类对象为新对象时无法使用@spring批注

Question

Actually i am having a spring main class as follows.

ClassLoader loader = null;

    try {
        loader = URLClassLoader.newInstance(new URL[]{new   

 File(plugins + "/" + pluginName + "/" + pluginName +   

 ".jar").toURI().toURL()}, getClass().getClassLoader());

    } catch (MalformedURLException e) {
        e.printStackTrace();
    }

 Class<?> clazz = null;

    try {

        clazz = Class.forName("com.sample.Specific", true, loader);

    } catch (ClassNotFoundException e) {

        e.printStackTrace();

    }

Method method = null;
    try {
        method = clazz.getMethod("run",new Class[]{});
    } catch (NoSuchMethodException e) {
        e.printStackTrace();
    }

 try {
        method.invoke(clazz.newinstance,new Object[]{});
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    } catch (InvocationTargetException e) {
        e.printStackTrace();
    }

Specific Class is follow :

package com.sample
@Service
public class Specific {

    @Autowired
    private FD fd;


    public void run(){

        fd.init();

    }

}

@Autowired FD comes to be null. Can anyone give me some solution as i also know new operator will not work for @autowired . As i am loading class with new instance then only it becomes null. Can anyone guide me in this thing

Answer 1

Add Specific Service bean inside your main class. As long as the service is inside one your component scan packages then you shall be fine. Do not use new operator.

@Autowired
private Specific specific;

Answer 2

Spring has its own way to provide you new objects. As long as you're consistent using @Autowired and @Component/@Service/@Repository/@Controller there should be no problem

And since all "business" object instantiation is handled by Spring you should never use new . If you have no other way of getting an instance (something I realy doubt about it) you can use ApplicationContext.getBean() but as I said, in most cases this is not required (and this is also a bad practice)

If you need several instances of a class instead of injecting them (by using @Autowired ) you can inject a Provider<T>

UPDATE

Since the class is known at runtime you need to inject an ApplicationContext and use it to get the bean:

public class TheClassWhereYouAreCreatingTheObject {

    @Autowired
    private ApplicationContext context;                  // You definitely need this

    public void theMethodWhereYouAreCreatingTheObject() {
         Class<?> clazz = ...                            // getting the object class
         Object instance = context.getBean(clazz);     // getting and instance trough Spring

         // If you know that kind of object you will get cast it at call its methods
         ((Specific) instance).run();

         // If you know anything about the class you will have to use reflection
         Method method = clazz.getMethod("run", new Class[]{});
         method.invoke(instance, new Object[]{});
    }
}

Answer 3

If you want to take advantage of autowiring then I think we have to think from spring terms.

you can use Beanutils to create a new instance and play with reflections supporting spring features. Please go through below methods:

https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/beans/BeanUtils.html