java spring boot @bean的用法

java spring boot @bean的用法

 

1 先看下spring bean xml中的應用

 

package tutorialspoint;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class MainApp {
    public static void main(String[] args) {
        ApplicationContext context =
                new ClassPathXmlApplicationContext("Beans.xml");
        HelloWorld obj = (HelloWorld) context.getBean("helloWorld");
        obj.getMessage();


    }
}

package tutorialspoint;

public class HelloWorld {
    private String message;
    public void setMessage(String message){
        this.message  = message;
    }
    public void getMessage(){
        System.out.println("Your Message : " + message);
    }
}

<?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-3.0.xsd">

    <bean id="helloWorld" class="tutorialspoint.HelloWorld">
        <property name="message" value="Hello World111!"/>
    </bean>

</beans>

A類調用B類 就是 A通過bean.xml 獲取B 。。。。。。 反正我不喜歡這種設計模式 感覺不太好用。。。

 

 

2 再看看還有個寫法

不用bean.xml 用@Configuration @Bean  代碼bean.xml

package tutorialspoint;
import org.springframework.context.annotation.*;
@Configuration
public class HelloWorldConfig {
    @Bean
    public HelloWorld helloWorld(){
        return new HelloWorld();
    }
}

package tutorialspoint;

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class MainApp {
    public static void main(String[] args) {
        ApplicationContext ctx =
                new AnnotationConfigApplicationContext(HelloWorldConfig.class);
        HelloWorld helloWorld = ctx.getBean(HelloWorld.class);
        helloWorld.setMessage("Hello World!");
        helloWorld.getMessage();


    }
}

感覺還是看xml舒服。。