Arouter source code analysis (III)

arouter-api version : 1.4.1

Preface

Up to now ,ARouter And the last dependency injection has not been resolved , So today, let's explore its implementation principle .

PS : Because the principle of dependency injection is relatively simple , So this article will be short .

@Autowired analysis

Want to use ARouter Implement dependency injection , Need to be in Activity/Fragment Medium plus

ARouter.getInstance().inject(this);

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Then our code becomes the entry point for our analysis .

public void inject(Object thiz) {
    _ARouter.inject(thiz);
}

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ARouter It's called internally _ARouter Of inject Method .

static void inject(Object thiz) {
    AutowiredService autowiredService = ((AutowiredService) ARouter.getInstance().build("/arouter/service/autowired").navigation());
    //  If  autowiredService  Not empty , Complete dependency injection 
    if (null != autowiredService) {
        autowiredService.autowire(thiz);
    }
}

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It is found that dependency injection is very similar to interceptors , It is all done by using service components . The service component of dependency injection is called AutowiredService , Tracking can find , Its implementation class is AutowiredServiceImpl .

@Route(path = "/arouter/service/autowired")
public class AutowiredServiceImpl implements AutowiredService {
    private LruCache<String, ISyringe> classCache;
    private List<String> blackList;

    @Override
    public void init(Context context) {
        classCache = new LruCache<>(66);
        blackList = new ArrayList<>();
    }

    @Override
    public void autowire(Object instance) {
        String className = instance.getClass().getName();
        try {
            //  If  instance  This class is on the blacklist , Dependency injection will not be completed 
            if (!blackList.contains(className)) {
                //  Fetch from cache first 
                ISyringe autowiredHelper = classCache.get(className);
                //  Create objects without caching 
                if (null == autowiredHelper) {  // No cache.
                    autowiredHelper = (ISyringe) Class.forName(instance.getClass().getName() + SUFFIX_AUTOWIRED).getConstructor().newInstance();
                }
                //  Complete dependency injection 
                autowiredHelper.inject(instance);
                //  Put in cache 
                classCache.put(className, autowiredHelper);
            }
        } catch (Exception ex) {
            //  If something goes wrong, you will be added to the blacklist 
            blackList.add(className);    // This instance need not autowired.
        }
    }
}

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among ISyringe Is the interface extracted by dependency injection ,

public interface ISyringe {
    void inject(Object target);
}

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that ISyringe Who is the implementation class of ？ The answer is automatically generated classes at compile time XXXX

ARouter

Autowired , Let's find demo Generated in the Test1Activity

ARouter

Autowired Let's see

public class Test1Activity$$ARouter$$Autowired implements ISyringe {
  private SerializationService serializationService;

  @Override
  public void inject(Object target) {
    serializationService = ARouter.getInstance().navigation(SerializationService.class);
    Test1Activity substitute = (Test1Activity)target;
    substitute.name = substitute.getIntent().getStringExtra("name");
    substitute.age = substitute.getIntent().getIntExtra("age", substitute.age);
    substitute.height = substitute.getIntent().getIntExtra("height", substitute.height);
    substitute.girl = substitute.getIntent().getBooleanExtra("boy", substitute.girl);
    substitute.ch = substitute.getIntent().getCharExtra("ch", substitute.ch);
    substitute.fl = substitute.getIntent().getFloatExtra("fl", substitute.fl);
    substitute.dou = substitute.getIntent().getDoubleExtra("dou", substitute.dou);
    substitute.ser = (com.alibaba.android.arouter.demo.testinject.TestSerializable) substitute.getIntent().getSerializableExtra("ser");
    substitute.pac = substitute.getIntent().getParcelableExtra("pac");
    if (null != serializationService) {
      substitute.obj = serializationService.parseObject(substitute.getIntent().getStringExtra("obj"), new com.alibaba.android.arouter.facade.model.TypeWrapper<TestObj>(){}.getType());
    } else {
      Log.e("ARouter::", "You want automatic inject the field 'obj' in class 'Test1Activity' , then you should implement 'SerializationService' to support object auto inject!");
    }
    if (null != serializationService) {
      substitute.objList = serializationService.parseObject(substitute.getIntent().getStringExtra("objList"), new com.alibaba.android.arouter.facade.model.TypeWrapper<List<TestObj>>(){}.getType());
    } else {
      Log.e("ARouter::", "You want automatic inject the field 'objList' in class 'Test1Activity' , then you should implement 'SerializationService' to support object auto inject!");
    }
    if (null != serializationService) {
      substitute.map = serializationService.parseObject(substitute.getIntent().getStringExtra("map"), new com.alibaba.android.arouter.facade.model.TypeWrapper<Map<String, List<TestObj>>>(){}.getType());
    } else {
      Log.e("ARouter::", "You want automatic inject the field 'map' in class 'Test1Activity' , then you should implement 'SerializationService' to support object auto inject!");
    }
    substitute.url = substitute.getIntent().getStringExtra("url");
    substitute.helloService = ARouter.getInstance().navigation(HelloService.class);
  }
}

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From the automatically generated code above , Dependency injection is actually used internally getIntent.getXxxExtra In the form of （ Empathy ,Fragment It's using getArguments().getXxx() ）. It should be noted that ,@Autowired The decorated field cannot be private Of , Otherwise, an error will be reported when automatically generating code .

in addition , There's one in the code above SerializationService What is it for ？ Actually SerializationService yes json For serialization . stay demo An implementation class is officially given in JsonServiceImpl , Alibaba's is used internally fastjson . If there are children's shoes that need to be customized , You can refer to JsonServiceImpl Do it yourself .

end

See this , Basically ARouter That's all about dependency injection .

This series comes down ,ARouter The process at the code level is almost the same . The rest is gradle-plugin and compiler These two parts have not been resolved , I'll tell you later .

bye bye