01 Spring Foundations

8/8/2019 01 Spring Foundations

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2008 coreservlets.com

Foundations

Originals of Slides and Source Code for Examples:

http://courses.coreservlets.com/Course-Materials/spring.html

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Topics in This Section

Motivation Spring Hello World POJO development Runtime environment Dependency injection Inversion of control

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o va on




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Software Development

Solutions are complex equ remen s are cons an y n ux

Software architecture must be flexible


EJB 2.0 Approach Complex products nma n a na e sys ems Non-portable, framework-committed

Unpredictable systems



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Spring Approach

Products based on simplicity a n a na e sys ems

Framework-independent software

Testable components


Pure Java Founded on POJO-based development

r nary ava c asses t at o ow no spec a s Non-invasive for pre-existing POJOs -

logic

Encourages new software to be written asPOJOs Results in highly portable, reusable, and



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More With Less Custom Code

Expand capabilities with less code Extensive and tested service abstractions

Email JMX JDBC etc

Replaces generic corporate libraries

Mitigates custom integration activities

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Consistency eases integration becausespring platform is easy to use

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Modular Helps only where needed

o u ar ty a ows on y re evant components to eintroduced into the application

For instance choose one: Spring BeanFactory Spring JMX

Spring JDBC Framework can be interfaced in deep or shallow layers. Interfaces are consistent at each layer

- Spring components can be integrated quickly, with

minimal effort and predictable results


n er aces are c ear an cons s en

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Widely Available

Spring is integrated into numerousframeworks

Broad adoption possible because the

The container itself is designed as a POJO

Performance overhead is rarely aconsideration


Spring Jobs From indeed.com

Claims to compile data from most major job sites



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pr ng e up



Spring Download http://www.springframework.org/download

Current version: 2.5.5 (6/2008) Requires JDK 1.4+

- - - -. . . Spring Framework binaries and source

Third-party binaries ocumen a on API HTML reference Project samples HOW-TO guides



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Spring Blank Project

spring-blank.zip Available from


Path Descri tion

src Empty applicationContext.xml. For new Java source files.

lib Minimum Spring JARs for API and runtime access to the Spring IoCcontainer

build.xml Optional Apache ANT build configuration

pom.xml Optional Maven 2 build configuration


Spring Blank Project and Download spring-blank.zip


Import archive as an existing project into

From the Eclipse menu bar select File and Import

From the Im ort Select dialo , select ExistinProjects into Workspace and Next

From the Import (Import Projects) dialog, select the

Locate and select spring-blank.zip and select Open Verif the ro ect entr , s rin -blank , to be resent in


the project list Select Finish

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Spring Blank Project and

Download and unpack spring-blank.zip Install Apache Ant, version 1.6.5+ Execute various Ant build commands

Command Description

clean Removes the build directory target and all nestedbuild artifacts

compile Compiles production Java source contents under src/main/java and places class binaries intotarget/classes

test Executes the compile command and compiles andexecutes tests found under src/test/java

package Packages production Java source and resource


contents into a jar file. The jar package is placed inthe build directory, target

Spring Blank Project and Download and unpack spring-blank.zip Execute various Maven commands

Command Description

build artifacts

compile Compiles production Java source contents under

target/classes

test Executes the compile command and compiles andexecutes tests found under src/test/java

package Packages production Java source and resourcecontents into a jar file. The jar package is placed inthe build directory, target


See pom.xml configuration for additional dependencyoptions

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Spring Documentation

Top-level documentation page http://www.springframework.org/documentation

Wiki ttp: opensource.at ass an.com con uence spr ng

Forum . .

Books . Spring in Action. Manning 2007 Agile Java Development with Spring, Hibernate and


Eclipse. Sams 2006

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pr ng e o or




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Spring Hello World

Code a plain Java class model se e n er ace pa ern y co ng a e o or n er ace an a

HelloWorldImpl implementation

Configure the Spring IoC container ns an a e e pr ng o con a ner Acquire the object from the Spring IoC container

The client must only have knowledge of the interface, HelloWorld


Plain Java Class Model public interface HelloWorld {

public void execute();

}

public class HelloWorldImplimplements HelloWorld {

pu c vo execute() {System.out.println("Hello World!");

}


}

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Spring IoC Configuration


Executing Spring Hello Worldimport org.springframework.beans.factory.*;

*

public class Main{ public static void main(String[] args) {

BeanFactory beanFactory =new ClassPathXmlApplicationContext (

"applicationContext.xml");

HelloWorld Interface

HelloWorld helloWorld =( HelloWorld ) beanFactory.getBean(" helloWorld ");

Spring-managed bean name

helloWorld.execute();}


Standard output

Hello World!


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POJO Development



Introduction Plain Old Java Object What is it?

