Dubbo之ProxyFactory解析

開篇

閱讀Dubbo的服務釋出的源碼的時候發現有PROXY_FACTORY.getInvoker()的代碼，這部分涉及了javassist動态生成源碼的邏輯，因為動态生成代碼是以沒法直覺看到邏輯，借此寫一篇分析文章，便于看到這部分邏輯的人能夠更好的了解。

因為涉及到檢視動态生成代碼的邏輯，需要使用arthas工具反編譯類檢視動态生成的Wrapper類内容，涉及

arthas

)工具的簡單使用。

ProxyFactory擴充卡

private static final ProxyFactory PROXY_FACTORY = ExtensionLoader.getExtensionLoader(ProxyFactory.class).getAdaptiveExtension();

以上是ProxyFactory生成的代碼邏輯，非常簡單，通過getAdaptiveExtension()方法生成代碼。繼續檢視ProxyFactory的擴充卡代碼。
PROXY_FACTORY這裡是ProxyFactory$Adaptive。

ProxyFactory

@SPI("javassist")
public interface ProxyFactory {

    @Adaptive({PROXY_KEY})
    <T> T getProxy(Invoker<T> invoker) throws RpcException;

    @Adaptive({PROXY_KEY})
    <T> T getProxy(Invoker<T> invoker, boolean generic) throws RpcException;

    @Adaptive({PROXY_KEY})
    <T> Invoker<T> getInvoker(T proxy, Class<T> type, URL url) throws RpcException;

}

以上是ProxyFactory包括的幾個方法，且都用@Adaptive進行修飾，是以在擴充卡生成的代碼當中這幾個方法都會被重新實作。
@SPI("javassist")的注解表明動态擴充extName預設值使用“javassist”。
繼續閱讀ProxyFactory生成的代碼ProxyFactory$Adaptive。

ProxyFactory$Adaptive

package org.apache.dubbo.rpc;

import org.apache.dubbo.common.extension.ExtensionLoader;


public class ProxyFactory$Adaptive implements org.apache.dubbo.rpc.ProxyFactory {

    public org.apache.dubbo.rpc.Invoker getInvoker(java.lang.Object arg0,
        java.lang.Class arg1, org.apache.dubbo.common.URL arg2)
        throws org.apache.dubbo.rpc.RpcException {
        if (arg2 == null) {
            throw new IllegalArgumentException("url == null");
        }

        org.apache.dubbo.common.URL url = arg2;
        String extName = url.getParameter("proxy", "javassist");

        if (extName == null) {
            throw new IllegalStateException(
                "Failed to get extension (org.apache.dubbo.rpc.ProxyFactory) name from url (" +
                url.toString() + ") use keys([proxy])");
        }

        org.apache.dubbo.rpc.ProxyFactory extension = (org.apache.dubbo.rpc.ProxyFactory) ExtensionLoader.getExtensionLoader(org.apache.dubbo.rpc.ProxyFactory.class).getExtension(extName);

        return extension.getInvoker(arg0, arg1, arg2);
    }

    public java.lang.Object getProxy(org.apache.dubbo.rpc.Invoker arg0,
        boolean arg1) throws org.apache.dubbo.rpc.RpcException {
        if (arg0 == null) {
            throw new IllegalArgumentException(
                "org.apache.dubbo.rpc.Invoker argument == null");
        }

        if (arg0.getUrl() == null) {
            throw new IllegalArgumentException(
                "org.apache.dubbo.rpc.Invoker argument getUrl() == null");
        }

        org.apache.dubbo.common.URL url = arg0.getUrl();
        String extName = url.getParameter("proxy", "javassist");

        if (extName == null) {
            throw new IllegalStateException(
                "Failed to get extension (org.apache.dubbo.rpc.ProxyFactory) name from url (" +
                url.toString() + ") use keys([proxy])");
        }

