Java EE web project introduction

Contents
● Java EE project setup
● Introduction to Maven
● Web application structure
● JSF basics
● CDI basics
● GIT overview (optional)

Java EE project setup in Eclipse
Prerequisites:
● Eclipse Luna
● WildFly application server
● Maven support in Eclipse - m2eclipse
● Git support in Eclipse eGIT
● JBoss Tools for Eclipse
● Download prepared sources from GitHub

Java EE project setup in Netbeans
Prerequisites:
● Netbeans 7 or 8
● Glassfish application server
● Download prepared sources from GitHub

DEMO
Presentation of the demo application in IDE
and running on app server

Introduction to Maven
● project build and configuration tool
● it can:
o execute build tasks using command line
o automatically download necessary libriaries
(dependencies)
o configure project independently from IDE

Introduction to Maven - artifacts
Artifacts are files produced by a maven build.
They are specified by:
● groupId
● artifactId
● version
● packaging - JAR, WAR, EJB, EAR, POM, ...
An artifact can be dependency of another module

Maven - goals and phases
To execute maven build: > mvn goal
Goal can be a name of phase that we want to complete. All phases before that
phase are completed in order.
The order of basic maven phases:
compile, test, package, integration-test, install
Steps to complete each phase may differ between module
types (packging)

Maven - dependencies
Specified by: groupId, artifactId, version, type
(jar is default type)
Scope of a dependency:
● compile (default)
● test - only used when running unit tests
● provided - not included in artifact

DEMO
Example of Maven pom.xml.
Example of running maven in IDE.

Java EE Web application
In simplest for a single WAR file.
● WEB-INF folder
o web.xml
o faces-config.xml
o optionally beans.xml for CDI
o classes folder with compiled java classes
● web resources in root folder
o JSF facelets, css, images, etc.

WAR Maven module
Single module of type WAR
● pom.xml specifies:
o packaging WAR
o dependency on javaee-api (scope=provided)
● src/main/java - java sources
● src/main/webapp - Web resources
● src/main/resources - classpath resources

JSF overview
● run by FacesServlet mapped in web.xml
● configured by faces-config.xml and contex
parameters in web.xml
● FacesServlet executes several phases in
MVC style
o Request -> Execute code in Java Bean -> Create
view from Facelet -> Response

JSF lifecycle
● Restore view phase
● Apply request values phase; process events
● Process validations phase; process events
● Update model values phase; process events
● Invoke application phase; process events
● Render response phase

JSF component tree
● logical tree of UI components
● created from a definition in facelet
● encoded to xhtml at the end of the request
o to bring new state of the view to browser (new page)
● recreated at the begining of the request
o to represent the current state of the view before
request is processed

JSF Facelets
● XHTML based templates for a web page
● define components in a component tree
● specify binding to Java code
o data
o conditional rendering
o controller methods / listeners

JSF Managed Beans
● provide controller methods and data model
for facelets
● bound to component properties using
Expression Language
● identified in facelets by textual name
● marked by @Named CDI qualifier

Expression language
EL is a script used in facelets to bind values to
component properties
● Results in a value - primitive values, object,
even a method pointer
● Fields are converted to getters and setters
● Never throws a Null Pointer -> blank value
instead

Usage of Expression language
● enclosed in #{ ... }
● do not mix with ${ … } used in JSP
o JSP and JSTL tags should not be mixed with JSF
● in facelet: rendered="#{ bookView.displayed }
● in BookView bean:
@Named class BookView {
public boolean isDisplayed() { return true; }
}

Basic components - display
● h:outputText - textual output in <span>
● h:outputLabel - <label>
● h:outputLink - <a href…>
● h:messages - display of JSF messages
● h:graphicImage - <img>
● h:dataTable - table for collection of rows

Basic components - layout
● h:panelGroup - container - <span> or <div>
● h:panelGrid - grid layout container (table)

Basic components - Forms
● h:inputText
● h:inputTextarea
● h:selectManyListbox, h:selectOneMenu, etc.
- selection components, listboxes,
checkboxes
● h:form - all input components must be in
some form to function

Basic components - actions
● All action components submit form and call
action on web server via javascript
● They accept link to a listener method
● h:commandButton
● h:commandLink

Contexts & Dependency Injection
● Injection: instead of myVar = Factory.getVar()
or myVar = new Var() declare that I need Var
● @Inject Var myVar
● instance of Var is created by the container
● works only in container managed beans
o JSF beans, Servlets, EJBs, all injected beans -
generally Java objects created by the container

Dependency injection rules
● never use “new” on a bean with a CDI
dependency
● all injected beans must have constructor
without parameters
● do not put initialization to constructor but to
method marked with @PostConstruct

Lifecycle of injected beans
● when bean created
o constructor is executed first
o then are dependencies injected
o method marked with @PostConstruct is called
● during injection, beans are either created or
reused
o it depends on current context of execution and
scope of injected bean

Basic scopes
● Dependent (default)
o a new bean is always created for injection
o similar to calling constructor directly
● Application scope
o single bean is created for whole application
o the same bean is reused afterwards, retaining its
complete state
o singleton pattern

Basic Java EE scopes
Most scopes are bound to a lifecycle of a
specific action
● Request scope
o bound to lifecycle of HTTP request
o within HTTP request, only single instance of request
scoped bean is created and reused
● Session scope
o bound to lifecycle of HTTP session

Java EE scope annotations
package javax.enterprise.context:
● Dependent (optional)
● ApplicationScoped
● RequestScoped
● SessionScoped
Only single instance of Java object with defined scope is created and
reused for single application, request, session

Dependency declaration
● inject by class
o inject instance of the class or its subclass
● inject by interface
o inject instance of java class with given interface
● inject by qualifier
o inject instance with given qualifier
o qualifier is a java annotation marked with @Qualifier
For one injection point, one class should match

Runtime / conditional injection
@Inject Instance<Var> myVarInjector;
…
myVar = myVarInjector.get();
● matching bean is resolved when necessary
● can be injected directly when needed
● resolution errors can be treted at runtime

Creating new CDI beans
● possible to create a completely new CDI
bean regardless of context
● @New annotation overrides bean scope
● can be used instead of new keyword:
@Inject @New Instance<Var> varInjector;
...Var myVar1 = varInjector.get();
...Var myVar2 = varInjector.get();

Producers
● CDI usually creates new beans via
constructor without parameters
● Producers allow to customize creation
● instead of a class, a method of a producer is
marked with annotations and scope
o this method returns created bean of matching type
o it is called when bean with the same definition is
requested

Producers - example
class MyVarProducer {
@Produces @RequestScoped
public Var createVar(@New Var var) {
var.setState("NEW");
return var;
}
}

Introduction to GIT
GIT is a source code version control system.
It is a distributed version control system.
● multiple repositories can be interconnected
and synchronized

GIT repository
● single instance of storage of versioned files
● stores latest version of files, history of
changes, metadata (commit messages), and
connection to other upstream repositories
● repositories are organized in a tree
o from upstream repositories to downstream

Simplest GIT topology
● Central GIT repository - accesible via public
link
o local GIT repository
● Local repositories exist only on local
computers
o they are created from central using clone command

2-step synchronisation
● clone - downloads new copy of repository
● edit files
o add (add new files if created)
o edited and removed files are already handled
● commit - save changes locally (checkpoint)
● pull - download changes from central repo
o merge and resolve conflicting changes
o commit if files changed
● push - upload locally commited changes

Java EE web project introduction

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