为什么需要这个东西
因为我们有的时候在配置一个bean的时候,我们需要用到IOC容器里面的其他bean,这个时候通过FactoryBean去配置是最合适的
例子程序
基本结构
Car.java
package com.spring.beans.factorybean;
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;
}
public Car(){
System.out.println("Car's Constructor...");
}
@Override
public String toString() {
return "Car{" +
"brand='" + brand + '\'' +
", price=" + price +
'}';
}
public Car(String brand, double price){
super();
this.brand = brand;
this.price = price;
}
}
CarFactoryBean.java (需要实现FactoryBean接口)
package com.spring.beans.factorybean;
import org.springframework.beans.factory.FactoryBean;
//自定义的FactoryBean 需要实现FactoryBean接口
public class CarFactoryBean implements FactoryBean {
private String brand;
public void setBrand(String brand) {
this.brand = brand;
}
//返回bean 的对象
@Override
public Object getObject() throws Exception {
return new Car(brand,500000);
}
/**
* 返回bean的类型
* @return
*/
@Override
public Class<?> getObjectType() {
return Car.class;
}
@Override
public boolean isSingleton() {
return true;
}
}
beans-beanfactory.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">
<!--
通过FactoryBean 来配置Bean 的实例
class : 指向FactoryBean 的全类名
property:配置FactoryBean 的属性
但实际返回的实例却是FactoryBean的getObject()方法返回的实例!
-->
<bean id="car" class="com.spring.beans.factorybean.CarFactoryBean">
<property name="brand" value="BWM"></property>
</bean>
</beans>
Main.java
package com.spring.beans.factorybean;
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-beanfactory.xml");
Car car = (Car) ctx.getBean("car");
System.out.println(car);
}
}