【跟我學spring 4.0 】之第五節-配置bean之間的關係：繼承、依賴

配置bean之間的關係：繼承、依賴

1.繼承Bean配置：

        -Spring允許繼承bean的配置，被繼承的bean稱爲父bean，繼承這個父bean的bean稱爲子bean。

-子bean從父bean中繼承配置，包括bean的屬性配置

-子bean也可以覆蓋從父bean繼承過來的配置。

-父bean可以作爲配置模板，也可以作爲Bean實例，若只想把父Bean作爲模板，可以設置<Bean>的abstract屬性爲true，這樣spring將不會實例化這個Bean。

-並不是<bean>元素裏的 所有屬性都會繼承，比如autowire，abstract等。

-也可以忽略父Bean的class屬性，讓子Bean指定自己的類，而共享相同的屬性配置，但此時abstract必須設爲true。

2.依賴Bean配置

-spring允許用戶通過depends-on 屬性設定Bean前置依賴的Bean，前置依賴的Bean會在本Bean實例化之前創建好。

-如果前置依賴於多個Bean，則可以通過逗號，空格或的方式配置Bean的名稱。

3.實例：

配置文件spring-relation.xml：

<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:util="http://www.springframework.org/schema/util" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:context="http://www.springframework.org/schema/context" xmlns:tx="http://www.springframework.org/schema/tx"
	xmlns:p="http://www.springframework.org/schema/p"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
    http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-2.5.xsd
    http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd
    http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd"
	default-autowire="byName" default-lazy-init="true">
	
	<bean id="address"  class="com.zd.runsharing.maven.springAutowire.Address"
	 p:city="北京" p:street="天安門街道">
	 </bean>
	 
	 <bean id="address2"  class="com.zd.runsharing.maven.springAutowire.Address"
	 p:city="北京" p:street="朝天門街道">
	 </bean>
	
	<!--  抽象bean：bean的abstract屬性爲true的bean，這樣的bean不能被IOC容器實例化，只用來繼承配置	
	 		若某一個bean的class屬性沒有指定，則該bean必須是一個抽象bean -->
	 <bean id="address3"  abstract="true"  p:city="北京" p:street="朝天門街道">
	 </bean>
	 <!-- bean配置的繼承，使用bean的parent屬性指定繼承 哪個bean的配置 -->
	  <bean id="addressRelation"  p:city="北京"  parent="address3" class="com.zd.runsharing.maven.springAutowire.Address">
	 </bean>
	 
	 <bean id="car"  class="com.zd.runsharing.maven.springAutowire.Car"
	 p:brand="寶馬汽車" p:price="34000000">
	 </bean>
	 <!-- 要求配置personRelation時，必須有一個關聯的car！換句話說Person這個bean依賴於Car這個bean -->
	 <bean id="personRelation"   class="com.zd.runsharing.maven.springAutowire.autoPerson"
	 		p:name="張三丰" p:address-ref="address" depends-on="car">
	 </bean>
	</beans>

Address類：

public class Address {

	private String city;
	private String 	street;
	public String getCity() {
		return city;
	}
	public void setCity(String city) {
		this.city = city;
	}
	public String getStreet() {
		return street;
	}
	public void setStreet(String street) {
		this.street = street;
	}
	@Override
	public String toString() {
		return "Address [city=" + city + ", street=" + street + "]";
	}
	
}

Car類：

public class Car {
	private String brand;
	private double price;
	public String getBrand() {
		return brand;
	}
	public void setBrand(String brand) {
		this.brand = brand;
	}
	public double getPrice() {
		return price;
	}
	public void setPrice(double price) {
		this.price = price;
	}
	@Override
	public String toString() {
		return "Car [brand=" + brand + ", price=" + price + "]";
	}
	

}

autoPerson類：

public class autoPerson {

	private String name;
	private Address address;
	private Car car;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Address getAddress() {
		return address;
	}
	public void setAddress(Address address) {
		this.address = address;
	}
	public Car getCar() {
		return car;
	}
	public void setCar(Car car) {
		this.car = car;
	}
	@Override
	public String toString() {
		return "autoPerson [name=" + name + ", address=" + address + ", car=" + car + "]";
	}
	
	
}

主函數測試類：

public class BeanRelationMainTest {

	public static void main(String[] args) {
		 ApplicationContext atx = new ClassPathXmlApplicationContext("spring-relation.xml");
		  Address  address = (Address) atx.getBean("address");
		  System.out.println(  address);
		  Address  address2 = (Address) atx.getBean("address2");
		  System.out.println(  address2);
		
		  /*bean配置裏使用parent繼承*/
		  Address  addressRelation = (Address) atx.getBean("addressRelation");
		  System.out.println( "bean配置裏使用parent繼承："+ addressRelation);
		  
		  /*bean配置裏使用depends-on依賴*/
		  autoPerson  personRelation = (autoPerson) atx.getBean("personRelation");
		  System.out.println( "bean配置裏使用depends-on依賴："+ personRelation);
	}

}

運行結果：

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