CRUD..
1

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Hands-on 4
 Domain model:
 Business logic model:
4. Business Logic Layer