spring的bean管理（xml方式）

Bean實例化的方式

1.在spring裏面通過配置文件創建對象

 

2.bean實例化三種方式實現

第一種 使用類的無參數構造創建（重點）

<?xml version="1.0" encoding="UTF-8"?>

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

    <bean id="user" class="cn.itcast.ioc.User"></bean>
</beans>

注意：類裏面沒有無參的構造會出現異常

第二種 使用靜態工廠創建

（1）創建靜態的方法，返回類對象

public class Bean2Factory {
	
	//靜態的方法，返回Bean2對象
	public static Bean2 getBean2() {
		return new Bean2();		
	}
}

<?xml version="1.0" encoding="UTF-8"?>

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

		
    <!-- 使用靜態工廠創建對象 -->
    <bean id="bean2" class="cn.itcast.bean.Bean2Factory" factory-method="getBean2">                
    </bean>
</beans>

第三種 使用實例工廠創建

（1）創建不是靜態的方法，返回類對象

public class Bean3Factory {
	
	//普通的方法，返回Bean3對象
	public Bean3 getBean3() {
		return new Bean3();
	}
}

<?xml version="1.0" encoding="UTF-8"?>

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

		<!-- 使用靜態工廠創建對象 -->
		<!-- 創建工廠對象 -->
		<bean id="bean3Factory" class="cn.itcast.bean.Bean3Factory"></bean>
		<bean id="bean3" factory-bean="bean3Factory" factory-method="getBean3"></bean>
</beans>