GWT和AOP

上文http://gwbasic.iteye.com/admin/show/39079提到的GWTSpringController.java,继承的是GWT中的RemoteServiceServlet类,在使用过程中发现这个类不支持AOP,原因

public String processCall(String payload) throws SerializationException {
  // .............
  // ............
      // Actually get the service interface, so that we can query its methods.
    //
    Class serviceIntf; 
    try {
      // 此处的serviceIntf,是用getClassForName获取的,没有经过proxy代理
      serviceIntf = getClassFromName(serviceIntfName);
    } catch (ClassNotFoundException e) {
      throw new SerializationException("Unknown service interface class '"
          + serviceIntfName + "'", e);
    }

    // Read the method name.
    //
    String methodName = streamReader.readString();

    // Read the number and names of the parameter classes from the stream.
    // We have to do this so that we can find the correct overload of the
    // method.
    //
    int paramCount = streamReader.readInt();
    Class[] paramTypes = new Class[paramCount];
    for (int i = 0; i < paramTypes.length; i++) {
      String paramClassName = streamReader.readString();
      try {
        paramTypes[i] = getClassOrPrimitiveFromName(paramClassName);
      } catch (ClassNotFoundException e) {
        throw new SerializationException("Unknown parameter " + i + " type '"
            + paramClassName + "'", e);
      }
    }

    // For security, make sure the method is found in the service interface
    // and not just one that happens to be defined on this class.
    //
    Method serviceIntfMethod = findInterfaceMethod(serviceIntf, methodName,
        paramTypes, true);
}

于是参照RemoteServiceServlet重新写了一个在Spring中使用的Controller
GWTServiceController

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;
import java.util.zip.GZIPOutputStream;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.context.ServletContextAware;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.Controller;

import com.google.gwt.user.client.rpc.RemoteService;
import com.google.gwt.user.client.rpc.SerializationException;
import com.google.gwt.user.server.rpc.impl.ServerSerializableTypeOracle;
import com.google.gwt.user.server.rpc.impl.ServerSerializableTypeOracleImpl;
import com.google.gwt.user.server.rpc.impl.ServerSerializationStreamReader;
import com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter;

public class GWTServiceController implements ServletContextAware, Controller {
	private ServletContext servletContext;

	/** Object we'll invoke methods on. Defaults to this. */
	private Object delegate;

	public void setServletContext(ServletContext servletContext) {
		this.servletContext = servletContext;
	}

	public ServletContext getServletContext() {
		return servletContext;
	}

	public Object getDelegate() {
		return delegate;
	}

	public void setDelegate(Object delegate) {
		this.delegate = delegate;
		registerImplementedRemoteServiceInterface(this.delegate);
	}

	public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response)
			throws Exception {
		doPost(request, response);
		return null;
	}

	/*
	 * These members are used to get and set the different HttpServletResponse and
	 * HttpServletRequest headers.
	 */
	private static final String ACCEPT_ENCODING = "Accept-Encoding";

	private static final String CHARSET_UTF8 = "UTF-8";

	private static final String CONTENT_ENCODING = "Content-Encoding";

	private static final String CONTENT_ENCODING_GZIP = "gzip";

	private static final String CONTENT_TYPE_TEXT_PLAIN_UTF8 = "text/plain; charset=utf-8";

	private static final String GENERIC_FAILURE_MSG = "The call failed on the server; see server log for details";

	private static final HashMap TYPE_NAMES;

	/**
	 * Controls the compression threshold at and below which no compression will
	 * take place.
	 */
	private static final int UNCOMPRESSED_BYTE_SIZE_LIMIT = 256;

	static {
		TYPE_NAMES = new HashMap();
		TYPE_NAMES.put("Z", boolean.class);
		TYPE_NAMES.put("B", byte.class);
		TYPE_NAMES.put("C", char.class);
		TYPE_NAMES.put("D", double.class);
		TYPE_NAMES.put("F", float.class);
		TYPE_NAMES.put("I", int.class);
		TYPE_NAMES.put("J", long.class);
		TYPE_NAMES.put("S", short.class);
	}

	/**
	 * Return true if the response object accepts Gzip encoding. This is done by
	 * checking that the accept-encoding header specifies gzip as a supported
	 * encoding.
	 */
	private static boolean acceptsGzipEncoding(HttpServletRequest request) {
		assert (request != null);

		String acceptEncoding = request.getHeader(ACCEPT_ENCODING);
		if (null == acceptEncoding) {
			return false;
		}

		return (acceptEncoding.indexOf(CONTENT_ENCODING_GZIP) != -1);
	}

	/**
	 * This method attempts to estimate the number of bytes that a string will
	 * consume when it is sent out as part of an HttpServletResponse. This really
	 * a hack since we are assuming that every character will consume two bytes
	 * upon transmission. This is definitely not true since some characters
	 * actually consume more than two bytes and some consume less. This is even
	 * less accurate if the string is converted to UTF8. However, it does save us
	 * from converting every string that we plan on sending back to UTF8 just to
	 * determine that we should not compress it.
	 */
	private static int estimateByteSize(final String buffer) {
		return (buffer.length() * 2);
	}

