Spring學習--靜態工廠方法、實例工廠方法創建 Bean

通過調用靜態工廠方法創建 bean：

• 調用靜態工廠方法創建 bean 是將對象創建的過程封裝到靜態方法中 , 當客戶端需要對象時 , 只需要簡單地調用靜態方法 , 而不需要關心創建對象的細節。
• 要聲明通過靜態方法創建的 bean , 需要在 bean 的 class 屬性里面指定擁有該工廠的方法的類 , 同時在 factory-method 屬性里指定工廠方法的名稱。最后 , 使用 <constructor-arg> 元素為該方法傳遞方法參數。

<?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.spring.factory.StaticFactory"
          factory-method="getCar">
        <constructor-arg value="Maserati"/>
    </bean>

</beans>

package com.itdoc.spring.factory;

/**
 * http://www.cnblogs.com/goodcheap
 *
 * @author: Wáng Chéng Dá
 * @create: 2017-03-02 19:30
 */
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(String brand, double price) {
        this.brand = brand;
        this.price = price;
    }

    public Car() {
    }

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

package com.itdoc.spring.factory;

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

/**
 * 靜態工廠方法
 * http://www.cnblogs.com/goodcheap
 *
 * @author: Wáng Chéng Dá
 * @create: 2017-03-02 19:27
 */
public class StaticFactory {

    public static Map<String, Car> cars = new HashMap<String, Car>();

    static {
        cars.put("Ferrari", new Car("Ferrari", 25000000));
        cars.put("Maserati", new Car("Maserati", 2870000));
    }

    public static Car getCar(String name) {
        return cars.get(name);
    }
    
}

package com.itdoc.spring.factory;

import org.springframework.beans.factory.FactoryBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * http://www.cnblogs.com/goodcheap
 *
 * @author: Wáng Chéng Dá
 * @create: 2017-03-02 19:41
 */
public class Main {

    public static void main(String[] args) {

        ApplicationContext ctx = new ClassPathXmlApplicationContext("factory-beans.xml");
        Car car = (Car) ctx.getBean("car");
        System.out.println(car);

    }
}

 

控制台輸出：

Car{brand='Maserati', price=2870000.0}

 

通過調用實例工廠方法創建 bean：

• 實例工廠方法：將對象的創建過程封裝到另外一個對象實例的方法里。當客戶端需要請求對象時 , 只需要簡單的調用該實例方法而不需要關心對象的創建細節。
• 要聲明通過實例工廠方法創建的 bean

1. 在 bean 的factory-bean 屬性里指定擁有該工廠方法的bean。
2. 在 factory-method 屬性里指定該工廠方法的名稱。
3. 使用 <constructor-arg> 元素為工廠方法傳遞方法參數。

<?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="carFactory" class="com.itdoc.spring.factory.InstanceFactory"></bean>

    <bean id="car2" factory-bean="carFactory" factory-method="getCar">
        <constructor-arg value="Ferrari"/>
    </bean>

</beans>

package com.itdoc.spring.factory;

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

/**
 * 實例工廠方法
 * http://www.cnblogs.com/goodcheap
 *
 * @author: Wáng Chéng Dá
 * @create: 2017-03-02 20:02
 */
public class InstanceFactory {

    private Map<String, Car> cars = null;

    public InstanceFactory() {
        cars = new HashMap<String, Car>();
        cars.put("Ferrari", new Car("Ferrari", 25000000));
        cars.put("Maserati", new Car("Maserati", 2870000));
    }

    public Car getCar(String name) {
        return cars.get(name);
    }
}

package com.itdoc.spring.factory;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * http://www.cnblogs.com/goodcheap
 *
 * @author: Wáng Chéng Dá
 * @create: 2017-03-02 19:41
 */
public class Main {

    public static void main(String[] args) {

        ApplicationContext ctx = new ClassPathXmlApplicationContext("factory-beans.xml");
       
        car = (Car) ctx.getBean("car2");
        System.out.println(car);

    }
}

 

控制台輸出：

Car{brand='Ferrari', price=2.5E7}