spring - users.csc.calpoly.eduusers.csc.calpoly.edu/~djanzen/courses/509s09/spring.pdf ·...

Copyright ©2009 David S. Janzen

Spring Tutorial

David Janzen

4/24/09


Spring Motivation• Problems:

• Web and GUI applications are traditionally hard to test

• Screen-scraping is difficult

• Decoupling testable code from view and flow code

is difficult

• Web applications contain a lot of “plumbing” or

“glue” code

• Servlet controllers

• Configuration

• JNDI lookups

• Persistence mechanisms


Spring Background

• Opportunities:

• We’ve learned a lot about improving design in the

last ten years

• UML

• Design Patterns

• Frameworks

• Plethora of good code available for reuse

• Open-Source projects

• COTS


Your Code

Spring Overview• Spring is a lightweight framework for building Java

applications (Spring Home: http://www.springsource.org/)

• Any application (web, GUI, …)

• Lightweight means minimal impact to your code

• Spring is based on the principle of Inversion of Control

• Rather than class A declaring an instance of class B,

…

Class A

Class B


Your Code

Spring

Spring Overview• Spring is a lightweight framework for building Java

applications

• Any application (web, GUI, …)

• Lightweight means minimal impact to your code

• Spring is based on the principle of Inversion of Control

• Rather than class A declaring an instance of class B,

some external process provides A with B

Class A

Class B

Interface I

Container


Spring Overview• Dependency Injection is the run-time injecting of

dependencies

Your Code

SpringClass A

Class B

Interface I

Container

dependency


POJO: Plain Old Java Objectpublic class Person {

private String firstName;

private String lastName;

public String getFirstName() {

return firstName;

}

public void setFirstName(String firstName) {

this.firstName = firstName;

}

public String getLastName() {

return lastName;

}

public void setLastName(String lastName) {

this.lastName = lastName;

}

}

Your Code

Class A

Person

Interface I


Another POJOpublic class Book {

private int isbn;

private String title;

private Person author;

public void setIsbn(int i) {

isbn = i;

}

public void setTitle(String t) {

title = t;

}

public void setAuthor(Person a) {

author = a;

}

public Person getAuthor() {

return author;

}

…

}

Your Code

Book

Person

Interface I


Typical Clientpublic class Client {

public static void main(String [] args) {

Person p = new Person();

Book b = new Book();

p.setFirstName(“David”);

p.setLastName(“Janzen”);

b.setIsbn(123456789);

b.setTitle(“TDD for Dummies by Dummies”);

b.setAuthor(p);

}

…

}


Dependency Injection with Spring

• Spring provides a container that will

• Construct objects

• Populate object fields

• Inject references between objects

• You wire the objects together through a configuration

file such as xml


Setter Injection• Declaration of a bean instantiates an object

• Values can be injected into the object


Injecting Other Beans

123456789

TDD for Dummies by Dummies


Constructor Injection• Constructor-arg tag is used to pass dependency via

constructor

David Janzen

public class Person {

private String name;

public Person(String name) {

this.name = name;

}

public String getName() {

return name;

}

}


Multi-Type Constructor Injection• What if two constructors have an argument of

different types?

• Constructor-arg tag can specify a type

24


private String name; private int age;

public Person(String name) { this.name = name; }

public Person(int age) { this.age = age; }

}

Invokes String constructor

24


Multi-Arg Constructor Injection• We can specify the order of constructor arguments

with index

David

Janzen


private String firstName, lastName;

public Person(String fname, String lname) {

this.firstName = fname;

this.lastName = lname;

}

}


Wiring beans in XML

� Root element is

� Contains one or more elements

� Beans can be named by▪ id

▪ name (used as name if no id given)

▪ class (fully-qualified classname used as name if no id or name given)

Preferred because XML editors can verify this


Bean Name Aliasing

� Beans can have multiple names

▪ First is default

▪ Could aid in maintenance

▪ Ex. consolidate two classes into one


Typical Spring Application

POJI/POJO

Spring BeanFactory

Bean Wiring

main() or Servlet


Spring Overview• Spring acts more like a container than a framework

• Constructs instances of classes

• With desired dependencies (DI)

• Integrates with data access options

• JDBC or ORM (Hibernate, iBATIS, JDO)

• Transaction management

• Web MVC

• Aspect oriented programming

• Remoting

• E-Mail support

• Job scheduling support


Spring Organization

Diagram from “Spring in Action” by Walls and Breidenbach


Spring Packages

Spring’s MVC frameworkspring-webmvc.jar

Most of above w/o mocksspring.jar

Struts integration, file upload, …spring-web.jar

Extend dao for Hibernate, other ORMsspring-orm.jar

Mocks to aid in testingspring-mock.jar

Data access with JDBC, transactionsspring-dao.jar

Basic DI supportspring-core.jar

Extensions, remoting,…spring-context.jar

Aspect-oriented programmingspring-aop.jar

ContainsJar File


Declarative vs. Programmatic• Most Spring facilities can be configured in either a

declarative or programmatic way

• Declarative generally means the configuration is defined

in a file (XML, properties, …)

• Programmatic generally means the configuration is

defined in software

• Declarative configuration allows you to make changes

to the system without recompiling


Exercise Preparation• Examine BooksMap files

• Read TestBooksMap.java carefully

• Examine run.sh

• Run run.sh

• Examine testTitlesMapbean.xml

• Examine coverage.txt


Exercise• Retrieve the BooksMap example from

http://users.csc.calpoly.edu/~djanzen/courses/509S09/BooksMap.tar

• Untar in a directory on vogon

tar xvf BookMaps.tar

• Ensure that all tests pass

• Add another test or two to TestBooksMap.java

• Create a new book and check that it exists

• Stretch: What happens if you ask for a book that is

not in the map?

