Spring 依赖注入四种方式

纸上得来终觉浅

1.构造器注入

AnimalDao:

package com.roadArchitectWeb.dao;public interface AnimalDao {/*所有动物有一个说话的方法*/public void say();}

CatDaoImpl:

package com.roadArchitectWeb.dao;public class CatDaoImpl implements AnimalDao{/*这个时候并没有值，会有xml文件注入*/private String says;public void say(){System.out.println("CatDaoImpl.say():"+says);}/*带参数，方便利用构造器进行注入*/public CatDaoImpl(String says){this.says=says;}}

AnimalMain:

package com.roadArchitectWeb.dao;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;class AnimalSay1{private AnimalDao animalDao;public void setAnimalDao(AnimalDao animalDao) {this.animalDao = animalDao;}public void Say(){animalDao.say();}public AnimalSay1(AnimalDao animalDao){this.animalDao=animalDao;}}public class AnimalMain {public static void main(String[] args) {/*创建Spring的IOX容器对象*/ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");/*从IOC容器中获取Bean实例*/AnimalSay1 animalSay1 = (AnimalSay1)ctx.getBean("AnimalSay1");/*调用其中的say方法*/animalSay1.Say();}}

ApplicationContext.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"><bean id="CatDaoImpl" class="com.roadArchitectWeb.dao.CatDaoImpl"><constructor-arg value="喵喵喵"></constructor-arg></bean><bean id="AnimalSay1" class="com.roadArchitectWeb.dao.AnimalSay1"><constructor-arg ref="CatDaoImpl"></constructor-arg></bean></beans>

输出结果：

CatDaoImpl.say():喵喵喵

所谓构造器注入，即类中有一个构造方法，同时在配置文件中利用该构造方法进行注入,上述例子用了两次构造器注入。

2.setter方法注入

上一篇文章是setter方法的具体应用。

3.静态工厂

既然是静态工厂方式注入，首先新建一个工厂用于获取CatDaoImpl实例：

package com.roadArchitectWeb.dao;public class DaoFactory {/*静态工厂方法*/public static AnimalDao getStaticInstance(String says){return new CatDaoImpl(says);}}

applicationContext.xml变为：

<?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="CatDaoImpl" class="com.roadArchitectWeb.dao.CatDaoImpl"><constructor-arg value="喵喵喵"></constructor-arg></bean><bean id="AnimalSay1" class="com.roadArchitectWeb.dao.AnimalSay1"><constructor-arg ref="CatDaoImpl"></constructor-arg></bean><bean id="DaoFactory" class="com.roadArchitectWeb.dao.DaoFactory" factory-method="getStaticInstance"><constructor-arg value="哇哇哇"></constructor-arg></bean></beans>

AnimalMain修改为：

package com.roadArchitectWeb.dao;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;class AnimalSay1{private AnimalDao animalDao;public void setAnimalDao(AnimalDao animalDao) {this.animalDao = animalDao;}public void Say(){animalDao.say();}public AnimalSay1(AnimalDao animalDao){this.animalDao=animalDao;}}public class AnimalMain {public static void main(String[] args) {/*创建Spring的IOX容器对象*/ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");/*从IOC容器中获取Bean实例*/AnimalSay1 animalSay1 = (AnimalSay1)ctx.getBean("AnimalSay1");/*调用其中的say方法*/animalSay1.Say();AnimalDao animalDao = (AnimalDao)ctx.getBean("DaoFactory");animalDao.say();}}

结果为：

CatDaoImpl.say():喵喵喵
CatDaoImpl.say():哇哇哇

所谓静态工厂，不同于构造函数注入和setter方法注入，它通过factory-method指定方法，从而获得实例的引用。

4.实例工厂

同静态工厂相同，只是新增一个工厂DaoInstanceFactory：

package com.roadArchitectWeb.dao;public class DaoInstanceFactory {/*实例工厂方法*/public  AnimalDao getStaticInstance(String says){return new CatDaoImpl(says);}}

applicationContext.xml变为：

<?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="CatDaoImpl" class="com.roadArchitectWeb.dao.CatDaoImpl"><constructor-arg value="喵喵喵"></constructor-arg></bean><bean id="AnimalSay1" class="com.roadArchitectWeb.dao.AnimalSay1"><constructor-arg ref="CatDaoImpl"></constructor-arg></bean><bean id="DaoFactory" class="com.roadArchitectWeb.dao.DaoFactory" factory-method="getStaticInstance"><constructor-arg value="哇哇哇"></constructor-arg></bean><bean id="DaoInstanceFactory" class="com.roadArchitectWeb.dao.DaoFactory" factory-method="getStaticInstance"><constructor-arg value="呜呜呜"></constructor-arg></bean></beans>

AnimalMain修改为：

package com.roadArchitectWeb.dao;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;class AnimalSay1{private AnimalDao animalDao;public void setAnimalDao(AnimalDao animalDao) {this.animalDao = animalDao;}public void Say(){animalDao.say();}public AnimalSay1(AnimalDao animalDao){this.animalDao=animalDao;}}public class AnimalMain {public static void main(String[] args) {/*创建Spring的IOX容器对象*/ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");/*从IOC容器中获取Bean实例*/AnimalSay1 animalSay1 = (AnimalSay1)ctx.getBean("AnimalSay1");/*调用其中的say方法*/animalSay1.Say();AnimalDao animalDao = (AnimalDao)ctx.getBean("DaoFactory");animalDao.say();AnimalDao animalDao2 = (AnimalDao)ctx.getBean("DaoInstanceFactory");animalDao2.say();}}

结果为：

CatDaoImpl.say():喵喵喵
CatDaoImpl.say():哇哇哇
CatDaoImpl.say():呜呜呜