        org.apache.dubbo.rpc.ProxyFactory extension = (org.apache.dubbo.rpc.ProxyFactory) ExtensionLoader.getExtensionLoader(org.apache.dubbo.rpc.ProxyFactory.class).getExtension(extName);

        return extension.getProxy(arg0, arg1);
    }

    public java.lang.Object getProxy(org.apache.dubbo.rpc.Invoker arg0)
        throws org.apache.dubbo.rpc.RpcException {
        if (arg0 == null) {
            throw new IllegalArgumentException(
                "org.apache.dubbo.rpc.Invoker argument == null");
        }

        if (arg0.getUrl() == null) {
            throw new IllegalArgumentException(
                "org.apache.dubbo.rpc.Invoker argument getUrl() == null");
        }

        org.apache.dubbo.common.URL url = arg0.getUrl();
        String extName = url.getParameter("proxy", "javassist");

        if (extName == null) {
            throw new IllegalStateException(
                "Failed to get extension (org.apache.dubbo.rpc.ProxyFactory) name from url (" +
                url.toString() + ") use keys([proxy])");
        }

        org.apache.dubbo.rpc.ProxyFactory extension = (org.apache.dubbo.rpc.ProxyFactory) ExtensionLoader.getExtensionLoader(org.apache.dubbo.rpc.ProxyFactory.class).getExtension(extName);

        return extension.getProxy(arg0);
    }
}

以上代碼針對ProxyFactory的帶有@Adaptive的注解的方法重新生成了代碼。
方法内部通過 ExtensionLoader.getExtensionLoader(ProxyFactory.class)

.getExtension(extName)動态根據extName擷取子類對象。
擴充名從URL中擷取，通過extName = url.getParameter("proxy", "javassist")。
ProxyFactory的實作類圖如下圖所示，這裡關注JavassistProxyFactory。

exportLocal()方法

exportLocal方法調用PROXY_FACTORY.getInvoker()擷取Invoker對象，外面通過協定protocol.export()導出一下。
PROXY_FACTORY.getInvoker()調用ProxyFactory$Adaptive的getInvoker()方法。
getInvoker()方法内部執行 extension = (org.apache.dubbo.rpc.ProxyFactory) ExtensionLoader.getExtensionLoader(org.apache.dubbo.rpc.ProxyFactory.class).getExtension(extName)傳回JavassistProxyFactory對象。
暫時隻關注getInvoker()方法，ref是接口類對象如DemoServiceImpl，interfaceClass為接口類如DemoService。

private void exportLocal(URL url) {
        URL local = URLBuilder.from(url)
                .setProtocol(LOCAL_PROTOCOL)
                .setHost(LOCALHOST_VALUE)
                .setPort(0)
                .build();
        Exporter<?> exporter = protocol.export(
                PROXY_FACTORY.getInvoker(ref, (Class) interfaceClass, local));
        exporters.add(exporter);
        logger.info("Export dubbo service " + interfaceClass.getName() + " to local registry url : " + local);
    }

JavassistProxyFactory

JavassistProxyFactory的getInvoker()方法内部執行動作：建立包裝類Wrapper和建立AbstractProxyInvoker對象。
Wrapper.getWrapper()方法内部通過javassist方法生成包裝類。
AbstractProxyInvoker類實作Invoker，通過調用invoke() => doInvoke() => wrapper.invokeMethod()實作調用。

public class JavassistProxyFactory extends AbstractProxyFactory {

    @Override
    @SuppressWarnings("unchecked")
    public <T> T getProxy(Invoker<T> invoker, Class<?>[] interfaces) {
        return (T) Proxy.getProxy(interfaces).newInstance(new InvokerInvocationHandler(invoker));
    }

