Spring Framework - Basics - Web Application...

Spring Framework - BasicsWeb Application Development

Zsolt Tóth

University of Miskolc

2017

Zsolt Tóth (University of Miskolc) Spring Framework - Basics 2017 1 / 31

Instantiation

Table of Contents

1 Instantiation

2 Dependency Injection

3 Spring Core


Instantiation

Static Type vs. Dynamic Type

Collection<User> users = new ArrayList<User>();

Static TypeType DeclarationDefines

MethodsIntentionLimits Behavior

Could beClassAbstract ClassInterface

Dynamic TypeInstantiationActual TypeDetermine Behaviorinstanceof Static Type

implementsextends

Can be Instantiated.


Instantiation

Inheritance and Implementation

InheritanceSpecificationClass Extension

FieldsMethods

@Override

Only One Parentabstract

final

ImplementationInterfaceBehavior Only

Return TypeNameParametersExceptions

? JavaDoc

Public Methods and ServicesAbstract Methods

Java 8 default


Instantiation

Abstraction

Liskov Substitution PrincipleGeneral ↔ AbstractExpected BehaviorVarious ImplementationStatic Type should be

as abstract as possible.as specific as necessary.

Collection<User> users =new ArrayList<User>();

List<User> users = newArrayList<User>();

ArrayList<User> users =new ArrayList<User>();


Instantiation

new Operator

Creates an ObjectMemory AllocationInvoke ConstructorInitialize Object

CostlyIssues

Hard Code Dynamic TypeWhen use?Where use?Testing

class Rectanble{private Point p1,p2;

Rectangle(Point p1,Point p2){

this.p1 = p1;this.p2 = p2;

}}


Instantiation

new Operator

Rectangle r = new Rectangle(0,0,1,1);/* whereRectangle(double p1x,double p1y,..){this.p1 = new Point(p1x,p1y); ...}

*///orPoint p1 = new Point(0,0);Point p2 = new Poit(1,1);Rectangle r = new Rectangle(p1,p2);//orRectangle r = new Rectangle(

new Point(0,0),new Point(1,1);

);


Instantiation

Instantiation vs. Usage

InstantiationCostly

Resource AllocationMemory Allocation

Takes TimeEstablish NetworkConnection

Could be DifficultTons of ParametersJDBC

Defines Dynamic Type

UsageUse Object via MethodsDepends on ExpectedBehavior

Static TypeInterface Required

Should not Create Object.Dynamic Type could beChangedReusability

Object creation and usage should be separated!


Instantiation

Consequences

ProInstantiation could be Centralized.Testing Become Easier.

See "Software Projects & Testing" subject.

Increase Reusability.More General Code

QuestionHow will we get the dependencies?


Dependency Injection

Table of Contents

1 Instantiation


3 Spring Core



Participants

service an object that will be usedclient object that uses the service

interface defines how the client uses the service

injector creates the service and gives it into the client.

GoalSeparation of the creation of the client’s dependencies from theclient’s behavior.



Types of Dependency Injection

Field InjectionDependency Injection Frameworks knowShould not be used.Reflection

Constructor InjectionDependencies are Passed as Constructor ArgumentsCannot Create object when a Dependency is MissingMandatory Dependencies

Setter InjectionSetter Methods are Invoked After Constructor UsedOptional Dependencies



Constructor Injection

Mandatory DependenciesPart of Client InitializationBlock the Client’sFunctionalityExamples

Database Access

class Client{private

MandatoryService ms;private OptionalService

os;public

Client(MandatoryServicems){

this.ms = ms;}}



Setter Injection

Optional DependenciesNot Required for the ClientExtends, Enhance itsFunctionsExamples

LoggingPublishing Event

class Client{private

MandatoryService ms;private OptionalService

os;public

setOptionalService(OptionalService os ){

this.os = os;}}



Typical Service Categories

StorageDatabase Access Objects

Business LogicOther FunctionsMicro Services

3rd Party ServicesSystem Integration"Distributed Systems" subject in MSc.Social MediaCurrency Changewww.programmableweb.com


www.programmableweb.com


Consequences

+ Flexibility and Configurability+ Refactoring+ Increase Abstractness+ Cleaner Code+ Independent Development+ Facilitates Testing and Mocking- Configuration Required- Difficult to Understand- Dependency Injection Framework is Required


Spring Core

Table of Contents

1 Instantiation


3 Spring Core


Spring Core

Spring Framework

JavaCurrent Version 4.3Open SourceInversion of ControlFramework

Core, AOP, DataWeb, WebMVCIntegration, Cloud

<dependency><groupId>org.springframework</groupId><artifactId>spring-core</artifactId><version>4.3.9.RELEASE</version></dependency>