• What is different about the third test

(testBookTitlesAutoWire)? Add a second Person in this

test. What happens?


Singleton Bean Instantiation� By default, all beans are singletons

▪ So calling getBean() always returns the same one

public class TestPerson {

@Test public void testSingleton() {

try {

//write testSingletonbeans.xml

XmlBeanFactory factory =

new XmlBeanFactory(new FileSystemResource("testSingletonbeans.xml"));

Person p1 = (Person)factory.getBean("jd");


assertEquals(p1.getFirstName(),"John");


assertTrue(p1 == p2);

assertTrue(p1.getFirstName().equals(p2.getFirstName()));

assertTrue(p1.getLastName().equals(p2.getLastName()));

John

Doe


Non-Singleton Bean Instantiation� The instantiation mode can be changed

▪ Specify singleton=“false”

public class TestPerson {

@Test public void testNonSingleton () {

try {

//write testSingletonbeans.xml

XmlBeanFactory factory =

new XmlBeanFactory(new FileSystemResource("testSingletonbeans.xml"));





assertTrue(p1 != p2);

assertTrue(p1.getFirstName().equals(p2.getFirstName()));

assertTrue(p1.getLastName().equals(p2.getLastName()));

John

Doe


ApplicationContext

� See JavaDocs for ApplicationContext

� Everything we know about BeanFactory we can apply to ApplicationContext


Stand-alone ApplicationContext

POJI/POJO

ApplicationContext

Bean Wiring

client


Web ApplicationContext

POJI/POJO

ApplicationContext

Bean Wiring

servlet

Automatically loaded


Spring MVC Architecture

Dispatcher Servlet

Controller

View

Model

Based on http://www.springframework.org/docs/MVC-step-by-step/Spring-MVC-step-by-step.html by Thomas Risberg

See sample of files in WebMVC


Configuring web.xml� war/WEB-INF/web.xml (applicationContext.xml)

springapp

org.springframework.web.servlet.DispatcherServlet

1

springapp

*.htm

index.jsp

Route all *.htm to this servlet

Identify a Spring DispatcherServlet


Configuring DispatcherServlet

Dispatcher Servlet

Controller

View

Model

build.xml build.properties

web.xml


Configuring springapp-servlet.xml� war/WEB-INF/springapp-servlet.xml

springappController

Map hello.htm to springappController

Identify a controller


Configuring a Controller

Dispatcher Servlet

Controller

View

Model


web.xmlspringapp-servlet.xml


Configuring libraries

� Create a lib folder under war/WEB-INF

� Copy the follow jars from where you extracted

the Spring download to war/WEB-INF/lib

▪ spring.jar (from spring-framework-1.2.3/dist)

▪ commons-logging.jar (from spring-framework-

1.2.3/lib/jakarta-commons)

▪ log4j-1.2.9.jar (from spring-framework-1.2.3/lib/log4j)


Creating the Controller� src/SpringappController.javaimport org.springframework.web.servlet.mvc.Controller;

import org.springframework.web.servlet.ModelAndView;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.io.IOException;

public class SpringappController implements Controller {

public ModelAndView handleRequest(HttpServletRequest request,

HttpServletResponse response)

throws ServletException, IOException {

return new ModelAndView("");

}

}


Configuring a View

Dispatcher Servlet

Controller

View

Model



SpringappController.java

hello.htm


Creating a View

� Create the file hello.jsp in war

� Include something like this in hello.jsp

My First Spring Application

My First Spring Application

Isn't this cool.

You entered hello.htm.

The DispatcherServlet noticed it was a *.htm request

(according to web.xml) ...

so it mapped the request to the SpringappController (as

defined in springapp-servlet.xml).

SpringappController logged what was happening then returned

the view "hello.jsp“ and voila, here we are!


Set View in Controller� Modify SpringappController.java in src

import org.springframework.web.servlet.mvc.Controller;

import org.springframework.web.servlet.ModelAndView;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.io.IOException;

public class SpringappController implements Controller {

public ModelAndView handleRequest(

HttpServletRequest request, HttpServletResponse response)


return new ModelAndView("hello.jsp");

}

}


Configuring a View

Dispatcher Servlet

Controller

View

Model




hello.jsp

hello.htm


Modify Modelpublic class SpringappController implements Controller {

private ProductManager prodMan;

public ModelAndView handleRequest(

HttpServletRequest request, HttpServletResponse response)


String now = (new java.util.Date()).toString();

Map myModel = new HashMap();

myModel.put("now", now);

myModel.put("products",

getProductManager().getProducts());

return new ModelAndView("hello", "model", myModel);

}

public void setProductManager(ProductManager pm){

prodMan = pm;

}

public ProductManager getProductManager() {

return prodMan;

}


View can access Model

Products

$

Increase Prices


Business Data in Model

Dispatcher Servlet

Controller

View

Model




hello.jsp

hello.htm

Product.javaProductManager.java


Testing Controller and Model

Dispatcher Servlet

Controller

View

Model




hello.jsp

hello.htm

Product.javaProductManager.java

TestProductManager.java

TestSpringappController.java

springapp-servlet.xml


Adding a Controller and Validator

Dispatcher Servlet

Controller

View

Model




hello.jsp

hello.htm

PriceIncreaseValidator.java

ProductManager.java

PriceIncreaseFormController.java

priceincrease.jsp

PriceIncrease.java

priceincrease.htm

messages.properties


Spring Resources

� www.springsource.org

� Professional Java Development with the Spring Framework

� Spring in Action

� Pro Spring

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