    @Override
    public <T> Invoker<T> getInvoker(T proxy, Class<T> type, URL url) {
        // TODO Wrapper cannot handle this scenario correctly: the classname contains '$'
        final Wrapper wrapper = Wrapper.getWrapper(proxy.getClass().getName().indexOf('$') < 0 ? proxy.getClass() : type);
        return new AbstractProxyInvoker<T>(proxy, type, url) {
            @Override
            protected Object doInvoke(T proxy, String methodName,
                                      Class<?>[] parameterTypes,
                                      Object[] arguments) throws Throwable {
                return wrapper.invokeMethod(proxy, methodName, parameterTypes, arguments);
            }
        };
    }
}

public abstract class AbstractProxyInvoker<T> implements Invoker<T> {
    Logger logger = LoggerFactory.getLogger(AbstractProxyInvoker.class);

    private final T proxy;

    private final Class<T> type;

    private final URL url;

    public AbstractProxyInvoker(T proxy, Class<T> type, URL url) {
        if (proxy == null) {
            throw new IllegalArgumentException("proxy == null");
        }
        if (type == null) {
            throw new IllegalArgumentException("interface == null");
        }
        if (!type.isInstance(proxy)) {
            throw new IllegalArgumentException(proxy.getClass().getName() + " not implement interface " + type);
        }
        this.proxy = proxy;
        this.type = type;
        this.url = url;
    }

    @Override
    public Result invoke(Invocation invocation) throws RpcException {
        try {
            Object value = doInvoke(proxy, invocation.getMethodName(), invocation.getParameterTypes(), invocation.getArguments());
            CompletableFuture<Object> future = wrapWithFuture(value, invocation);
            AsyncRpcResult asyncRpcResult = new AsyncRpcResult(invocation);
            future.whenComplete((obj, t) -> {
                AppResponse result = new AppResponse();
                if (t != null) {
                    if (t instanceof CompletionException) {
                        result.setException(t.getCause());
                    } else {
                        result.setException(t);
                    }
                } else {
                    result.setValue(obj);
                }
                asyncRpcResult.complete(result);
            });
            return asyncRpcResult;
        } catch (InvocationTargetException e) {
            if (RpcContext.getContext().isAsyncStarted() && !RpcContext.getContext().stopAsync()) {
                logger.error("Provider async started, but got an exception from the original method, cannot write the exception back to consumer because an async result may have returned the new thread.", e);
            }
            return AsyncRpcResult.newDefaultAsyncResult(null, e.getTargetException(), invocation);
        } catch (Throwable e) {
            throw new RpcException("Failed to invoke remote proxy method " + invocation.getMethodName() + " to " + getUrl() + ", cause: " + e.getMessage(), e);
        }
    }
}

getWrapper()方法

通過makeWrapper()方法生成Wrapper對象。
makeWrapper()方法通過javassist生成代碼，邏輯複雜，通過arthas方法反編譯檢視。

public static Wrapper getWrapper(Class<?> c) {
        while (ClassGenerator.isDynamicClass(c)) // can not wrapper on dynamic class.
        {
            c = c.getSuperclass();
        }

        if (c == Object.class) {
            return OBJECT_WRAPPER;
        }
        // 緩存作用
        Wrapper ret = WRAPPER_MAP.get(c);
        if (ret == null) {
            // 生成Wrapper類,這邊邏輯比較難懂,下面先通過arthas生成具體的Wrapper類觀察一下
            ret = makeWrapper(c);
            WRAPPER_MAP.put(c, ret);
        }
        return ret;
    }

    private static Wrapper makeWrapper(Class<?> c) {
        if (c.isPrimitive()) {
            throw new IllegalArgumentException("Can not create wrapper for primitive type: " + c);
        }

        String name = c.getName();
        ClassLoader cl = ClassUtils.getClassLoader(c);