Business logic ramewor n epen ent

What its not Framework implementation software

Portable Testable


Flexible

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POJO Development Process

Describe the system agents and interactions POJO behavioral classes, domain model, and

dependencies

Methods

program execution Method parameters

Identify information available during

initialization


Initialization parameters for constructor, setter, or factory

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Agents BookLibrary and Client

n erac ons Client uses BookLibrary

Responsibilities


Clients must supply search parameters; i.e. title values

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Develop implementation



Plan for change



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Plan for new and additional dependencies



Plan for complex configuration requirements



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POJO Implementation Example


Book Implementation

private String title;

public Book(String title) {this.title = title;

}

public String getTitle() {return title;

}

public String toString() {


}

}36


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BookLibrary Implementation

public interface BookLibrary {

public List search(String title);

}


BookLibrary Implementation public class JavaBookLibrary

implements BookLibrary {

private List books;

this.books = Arrays.asList(

new Book("Core Servlets and JavaServer Pages"),new Book("More Servlets and JavaServer Pages"));

}

public List search(String title) {Listresults = new ArrayList();for(Book book : books){

( oo .getT t e().conta ns(t t e)){results.add(book);

}}


}

}

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Client Implementation

ublic class BookReader

private BookLibrary bookLibrary;

public BookReader() {this.bookLibrary = new JavaBookLibrary();

}

public List read() {List books = bookLibrary.search("Java");for(Book book : books) {

System.out.printf("Reading: %s%n", book);}

return books;


}}

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un me nv ronmen




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Runtime Model

Transition from a class system to an objectsystem

An object model provides a unique and

specification


Runtime Context Multiple deployment contexts Complex object models should be portable Object models should be configurable to

suppor c anges e ween env ronmen s



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Runtime Example public class Main {

public static void main(String[] args) {

BookReader client = new BookReader();

List books = client.read();

System.out.printf("Client read: %s books%n",books.size());

}}

Standard output

Readin : Core Servlets and JavaServer Pa es


Reading: More Servlets and JavaServer PagesClient read: 2 books

Model Analysis Hard-coded implementation choices

Object model cannot be reconfigured Future implementation types cannot be used without



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Model Analysis

Hard-coded model configuration Object model is not portable



-Dependency Injection




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Dependency Injection

Delivers object dependencies at runtime Encourages the separation of

responsibilities en use w e n er ace pa ern

Isolates implementations from clients

evolve


Dependency Injection Process Design depending types to receive

implementations Allow dependencies to be supplied using property setters

Other dependency injection methods are also available,such as field injection, but requires third-party or Java

Avoid constructing objects from the clientto fulfill dependencies For example, do not use the new operator to manage

services



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Dependency Injection Candidate


public BookReader() {this.bookLibrary = new JavaBookLibrary();

}

public List read() {List books = bookLibrary.search("Java");

Creates dependency

or(Boo oo : oo s){System.out.printf("Reading: %s%n", book);

}


}

}49

Dependency Injection Example


public BookReader( BookLibrary bookLibrary ) {this.bookLibrary = bookLibrary;

} Dependency injection interface

public List read() {List books = bookLibrary.search("Java");

Interface typeNOT the implementation type

or(Boo oo : oo s){System.out.printf("Reading: %s%n", book);

}


}

}50


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Runtime Example public class Main {

Dependency creation moved out of BookReader

public static void main(String[] args) {

BookLibrary service = new JavaBookLibrary();

Dependencyinjection

BookReader client = new BookReader( service );

Listbooks = client.read();

System.out.printf("Client read: %s books%n",oo s.s ze());

}

}Standard output




Model Analysis Dynamic implementation choices

Object model can be reconfigured Future implementation types can be used without



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Model Analysis

Hard-coded model configuration Object model is not portable



-Inversion of Control




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Introduction

Inversion of Control Separate program control responsibilities

Object instantiation epen ency n ect on

Dependency injection is a type of IoC


Inversion of Control Example Previously used IoC

Dependency injection example demonstrated inversion of control

out of BookReader and into Main



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IoC Framework

Service provider or plugin framework Interface

Providers Access API

-- Joshua Bloch from Effective Java

Process Framework uses supplied APIs

ramewor an es crea on Framework handles dependency injection

Runtime context uses framework


IoC Framework Exampleimport coreservlets.BookReader;

public class ServiceProviderFramework {

private BookReader bookReader;

public ServiceProviderFramework(){

Implicit registration

this.bookReader =new BookReader(new JavaBookLibrary());

}Access API

public BookReader getBookReaderInstance() {return this.bookReader;


}

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IoC Framework Example public class Main { Framework instantiation

ServiceProviderFramework framework =new ServiceProviderFramework();

Access API

BookReader client = framework.getBookReaderInstance() ;

List books = client.read();

System.out.printf("Client read: %s books%n",oo s.s ze());

}

}Standard output




Model Analysis Dynamic implementation choices Portable model configuration



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rapup



Summary Develop POJOs

Avo ramewor epen enc es Capture business logic Avoid implementation commitments by using inversion of control

and dependency injection patterns Create a new XML file, applicationContext.xml ,

based on spring-beans.xsd Place applicationContext.xml in the classpath

Register POJOs ec are s us ng ean e emen s Use bean attributes id and class for specifying the name and type,

respectively



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Summary (Continued)

Instantiate a Spring IoC container Use t e BeanFactory mp ementat on

ClassPathXmlApplicationContext for integration withconfiguration files located in the classpath

org.spr ng ramewor .con ex .suppor .ClassPathXmlApplicationContext

Access the Spring IoC container Retrieve objects from the Spring IoC container using the bean

accessor methods For example, BeanFactory#getBean(...):Object

Specify the object name for the method parameter beanFactory.getBean("bookLibrary");



ues ons

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01 Spring Foundations