	/**
	 * Find the invoked method on either the specified interface or any super.
	 */
	private static Method findInterfaceMethod(Class intf, String methodName, Class[] paramTypes,
			boolean includeInherited) {
		try {
			return intf.getDeclaredMethod(methodName, paramTypes);
		} catch (NoSuchMethodException e) {
			if (includeInherited) {
				Class[] superintfs = intf.getInterfaces();
				for (int i = 0; i < superintfs.length; i++) {
					Method method = findInterfaceMethod(superintfs[i], methodName, paramTypes, true);
					if (method != null) {
						return method;
					}
				}
			}

			return null;
		}
	}

	private final ServerSerializableTypeOracle serializableTypeOracle;

	/**
	 * The default constructor.
	 */
	public GWTServiceController() {
		serializableTypeOracle = new ServerSerializableTypeOracleImpl(getPackagePaths());
		this.delegate = this;
		registerImplementedRemoteServiceInterface(this.delegate);
	}

	/**
	 * This is called internally.
	 */
	public final void doPost(HttpServletRequest request, HttpServletResponse response) {
		Throwable caught;
		try {

			// Read the request fully.
			//
			String requestPayload = readPayloadAsUtf8(request);

			// Invoke the core dispatching logic, which returns the serialized
			// result.
			//
			String responsePayload = processCall(requestPayload);

			// Write the response.
			//
			writeResponse(request, response, responsePayload);
			return;
		} catch (IOException e) {
			caught = e;
		} catch (ServletException e) {
			caught = e;
		} catch (SerializationException e) {
			caught = e;
		} catch (Throwable e) {
			caught = e;
		}

		respondWithFailure(response, caught);
	}

	/**
	 * This is public so that it can be unit tested easily without HTTP.
	 */
	public String processCall(String payload) throws SerializationException {

		// Let subclasses see the serialized request.
		//
		onBeforeRequestDeserialized(payload);

		// Create a stream to deserialize the request.
		//
		ServerSerializationStreamReader streamReader = new ServerSerializationStreamReader(serializableTypeOracle);
		streamReader.prepareToRead(payload);

		// Read the service interface
		//
		String serviceIntfName = streamReader.readString();

		// TODO(mmendez): need a way to check the type signature of the service intf
		// Verify that this very servlet implements the specified interface name.
		// 从delegate中获取serviceIntf
		Class serviceIntf = getImplementedRemoteServiceInterface(serviceIntfName);
		if (serviceIntf == null) {
			// Bad payload, possible hack attempt.
			//
			throw new SecurityException(
					"Blocked attempt to access interface '"
							+ serviceIntfName
							+ "', which is either not implemented by this servlet or which doesn't extend RemoteService; this is either misconfiguration or a hack attempt");
		}

		// Read the method name.
		//
		String methodName = streamReader.readString();

		// Read the number and names of the parameter classes from the stream.
		// We have to do this so that we can find the correct overload of the
		// method.
		//
		int paramCount = streamReader.readInt();
		Class[] paramTypes = new Class[paramCount];
		for (int i = 0; i < paramTypes.length; i++) {
			String paramClassName = streamReader.readString();
			try {
				paramTypes[i] = getClassOrPrimitiveFromName(paramClassName);
			} catch (ClassNotFoundException e) {
				throw new SerializationException("Unknown parameter " + i + " type '" + paramClassName + "'", e);
			}
		}

		// For security, make sure the method is found in the service interface
		// and not just one that happens to be defined on this class.
		//
		Method serviceIntfMethod = findInterfaceMethod(serviceIntf, methodName, paramTypes, true);

		// If it wasn't found, don't continue.
		//
		if (serviceIntfMethod == null) {
			// Bad payload, possible hack attempt.
			//
			throw new SecurityException("Method '" + methodName + "' (or a particular overload) on interface '"
					+ serviceIntfName + "' was not found, this is either misconfiguration or a hack attempt");
		}

		// Deserialize the parameters.
		//
		Object[] args = new Object[paramCount];
		for (int i = 0; i < args.length; i++) {
			args[i] = streamReader.deserializeValue(paramTypes[i]);
		}

