Spring 源码学习(2) —— FactoryBean 的使用

一般情况下, Spring是通过反射机制利用bean的class属性指定实现类来完成实例化bean的。在某些特定的情况下, 想做一些定制，Spring为此提供了一个org.springframework.beans.factory.FactoryBean的工厂类接口, 用户可以通过实现该接口定制实例化bean的逻辑。

Spring从3.0开始, FactoryBean开始支持泛型, 即接口声明改为: FactoryBean<T> 的形式。

 package org.springframework.beans.factory;

 public interface FactoryBean<T> {

     /**

      *

      * @return 返回由FactoryBean创建的bean实例, 如果isSingleton()返回true, 则该实例则会放到Spring容器单实例缓存池中

      * @throws Exception

      */

     T getObject() throws Exception;

     /**

      *

      * @return 返回FactoryBean创建Bean的类型

      */

     Class<?> getObjectType();

     /**

      *

      * @return 返回有FactoryBean创建的bean实例的作用域是singleten还是prototype

      */

     boolean isSingleton();

 }

Action

创建一个pojo类<Car>。

 /**

  * @filename: Car.java

  * @author: Wang Chinda

  * @date: 2018-05-22

  * @version: v1.0

  * @modify_history: -

  * 20180522   Wang Chinda   create

  * 20180522   Wang Chinda   modify   method()

  */

 package com.itdoc.learn.source.factory;

 /**

  * @desc FactoryBean 的使用

  * @author Wang Chinda

  * @create 2018-05-22 16:07

  */

 public class Car {

     /** 最大速度 */

     private int maxSpeed;

     /** 品牌 */

     private String brand;

     /** 价钱 */

     private double price;

     public int getMaxSpeed() {

         return maxSpeed;

     }

     public void setMaxSpeed(int maxSpeed) {

         this.maxSpeed = maxSpeed;

     }

     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{" +

                 "maxSpeed=" + maxSpeed +

                 ", brand='" + brand + '\'' +

                 ", price=" + price +

                 '}';

     }

 }

创建一个定制实例化bean逻辑的类<CarFactoryBean>:

 /**

  * @filename: CarFactoryBean.java

  * @author: Wang Chinda

  * @date: 2018-05-22

  * @version: v1.0

  * @modify_history: -

  * 20180522   Wang Chinda   create

  * 20180522   Wang Chinda   modify   method()

  */

 package com.itdoc.learn.source.factory;

 import org.springframework.beans.factory.FactoryBean;

 /**

  * @desc FactoryBean测试的工厂类

  * @author Wang Chinda

  * @create 2018-05-22 16:17

  */

 public class CarFactoryBean implements FactoryBean<Car> {

     /** 车的详细信息 */

     private String carInfo;

     @Override

     public Car getObject() throws Exception {

         Car car = new Car();

         String[] infos = carInfo.split(",");

         car.setBrand(infos[0].trim());

         car.setMaxSpeed(Integer.valueOf(infos[1].trim()));

         car.setPrice(Double.valueOf(infos[2].trim()));

         return car;

     }

     @Override

     public Class<Car> getObjectType() {

         return Car.class;

     }

     @Override

     public boolean isSingleton() {

         return false;

     }

     public String getCarInfo() {

         return carInfo;

     }

     public void setCarInfo(String carInfo) {

         this.carInfo = carInfo;

     }

 }

配置xml<car-factory-bean.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.itdoc.learn.source.factory.CarFactoryBean">

         <property name="carInfo" value="超级跑车, 400, 300000000"></property>

     </bean>

 </beans>

测试<Car>:

 /**

  * @filename: CarClient.java

  * @author: Wang Chinda

  * @date: 2018-05-22

  * @version: v1.0

  * @modify_history: -

  * 20180522   Wang Chinda   create

  * 20180522   Wang Chinda   modify   method()

  */

 package com.itdoc.learn.source.factory;

 import org.springframework.context.ApplicationContext;

 import org.springframework.context.support.ClassPathXmlApplicationContext;

 /**

  * @desc FactoryBean使用测试客户端入口

  * @author Wang Chinda

  * @create 2018-05-22 16:27

  */

 public class CarClient {

     public static void main(String[] args) {

         ApplicationContext applicationContext = new ClassPathXmlApplicationContext("test/car-factory-bean.xml");

         Car car = (Car) applicationContext.getBean("car");

         System.out.println(car);

     }

 }