Spring Basic IOC concepts

[Prakash Rai]

package com.basic.spring.ioc;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class IOCLab3 {
	public static void main(String[] args){
		ApplicationContext ctx=new ClassPathXmlApplicationContext("ApplicationContext.xml");
		System.out.println("Executon Starts in this way");
		B obj1=(B)ctx.getBean("bobj");
		obj1.m1();
		C obj2=(C)ctx.getBean("cobj");
		obj2.m1();
		D obj3=(D)ctx.getBean("dobj");
		obj3.m1();
		A obj=(A)ctx.getBean("aobj");
		obj.m1();
	}
	}

package com.basic.spring.ioc;

public class Hello {
	int a;
	String str;
	Hello(){
		System.out.println("Hello-0 arg constr");
	}
	public void setA(int a){
		System.out.println("SetA()");
		this.a=a;
	}
	public void setStr(String str){
		System.out.println("SetStr()");
		this.str=str;
	}
	void show(){
		System.out.println(a);
		System.out.println(str);
	}
}

package com.basic.spring.ioc;

public class Hai {
	int x;
	String msg;
	Hai(int x,String msg){
		System.out.println("Hai-- 2 arg constr");
		this.x=x;
		this.msg=msg;
	}
	void show(){
		System.out.println(x);
		System.out.println(msg);
	}

package com.baisc.spring.ioc;

public class A {
	Hello hello;
	Hai hai;
	/*A(Hello hello,Hai hai){
		System.out.println("A--2 arg constr Hello and hai");
		this.hello=hello;
		this.hai=hai;
	}*/
	/*A(Hello hello){
		System.out.println("A-1 arg constr Hello");
		this.hai=hai;
	}
	A(Hai hai){
		System.out.println("A-1 arg constr Hai");
	}
	*/
	public void setHai(Hai hai){
		System.out.println("SetHai()");
		this.hai=hai;
	}
	public void setHello(Hello hello){
		System.out.println("setHello()");
		this.hello=hello;
	}
	void m1(){
		System.out.println("A-  m1()");
		hai.show();
		hello.show();
	}
}

package com.basic.spring.ioc;

public class B {
	Hello hello;
	public void setHello(Hello hello){
		this.hello=hello;
	}
	void m1(){
		System.out.println("B-m1");
		hello.show();
	}
}

package com.basic.spring.ioc;

public class C {
	Hai hai;
	C(Hai hai1){
		System.out.println("C-1 arg constr");
		this.hai=hai1;
	}
	public void setHai(Hai hai){
		System.out.println("SetHai()");
		this.hai=hai;
	}
	void m1(){
		System.out.println("C- m1");
		hai.show();
	}
}

package com.basic.spring.ioc;

public class D {
	Hello hello1;
	Hello hello2;
	public void setHello1(Hello hello1) {
		this.hello1 = hello1;
	}
	public void setHello2(Hello hello2) {
		this.hello2 = hello2;
	}
	void m1(){
		System.out.println("D-m1");
		hello1.show();
		hello2.show();
		System.out.println(hello1==hello2);
	}
}

<?xml version="1.0" encoding="UTF-8"?>
<beans
	xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">


<bean id="hello" class="com.jlcindia.basic.ioc.Hello">
	<property name="a" value="99"/>
	<property name="str">
	<value>Hello Guys</value>
	</property>
</bean>

<bean id="hai" class="com.basic.spring.ioc.Hai">
<constructor-arg value="88"/>
<constructor-arg value="Hai Guys"/>
</bean>
<bean id="aobj" class="com.basic.spring.ioc.A" autowire="autodetect"/>
<bean id="bobj" class="com.basic.spring.ioc.B" autowire="byName"/>
<bean id="cobj" class="com.basic.spring.ioc.C" autowire="constructor"/>
<bean id="dobj" class="com.basic.spring.ioc.D" autowire="byType"/>
</beans>

Output of this program is:
Hello-0 arg constr
SetA()
SetStr()
Hai-- 2 arg constr
SetHai()
setHello()
C-1 arg constr
Executon Starts in this way
B-m1
99
Hello Guys
C- m1
88
Hai Guys
D-m1
99
Hello Guys
99
Hello Guys
true
A- m1()
88
Hai Guys
99
Hello Guys

Q1. In this code I understand particular code.
But I am not able to find out flow. Please tell me proper flow .

Q2. ApplicationContext ctx=new ClassPathXmlApplicationContext("ApplicationContext.xml")
( code is creating container is it correct ?) What will be the timeout for container.

[Mark Spritzler]

Q2. There is no such thing as a Timeout for the container. When your application finishes and closes and in this scenario the jvm stops, then the ApplicationContext goes away.

Q1. The beginning parts is about the Initialization phase of the ApplicationContext and the steps and order that they occur.
http://tech-tauk.blogspot.com/2010/11/spring-bean-life-cycle-phases.html

The initialization phase
1) Read the xml, all the xml and all the Configuration annotations in your classes and create BeanDefinition objects of it.
2) BeanFactoryPostProcessor step. Can change the BeanDefinition objects
3) Instantiate your objects, set dependenies, set properties
4) BeanPostProcessors

So in #3 above that is when your printlns are printing at the top.

Hope that helps, and hope the link explains it in much more detail for you.

Mark

[Prakash Rai]

I am going to face my 1st interview on spring... Can anyone give me the list of interview question for spring IOC and AOP ?

[Raghavan Muthu]

Somprakash Rai wrote: I am going to face my
1st interview on spring... Can anyone give me the list of interview question for spring IOC and AOP ?

Simple Googling will help.

[Christophe Verré]

Somprakash Rai wrote: I am going to face my 1st interview on spring... Can anyone give me the list of interview question for spring IOC and AOP ?

A list of interview questions ? What are you planning to do with it ? Remember it ? You think it will give you a job ? I think it would be wiser to go to the interview with what you know, rather than with what you don't.

[Prakash Rai]

Thanks Christophe Verré.
Really I like your suggestion... Can you tell me how can I improve my Spring skills..?

[Raghavan Muthu]

Somprakash Rai wrote: Can you tell me how can I improve my Spring skills..?

Typically, start reading and practicing first to get a good exposure.

Once you are comfortable with the framework, read some best practices to avoid the pitfalls and also to strengthen your knowledge in it!

"Practice makes a man perfect!"