dubbo之SPI Wrapper分析

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1：统计调用时长。
2：记录调用日志。

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BusinessTopInterface：SPI接口类。
MyConcreteBusinessTopInterface：目标扩展类。
CalWasteTimeWapper：统计调用耗时的Wapper类。
RecordInvokeLogWapper：记录调用日志的Wapper类。

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import com.alibaba.dubbo.common.extension.SPI;

@SPI
public interface BusinessTopInterface {
    void sayHi();
}

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public class MyConcreteBusinessTopInterface implements BusinessTopInterface {
    @Override
    public void sayHi() {
        System.out.println("MyConcreteBusinessTopInterface.sayHi ***111***");
    }
}

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public class CalWasteTimeWapper implements BusinessTopInterface {
    private BusinessTopInterface businessTopInterface;

    // 注意这里必须有一个接收BusinessTopInterface为唯一参数的构造函数，这样才会被识别为Wrapper类
    public CalWasteTimeWapper(BusinessTopInterface businessTopInterfaceIn) {
        this.businessTopInterface = businessTopInterfaceIn;
    }

    @Override
    public void sayHi() {
        System.out.println("*** cal waste time begin***");
        long startTime = System.currentTimeMillis();
        // 调用被包裹的类，这里是RecordInvokeLogWapper
        businessTopInterface.sayHi();
        System.out.println("invoke waste time is: " + (System.currentTimeMillis() - startTime));
    }
}

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public class RecordInvokeLogWapper implements BusinessTopInterface {
    private BusinessTopInterface businessTopInterface;

    public RecordInvokeLogWapper(BusinessTopInterface businessTopInterfaceIn) {
        this.businessTopInterface = businessTopInterfaceIn;
    }

    @Override
    public void sayHi() {
        System.out.println("record invoke log to database!");
        // 调用被包装的类，这里是真正的扩展类MyConcreteBusinessTopInterface
        this.businessTopInterface.sayHi();
    }
}

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myConcreteBusinessTopInterface=dongshi.daddy.wrapper.MyConcreteBusinessTopInterface
recordInvokeLogWapper=dongshi.daddy.wrapper.RecordInvokeLogWapper
calWasteTimeWapper=dongshi.daddy.wrapper.CalWasteTimeWapper

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public class WrapperMain {

    public static void main(String[] args) {
        BusinessTopInterface myConcreteBusinessTopInterface = ExtensionLoader
                .getExtensionLoader(BusinessTopInterface.class)
                .getExtension("myConcreteBusinessTopInterface");
        myConcreteBusinessTopInterface.sayHi();
    }
}

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*** cal waste time begin***
record invoke log to database!
MyConcreteBusinessTopInterface.sayHi ***111***
invoke waste time is: 2013

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class FakeCls {
    private T createExtension(String name) {
        Class<?> clazz = getExtensionClasses().get(name);
        if (clazz == null) {
            throw findException(name);
        }
        try {
            T instance = (T) EXTENSION_INSTANCES.get(clazz);
            if (instance == null) {
                EXTENSION_INSTANCES.putIfAbsent(clazz, clazz.newInstance());
                instance = (T) EXTENSION_INSTANCES.get(clazz);
            }
            injectExtension(instance);
            Set<Class<?>> wrapperClasses = cachedWrapperClasses;
            // 2022-01-23 14:45:21
            if (wrapperClasses != null && !wrapperClasses.isEmpty()) {
                for (Class<?> wrapperClass : wrapperClasses) {
                    instance = injectExtension((T) wrapperClass.getConstructor(type).newInstance(instance));
                }
            }
            return instance;
        } catch (Throwable t) {
            throw new IllegalStateException("Extension instance(name: " + name + ", class: " +
                    type + ")  could not be instantiated: " + t.getMessage(), t);
        }
    }
}

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古人学问无遗力，少壮工夫老始成。
纸上得来终觉浅，绝知此事要躬行。