1. Caucho

1.1 概况

spring-remoting代码的情况如下：

本节近分析caucho模块。

1.2 分类

其中以hession为例，Hessian远程服务调用过程：

 

　　　　　　　　　　　　　　　　　　　　　　　　　　Hessian远程服务调用过程

1.2.1 客户端

BurlapProxyFactoryBean，BurlapClientInterceptor；

HessianProxyFactoryBean，HessianClientInterceptor；

HessianProxyFactoryBean继承自HessianClientInterceptor，间接封装了HessianProxyFactory。HessianProxyFactory是hessian的client实现类，

示例:

public interface Basic {  public String hello();}import com.caucho.hessian.client.HessianProxyFactory;public class BasicClient {  public static void main(String []args)    throws Exception  {    String url = "http://www.caucho.com/hessian/test/basic";    HessianProxyFactory factory = new HessianProxyFactory();    Basic basic = (Basic) factory.create(Basic.class, url);    System.out.println("Hello: " + basic.hello());  }}

 create方法如下：

/**   * Creates a new proxy with the specified URL.  The returned object   * is a proxy with the interface specified by api.   *   * 
   * String url = "http://localhost:8080/ejb/hello");   * HelloHome hello = (HelloHome) factory.create(HelloHome.class, url);   * 
   *   * @param api the interface the proxy class needs to implement   * @param url the URL where the client object is located.   *   * @return a proxy to the object with the specified interface.   */  public Object create(Class
      api, URL url, ClassLoader loader)  {    if (api == null)      throw new NullPointerException("api must not be null for HessianProxyFactory.create()");    InvocationHandler handler = null;    handler = new HessianProxy(url, this, api);    return Proxy.newProxyInstance(loader,                                  new Class[] { api,                                                HessianRemoteObject.class },                                  handler);  }

其中HessianProxy实现了java的动态代理

/** * Proxy implementation for Hessian clients.  Applications will generally * use HessianProxyFactory to create proxy clients. */public class HessianProxy implements InvocationHandler, Serializable {  private static final Logger log    = Logger.getLogger(HessianProxy.class.getName());    protected HessianProxyFactory _factory;    private WeakHashMap
     
       _mangleMap    = new WeakHashMap
      
       ();  private Class
        _type;  private URL _url;  /**   * Protected constructor for subclassing   */  protected HessianProxy(URL url, HessianProxyFactory factory)  {    this(url, factory, null);  }  /**   * Protected constructor for subclassing   */  protected HessianProxy(URL url,                         HessianProxyFactory factory,                          Class
        type)  {    _factory = factory;    _url = url;    _type = type;  }}
      
     

 最重要的invoke方法如下：

/**   * Handles the object invocation.   *   * @param proxy the proxy object to invoke   * @param method the method to call   * @param args the arguments to the proxy object   */  public Object invoke(Object proxy, Method method, Object []args)    throws Throwable  {    String mangleName;    synchronized (_mangleMap) {      mangleName = _mangleMap.get(method);    }    if (mangleName == null) {      String methodName = method.getName();      Class
      []params = method.getParameterTypes();      // equals and hashCode are special cased      if (methodName.equals("equals")          && params.length == 1 && params[0].equals(Object.class)) {        Object value = args[0];        if (value == null || ! Proxy.isProxyClass(value.getClass()))          return Boolean.FALSE;        Object proxyHandler = Proxy.getInvocationHandler(value);        if (! (proxyHandler instanceof HessianProxy))          return Boolean.FALSE;        HessianProxy handler = (HessianProxy) proxyHandler;        return new Boolean(_url.equals(handler.getURL()));      }      else if (methodName.equals("hashCode") && params.length == 0)        return new Integer(_url.hashCode());      else if (methodName.equals("getHessianType"))        return proxy.getClass().getInterfaces()[0].getName();      else if (methodName.equals("getHessianURL"))        return _url.toString();      else if (methodName.equals("toString") && params.length == 0)        return "HessianProxy[" + _url + "]";            if (! _factory.isOverloadEnabled())        mangleName = method.getName();      else        mangleName = mangleName(method);      synchronized (_mangleMap) {        _mangleMap.put(method, mangleName);      }    }    InputStream is = null;    HessianConnection conn = null;        try {      if (log.isLoggable(Level.FINER))        log.finer("Hessian[" + _url + "] calling " + mangleName);            conn = sendRequest(mangleName, args);      is = getInputStream(conn);      if (log.isLoggable(Level.FINEST)) {        PrintWriter dbg = new PrintWriter(new LogWriter(log));        HessianDebugInputStream dIs          = new HessianDebugInputStream(is, dbg);        dIs.startTop2();        is = dIs;      }      AbstractHessianInput in;      int code = is.read();      if (code == 'H') {        int major = is.read();        int minor = is.read();        in = _factory.getHessian2Input(is);        Object value = in.readReply(method.getReturnType());        return value;      }      else if (code == 'r') {        int major = is.read();        int minor = is.read();        in = _factory.getHessianInput(is);        in.startReplyBody();        Object value = in.readObject(method.getReturnType());        if (value instanceof InputStream) {          value = new ResultInputStream(conn, is, in, (InputStream) value);          is = null;          conn = null;        }        else          in.completeReply();        return value;      }      else        throw new HessianProtocolException("'" + (char) code + "' is an unknown code");    } catch (HessianProtocolException e) {      throw new HessianRuntimeException(e);    } finally {      try {        if (is != null)          is.close();      } catch (Exception e) {        log.log(Level.FINE, e.toString(), e);      }            try {        if (conn != null)          conn.destroy();      } catch (Exception e) {        log.log(Level.FINE, e.toString(), e);      }    }  }

