1） 使用无参构造方法实例化

它会根据默认无参构造方法来创建类对象，如果bean中没有默认无参构造函数，将会创建失败

<?xml version="1.0" encoding="UTF-8"?>
<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.xsd">
<bean id="impl" class="com.Impl"></bean>
</beans>

2） 工厂静态方法实例化

工厂的静态方法返回Bean实例

<?xml version="1.0" encoding="UTF-8"?>
<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.xsd">
<bean id="impl" class="com.StaticFactoryBean" factory-method="create"></bean>
</beans>

public class StaticFactoryBean {public  static ImplDao create(){return new ImplDao();}
}

3） 工厂实例方法实例化

工厂的非静态方法返回Bean实例

public class DynamicFactoryBean {public   ImplDao create(){return new ImplDao();}
}

<?xml version="1.0" encoding="UTF-8"?>
<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.xsd"><bean id="factoryBean" class="com.DynamicFactoryBean"/><bean id="impl" factory-bean="factoryBean" factory-method="create"/>
</beans>