        StringBuilder c1 = new StringBuilder("public void setPropertyValue(Object o, String n, Object v){ ");
        StringBuilder c2 = new StringBuilder("public Object getPropertyValue(Object o, String n){ ");
        StringBuilder c3 = new StringBuilder("public Object invokeMethod(Object o, String n, Class[] p, Object[] v) throws " + InvocationTargetException.class.getName() + "{ ");

        c1.append(name).append(" w; try{ w = ((").append(name).append(")$1); }catch(Throwable e){ throw new IllegalArgumentException(e); }");
        c2.append(name).append(" w; try{ w = ((").append(name).append(")$1); }catch(Throwable e){ throw new IllegalArgumentException(e); }");
        c3.append(name).append(" w; try{ w = ((").append(name).append(")$1); }catch(Throwable e){ throw new IllegalArgumentException(e); }");

        Map<String, Class<?>> pts = new HashMap<>(); // <property name, property types>
        Map<String, Method> ms = new LinkedHashMap<>(); // <method desc, Method instance>
        List<String> mns = new ArrayList<>(); // method names.
        List<String> dmns = new ArrayList<>(); // declaring method names.

        // get all public field.
        for (Field f : c.getFields()) {
            String fn = f.getName();
            Class<?> ft = f.getType();
            if (Modifier.isStatic(f.getModifiers()) || Modifier.isTransient(f.getModifiers())) {
                continue;
            }

            c1.append(" if( $2.equals(\"").append(fn).append("\") ){ w.").append(fn).append("=").append(arg(ft, "$3")).append("; return; }");
            c2.append(" if( $2.equals(\"").append(fn).append("\") ){ return ($w)w.").append(fn).append("; }");
            pts.put(fn, ft);
        }

        Method[] methods = c.getMethods();
        // get all public method.
        boolean hasMethod = hasMethods(methods);
        if (hasMethod) {
            c3.append(" try{");
            for (Method m : methods) {
                //ignore Object's method.
                if (m.getDeclaringClass() == Object.class) {
                    continue;
                }

                String mn = m.getName();
                c3.append(" if( \"").append(mn).append("\".equals( $2 ) ");
                int len = m.getParameterTypes().length;
                c3.append(" && ").append(" $3.length == ").append(len);

                boolean override = false;
                for (Method m2 : methods) {
                    if (m != m2 && m.getName().equals(m2.getName())) {
                        override = true;
                        break;
                    }
                }
                if (override) {
                    if (len > 0) {
                        for (int l = 0; l < len; l++) {
                            c3.append(" && ").append(" $3[").append(l).append("].getName().equals(\"")
                                    .append(m.getParameterTypes()[l].getName()).append("\")");
                        }
                    }
                }

                c3.append(" ) { ");

                if (m.getReturnType() == Void.TYPE) {
                    c3.append(" w.").append(mn).append('(').append(args(m.getParameterTypes(), "$4")).append(");").append(" return null;");
                } else {
                    c3.append(" return ($w)w.").append(mn).append('(').append(args(m.getParameterTypes(), "$4")).append(");");
                }

                c3.append(" }");

                mns.add(mn);
                if (m.getDeclaringClass() == c) {
                    dmns.add(mn);
                }
                ms.put(ReflectUtils.getDesc(m), m);
            }
            c3.append(" } catch(Throwable e) { ");
            c3.append("     throw new java.lang.reflect.InvocationTargetException(e); ");
            c3.append(" }");
        }

        c3.append(" throw new " + NoSuchMethodException.class.getName() + "(\"Not found method \\\"\"+$2+\"\\\" in class " + c.getName() + ".\"); }");

