Spring使用@Autowired注解自動裝配

1. Beans

package com.yiibai.common;

public class Customer 
{
	//you want autowired this field.
	private Person person;
	
	private int type;
	private String action;
	
	//getter and setter method
	
}

<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="CustomerBean" class="com.yiibai.common.Customer">
		<property name="action" value="buy" />
		<property name="type" value="1" />
	</bean>

	<bean id="PersonBean" class="com.yiibai.common.Person">
		<property name="name" value="yiibai" />
		<property name="address" value="address 123" />
		<property name="age" value="28" />
	</bean>
	
</beans>

2. 注冊AutowiredAnnotationBeanPostProcessor

1. Include <context:annotation-config />

<beans 
	//...
	xmlns:context="http://www.springframework.org/schema/context"
	//...
	http://www.springframework.org/schema/context
	http://www.springframework.org/schema/context/spring-context-2.5.xsd">
	//...

	<context:annotation-config />
	//...
</beans>

下面是完整的實例

<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-2.5.xsd
	http://www.springframework.org/schema/context
	http://www.springframework.org/schema/context/spring-context-2.5.xsd">

	<context:annotation-config />

	<bean id="CustomerBean" class="com.yiibai.common.Customer">
		<property name="action" value="buy" />
		<property name="type" value="1" />
	</bean>

	<bean id="PersonBean" class="com.yiibai.common.Person">
		<property name="name" value="yiibai" />
		<property name="address" value="address ABC" />
		<property name="age" value="29" />
	</bean>
	
</beans>

2.  包含 AutowiredAnnotationBeanPostProcessor

<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 
class="org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor"/>
	
	<bean id="CustomerBean" class="com.yiibai.common.Customer">
		<property name="action" value="buy" />
		<property name="type" value="1" />
	</bean>

	<bean id="PersonBean" class="com.yiibai.common.Person">
		<property name="name" value="yiibai" />
		<property name="address" value="address ABC" />
		<property name="age" value="29" />
	</bean>
	
</beans>

3. @Autowired示例

1. @Autowired setter 方法

package com.yiibai.common;

import org.springframework.beans.factory.annotation.Autowired;

public class Customer 
{
	private Person person;
	private int type;
	private String action;
	//getter and setter methods
	
	@Autowired
	public void setPerson(Person person) {
		this.person = person;
	}
}

2. @Autowired 構(gòu)造方法

package com.yiibai.common;

import org.springframework.beans.factory.annotation.Autowired;

public class Customer 
{
	private Person person;
	private int type;
	private String action;
	//getter and setter methods
	
	@Autowired
	public Customer(Person person) {
		this.person = person;
	}
}

3. @Autowired 字段

package com.yiibai.common;

import org.springframework.beans.factory.annotation.Autowired;

public class Customer 
{
	@Autowired
	private Person person;
	private int type;
	private String action;
	//getter and setter methods
}

執(zhí)行它

package com.yiibai.common;

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

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

輸出

Customer [person=Person [name=YiibaiA], type=1, action=buy]

依賴檢查

默認情況下，@Autowired將執(zhí)行相關(guān)檢查，以確保屬性已經(jīng)裝配正常。當Spring無法找到匹配的Bean裝配，它會拋出異常。要解決這個問題，可以通過 @Autowired 的“required”屬性設(shè)置為false來禁用此檢查功能。

package com.yiibai.common;

import org.springframework.beans.factory.annotation.Autowired;

public class Customer 
{
	@Autowired(required=false)
	private Person person;
	private int type;
	private String action;
	//getter and setter methods
}

@Qualifier

<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-2.5.xsd
	http://www.springframework.org/schema/context
	http://www.springframework.org/schema/context/spring-context-2.5.xsd">

	<context:annotation-config />

	<bean id="CustomerBean" class="com.yiibai.common.Customer">
		<property name="action" value="buy" />
		<property name="type" value="1" />
	</bean>

	<bean id="PersonBean1" class="com.yiibai.common.Person">
		<property name="name" value="yiibai-1" />
		<property name="address" value="address-1" />
		<property name="age" value="29" />
	</bean>
	
	<bean id="PersonBean2" class="com.yiibai.common.Person">
		<property name="name" value="yiibai-2" />
		<property name="address" value="address-2" />
		<property name="age" value="28" />
	</bean>
	
</beans>

package com.yiibai.common;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;

public class Customer 
{
	@Autowired
	@Qualifier("PersonBean1")
	private Person person;
	private int type;
	private String action;
	//getter and setter methods
} 

這意味著，“PersonBean1” bean被自動裝配到customer的person屬性。閱讀下面完整的例子 – Spring自動裝配@Qualifier實例

總結(jié)