spring工厂(静态工厂/实例工厂)

Spring 的工厂方法

• IoC 通过工厂模式创建 bean 的方式有两种：
  • 静态工厂方法
  • 实例工厂方法
• 工厂：用来存储生产的东西

静态工厂方法

package com.zjh.entity;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Car {
    private long id;
    private String name;
    //无参构造 一定要有
    //get set方法
}

package com.zjh.factory;

import com.zjh.entity.Car;

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

public class StaticCarFactory {
    private static Map<Long, Car> carMap;
    static{
        carMap = new HashMap<Long, Car>();
        carMap.put(1L,new Car(1L,"宝马"));
        carMap.put(2L,new Car(2L,"奔驰"));
    }

    public static Car getCar(long id){
        return carMap.get(id);
    }
}

<!-- 配置静态工厂创建 Car -->
<bean id="car" class="com.zjh.factory.StaticCarFactory" factory-method="getCar">
    <constructor-arg value="2"></constructor-arg>
</bean>

ApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring-StaticCarFactory.xml");
Car car = (Car) applicationContext.getBean("car");
System.out.println(car);//输出 (2L,奔驰) 的Car

实例工厂方法

package com.zjh.factory;

import com.zjh.entity.Car;

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

public class InstanceCarFactory {
    private Map<Long, Car> carMap;
    public InstanceCarFactory(){
        carMap = new HashMap<Long, Car>();
        carMap.put(1L,new Car(1L,"宝马"));
        carMap.put(2L,new Car(2L,"奔驰"));
    }

    public Car getCar(long id){
        return carMap.get(id);
    }
}

<!-- 配置实例工厂 bean -->
<bean id="carFactory" class="com.zjh.factory.InstanceCarFactory"></bean>

<!-- 配置实例工厂创建 Car -->
<bean id="car2" factory-bean="carFactory" factory-method="getCar">
    <constructor-arg value="1"></constructor-arg>
</bean>

ApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring-InstanceCarFactory.xml");
Car car = (Car) applicationContext.getBean("car2");
System.out.println(car);//输出 (1L,宝马) 的Car