Spring Core

Spring Projects


Spring Core

Core Elements

CoreBasic TasksResource Finding

BeansBean DefinitionXML Mappingspring-beans-x.x.xsd

ContextApplicationContext

SpELSpring Expression LanguageText EvaluationXML based Bean Definition

#{string expr.}

#{systemProperties[’user’]}#{T(java.lang.Math).random()}


Spring Core

ApplicationContext

interface

Bean factory methodsLoad file resourcesPublish eventsResolve messagesSupport internationalization.Context inheritance

Super InterfacesBeanFactoryResourceLoader

ImplementationsAnnotation Config ApplicationContextClassPath Xml ApplicationContextXml Web Application Context


Spring Core

BeanFactoryinterface

Bean ContainerRegistry of ApplicationComponentsImplementations (27)

XMLAnnotation

BeanObjectString IDDependencyTypes

PrototypeSingleton

containsBean(String)

getBean(String)

getBean(Class<T>)

isPrototype(String)

isSingleton(String)

isTypeMatch(String,Class<T>)


Spring Core

Bean Life-cycle

1 BeanNameAware’ssetBeanName

2 BeanClassLoaderAware’ssetBeanClassLoader

3 BeanFactoryAware’ssetBeanFactory

4 EnvironmentAware’ssetEnvironment

5

EmbeddedValueResolverAware’ssetEmbeddedValueResolver

6 ResourceLoaderAware’ssetResourceLoader (onlyapplicable when running in anapplication context)

7

ApplicationEventPublisherAware’ssetApplicationEventPublisher(only applicable when runningin an application context)

8 MessageSourceAware’ssetMessageSource (onlyapplicable when running in anapplication context)


Spring Core

Bean Life-cycle

9 ApplicationContextAware’ssetApplicationContext (onlyapplicable when running in anapplication context)

10 ServletContextAware’ssetServletContext (onlyapplicable when running in aweb application context)

11

postProcessBeforeInitializationmethods ofBeanPostProcessors

12 InitializingBean’safterPropertiesSet

13 a custom init-methoddefinition

14 postProcessAfterInitializationmethods ofBeanPostProcessors


Spring Core

Application Context - XML

AbstractXmlApplicationContextClassPathXmlApplicationContextFileSystemXmlApplicationContext

XMLText basedHuman Readable

Security

Reconfigurable

Location$basedir/src/main/resources

WEB-INF/


Spring Core


<?xml version="1.0" encoding="UTF-8"?><beans xmlns="...xmlns:xsi="...xmlns:p="...xmlns:context="...xmlns:aop="...xmlns:mvc="...xsi:schemaLocation="...><import resource="si-config-measurement.xml"/>...


Spring Core


<bean id="wifiDistanceCalculator"class="<packages>.VectorIntersectionWiFiRSSIDistance"></bean>

<bean id="measurementDistanceCalculator"class="<packages>.MeasurementDistanceCalculatorImpl"><constructor-arg ref="wifiDistanceCalculator"/><constructor-arg name="wifiDistanceWeight"

value="1.0"/><constructor-arg name="magnetometerDistanceWeight"

value="0.5"/><constructor-arg name="gpsDistanceWeight"

value="0.0"/></bean>


Spring Core


<bean id="positioningService"class="<packages>.KNNSimplePositioning">

<constructor-arg name="distanceCalculator"ref="measurementDistanceCalculator"/>

<constructor-arg name="measurementGateway"ref="MeasurementGateway"/>

<constructor-arg name="k" value="3"/></bean></beans>


Spring Core

Application Context - Annotation

AnnotationMetadataNo Direct EffectUsage

Information for the compilerCompile-time anddeployment-timeprocessingRuntime processing

Sprint AnnotationsJava BasedXML is not required.Not ReadableConfiguration ???Annotations

@Component@Configuration@Bean


Spring Core


@Component

Meta AnnotationCandidates for Auto-detectionLogical Component Name

@Configuration

@Component

Contains @Bean methodsDescribe Application Context

@Bean

MethodReturns with a BeanBean Name

Method NameSpecified namesAlias

Optional Parametersautowire : AutowireinitMethod : StringdestroyMethod: Str.name : String[]value : String[]


Spring Core


@Configurationpublic class ExampleConfiguration {

@Bean(name = "greetingsService")public GreetingsService initGreetingsService(){return new GreetingsHU();}}


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