        // deal with get/set method.
        Matcher matcher;
        for (Map.Entry<String, Method> entry : ms.entrySet()) {
            String md = entry.getKey();
            Method method = entry.getValue();
            if ((matcher = ReflectUtils.GETTER_METHOD_DESC_PATTERN.matcher(md)).matches()) {
                String pn = propertyName(matcher.group(1));
                c2.append(" if( $2.equals(\"").append(pn).append("\") ){ return ($w)w.").append(method.getName()).append("(); }");
                pts.put(pn, method.getReturnType());
            } else if ((matcher = ReflectUtils.IS_HAS_CAN_METHOD_DESC_PATTERN.matcher(md)).matches()) {
                String pn = propertyName(matcher.group(1));
                c2.append(" if( $2.equals(\"").append(pn).append("\") ){ return ($w)w.").append(method.getName()).append("(); }");
                pts.put(pn, method.getReturnType());
            } else if ((matcher = ReflectUtils.SETTER_METHOD_DESC_PATTERN.matcher(md)).matches()) {
                Class<?> pt = method.getParameterTypes()[0];
                String pn = propertyName(matcher.group(1));
                c1.append(" if( $2.equals(\"").append(pn).append("\") ){ w.").append(method.getName()).append("(").append(arg(pt, "$3")).append("); return; }");
                pts.put(pn, pt);
            }
        }
        c1.append(" throw new " + NoSuchPropertyException.class.getName() + "(\"Not found property \\\"\"+$2+\"\\\" field or setter method in class " + c.getName() + ".\"); }");
        c2.append(" throw new " + NoSuchPropertyException.class.getName() + "(\"Not found property \\\"\"+$2+\"\\\" field or setter method in class " + c.getName() + ".\"); }");

        // make class
        long id = WRAPPER_CLASS_COUNTER.getAndIncrement();
        ClassGenerator cc = ClassGenerator.newInstance(cl);
        cc.setClassName((Modifier.isPublic(c.getModifiers()) ? Wrapper.class.getName() : c.getName() + "$sw") + id);
        cc.setSuperClass(Wrapper.class);

        cc.addDefaultConstructor();
        cc.addField("public static String[] pns;"); // property name array.
        cc.addField("public static " + Map.class.getName() + " pts;"); // property type map.
        cc.addField("public static String[] mns;"); // all method name array.
        cc.addField("public static String[] dmns;"); // declared method name array.
        for (int i = 0, len = ms.size(); i < len; i++) {
            cc.addField("public static Class[] mts" + i + ";");
        }

        cc.addMethod("public String[] getPropertyNames(){ return pns; }");
        cc.addMethod("public boolean hasProperty(String n){ return pts.containsKey($1); }");
        cc.addMethod("public Class getPropertyType(String n){ return (Class)pts.get($1); }");
        cc.addMethod("public String[] getMethodNames(){ return mns; }");
        cc.addMethod("public String[] getDeclaredMethodNames(){ return dmns; }");
        cc.addMethod(c1.toString());
        cc.addMethod(c2.toString());
        cc.addMethod(c3.toString());

        try {
            Class<?> wc = cc.toClass();
            // setup static field.
            wc.getField("pts").set(null, pts);
            wc.getField("pns").set(null, pts.keySet().toArray(new String[0]));
            wc.getField("mns").set(null, mns.toArray(new String[0]));
            wc.getField("dmns").set(null, dmns.toArray(new String[0]));
            int ix = 0;
            for (Method m : ms.values()) {
                wc.getField("mts" + ix++).set(null, m.getParameterTypes());
            }
            return (Wrapper) wc.newInstance();
        } catch (RuntimeException e) {
            throw e;
        } catch (Throwable e) {
            throw new RuntimeException(e.getMessage(), e);
        } finally {
            cc.release();
            ms.clear();
            mns.clear();
            dmns.clear();
        }
    }

Wrapper1

Wrapper1是通過javassist新生成的包裝類對象。
Wrapper1的invokeMethod()方法内部調用服務DemoServiceImpl的釋出的方法。

package org.apache.dubbo.common.bytecode;

import java.lang.reflect.InvocationTargetException;
import java.util.Map;
import org.apache.dubbo.common.bytecode.ClassGenerator;
import org.apache.dubbo.common.bytecode.NoSuchMethodException;
import org.apache.dubbo.common.bytecode.NoSuchPropertyException;
import org.apache.dubbo.common.bytecode.Wrapper;
import org.apache.dubbo.demo.provider.DemoServiceImpl;

