Spring 依赖注入四种方式-蒲公英云

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();
    }
}