【Spring】Bean 作用域

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作用域

singleton

默认值。 容器初始时创建 bean 实例，在整个容器的生命周期内只创建这一个 bean，单例的。

• beans-scope.xml

<?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="car"
          class="com.test.sping.beans.autowire.Car"
          scope="singleton">
        <property name="brand" value="Audi"></property>
        <property name="price" value="300000"></property>
    </bean>


</beans>

第一种情况

• Main.java

package com.test.sping.beans.scope;

import com.test.sping.beans.autowire.Car;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {
    public static void main(String[] args) {

        ApplicationContext ctx = new ClassPathXmlApplicationContext("beans-scope.xml");
    }

}

第二种情况

• Main.java

package com.test.sping.beans.scope;

import com.test.sping.beans.autowire.Car;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {
    public static void main(String[] args) {

        ApplicationContext ctx = new ClassPathXmlApplicationContext("beans-scope.xml");

        Car car = (Car) ctx.getBean("car");
        Car car2 = (Car) ctx.getBean("car");

        System.out.println(car == car2);
    }

}

prototype

原型的。 容器初始化时不创建 bean 的实例。 而在每次请求时都创建一个新的 Bean 实例，并返回。

• beans-scope.xml

<?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="car"
          class="com.test.sping.beans.autowire.Car"
          scope="prototype">
        <property name="brand" value="Audi"></property>
        <property name="price" value="300000"></property>
    </bean>

</beans>

第一种情况

• Main.java

package com.test.sping.beans.scope;

import com.test.sping.beans.autowire.Car;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {
    public static void main(String[] args) {

        ApplicationContext ctx = new ClassPathXmlApplicationContext("beans-scope.xml");
    }

}

第二种情况

• Main.java

package com.test.sping.beans.scope;

import com.test.sping.beans.autowire.Car;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {
    public static void main(String[] args) {

        ApplicationContext ctx = new ClassPathXmlApplicationContext("beans-scope.xml");

        Car car = (Car) ctx.getBean("car");
        Car car2 = (Car) ctx.getBean("car");

        System.out.println(car == car2);
    }

}

Car.java(com.test.sping.beans.autowire.Car)

package com.test.sping.beans.autowire;

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 +
                '}';
    }

    public Car() {
        System.out.println("Car's Constructor...");
    }
}