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JAVA EXAMPLE PROGRAMS

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Spring bean inheritance configuration


A spring bean definition contains lot of information like property values, constructor arguments, and container specific information like init and destroy method settings and so on. Spring allows to inherit all these bean properties. A child bean definition can inherit configurations from its parent definition. The child bean definition can override some values, or add new values.

This example shows how to inherit parent bean values with in child bean. We have Employee class, the parent bean sets the common value for the property called company. Any other bean definitions will inherits it.

package com.java2novice.beans;

public class Employee {

	private int empId;
	private String name;
	private String company;
	
	public int getEmpId() {
		return empId;
	}
	public void setEmpId(int empId) {
		this.empId = empId;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}

	public String getCompany() {
		return company;
	}
	public void setCompany(String company) {
		this.company = company;
	}
	
	@Override
	public String toString(){
		return this.empId+" | "+this.name+" | "+this.company;
	}
	
}

Here is the xml based configurations, you can see the bean reference "baseEmployeeBean" playing as parent bean and bean reference "myEmployeeBean" playing as child bean and inheriting property called company, and adding new properties empId and name.

<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="baseEmployeeBean" class="com.java2novice.beans.Employee">
		<property name="company" value="Java2novice" />
	</bean>
	<bean id="myEmployeeBean" parent="baseEmployeeBean">
		<property name="empId" value="1016" />
		<property name="name" value="Nataraja Gootooru" />
	</bean>
</beans>

Spring bean demo class:

package com.java2novice.test;

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

import com.java2novice.beans.Employee;

public class SpringDemo {

	public static void main(String a[]){
		String confFile = "applicationContext.xml";
		ConfigurableApplicationContext context 
					= new ClassPathXmlApplicationContext(confFile);
		Employee myEmp = (Employee) context.getBean("myEmployeeBean");
		System.out.println(myEmp.toString());
	}
}

Output:
1016 | Nataraja Gootooru | Java2novice

Abstract attribute in parent bean

With the above given xml based configuration, you can get object for even parent bean. Spring allows you to restrict parent bean by specifying abstract property. Below configuration makes the parent bean abstract, so you cannot creat object for parent bean.

<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="baseEmployeeBean" class="com.java2novice.beans.Employee" abstract="true">
		<property name="company" value="Java2novice" />
	</bean>
	<bean id="myEmployeeBean" parent="baseEmployeeBean">
		<property name="empId" value="1016" />
		<property name="name" value="Nataraja Gootooru" />
	</bean>
</beans>

Inheritance Template

You can create a inheritance template which can be inherited by other child bean definitions. While defining a inheritance template, you should not specify class attribute and should specify abstract attribute as true. Here is the example configuration:

<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="baseEmployeeBean" abstract="true">
		<property name="company" value="Java2novice" />
	</bean>
	<bean id="myEmployeeBean" parent="baseEmployeeBean" 
								class="com.java2novice.beans.Employee">
		<property name="empId" value="1016" />
		<property name="name" value="Nataraja Gootooru" />
	</bean>
</beans>
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Spring framework examples

  1. Spring 3 hello world example
  2. Spring bean java based configuration using @Configuration and @Bean
  3. How to get spring application context object reference?
  4. How to load multiple spring bean configuration files?
  5. Spring java based configuration @Import example
  6. Spring Dependency Injection and Types
  7. Spring Dependency Injection via setter method
  8. Spring Dependency Injection via Constructor
  9. Constructor overloading issue with spring constructor injection
  10. Constructor vs Setter dependency Injection in Spring
  11. How to inject value into spring bean instance variables?
  12. Spring bean tag properties
  13. Differen types of spring bean scopes
  14. How to inject inner bean in spring?
  15. Set spring bean scope using annotation
  16. How to invoke spring bean init and destroy methods?
  17. Spring bean initialization callback
  18. Spring bean destruction callback
  19. Configure default initialization and destroy method in all spring beans
  20. Spring bean init and destroy methods using annotations
  21. Spring Bean Post Processors
  22. How to read property file in spring using xml based configuration file?
  23. How to read property file in spring 3.0 using java based configuration?
  24. How to inject date into spring bean property?
  25. How to inject date into spring bean with CustomDateEditor?
  26. Spring bean inheritance configuration
  27. Spring dependency checking with @Required annotation
  28. How to define a custom Required-style annotation for dependency checking?
  29. How to inject List into spring bean?
  30. How to inject Set into spring bean?
  31. How to inject Map into spring bean?
  32. How to enable auto component scanning in spring?
  33. Difference between @Component, @Service, @Repository and @Controller
  34. How to filter components in auto scanning?
  35. Spring expression language basic example using xml based configuration.
  36. Spring expression language basic example using annotations.
  37. Bean reference example using spring expression language
  38. Spring expression language operators example
  39. Spring expression language ternary operator example
  40. How to use regular expressions with spring expression language?
  41. How to use collections with spring expression language?
  42. Spring bean auto-wiring modes
  43. Spring auto-wiring mode byName
  44. Spring auto-wiring mode byType
  45. Spring auto-wiring mode constructor
  46. Spring auto-wiring using @Autowired annotation example
  47. Spring auto-wiring using @Qualifier annotation example
  48. Spring log4j configuration
  49. How to schedule jobs using @Scheduled annotation in spring?
  50. Send E-mail using spring 3
  51. Send E-mail with attachment using spring 3
  52. Simple spring JDBC example
  53. Spring JDBC example with JdbcTemplate
  54. Spring JDBC example with JdbcDaoSupport
  55. Spring JDBC query example using JdbcDaoSupport
  56. How to query single column using spring JdbcTemplate?
  57. Spring JDBC batch updates using JdbcTemplate?
  58. Spring AOP Advices - Before advice example - xml based configuration
  59. Spring AOP Advices - After returning advice example - xml based configuration
  60. Spring AOP Advices - After throwing advice example - xml based configuration
  61. Spring AOP Advices - Around advice example - xml based configuration
  62. Spring AOP Advice - Pointcuts – Name match example
  63. Spring AOP Advice - Pointcuts – Regular expression example
  64. Spring AOP - AspectJ - @Before example
  65. Spring AOP - AspectJ - @After example
  66. Spring AOP - AspectJ - @AfterReturning example
  67. Spring AOP - AspectJ - @AfterThrowing example
  68. Spring AOP - AspectJ - @Around example
Knowledge Centre
What is abstract class or abstract method?
We cannot create instance for an abstract class. We can able to create instance for its subclass only. By specifying abstract keyword just before class, we can make a class as abstract class.

public abstract class MyAbstractClass{

}

Abstract class may or may not contains abstract methods. Abstract method is just method signature, it does not containes any implementation. Its subclass must provide implementation for abstract methods. Abstract methods are looks like as given below:

public abstract int getLength();
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About Author

I'm Nataraja Gootooru, programmer by profession and passionate about technologies. All examples given here are as simple as possible to help beginners. The source code is compiled and tested in my dev environment.

If you come across any mistakes or bugs, please email me to [email protected] or you can comment on the page.

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Reference: Java™ Platform Standard Ed. 7 - API Specification | Java is registered trademark of Oracle.
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