SpringBoot原理篇:bean的加载控制(编程式)

bean的加载控制:根据特定情况对bean进行选择性加载

代码

package com.qing.bean;

import org.springframework.context.annotation.ImportSelector;
import org.springframework.core.type.AnnotationMetadata;

public class MyImportSelector implements ImportSelector {
    @Override
    public String[] selectImports(AnnotationMetadata annotationMetadata) {
        try {
            Class clazz = Class.forName("com.qing.bean.Mouse");
            if (clazz != null) {
                return new String[]{"com.qing.bean.Cat"};
            }
        } catch (ClassNotFoundException e) {
            return new String[0];
        }

        return null;
    }


}

import

package com.qing.config;

import com.qing.bean.MyImportSelector;
import org.springframework.context.annotation.Import;

@Import(MyImportSelector.class)
public class SpringConfig1 {

}

测试

package com.qing.app;

import com.qing.config.SpringConfig1;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class App {
    public static void main(String[] args) {
        ApplicationContext context = new AnnotationConfigApplicationContext(SpringConfig1.class);
        String[] names = context.getBeanDefinitionNames();
        for (String name :names) {
            System.out.println(name);
        }

    }
}

结果

存在老鼠这个类,就加载猫这个bean → 存在老鼠 → 加载猫这个bean

 存在狼这个类,就加载猫这个bean → 不存在狼 → 不加载猫这个bean

 ImportSelector相关代码

 bean的加载控制(注解式)