Spring框架——IOC 工厂方法

IoC 是典型的⼯厂模式，如何使⽤用⼯厂模式创建 bean， IoC 通过⼯厂模式创建 bean 有以下两种⽅式

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">

    <!-- 静态工厂模式 -->
    <bean id="car" class="com.sunjian.factory.StaticCarFactory" factory-method="getCar">
        <constructor-arg value="1"></constructor-arg>
    </bean>

    <!-- 实例工厂模式 -->
    <bean id="carFactory" class="com.sunjian.factory.InstanceCarFactory"></bean>
    <bean id="car2" factory-bean="carFactory" factory-method="getCar">
        <constructor-arg value="2"></constructor-arg>
    </bean>

</beans>

class

package com.sunjian.entity;

public class Car {
    private Integer id;
    private String brand;

    public void setId(Integer id) {
        this.id = id;
    }

    public void setBrand(String brand) {
        this.brand = brand;
    }

    public Car(){
        System.out.println("创建了Car对象");
    }

    public Car(Integer id, String brand) {
        this.id = id;
        this.brand = brand;
    }

    @Override
    public String toString() {
        return "Car{" +
                "id=" + id +
                ", brand='" + brand + '\'' +
                '}';
    }
}

package com.sunjian.factory;

import com.sunjian.entity.Car;

import java.util.HashMap;
import java.util.Map;

/**
 * 实例工厂
 * @author sunjian
 * @date 2020/3/14 14:43
 */
public class InstanceCarFactory {
    private Map<Integer, Car> map;
    public InstanceCarFactory(){
        map = new HashMap<Integer, Car>();
        map.put(1, new Car(1, "起亚K2"));
        map.put(2, new Car(2, "起亚K5"));
    }

    public Car getCar(Integer id){
        return map.get(id);
    }
}

package com.sunjian.factory;

import com.sunjian.entity.Car;

import java.util.HashMap;
import java.util.Map;

/**
 * 静态工厂
 * @author sunjian
 * @date 2020/3/14 14:38
 */
public class StaticCarFactory {
    private static Map<Integer, Car> map;
    static {
        map = new HashMap<Integer, Car>();
        map.put(1, new Car(1, "起亚K2"));
        map.put(2, new Car(2, "起亚K5"));
    }

    public static Car getCar(Integer id){
        return map.get(id);
    }
}

test class

package com.sunjian.test;

import com.sunjian.entity.Car;
import com.sunjian.factory.InstanceCarFactory;
import com.sunjian.factory.StaticCarFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * @author sunjian
 * @date 2020/3/14 14:40
 */
public class Test2 {
    public static void main(String[] args) {
        Car car = StaticCarFactory.getCar(1);
        Car car2 = StaticCarFactory.getCar(2);
        System.out.println(car);
        System.out.println(car2);

        InstanceCarFactory instanceCarFactory = new InstanceCarFactory();
        Car car3 = instanceCarFactory.getCar(1);
        Car car4 = instanceCarFactory.getCar(2);
        System.out.println(car3);
        System.out.println(car4);

        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("factory.xml");
        Car car5 = (Car) applicationContext.getBean("car");
        System.out.println(car5);
    }
}

OK.