如何在具有自定义范围的spring应用程序中以编程方式“发布” bean

Question

Context :

I need to apply a treament to a message coming from JMS using Spring. I don't have any control on the biggest part of the whole process, but I do know that it take place in a single thread (typically some information are avaiable using ThreadLocals).

For the treament , I call a chain of service. I don't have any control on the methods's signature of these services, or how there are initialized, only on the implementation.

I need to pass down information from the entry point of the chain to the latest step of it. I could use for this a ThreadLocal, but I was wondering is there is way to do it using the Thread Scope of Spring.

What I could do :

public class ThreadHolder {
    private static final ThreadLocal<Object> objectThreadLocal = new ThreadLocal<>();
    public static Object getObject() {
        return objectThreadLocal.get();
    }

    public static void setObject(Object object) {
        objectThreadLocal.set(object);
    }

    public static void cleanObject() {
        objectThreadLocal.remove();
    }   
}

public class MyController { 
    public MandatoryInsurance process(JMSMessage message) {
        Object valueToPassDown = retrieveReferenceValueCode(); //Object here, but could be a String if easier
        ThreadHolder.setObject(valueToPassDown);
        TreamentResult treamentResult = chainEntryPoint.startTreament(message); //The chainEntryPoint will call chainStep.executeTreamentStep)

        return treatmentResult;
    }
}

public class ChainStep {
    public TreamentResult executeTreatmentStep(JMSMessage message) {
        Object valuePassedDown = ThreadHolder.getObject()
        // Do treament
    }
}

What I would like to do (sort of):

public class MyController { 

    @Autowired
    ApplicationContext context; 
    public MandatoryInsurance process(JMSMessage message) {
        Object valueToPassDown = retrieveReferenceValueCode(); //Object here, but could be a String if easier
        context.put("valueToPassDown", valueToPassDown, "thread");
        TreamentResult treamentResult = chainEntryPoint.startTreament(message); //The chainEntryPoint will call chainStep.executeTreamentStep)
        ThreadHolder.cleanOject();
        return treatmentResult;
    }
}

public class ChainStep {
    public TreamentResult executeTreatmentStep(JMSMessage message) {
        Object valuePassedDown = context.getBean("valueToPassDown");
        // Do treament
    }
}

Answer 1

I don't think there is any benefit in using a Spring bean for this.

1) You would have to create the "thread" scope, which would still be using the ThreadLocal implementation underneath. 2) There is no put() method in applicationContext. 3) All processors (chain steps) would need to autowire the spring context.

Conclusion: just use the ThreadLocal but don't forget to clean it up when you're done processing.

public class MyController { 
    public MandatoryInsurance process(JMSMessage message) {
        Object valueToPassDown = retrieveReferenceValueCode(); //Object here, but could be a String if easier
        try {
            ThreadHolder.setObject(valueToPassDown);
            TreamentResult treamentResult = chainEntryPoint.startTreament(message); //The chainEntryPoint will call chainStep.executeTreamentStep)
            return treatmentResult;
        } finally {
            ThreadHolder.cleanOject();
        }
    }
}

Having said that, here is a working example of using the SimpleThreadScope of Spring:

package com.test.boot;

import java.util.HashMap;
import java.util.Map;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.config.CustomScopeConfigurer;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Scope;
import org.springframework.context.support.SimpleThreadScope;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
public class App {

    public static void main(String[] args) {
        new SpringApplicationBuilder(App.class).build().run(args);
    }

    @Bean
    public CustomScopeConfigurer customScope() {
        CustomScopeConfigurer configurer = new CustomScopeConfigurer();
        Map<String, Object> threadScope = new HashMap<String, Object>();
        threadScope.put("thread", new SimpleThreadScope());
        configurer.setScopes(threadScope);
        return configurer;
    }

    @Component
    @Scope("thread")
    public static class MyThreadLocal {
        String value;
    }

    @RestController
    public static class Controller {

        @Autowired
        ApplicationContext appContext;

        @Autowired
        ChainStep chainStep;

        @RequestMapping(value = "/test")
        public String process() throws InterruptedException {
            MyThreadLocal bean = appContext.getBean(MyThreadLocal.class);
            bean.value = "" + Math.random();
            System.out.println(Thread.currentThread().getName() + " begin processing, value=" + bean.value);
            chainStep.executeStep();
            Thread.sleep(10000);
            System.out.println(Thread.currentThread().getName() + " end processing, value=" + bean.value);
            return "ok";
        }

    }

    @Component
    public static class ChainStep {

        @Autowired
        ApplicationContext appContext;

        public void executeStep() throws InterruptedException {
            MyThreadLocal bean = appContext.getBean(MyThreadLocal.class);
            System.out.println(Thread.currentThread().getName() + " middle processing, value=" + bean.value);
        }

    }
}

I'm using Spring Boot 1.3.3. This is in my pom.xml

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.3.3.RELEASE</version>
    <relativePath /> <!-- lookup parent from repository -->
</parent>

To test this hit the http://localhost:8080/test url multiple times within 10 seconds and see the console for the results. Each thread has its own value.