发送http请求

/**   * Sends the HTTP request to the Hessian connection.   */  protected HessianConnection sendRequest(String methodName, Object []args)    throws IOException  {    HessianConnection conn = null;        conn = _factory.getConnectionFactory().open(_url);    boolean isValid = false;    try {      addRequestHeaders(conn);      OutputStream os = null;      try {        os = conn.getOutputStream();      } catch (Exception e) {        throw new HessianRuntimeException(e);      }      if (log.isLoggable(Level.FINEST)) {        PrintWriter dbg = new PrintWriter(new LogWriter(log));        HessianDebugOutputStream dOs = new HessianDebugOutputStream(os, dbg);        dOs.startTop2();        os = dOs;      }            AbstractHessianOutput out = _factory.getHessianOutput(os);      out.call(methodName, args);      out.flush();      conn.sendRequest();      isValid = true;      return conn;    } finally {      if (! isValid && conn != null)        conn.destroy();    }  }

创建http连接代码

/**   * Opens a new or recycled connection to the HTTP server.   */  public HessianConnection open(URL url)    throws IOException  {    if (log.isLoggable(Level.FINER))      log.finer(this + " open(" + url + ")");    URLConnection conn = url.openConnection();    // HttpURLConnection httpConn = (HttpURLConnection) conn;    // httpConn.setRequestMethod("POST");    // conn.setDoInput(true);    long connectTimeout = _proxyFactory.getConnectTimeout();    if (connectTimeout >= 0)      conn.setConnectTimeout((int) connectTimeout);    conn.setDoOutput(true);    long readTimeout = _proxyFactory.getReadTimeout();    if (readTimeout > 0) {      try {        conn.setReadTimeout((int) readTimeout);      } catch (Throwable e) {      }    }

 

1.2.2 服务器端

HessianExporter及其实现类HessianServiceExporter，SimpleHessianServiceExporter.

 hessian服务端示例

package hessian.test;import com.caucho.hessian.server.HessianServlet;public class BasicService extends HessianServlet implements Basic {  public String hello()  {    return "Hello, world";  }}

 我们来看一下：

HessianServiceExporter

/** * Servlet-API-based HTTP request handler that exports the specified service bean * as Hessian service endpoint, accessible via a Hessian proxy. * * 
Note: Spring also provides an alternative version of this exporter, * for Sun's JRE 1.6 HTTP server: {@link SimpleHessianServiceExporter}. * * 
Hessian is a slim, binary RPC protocol. * For information on Hessian, see the * Hessian website. * Note: As of Spring 4.0, this exporter requires Hessian 4.0 or above. * * 
Hessian services exported with this class can be accessed by * any Hessian client, as there isn't any special handling involved. * * @author Juergen Hoeller * @since 13.05.2003 * @see HessianClientInterceptor * @see HessianProxyFactoryBean * @see org.springframework.remoting.httpinvoker.HttpInvokerServiceExporter * @see org.springframework.remoting.rmi.RmiServiceExporter */

处理客户端请求的方法：

/**     * Processes the incoming Hessian request and creates a Hessian response.     */    @Override    public void handleRequest(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        if (!"POST".equals(request.getMethod())) {            throw new HttpRequestMethodNotSupportedException(request.getMethod(),                    new String[] {"POST"}, "HessianServiceExporter only supports POST requests"); } response.setContentType(CONTENT_TYPE_HESSIAN); try { invoke(request.getInputStream(), response.getOutputStream()); } catch (Throwable ex) { throw new NestedServletException("Hessian skeleton invocation failed", ex); } }