public class Wrapper1 extends Wrapper implements ClassGenerator.DC {
    public static String[] pns;
    public static Map pts;
    public static String[] mns;
    public static String[] dmns;
    public static Class[] mts0;

    public String[] getMethodNames() {
        return mns;
    }

    public Class getPropertyType(String string) {
        return (Class)pts.get(string);
    }

    public String[] getDeclaredMethodNames() {
        return dmns;
    }

    public String[] getPropertyNames() {
        return pns;
    }

    public boolean hasProperty(String string) {
        return pts.containsKey(string);
    }

    public Object getPropertyValue(Object object, String string) {
        try {
            DemoServiceImpl demoServiceImpl = (DemoServiceImpl)object;
        }
        catch (Throwable throwable) {
            throw new IllegalArgumentException(throwable);
        }
        throw new NoSuchPropertyException(new StringBuffer().append("Not found property \"").append(string).append("\" field or setter method in class org.apache.dubbo.demo.provider.DemoServiceImpl.").toString());
    }

    public void setPropertyValue(Object object, String string, Object object2) {
        try {
            DemoServiceImpl demoServiceImpl = (DemoServiceImpl)object;
        }
        catch (Throwable throwable) {
            throw new IllegalArgumentException(throwable);
        }
        throw new NoSuchPropertyException(new StringBuffer().append("Not found property \"").append(string).append("\" field or setter method in class org.apache.dubbo.demo.provider.DemoServiceImpl.").toString());
    }

    public Object invokeMethod(Object object, String string, Class[] arrclass, Object[] arrobject) throws InvocationTargetException {
        DemoServiceImpl demoServiceImpl;
        try {
            demoServiceImpl = (DemoServiceImpl)object;
        }
        catch (Throwable throwable) {
            throw new IllegalArgumentException(throwable);
        }
        try {
            if ("sayHello".equals(string) && arrclass.length == 1) {
                return demoServiceImpl.sayHello((String)arrobject[0]);
            }
        }
        catch (Throwable throwable) {
            throw new InvocationTargetException(throwable);
        }
        throw new NoSuchMethodException(new StringBuffer().append("Not found method \"").append(string).append("\" in class org.apache.dubbo.demo.provider.DemoServiceImpl.").toString());
    }
}

整體流程概括

1、ProxyFactory擷取擴充卡對象ProxyFactory$Adaptive。
2、ProxyFactory$Adaptive對象内部擷取javassist對應的JavassistProxyFactory對象。
3、JavassistProxyFactory通過getInvoker()方法擷取包裝類對象Wrapper1，包裝類Wrapper1内部通過invokeMethod()方法執行真正釋出服務的方法。

Arthas代碼反編譯

1、首先啟動Provider服務提供者程式，将斷點放置到ret = makerWrapper(c)這裡，确定這裡的c是DemoServiceImpl，然後運作程式至下一步，觀察ret的名字。如下圖，可以發現生成的Wrapper類是叫Wrapper1，然後放開斷點，讓程式走完，服務提供者處于運作狀态。

2、通過Arthas檢視生成的Wrapper1到底是什麼? 首先下載下傳它的jar包，下載下傳位址。然後打開cmd，執行以下指令。注意2是對應Provider程式的序号，需要和你自己程式對應。輸入2後可以發現連上了Arthas。然後使用sc指令查找Wrapper1具體對應的是哪個class檔案，最後使用jad指令反編譯，檢視Wrapper1類對應的Java檔案具體内容。

最後，我們可以得到Wrapper1的Java檔案

參考文章

Dubbo中JavaAssist的Wrapper.getWrapper生成代理分析

Dubbo之ProxyFactory解析

開篇

ProxyFactory擴充卡

ProxyFactory

ProxyFactory$Adaptive

exportLocal()方法

JavassistProxyFactory

getWrapper()方法

Wrapper1

整體流程概括

Arthas代碼反編譯

參考文章

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