INTRODUCTION
Spring Framework enables injecting our beans by without mentioning the dependencies with the help of auto-wiring. No need to care about the bean's properties suppose if it is another bean.
There are three ways to achieve auto-wiring in spring framework. They are
- By Name
- By Type
- By Constructor
In this post, I will provide examples for all these 3 types.
EXAMPLE
Create a POJO for Person.
package springcore.autowiring;
public class Person {
private Address address;
private Education education;
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}
public Education getEducation() {
return education;
}
public void setEducation(Education education) {
this.education = education;
}
}
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Create another POJO for Address.
package springcore.autowiring;
public class Address {
private String streeName;
private String doorNo;
public String getStreeName() {
return streeName;
}
public void setStreeName(String streeName) {
this.streeName = streeName;
}
public String getDoorNo() {
return doorNo;
}
public void setDoorNo(String doorNo) {
this.doorNo = doorNo;
}
}
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Create another POJO for Education.
package springcore.autowiring;
public class Education {
private String qualification;
private String institute;
public String getQualification() {
return qualification;
}
public void setQualification(String name) {
this.qualification = name;
}
public String getInstitute() {
return institute;
}
public void setInstitute(String institute) {
this.institute = institute;
}
}
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Now configure the beans in beans configuration xml (autowiring-beans.xml)
<?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.xsd">
<bean id="address" class="springcore.autowiring.Address">
<property name="streeName" value="Gandhi Street" />
<property name="doorNo" value="15" />
</bean>
<bean id="education" class="springcore.autowiring.Education">
<property name="qualification" value="M.Tech" />
<property name="institute" value="SRM University" />
</bean>
</beans>
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Now time to test the auto-wiring. Create the main program and call the beans.
package springcore.autowiring;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.FileSystemXmlApplicationContext;
public class PersonMain {
ApplicationContext applicationContext;
Person person;
PersonMain() {
applicationContext = new FileSystemXmlApplicationContext(
"C:/config/autowiring-beans.xml");
person = (Person) applicationContext.getBean("person");
}
public Address getAddress() {
return person.getAddress();
}
public static void main(String[] args) {
PersonMain personMain = new PersonMain();
System.out.println("Person Address is: " + personMain.getAddress().getStreeName());
}
}
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AUTO-WIRING TYPES
- Auto-wiring by Name
When we apply auto-wiring by name, spring container will look for the matching bean Name and inject it.
<bean id="person" class="springcore.autowiring.Person"
autowire="byName" />
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- Auto-wiring by Type
When we apply auto-wiring by type, spring container will look for the matching bean and inject it.
<bean id="person" class="springcore.autowiring.Person"
autowire="byType" />
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- Auto-wiring by Constructor
When we apply auto-wiring by a constructor, the spring container will look for the constructor of the bean and inject it.
<bean id="person" class="springcore.autowiring.Person"
autowire="constructor" />
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Hope this post helps to understand the auto-wiring without annotation. I will cover the auto-wiring with annotation in another post.
Please share your comments and suggestions.
Happy Knowledge Sharing!!!
