Spring：Spring-IOC实例化bean的常用三种方式

Spring容器提供了三种对bean的实例化方式：

1）构造器实例化

public class Demo {

    private String name;

    //getter和setter方法略

}

<?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">

    <!-- 构造器实例化 -->

    <bean id="demo1" class="com.oak.junit.day01.Demo"></bean>

</beans>

测试：

@Test

    public void testCtx() {

        //实例化Spring容器

        ApplicationContext ctx = new ClassPathXmlApplicationContext("spring.xml");

        //取出demo1

        Demo demo1=ctx.getBean("demo1",Demo.class);

        System.out.println(demo1);

    }

2）静态工厂方法实例化

public class DemoBeanFactory {

    //静态工厂方法-返回一个Demo实例

    public static Demo staticDemoBean(){

        return new Demo();

    }

}

<?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">

    <!-- 构造器实例化 -->

    <bean id="demo1" class="com.oak.junit.day01.Demo"></bean>

    <!-- 静态工厂实例化 class为工厂类 factory-method为静态工厂方法  -->

    <bean id="demo2" class="com.oak.junit.day01.DemoBeanFactory"

    factory-method="staticDemoBean"></bean>

</beans>

测试：

    @Test

    public void testCtx() {

        //实例化Spring容器

        ApplicationContext ctx = new ClassPathXmlApplicationContext("spring.xml");

        //取出demo1

        Demo demo1=ctx.getBean("demo1",Demo.class);

        System.out.println(demo1);

        //取出demo2

        Demo demo2=ctx.getBean("demo2",Demo.class);

        System.out.println(demo2);

    }

3）实例工厂方法是实例化

工厂类中加入实例工厂方法：

public class Demo {

    private String name;

    //getter和setter方法略

}

public class DemoBeanFactory {

    //静态工厂方法-返回一个Demo实例

    public static Demo staticDemoBean(){

        return new Demo();

    }

    //实例工厂方法-返回一个Demo实例

    public Demo constructorDemoBean(){

        return new Demo();

    }

}

<?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">

    <!-- 构造器实例化 -->

    <bean id="demo1" class="com.oak.junit.day01.Demo"></bean>

    <!-- 静态工厂实例化 class为工厂类 factory-method为静态工厂方法  -->

    <bean id="demo2" class="com.oak.junit.day01.DemoBeanFactory"

    factory-method="staticDemoBean"></bean>

    <!-- 先实例化工厂类 -->

    <bean id="demoBeanFactory" class="com.oak.junit.day01.DemoBeanFactory"></bean>

    <!-- 实例工厂实例化 class为工厂类 factory-bean指定工厂类  factory-method为实例工厂方法  -->

    <bean id="demo3" factory-bean="demoBeanFactory"

    factory-method="constructorDemoBean"></bean>

</beans>

测试：

@Test

        public void testCtx() {

            //实例化Spring容器

            ApplicationContext ctx = new ClassPathXmlApplicationContext("spring.xml");

            //取出demo1

            Demo demo1=ctx.getBean("demo1",Demo.class);

            System.out.println(demo1);

            //取出demo2

            Demo demo2=ctx.getBean("demo2",Demo.class);

            System.out.println(demo2);

            //取出demo2

            Demo demo3=ctx.getBean("demo3",Demo.class);

            System.out.println(demo3);

        }

文章转载至：https://blog.csdn.net/qq_34598667/article/details/83246492

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Spring：Spring-IOC实例化bean的常用三种方式

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