Ioc中装配bean的几种方式

装配方式有如下几种：一：属性注入

                                       二：构造方法注入

                                       三：工厂方法注入

优缺点：构造方法注入可以保证属性在bean实例化时就设置好，不需要为每个属性提供setter方法；多个构造函数让配置文件复杂；不利于继承和扩展；有时候会造成循环依赖；属性太多，构造函数复杂，可读性差；对于一个全新的应用来说不推荐使用工厂方式，因为还需要添加工厂类；所以建议使用属性注入方式；

         此外，如果想要在singleton 的bean中获取 prototype 类型的bean，则需要lookup方法注入，详细见点击打开链接；如果bean的实例化过程比较复杂，通过配置就不是很方便， spring提供了FactoryBean<T>类，该接口中定义了 T getObject()方法，返回自定义实例化的bean，如果希望得到spring提供的实例化bean,则可以通过getBean("&beanId")获取；

举例：将下面三个类按照三种不同的方式装配到容器中

package com.yaspeed.spring.bean.assembly;public class Iphone7{private String name;private int price;private int contain;public Iphone7(){System.out.println("调用构造函数Iphone7()...");}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getPrice() {return price;}public void setPrice(int price) {this.price = price;}public int getContain() {return contain;}public void setContain(int contain) {this.contain = contain;}}

package com.yaspeed.spring.bean.assembly;public class Iphone7Plus{private String name;private int price;private int contain;public Iphone7Plus(){System.out.println("调用构造函数Iphone7()...");}public Iphone7Plus(String name, int price, int contain) {super();this.name = name;this.price = price;this.contain = contain;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getPrice() {return price;}public void setPrice(int price) {this.price = price;}public int getContain() {return contain;}public void setContain(int contain) {this.contain = contain;}}

package com.yaspeed.spring.bean.assembly;public class Iphone7s{private String name;private int price;private int contain;public Iphone7s(){System.out.println("调用构造函数Iphone7s()...");}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getPrice() {return price;}public void setPrice(int price) {this.price = price;}public int getContain() {return contain;}public void setContain(int contain) {this.contain = contain;}}

下面是配置文件：

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:p="http://www.springframework.org/schema/p"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"><!-- 属性装配bean --><bean id="iphone7" class="com.yaspeed.spring.bean.assembly.Iphone7" scope="singleton"><property name="name" value="iphone7"></property><property name="price" value="7188"></property><property name="contain" value="128"></property></bean><!-- <bean id="iphone7" class="com.yaspeed.spring.bean.cycle.Iphone7" scope="singleton"  p:name="iphone7" p:price="7188"></bean> --><!-- 构造装配bean --><bean id="iphone7Plus" class="com.yaspeed.spring.bean.assembly.Iphone7Plus"><constructor-arg  value="iphone7Plus" index="0" type="java.lang.String"></constructor-arg><!-- type不要写成java.lang.Integer --><constructor-arg  value="7188" index="1" type="int"></constructor-arg><constructor-arg  value="128" index="2" type="int"></constructor-arg></bean><!-- 工厂方法装备bean --> <!-- 非静态方法装配bean --><bean id="phoneFactory" class="com.yaspeed.spring.bean.assembly.PhoneFactory"></bean><bean id="iphone7s" factory-bean="phoneFactory" factory-method="createIphone7s"></bean><!-- 静态方法装配bean --><!-- <bean id="iphone7s" class="com.yaspeed.spring.bean.assembly.PhoneFactory" factory-method="createIphone7sStatic"></bean> --></beans>

测试方法：

package com.yaspeed.spring.bean.assembly;import org.springframework.context.support.AbstractApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;public class Main {public static void main(String[] args) {//测试Ioc容器装配bean的几种方式AbstractApplicationContext ctx = new ClassPathXmlApplicationContext("bean-assembly.xml");Iphone7 iphone7 =(Iphone7)ctx.getBean("iphone7");System.out.println(iphone7.getName());Iphone7Plus iphone7Plus =(Iphone7Plus)ctx.getBean("iphone7Plus");System.out.println(iphone7Plus.getName());Iphone7s iphone7s =(Iphone7s)ctx.getBean("iphone7s");System.out.println(iphone7s.getName());}}