In Spring we can create bean using Spring FactoryBean, FactoryBean is an interface and we need to give implementations for the methods in it. If you don’t want to go by that methodology but still want Java Factory Pattern to be implemented then we can go for Static Factory Method and Instance Factory Method.
The client who requests for an object can simply make a call to the factory method which we have defined without knowing about the creation detail. We will be using factory-method and factory-bean attribute in our configuration for the Injection of Bean, through the below spring factory pattern example lets learn more about it.
- factory-method: factory-method is the method that will be invoked while injecting the bean. It is used when the factory method is static
- factory-bean: factory-bean represents the reference of the bean by which factory method will be invoked. It is used if factory method is non-static.
Spring Bean Creation – Static Factory Method
Folder Structure:
- Create a new Java Project “SpringCoreTutorial” and create a package for our src files “com.javainterviewpoint“
- Add the required libraries to the build path. Java Build Path ->Libraries ->Add External JARs and add the below jars.
commons-logging-1.2.jar
spring-beans-4.2.4.RELEASE.jar
spring-core-4.2.4.RELEASE.jar
spring-context-4.2.4.RELEASE.jar
spring-expression-4.2.4.RELEASE.jar - Create the Java classes Employee.java,EmployeeFactory.java and EmployeeLogic.java under com.javainterviewpoint.springfactory folder.
- Place our configuration file SpringConfig.xml in the src directory
Employee.java
package com.javainterviewpoint.springfactory;
public class Employee
{
private String name;
private String age;
private String designation;
public Employee()
{
super();
}
public Employee(String name, String age, String designation)
{
super();
this.name = name;
this.age = age;
this.designation = designation;
}
public String getName()
{
return name;
}
public void setName(String name)
{
this.name = name;
}
public String getAge()
{
return age;
}
public void setAge(String age)
{
this.age = age;
}
public String getDesignation()
{
return designation;
}
public void setDesignation(String designation)
{
this.designation = designation;
}
@Override
public String toString()
{
return "***Employee Details***\n Name :" + name +"\n "
+ "Age : " + age + "\n Designation : " + designation;
}
}
Employee class is a simple POJO consisting of the getters and setters of the properties name, age and designation
Spring Factory Pattern Example – EmployeeFactory.java
package com.javainterviewpoint.springfactory;
public class EmployeeFactory
{
private EmployeeFactory()
{
}
public static Employee createEmployee(String designation)
{
Employee emp = new Employee();
if ("manager".equals(designation))
{
emp.setName("Manager JavaInterviewPoint");
emp.setAge("111");
emp.setDesignation(designation);
}
else if("seniormanager".equals(designation))
{
emp.setName("SeniorManager JavaInterviewPoint");
emp.setAge("222");
emp.setDesignation(designation);
}
else
{
throw new RuntimeException();
}
return emp;
}
}
EmployeeFactory is the factory class, which has a private constructor and the only way we can create object for the “EmployeeFactory” class is through the static method createEmployee(). We will be passing the value to our designation property from the spring bean property file.
SpringConfig.xml
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<context:annotation-config></context:annotation-config>
<bean id="employee" class="com.javainterviewpoint.springfactory.EmployeeFactory"
factory-method="createEmployee">
<constructor-arg value="seniormanager"></constructor-arg>
</bean>
</beans>
- In our spring bean property file we have created a bean for our EmployeeFactory class and have mentioned the factory-method as “createEmployee”.
- We have used Spring’s constructor injection to inject value to the argument “designation” of our createEmployee() method. You may wonder why ? As per the Official Spring documentation section 5.4.1 Arguments to the static factory method can be supplied through <constructor-arg>, exactly the same as if a constructor had actually been used.
EmployeeLogic.java
package com.javainterviewpoint.springfactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class EmployeeLogic
{
public static void main(String args[])
{
//Read the Configuration file using ApplicationContext
ApplicationContext applicationContext =
new ClassPathXmlApplicationContext("SpringConfig.xml");
//Get the Employee class instance
Employee employee = (Employee)applicationContext.getBean("employee");
System.out.println(employee);
}
}
- In our EmployeeLogic class we have read the Configuration file(SpringConfig.xml) and get all the bean definition through ApplicationContext
- Get the Employee Class instance by calling the getBean() method over the context created.
- Since we have passed the value to the designation argument as “seniormanager” through <constructor-arg> it will be printing the details of the SeniorManager
Output:
Once we run the EmployeeLogic class we will be getting the below output
Spring Bean Creation – Instance Factory Method
EmployeeFactory.java
package com.javainterviewpoint.springfactory;
public class EmployeeFactory
{
private EmployeeFactory()
{
}
public static EmployeeFactory createEmployee()
{
return new EmployeeFactory();
}
public Employee getManager()
{
Employee emp = new Employee();
emp.setName("Manager JavaInterviewPoint");
emp.setAge("111");
emp.setDesignation("Manager");
return emp;
}
public Employee getSeniorManager()
{
Employee emp = new Employee();
emp.setName("SeniorManager JavaInterviewPoint");
emp.setAge("222");
emp.setDesignation("SeniorManager");
return emp;
}
}
- In our EmployeeFactory we have a private constructor and a static method createEmployee() returning EmployeeFactory object
- Apart from it, we have two non-static methods getManager() and getSeniorManger() method both returning Employee type of object and sets the value to its properties.
SpringConfig.xml
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<context:annotation-config></context:annotation-config>
<bean id="employee" class="com.javainterviewpoint.springfactory.EmployeeFactory"
factory-method="createEmployee">
</bean>
<bean id="manager" class="com.javainterviewpoint.springfactory.Employee"
factory-bean ="employee" factory-method="getManager"/>
<bean id="seniormanager"
factory-bean ="employee" factory-method="getSeniorManager"/>
</beans>
- In our spring bean property file, We have a bean created for our EmployeeFactory class and we have mentioned the factory-method as “createEmployee”
- Two other spring bean property for the same Employee class, one for “manager” and other for “seniormanager”, the bean “manager” and “seniormanager” are created by invoking the instance method getManager() and getSeniorManager() on the bean employee [factory-bean mentioned as “employee” which is the bean id of EmployeeFactory class].
You could have noticed that for the bean “seniormanager” we have not added the attribute ‘class’ whereas for the bean “manager” we have given the attribute ‘class’. The point to be noted is that we don’t have to specify the implementation class while using static factory or instance factory. Spring IoC container will take the class name from the return type of the factory method.
EmployeeLogic.java
package com.javainterviewpoint.springfactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class EmployeeLogic
{
public static void main(String args[])
{
//Read the Configuration file using ApplicationContext
ApplicationContext applicationContext =
new ClassPathXmlApplicationContext("SpringConfig.xml");
//Get the Employee(Manager) class instance
Employee manager = (Employee)applicationContext.getBean("manager");
System.out.println("**** Manager Details ****");
System.out.println("Name : "+manager.getName());
System.out.println("Age : "+manager.getAge());
System.out.println("Designation : "+manager.getDesignation());
//Get the Employee(SeniorManager) class instance
Employee seniormanager = (Employee)applicationContext.getBean("seniormanager");
System.out.println("**** seniormanager Details ****");
System.out.println("Name : "+seniormanager.getName());
System.out.println("Age : "+seniormanager.getAge());
System.out.println("Designation : "+seniormanager.getDesignation());
}
}
Output
Leave a Reply