Detailed Explanation and Example Code of Automatic Scanning of Spring Component

Detailed Explanation and Example Code of Automatic Scanning of Spring Component

Problem description

A system often has thousands of components. If you need to manually manage all components in spring container, it is a huge project.

Solutions

Spring provides component scanning (component scanning). It can automatically scan, detect and instantiate components with specific annotations from classpath. The basic annotation is @ Component, which identifies a component managed by Spring. Other specific annotations are @ Repository, @ Service, and @ Controller, which identify components of the persistence layer, services layer, and presentation layer, respectively.

Implementation method

User.Java

package com.zzj.bean; 
 
import javax.annotation.Resource; 
 
import org.springframework.stereotype.Component; 
@Component 
public class User { 
  @Resource 
  private Car car; 
 
  public void startCar(){ 
    car.start(); 
  } 
} 

Car.java

package com.zzj.bean; 
 
import org.springframework.stereotype.Component; 
 
@Component 
public class Car { 
  public void start(){ 
    System.out.println("starting car..."); 
  } 
} 

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" 
    xmlns:context="http://www.springframework.org/schema/context" 
    xsi:schemaLocation="http://www.springframework.org/schema/beans  
      http://www.springframework.org/schema/beans/spring-beans.xsd 
      http://www.springframework.org/schema/context  
     http://www.springframework.org/schema/context/spring-context.xsd"> 
      
    <context:component-scan base-package="com.zzj.bean"/> 
</beans> 

Note: When the automatic scan function of Spring is turned on, the automatic injection function is also turned on.

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