invoke调用

/**     * Actually invoke the skeleton with the given streams.     * @param skeleton the skeleton to invoke     * @param inputStream the request stream     * @param outputStream the response stream     * @throws Throwable if invocation failed     */    protected void doInvoke(HessianSkeleton skeleton, InputStream inputStream, OutputStream outputStream)            throws Throwable {        ClassLoader originalClassLoader = overrideThreadContextClassLoader();        try {            InputStream isToUse = inputStream;            OutputStream osToUse = outputStream; if (this.debugLogger != null && this.debugLogger.isDebugEnabled()) { PrintWriter debugWriter = new PrintWriter(new CommonsLogWriter(this.debugLogger)); @SuppressWarnings("resource") HessianDebugInputStream dis = new HessianDebugInputStream(inputStream, debugWriter); @SuppressWarnings("resource") HessianDebugOutputStream dos = new HessianDebugOutputStream(outputStream, debugWriter); dis.startTop2(); dos.startTop2(); isToUse = dis; osToUse = dos; } if (!isToUse.markSupported()) { isToUse = new BufferedInputStream(isToUse); isToUse.mark(1); } int code = isToUse.read(); int major; int minor; AbstractHessianInput in; AbstractHessianOutput out; if (code == 'H') { // Hessian 2.0 stream major = isToUse.read(); minor = isToUse.read(); if (major != 0x02) { throw new IOException("Version " + major + "." + minor + " is not understood"); } in = new Hessian2Input(isToUse); out = new Hessian2Output(osToUse); in.readCall(); } else if (code == 'C') { // Hessian 2.0 call... for some reason not handled in HessianServlet!  isToUse.reset(); in = new Hessian2Input(isToUse); out = new Hessian2Output(osToUse); in.readCall(); } else if (code == 'c') { // Hessian 1.0 call major = isToUse.read(); minor = isToUse.read(); in = new HessianInput(isToUse); if (major >= 2) { out = new Hessian2Output(osToUse); } else { out = new HessianOutput(osToUse); } } else { throw new IOException("Expected 'H'/'C' (Hessian 2.0) or 'c' (Hessian 1.0) in hessian input at " + code); } if (this.serializerFactory != null) { in.setSerializerFactory(this.serializerFactory); out.setSerializerFactory(this.serializerFactory); } if (this.remoteResolver != null) { in.setRemoteResolver(this.remoteResolver); } try { skeleton.invoke(in, out); } finally { try { in.close(); isToUse.close(); } catch (IOException ex) { // ignore  } try { out.close(); osToUse.close(); } catch (IOException ex) { // ignore  } } } finally { resetThreadContextClassLoader(originalClassLoader); } }

调用skeleton的invoke方法

/**   * Invoke the object with the request from the input stream.   *   * @param in the Hessian input stream   * @param out the Hessian output stream   */  public void invoke(Object service,                     AbstractHessianInput in,                     AbstractHessianOutput out)    throws Exception  {    ServiceContext context = ServiceContext.getContext();    // backward compatibility for some frameworks that don't read    // the call type first    in.skipOptionalCall();    // Hessian 1.0 backward compatibility    String header;    while ((header = in.readHeader()) != null) { Object value = in.readObject(); context.addHeader(header, value); } String methodName = in.readMethod(); int argLength = in.readMethodArgLength(); Method method; method = getMethod(methodName + "__" + argLength); if (method == null) method = getMethod(methodName); if (method != null) { } else if ("_hessian_getAttribute".equals(methodName)) { String attrName = in.readString(); in.completeCall(); String value = null; if ("java.api.class".equals(attrName)) value = getAPIClassName(); else if ("java.home.class".equals(attrName)) value = getHomeClassName(); else if ("java.object.class".equals(attrName)) value = getObjectClassName(); out.writeReply(value); out.close(); return; } else if (method == null) { out.writeFault("NoSuchMethodException", escapeMessage("The service has no method named: " + in.getMethod()), null); out.close(); return; } Class
      []args = method.getParameterTypes(); if (argLength != args.length && argLength >= 0) { out.writeFault("NoSuchMethod", escapeMessage("method " + method + " argument length mismatch, received length=" + argLength), null); out.close(); return; } Object []values = new Object[args.length]; for (int i = 0; i < args.length; i++) { // XXX: needs Marshal object values[i] = in.readObject(args[i]); } Object result = null; try { result = method.invoke(service, values); } catch (Exception e) { Throwable e1 = e; if (e1 instanceof InvocationTargetException) e1 = ((InvocationTargetException) e).getTargetException(); log.log(Level.FINE, this + " " + e1.toString(), e1); out.writeFault("ServiceException", escapeMessage(e1.getMessage()), e1); out.close(); return; } // The complete call needs to be after the invoke to handle a // trailing InputStream  in.completeCall(); out.writeReply(result); out.close(); }

反射触发类的方法。

 

BurlapExporter及其实现类BurlapServiceExporter，SimpleBurlapServiceExporter，因已经depressed，故略。

1.3 小结

　　Spring封装了hessian客户端和服务端的通用代码，把实现者和调用者作为bean放到spring容器中管理，简化了开发。分析源码的过程中，发现在客户端使用了动态代理，在服务端使用反射，让我们加深了对java基础知识的理解。