【Spring】10 Bean 的配置方法(通过XML的方式)_bean 属性怎么配置 xml-优快云博客

博客介绍了Spring中的三种创建对象方式，包括静态工厂方法、实例工厂方法和FactoryBean。详细列出了每种方式涉及的文件，如beans-factory.xml、Main.java等，展示了不同方式下的代码文件结构和使用示例。

Bean 的配置方法—通过XML的方式

静态工厂方法

beans-factory.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">

    <!-- 通过静态工厂方法来配置 bean， 注意不是配置静态工厂方法实例， 而是配置 bean 实例 -->
    <!--
        class 属性： 指向静态工厂方法的全类名
        factory-method： 指向静态工厂方法的名字
        constructor-arg： 如果工厂方法需要传入参数，则使用 constructor-arg 来配置参数
    -->
    <bean id="car1"
          class="com.test.sping.beans.factory.StaticCarFactory"
          factory-method="getCar">
        <constructor-arg value="audi"></constructor-arg>
    </bean>

</beans>

Main.java(com.test.sping.beans.factory.Main)

package com.test.sping.beans.factory;

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

public class Main {

    public static void main(String[] args) {

        ApplicationContext ctx = new ClassPathXmlApplicationContext("beans-factory.xml");
        Car car1 = (Car) ctx.getBean("car1");
        System.out.println(car1);
    }
}

StaticCarFactory.java(com.test.sping.beans.factory.StaticCarFactory)

package com.test.sping.beans.factory;

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

/**
 *  静态工厂方法： 直接调用某一个类的静态方法就可以返回 Bean 的实例
 */
public class StaticCarFactory {

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

    static{
        cars.put("audi", new Car("audi", 300000));
        cars.put("ford", new Car("ford", 400000));
    }

    // 静态工厂方法
    public static Car getCar(String name){
         return cars.get(name);
    }
}

Car.java()

package com.test.sping.beans.factory;

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;
    }

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

    public Car() {
        System.out.println("Car's Constructor...");
    }

    public Car(String brand, double price) {
        this.brand = brand;
        this.price = price;
    }
}

实例工厂方法

beans-factory.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">

    <!-- 配置工厂的实例 -->
    <bean id="carFactory" class="com.test.sping.beans.factory.InstanceCarFactory"></bean>

    <!-- 通过实例工厂方法来配置 bean -->
    <!--
        factory-bean 属性： 指向实例工厂方法的 bean
        factory-method： 指向静态工厂方法的名字
        constructor-arg： 如果工厂方法需要传入参数，则使用 constructor-arg 来配置参数
    -->
    <bean id="car2" factory-bean="carFactory" factory-method="getCar">
        <constructor-arg value="ford"></constructor-arg>
    </bean>

</beans>

InstanceCarFactory.java(com.test.sping.beans.factory.InstanceCarFactory)

package com.test.sping.beans.factory;

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

/**
 *  实例工厂方法： 实例工厂的方法， 即现需要创建工厂本身， 再调用工厂的实例方法来返回 bean 的实现
 */
public class InstanceCarFactory {

    private Map<String, Car> cars = null;

    public InstanceCarFactory(){
        cars = new HashMap<>();
        cars.put("audi", new Car("audi", 300000));
        cars.put("ford", new Car("ford", 400000));
    }

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

Main.java(com.test.sping.beans.factory.Main)

package com.test.sping.beans.factory;

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

public class Main {

    public static void main(String[] args) {

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

Car.java(com.test.sping.beans.factory.Car) (同上)

FactoryBean

beans-beanfactory.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">

    <!--
        通过 FactoryBean 来配置 Bean 的实例
        class： 指向 FactoryBean 的全类名
        property： 配置 FactoryBean 的属性

        但实际返回的实例却是 FactoryBean 的 getObject() 方法返回的实例！
    -->
    <bean id="car" class="com.test.sping.beans.factorybean.CarFactoryBean">
        <property name="brand" value="BMW"></property>
    </bean>

</beans>

Main.java(com.test.sping.beans.factorybean.Main)

package com.test.sping.beans.factorybean;

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

public class Main {

    public static void main(String[] args) {

        ApplicationContext ctx = new ClassPathXmlApplicationContext("beans-beanfactory.xml");
        Car car = (Car) ctx.getBean("car");

        System.out.println(car);

    }
}

CarFactoryBean.java(com.test.sping.beans.factorybean.CarFactoryBean)

package com.test.sping.beans.factorybean;

import org.springframework.beans.factory.FactoryBean;

// 自定义的 FactoryBean 需要实现 FactoryBean 接口
public class CarFactoryBean implements FactoryBean<Car> {

    private String brand;

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

    // 返回 bean 的对象
    @Override
    public Car getObject() throws Exception {
        return new Car(brand, 5000000);
    }


    /**
     * 返回 bean 的类型
     */
    @Override
    public Class<?> getObjectType() {
        return Car.class;
    }

    @Override
    public boolean isSingleton() {
        return true;
    }
}