2. Three Methods for Spring IoC to instantiate bean, 2. springiocbean

2. Three Methods for Spring IoC to instantiate bean, 2. springiocbean

1. Constructor

That is, in the example mentioned in the previous article, the default no-argument constructor is called.

2. Static factory Method

1) create a class for the method to be executed

public class HelloWorld {public HelloWorld(){System.out.println("aaaa");}public void hello(){System.out.println("hello world");}}

2) create a static Factory

public class HelloWorldFactory {public static HelloWorld getInstance(){return new HelloWorld();}}

3) Compile the applicationContext. xml configuration file.

<? 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-2.5.xsd"> <! -- In this configuration, the spring container uses the default constructor to create an object for HelloWorld --> <bean id = "helloWorld" class = "HelloWorld"> </bean> <! -- Use the static factory method to create an object factory-method as the factory method --> <bean id = "helloWorld2" class = "HelloWorldFactory" factory-method = "getInstance"> </bean> </beans>

4) Start the container, create an object, and call the method.

@Testpublic void test(){ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");HelloWorld world = (HelloWorld)context.getBean("helloWorld2");world.hello();}

3. instance factory method (omitted)