Quick to the point introduction to Spring Framework

User can inject the object dependency implicitly by using Auto-wiring framework of spring. We cannot inject string and primitive values by using this Auto-wiring and it works only with reference.

The Auto-wiring modes of Spring are:

• no: It is Default, no auto wiring by default need to set manually by using “ref” attribute
• byName: It is used to inject the dependency object according to the bean name and it Auto wiring by name property.
• byType: It is used to inject the dependency object according to the bean type and it Auto wiring by data type property.
• constructor: It is used to inject the dependency by calling the class constructor.
• autodetect: “autowired by constructor” is used for a default constructor or else use “autowire by type”.

byName autowiring mode:

The id of bean and reference name must be same in the byName auto-wiring mode.

Example:

Java file: Student

package pack1;  
public class Student {  
private Student_Details  stud;  

public void setName(Student stud) {
      System.out.println("Inside setName");
      this.stud = stud;
   }
public Student getName() {
      return stud;
   }
public void display(){
      stud.Stud_Address();
   }
}  

Java file: Student_Details

package pack1;  

public class Student_Details {  
  
    public Student_Details ()   {
       System.out.println("Inside Student_Details  constructor" );
    }
    public void Stud_Address(){
       System.out.println("Inside Stud_Address");
    }
}  

Java file: ExmTest

package pack1;  
  
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
  
public class ExmTest {  
      public static void main(String[] args) {  
        ApplicationContext cont = new ClassPathXmlApplicationContext("Beans.xml");
        Student st = (Student) cont.getBean("studentBean");
        st. Stud_Address();
      }  
}  

The configuration file is Beans.xml:

To use auto-wiring 'byName', then XML configuration file as shown below:

<?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-3.0.xsd">

   <bean id="studentBean" class="pack1.Student" autowire="byName">
            <property name="stud" value="Suman"/>
   </bean>
         <bean id=" Student_Details" class="pack1.Student_Details"/>
       </property>
   </bean>
</beans>

Compile and run the program will get the below result:

Result:

Inside Student_Details constructor
Inside setName
Inside Stud_Address

byType autowiring mode:

The id of bean and reference name may be different in the byType auto-wiring mode.

Example:

Java file: Student

package pack1;
public class Student {
	private Student_Details stud;

	public void setName(Student stud) {
		System.out.println("Inside setName");
		this.stud = stud;
	}
	public Student getName() {
		return stud;
	}
	public void display() {
		stud.Stud_Address();
	}
}

Java file: Student_Details

package pack1;

public class Student_Details {

	public Student_Details() {
		System.out.println("Inside Student_Details  constructor");
	}
	public void Stud_Address() {
		System.out.println("Inside Stud_Address");
	}
}

Java file: ExmTest

package pack1;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class ExmTest {
	public static void main(String[] args) {
		ApplicationContext cont = new ClassPathXmlApplicationContext("Beans.xml");
		Student st = (Student) cont.getBean("studentBean");
		st.Stud_Address();
	}
}

The XML configuration file by using auto-wiring 'byType', is as shown below:

<?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-3.0.xsd">

   <bean id="studentBean" class="pack1.Student" autowire="byType">
            <property name="stud" value="Suman"/>
   </bean>
         <bean id=" Student_Details" class="pack1.Student_Details"/>
       </property>
   </bean>
</beans>

Compile and run the program will get the below result:

Result:

Inside Student_Details constructor
Inside setName
Inside Stud_Address

constructor autowiring mode:

Spring container injects the dependency by parameterized constructor when using constructor auto-wiring mode.

For the above Java program the XML configuration file by using auto-wiring 'constructor', is as shown below:

<?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-3.0.xsd">

   <bean id="studentBean" class="pack1.Student" autowire="constructor">
            <property name="stud" value="Suman"/>
   </bean>
         <bean id=" Student_Details" class="pack1.Student_Details"/>
       </property>
   </bean>
</beans>

no autowiring mode:

Spring container doesn't inject the dependency by auto-wiring mode when using no auto-wiring mode.

For the above Java program the XML configuration file by using auto-wiring 'no', is as shown below:

<?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-3.0.xsd">

   <bean id="studentBean" class="pack1.Student" autowire="no">
            <property name="stud" value="Suman"/>
   </bean>
         <bean id=" Student_Details" class="pack1.Student_Details"/>
       </property>
   </bean>
</beans>

Autowiring Advantage:

• Here user need not to write the code to inject the dependency explicitly, hence it requires the minimum code.

Autowiring Disadvantage:

• Autowiring doesn’t support string and primitive values.
• If possible prefer using explicit wiring because Auto-wiring is not much same than explicit wiring.
• There is no control by user.
• User cannot autowire the properties like Strings classes and also primitives.