Introduction to springioc instantiation bean method

The following editor will bring you a brief discussion of the three methods of springioc instantiating beans. The editor thinks it’s pretty good, and now I want to give it to you and give it as a reference. Let’s follow the editor and take a look.

1. Constructor

is the example mentioned in the previous article, calling the default No-argument constructor

2. Static factory method

1) Create the class of the method that needs 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) Write 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">
  <!--
    在这个配置中，spring容器要用默认的构造函数为HelloWorld创建对象
   -->
  <bean id="helloWorld" class="HelloWorld"></bean>
   
  <!--
    采用静态工厂方法创建对象
      factory-method为工厂方法
   -->
   <bean id="helloWorld2" class="HelloWorldFactory" factory-method="getInstance"></bean>
</beans>

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

##

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

3. Instance factory method (omitted)

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