To the ordinary bean Conduct Autowired Field injection

• To the ordinary bean Conduct Autowired Field injection
  • Tool class
  • Use tests

Tool class

import lombok.Getter;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.SmartInitializingSingleton;
import org.springframework.beans.factory.config.AutowireCapableBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.lang.NonNull;
import org.springframework.stereotype.Component;

import java.util.Objects;
import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;

/** *  To the ordinary bean( namely : Not spring-bean) Of autowired Injection support  * * @author JustryDeng * @since 2020/7/5 13:20:19 */
@Slf4j
public abstract class ExtAutowiredInjector {
    
    
    public ExtAutowiredInjector() {
    
        Object obj = applyAutowired();
        ExtAutowiredInjector.inject(obj);
    }
    
    /** *  For returned object Conduct autowired Injection treatment  * * @return  To be injected Object */
    protected Object applyAutowired() {
    
        return this;
    }
    
    /** *  On the target object @Auwired Annotated fields are injected  * * @param obj *  The goal is obj */
    public static void inject(Object obj) {
    
        if (obj == null) {
    
            log.warn("obj is null, skip inject.");
            return;
        }
        if (ExtAutowiredInjectorProcessor.applicationContext != null) {
    
            ExtAutowiredInjectorProcessor.applicationContext.publishEvent(new AutowiredInjectEvent(obj));
        } else {
    
            ExtAutowiredInjectorProcessor.queue.add(obj);
        }
    }
    
    /** * Autowired Inject support events  * * @author JustryDeng * @since 2020/7/5 15:02:19 */
    public static class AutowiredInjectEvent extends ApplicationEvent {
    
        
        @Getter
        private final Object bean;
        
        /** * Create a new ApplicationEvent. * * @param source * the object on which the event initially occurred (never {@code null}) */
        public AutowiredInjectEvent(Object source) {
    
            super(source);
            Objects.requireNonNull(source, "source cannot be null.");
            this.bean = source;
        }
    }
    
    /** * {@link ExtAutowiredInjector} processor  * * @author JustryDeng * @since 2020/7/5 13:46:25 */
    @Slf4j
    @Component
    public static class ExtAutowiredInjectorProcessor implements SmartInitializingSingleton, ApplicationListener<AutowiredInjectEvent> {
    
        
        static ApplicationContext applicationContext;
        
        static Queue<Object> queue = new ConcurrentLinkedQueue<>();
        
        private final AutowireCapableBeanFactory autowireCapableBeanFactory;
        
        public ExtAutowiredInjectorProcessor(AutowireCapableBeanFactory autowireCapableBeanFactory,
                                             ApplicationContext applicationContext) {
    
            this.autowireCapableBeanFactory = autowireCapableBeanFactory;
            ExtAutowiredInjectorProcessor.applicationContext = applicationContext;
        }
        
        @Override
        public void onApplicationEvent(@NonNull AutowiredInjectEvent event) {
    
            Object bean = event.getBean();
            autowireCapableBeanFactory.autowireBean(bean);
            afterSingletonsInstantiated();
        }
        
        @Override
        public void afterSingletonsInstantiated() {
    
            Object obj = queue.poll();
            while (obj != null) {
    
                autowireCapableBeanFactory.autowireBean(obj);
                obj = queue.poll();
            }
        }
    }
}

Use tests

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.stereotype.Component;

/** * start class * * @author JustryDeng * @since 2022/4/21 11:41 */
@SpringBootApplication
public class DemoApplication implements ApplicationRunner {
    
    
    public static void main(String[] args) {
    
        SpringApplication.run(DemoApplication.class, args);
    }
    
    
    @Override
    public void run(ApplicationArguments args) throws Exception {
    
        //  start-up springboot project ,  Observe the input 
        
        //  Test one , Output ：hello  Deng eryang ~
        new TestClassOne().who();
        
        
        //  Test two , Output ：hello  Deng Shuai ~
        TestClassTwo testClassTwo = new TestClassTwo();
        ExtAutowiredInjector.inject(testClassTwo);
        testClassTwo.who();
        //  It doesn't matter to inject repeatedly 
        //ExtAutowiredInjector.inject(testClassTwo);
        //ExtAutowiredInjector.inject(testClassTwo);
        //ExtAutowiredInjector.inject(testClassTwo);
        //testClassTwo.who();
    }
    
    /** *  Test usage I ： To use by inheritance , Automatically complete the injection  */
    public static class TestClassOne extends ExtAutowiredInjector {
    
        
        @Autowired
        @Qualifier("demoApplication.DengErYang")
        private Mine mine;
        
        public void who() {
    
            System.err.println(mine.hello());
        }
        
        @Override
        protected Object applyAutowired() {
    
            return this;
        }
    }
    
    /** *  Test usage I ： No inheritance ,  Direct use {@link ExtAutowiredInjector#inject(Object)} Inject  */
    public static class TestClassTwo {
    
        
        @Autowired
        @Qualifier("demoApplication.DengShuai")
        private Mine mine;
        
        public void who() {
    
            System.err.println(mine.hello());
        }
    }
    
    public interface Mine {
    
        String hello();
    }
    
    @Component(value = "demoApplication.DengErYang")
    public static class DengErYang implements Mine {
    
        @Override
        public String hello() {
    
            return "hello  Deng eryang ~";
        }
    }
    
    @Component(value = "demoApplication.DengShuai")
    public static class DengShuai implements Mine {
    
        @Override
        public String hello() {
    
            return "hello  Deng Shuai ~";
        }
    }
    
}

Start the program , Console output ：

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \ ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v2.6.6)

2022-04-21 13:47:39.176  INFO 15784 --- [           main] com.example.demo.DemoApplication         : Starting DemoApplication using Java 1.8.0_291 on DESKTOP-K08MNSB with PID 15784 (E:\working\demo\demo\target\classes started by  Dunsullivan  in E:\java\flex-server)
2022-04-21 13:47:39.179  INFO 15784 --- [           main] com.example.demo.DemoApplication         : No active profile set, falling back to 1 default profile: "default"
2022-04-21 13:47:39.480  INFO 15784 --- [           main] com.example.demo.DemoApplication         : Started DemoApplication in 0.509 seconds (JVM running for 0.9)
hello  Deng eryang ~
hello  Deng Shuai ~

Process finished with exit code 0

Related information

• This article has been included in 《 Programmer growth notes 》 , The author JustryDeng