Analysis of getObject() method instance in FactoryBean in spring

The main research in this article is the relevant content of the getObject() method in FactoryBean in spring, as follows.

The FactoryBean interface defines the following 3 interface methods:

• Object getObject(): Returns a Bean instance created by FactoryBean. If isSingleton() returns true, the instance will be placed in the single instance cache pool of the Spring container.
• boolean isSingleton(): Determines whether the scope of the bean created by FactoryBean is singleton or prototype.
• Class getObjectType(): Returns the type of the Bean created by FactoryBean.

When the implementation class configured by the class attribute of <bean> in the configuration file is FactoryBean, the getBean method returns not the FactoryBean itself, but the object returned by the FactoryBean#getObject() method, which is equivalent to FactoryBean#getObject() proxying the getBean() method.

When configuring Car, each property of Car corresponds to a <property> element tag. Suppose we think this method is meticulous and concise, and hope to set configuration values ​​for all the Car properties at one time through comma-separated methods, then we can achieve our goal by writing a FactroyBean:

 import org.springframework.beans.factory.FactoryBean;public class CarFactoryBean implements FactoryBean{private String carInfo;public Stirng getCarInfo(){return carInfo;}public void setCarInfo(String carInfo){this.carInfo=carInfo;}public Object getObject()throws Exception{Car car=new Car();String[]infos = carInfo.split(",");car.setBrand(infos[0]);car.setMaxSpeed(Integer.aarseint(infos[1]));car.setPrice(double.parsedouble(infos[2]));return car;}public Class getObjectType(){return Car.class;}public Boolean isSingleton() {return true;}}

With this CarFactoryBean, we can use the following configuration method to define the Car Bean in the configuration file:

 <bean id="car"> <property name="carInfo" value="Red Flag CA72,200,20000.00"/> </bean>

When gettingBean("car"), Spring discovers through the reflection mechanism that CarFactoryBean implements the FactoryBean interface. At this time, the Spring container calls the interface method CarFactoryBean#getObject() to return the object created by the factory class. If the user wants to get an instance of CarFactoryBean, he or she needs to explicitly prefix the beanName with the "&" prefix: getBean("&car") when using the getBean(beanName) method.

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