Spring之FactoryBean

FactoryBean

Spring中有两种类型的Bean，一种是普通Bean，另一种是工厂Bean，即FactoryBean。工厂Bean跟普通Bean不同，其返回的对象不是指定类的一个实例，其返回的是该工厂Bean的getObject方法所返回的对象。

Spring的配置文件

<!--通过FactoryBean获取bean-->
<bean id="car3" class="com.an.factory.FactoryBean">
    <constructor-arg name="brand" value="BMW"/>
</bean>

FactoryBean的类

需要实现FactoryBean接口 重写三种方法 通过getObject方法得到对象实例bean

package com.an.factory;

import com.an.things.Car;

public class FactoryBean implements org.springframework.beans.factory.FactoryBean {
    private String brand;
    
    public void setBrand(String brand) {
        this.brand = brand;
    }
    
    public FactoryBean(String brand) {
        this.brand = brand;
    }
    
    @Override
    public Car getObject() throws Exception {
        return new Car(brand,"shanghai",5000.0);
    }
    
    @Override
    public Class<?> getObjectType() {
        return Car.class;
    }
    
    @Override
    public boolean isSingleton() {
        return true;
    }
}

Car 的类

package com.an.things;

public class Car {
    private String brand;
    private String corp;
    private double price;
    private int maxSpeed;
    public Car(){
        System.out.println("创建了一个汽车！");
    }
    public Car(String brand, String corp, double price) {
        this.brand = brand;
        this.corp = corp;
        this.price = price;
    }
    
    public Car(String brand, String corp, int maxSpeed) {
        this.brand = brand;
        this.corp = corp;
        this.maxSpeed = maxSpeed;
    }
    
    public String getBrand() {
        return brand;
    }
    
    public void setBrand(String brand) {
        this.brand = brand;
    }
    
    public String getCorp() {
        return corp;
    }
    
    public void setCorp(String corp) {
        this.corp = corp;
    }
    
    public double getPrice() {
        return price;
    }
    
    public void setPrice(double price) {
        this.price = price;
    }
    
    public int getMaxSpeed() {
        return maxSpeed;
    }
    
    public void setMaxSpeed(int maxSpeed) {
        this.maxSpeed = maxSpeed;
    }
    
    @Override
    public String toString() {
        return "Car{" +
            "brand='" + brand + '\'' +
            ", corp='" + corp + '\'' +
            ", price=" + price +
            ", maxSpeed=" + maxSpeed +
            '}';
    }
}

主函数

package com.an.factory;

import com.an.things.Car;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {
    public static void main(String[] args) {
        Car car3 = (Car)ctx.getBean("car3");
        System.out.println(car3);
    }
}

输出结果

Car{brand='BMW', corp='shanghai', price=5000.0, maxSpeed=0}