Spring中bean配置的繼承

In Spring, the inheritance is supported in bean configuration for a bean to share common values, properties or configurations.

A child bean or inherited bean can inherit its parent bean configurations, properties and some attributes. In additional, the child beans are allow to override the inherited value.

例子如下：

public class Customer {
 
	private int type;
	private String action;
	private String Country;
 
	//...
 
}

　　

<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="BaseCustomerMalaysia" class="com.mkyong.common.Customer">
		<property name="country" value="Malaysia" />
	</bean>
 
	<bean id="CustomerBean" parent="BaseCustomerMalaysia">
		<property name="action" value="buy" />
		<property name="type" value="1" />
	</bean>
 
</beans>

　　

public class App 
{
    public static void main( String[] args )
    {
    	ApplicationContext context = 
			new ClassPathXmlApplicationContext("SpringBeans.xml");
 
    	Customer cust = (Customer)context.getBean("CustomerBean");
    	System.out.println(cust);
 
    }
}

　　運行結果為：Customer [type=1, action=buy, Country=Malaysia]

In above example, the ‘BaseCustomerMalaysia’ is still able to instantiate, for example,

 

Customer cust = (Customer)context.getBean("BaseCustomerMalaysia");

　　類似於java的抽象類，我們可以有：(注意abstract="true")

<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="BaseCustomerMalaysia" class="com.mkyong.common.Customer" abstract="true">
		<property name="country" value="Malaysia" />
	</bean>
 
	<bean id="CustomerBean" parent="BaseCustomerMalaysia">
		<property name="action" value="buy" />
		<property name="type" value="1" />
	</bean>
 
</beans>

　　現在當你運行：

Customer cust = (Customer)context.getBean("BaseCustomerMalaysia");

　　將會出現：

org.springframework.beans.factory.BeanIsAbstractException: 
	Error creating bean with name 'BaseCustomerMalaysia': 
	Bean definition is abstract

Pure Inheritance Template

<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="BaseCustomerMalaysia" abstract="true">
		<property name="country" value="Malaysia" />
	</bean>
 
	<bean id="CustomerBean" parent="BaseCustomerMalaysia" 
	    class="com.mkyong.common.Customer">
 
		<property name="action" value="buy" />
		<property name="type" value="1" />
	</bean>
 
</beans>

　　也可以重寫值：

<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="BaseCustomerMalaysia" class="com.mkyong.common.Customer" abstract="true">
		<property name="country" value="Malaysia" />
	</bean>
 
	<bean id="CustomerBean" parent="BaseCustomerMalaysia">
	    <property name="country" value="Japan" />
		<property name="action" value="buy" />
		<property name="type" value="1" />
	</bean>
 
</beans>