【Spring】06 Bean 作用域

Z时代
2024-01-10
分类：综合

本文内容纲要：

- Bean 作用域 - 作用域 - singleton - prototype - Car.java(com.test.sping.beans.autowire.Car)

Bean 作用域

作用域
- singleton
- - 第一种情况
  - 第二种情况
- prototype
- - 第一种情况
  - 第二种情况
Car.java(com.test.sping.beans.autowire.Car)

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

<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>

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

<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>

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...");
    }
}