Spring的IOC容器实例化bean的方式总结

// applicationContext.xml
<bean id="flowService" class="com.lwb.services.impl.FlowServiceImpl">

// FlowServiceImpl.java
public class FlowServiceImpl implements FlowService {
    private FlowServiceImpl(){
        System.out.println(this.getClass() + "-----进入FlowServiceImpl" +
                "无参构造器");
    }
    @Override
    public void saveService() {
        System.out.println(this.getClass() + "-----进入FlowServiceImpl");
    }
}

// App.java
public class App {
    public static void main(String[] args){
        ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
    }
}

// applicationContext.xml
<!--静态工厂实例化方法
        class为静态工厂类路径，factory-method 为方法名
    -->
    <bean id="flowDao1" class="com.lwb.factory.FlowDaoStaticFactory" factory-method="getFlowDao"/>

// FlowDaoStaticFactory.java
//注意getFlowDao是static的，所以叫静态工厂
public class FlowDaoStaticFactory {
     public static FlowDao getFlowDao(){
        System.out.println("-----进入静态工厂方法StaticFactory");
        return new FlowDaoImpl();
    }
}

// App.java
public class App {
    public static void main(String[] args){
        ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
    }
}

// applicationContext.xml
	<bean id="flowDaoExFactory" class="com.lwb.factory.FlowDaoExFactory"/>
    <bean id="flowDao2" factory-method="getFlowDao" factory-bean="flowDaoExFactory"/>

// FlowDaoExFactory .java
//注意getFlowDao是public的，对比静态工厂
public class FlowDaoExFactory {
    public FlowDao getFlowDao(){
        System.out.println(this.getClass() + "------进入实例工厂类FlowDaoExFactory");
        return new FlowDaoImpl();
    }
}

// App.java
public class App {
    public static void main(String[] args){
        ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
    }
}

// applicationContext.xml
	<bean id="flowDao3" class="com.lwb.factory.FlowDaoFactoryBean"/>

// FlowDaoFactoryBean .java
public class FlowDaoFactoryBean implements FactoryBean<FlowDao> {
    //返回实例化对象
    @Override
    public FlowDao getObject() throws Exception{
        System.out.println(this.getClass() + "------进入实例工厂FlowDaoFactoryBean，getObject");
        return new FlowDaoImpl();
    }
    //返回class对象
    @Override
    public Class<?> getObjectType() {
        System.out.println(this.getClass() + "------进入实例工厂FlowDaoFactoryBean，getObjectType");
        return FlowDao.class;
    }
}

// App.java
public class App {
    public static void main(String[] args){
        ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
    }
}