2014 Pre-MSc-IS-4 Business Logic Layer

Andreas Martin - Page 1

Master of Science in Business Information Systems FHNW Pre-Master Information Systems

4. Business Logic Layer

Andreas Martin


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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


The Latte Macchiato «Layering» Principle

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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)

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.



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.


Source: http://java.sun.com/developer/onlineTraining/EJBIntro/EJBIntro.html


Business Layer

Java EE 7 – Typical Layering including injected POJO’s


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


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.



Simple Stateless EJB


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; }

}


@Startup and @Singleton Style Dirty Java EE Testing



@Startup and @Singleton Style - Example


@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); } }


Hands-on 3 ENTERPRISE JAVA BEANS I


Based on: Goncalves, 2010: Beginning Java™ EE 6 Platform with GlassFish™ 3


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 +---src\main\webapp\WEB-INF ¦ faces-config.xml ¦ jboss-web.xml ¦ MySQL_premscis-ds.xml

Choose another student ‘number’ (DatabaseName) to avoid overwriting.


<?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>


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



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.


@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); }}


Hands-on 4 ENTERPRISE JAVA BEANS II



Book EJB Customer 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.


<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


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.




Book Lending EJB

<Entity> Address

<Entity> Customer


<Entity> Book

n 1 0..1 0..1 1



1


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.




Book Lending EJB

<Entity> Address

<Entity> Customer


<Entity> Book

n 1 0..1 0..1 1



1


Hands-on 4

Domain model:

Business logic model:


Date post:	13-Jul-2015
Category:	Technology
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2014 Pre-MSc-IS-4 Business Logic Layer

Technology