dubbo起停之服务暴露

由上一节可知带上dubbo@Service注解的对象，在注册成为bean之后会进一步注册一个ServiceBean，服务暴露便是在这里

 public void afterPropertiesSet() throws Exception {
        if (getProvider() == null) {
            Map<String, ProviderConfig> providerConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ProviderConfig.class, false, false);
            if (providerConfigMap != null && providerConfigMap.size() > 0) {
                Map<String, ProtocolConfig> protocolConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ProtocolConfig.class, false, false);
                if ((protocolConfigMap == null || protocolConfigMap.size() == 0)
                        && providerConfigMap.size() > 1) { // backward compatibility
                    List<ProviderConfig> providerConfigs = new ArrayList<ProviderConfig>();
                    for (ProviderConfig config : providerConfigMap.values()) {
                        if (config.isDefault() != null && config.isDefault().booleanValue()) {
                            providerConfigs.add(config);
                        }
                    }
                    if (!providerConfigs.isEmpty()) {
                        setProviders(providerConfigs);
                    }
                } else {
                    ProviderConfig providerConfig = null;
                    for (ProviderConfig config : providerConfigMap.values()) {
                        if (config.isDefault() == null || config.isDefault().booleanValue()) {
                            if (providerConfig != null) {
                                throw new IllegalStateException("Duplicate provider configs: " + providerConfig + " and " + config);
                            }
                            providerConfig = config;
                        }
                    }
                    if (providerConfig != null) {
                        setProvider(providerConfig);
                    }
                }
            }
        }
　　　　......
 if (getPath() == null || getPath().length() == 0) {

        if (beanName != null && beanName.length() > 0
                && getInterface() != null && getInterface().length() > 0
                && beanName.startsWith(getInterface())) {
            setPath(beanName);
        }
    }
    if (!isDelay()) {
        export();
    }
}

protected synchronized void doExport() {
        if (unexported) {
            throw new IllegalStateException("Already unexported!");
        }
        if (exported) {
            return;
        }
        exported = true;
        if (interfaceName == null || interfaceName.length() == 0) {
            throw new IllegalStateException("<dubbo:service interface=\"\" /> interface not allow null!");
        }
......
  checkApplication();
        checkRegistry();
        checkProtocol();
        appendProperties(this);
        checkStubAndMock(interfaceClass);
        if (path == null || path.length() == 0) {
            path = interfaceName;
        }
        doExportUrls();
        ProviderModel providerModel = new ProviderModel(getUniqueServiceName(), this, ref);
        ApplicationModel.initProviderModel(getUniqueServiceName(), providerModel);
    }

doExportUrlsFor1Protocol一进去有相当长的逻辑是在各配置对象里搜罗必要的配置信息，在具体的暴露服务的代码之前我们可以得到这样一个map：

接着是暴露服务的逻辑

注意这里有个扩展点，大致的过程是根据url取到物理ip和端口 并从url中根据scope判断是本地的服务还是远程，这里先不关心本地服务的暴露 看下非本地的情况：

在为url和registryURL填充若干属性之后，url便填充registryURL的export属性，registryURL作为参数通过代理工厂实例化一个invoker对象。在之后invoker和serviceBean一起作为参数，暴露服务

仔细看一下

Invoker<?> invoker = proxyFactory.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(Constants.EXPORT_KEY, url.toFullString()));

调试时的参数，各入参值如下：

proxy指向EchoServiceImpl的实例，type为接口Class类，url为

registry://localhost:2181/com.alibaba.dubbo.registry.RegistryService?application=echo-annotation-provider&dubbo=2.0.2&export=dubbo://10.1.81.210:20880/facade.EchoService?anyhost=true&application=echo-annotation-provider&bean.name=ServiceBean:facade.EchoService&bind.ip=10.1.81.210&bind.port=20880&dubbo=2.0.2&generic=false&interface=facade.EchoService&methods=echo&pid=84968&side=provider&timestamp=1572767833008&pid=84968&registry=zookeeper&timestamp=1572767833000

深入getWrapper（）：

 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;

        Wrapper ret = WRAPPER_MAP.get(c);
        if (ret == null) {
            ret = makeWrapper(c);
            WRAPPER_MAP.put(c, ret);
        }
        return ret;
    }

Wrapper为每个Class维护了一个WRAPPER_MAP缓存，如果没有命中则初始化makeWrapper(c)：

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 = ClassHelper.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<String, Class<?>>(); // <property name, property types>
        Map<String, Method> ms = new LinkedHashMap<String, Method>(); // <method desc, Method instance>
        List<String> mns = new ArrayList<String>(); // method names.
        List<String> dmns = new ArrayList<String>(); // 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) {
            if (m.getDeclaringClass() == Object.class) //ignore Object's method.
                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);
        }
        if (hasMethod) {
            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 = (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+\"\\\" filed or setter method in class " + c.getName() + ".\"); }");
        c2.append(" throw new " + NoSuchPropertyException.class.getName() + "(\"Not found property \\\"\"+$2+\"\\\" filed 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();
        }
    }

我们修改源码试图将javasisst生成的代码导出：

mCtc.writeFile("/Users/lichengcheng/dubbo");

重新打包，可以看到生成的代理class如下：

package com.alibaba.dubbo.common.bytecode;

import facade.EchoService;
import java.lang.reflect.InvocationTargetException;
import java.util.Map;

public class Wrapper0
  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[] getPropertyNames()
  {
    return pns;
  }

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

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

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

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

  public void setPropertyValue(Object paramObject1, String paramString, Object paramObject2)
  {
    try
    {
      EchoService localEchoService = (EchoService)paramObject1;
    }
    catch (Throwable localThrowable)
    {
      throw new IllegalArgumentException(localThrowable);
    }
    throw new NoSuchPropertyException("Not found property \"" + paramString + "\" filed or setter method in class facade.EchoService.");
  }

  public Object getPropertyValue(Object paramObject, String paramString)
  {
    try
    {
      EchoService localEchoService = (EchoService)paramObject;
    }
    catch (Throwable localThrowable)
    {
      throw new IllegalArgumentException(localThrowable);
    }
    throw new NoSuchPropertyException("Not found property \"" + paramString + "\" filed or setter method in class facade.EchoService.");
  }

  public Object invokeMethod(Object paramObject, String paramString, Class[] paramArrayOfClass, Object[] paramArrayOfObject)
    throws InvocationTargetException
  {
    EchoService localEchoService;
    try
    {
      localEchoService = (EchoService)paramObject;
    }
    catch (Throwable localThrowable1)
    {
      throw new IllegalArgumentException(localThrowable1);
    }
    try
    {
      if ((!"echo".equals(paramString)) || (paramArrayOfClass.length == 1)) {
        return localEchoService.echo((String)paramArrayOfObject[0]);
      }
    }
    catch (Throwable localThrowable2)
    {
      throw new InvocationTargetException(localThrowable2);
    }
    throw new NoSuchMethodException("Not found method \"" + paramString + "\" in class facade.EchoService.");
  }
}

这里开始是一连串的拦截器，最后会到DubboProtocol#export暴露服务：