		// Make the call via reflection.
		//
		String responsePayload = GENERIC_FAILURE_MSG;
		ServerSerializationStreamWriter streamWriter = new ServerSerializationStreamWriter(serializableTypeOracle);
		Throwable caught = null;
		try {
			Class returnType = serviceIntfMethod.getReturnType();
			Object returnVal = serviceIntfMethod.invoke(this.delegate, args);
			responsePayload = createResponse(streamWriter, returnType, returnVal, false);
		} catch (IllegalArgumentException e) {
			caught = e;
		} catch (IllegalAccessException e) {
			caught = e;
		} catch (InvocationTargetException e) {
			// Try to serialize the caught exception if the client is expecting it,
			// otherwise log the exception server-side.
			caught = e;
			Throwable cause = e.getCause();
			if (cause != null) {
				// Update the caught exception to the underlying cause
				caught = cause;
				// Serialize the exception back to the client if it's a declared
				// exception
				if (isExpectedException(serviceIntfMethod, cause)) {
					Class thrownClass = cause.getClass();
					responsePayload = createResponse(streamWriter, thrownClass, cause, true);
					// Don't log the exception on the server
					caught = null;
				}
			}
		}

		if (caught != null) {
			responsePayload = GENERIC_FAILURE_MSG;
			ServletContext servletContext = getServletContext();
			// servletContext may be null (for example, when unit testing)
			if (servletContext != null) {
				// Log the exception server side
				servletContext.log("Exception while dispatching incoming RPC call", caught);
			}
		}

		// Let subclasses see the serialized response.
		//
		onAfterResponseSerialized(responsePayload);

		return responsePayload;
	}

	/**
	 * Override this method to examine the serialized response that will be
	 * returned to the client. The default implementation does nothing and need
	 * not be called by subclasses.
	 */
	protected void onAfterResponseSerialized(String serializedResponse) {
	}

	/**
	 * Override this method to examine the serialized version of the request
	 * payload before it is deserialized into objects. The default implementation
	 * does nothing and need not be called by subclasses.
	 */
	protected void onBeforeRequestDeserialized(String serializedRequest) {
	}

	/**
	 * Determines whether the response to a given servlet request should or should
	 * not be GZIP compressed. This method is only called in cases where the
	 * requestor accepts GZIP encoding.
	 * <p>
	 * This implementation currently returns <code>true</code> if the response
	 * string's estimated byte length is longer than 256 bytes. Subclasses can
	 * override this logic.
	 * </p>
	 * 
	 * @param request the request being served
	 * @param response the response that will be written into
	 * @param responsePayload the payload that is about to be sent to the client
	 * @return <code>true</code> if responsePayload should be GZIP compressed,
	 *         otherwise <code>false</code>.
	 */
	protected boolean shouldCompressResponse(HttpServletRequest request, HttpServletResponse response,
			String responsePayload) {
		return estimateByteSize(responsePayload) > UNCOMPRESSED_BYTE_SIZE_LIMIT;
	}

	/**
	 * @param stream
	 * @param responseType
	 * @param responseObj
	 * @param isException
	 * @return response
	 */
	private String createResponse(ServerSerializationStreamWriter stream, Class responseType,
			Object responseObj, boolean isException) {
		stream.prepareToWrite();
		if (responseType != void.class) {
			try {
				stream.serializeValue(responseObj, responseType);
			} catch (SerializationException e) {
				responseObj = e;
				isException = true;
			}
		}

		String bufferStr = (isException ? "{EX}" : "{OK}") + stream.toString();
		return bufferStr;
	}

	/**
	 * Returns the {@link Class} instance for the named class.
	 * 
	 * @param name the name of a class or primitive type
	 * @return Class instance for the given type name
	 * @throws ClassNotFoundException if the named type was not found
	 */
	private Class getClassFromName(String name) throws ClassNotFoundException {
		return Class.forName(name, false, this.getClass().getClassLoader());
	}

	/**
	 * Returns the {@link Class} instance for the named class or primitive type.
	 * 
	 * @param name the name of a class or primitive type
	 * @return Class instance for the given type name
	 * @throws ClassNotFoundException if the named type was not found
	 */
	private Class getClassOrPrimitiveFromName(String name) throws ClassNotFoundException {
		Object value = TYPE_NAMES.get(name);
		if (value != null) {
			return (Class) value;
		}

		return getClassFromName(name);
	}

	/**
	 * Obtain the special package-prefixes we use to check for custom serializers
	 * that would like to live in a package that they cannot. For example,
	 * "java.util.ArrayList" is in a sealed package, so instead we use this prefix
	 * to check for a custom serializer in
	 * "com.google.gwt.user.client.rpc.core.java.util.ArrayList". Right now, it's
	 * hard-coded because we don't have a pressing need for this mechanism to be
	 * extensible, but it is imaginable, which is why it's implemented this way.
	 */
	private String[] getPackagePaths() {
		return new String[] { "com.google.gwt.user.client.rpc.core" };
	}

	/**
	 * Returns true if the {@link java.lang.reflect.Method Method} definition on
	 * the service is specified to throw the exception contained in the
	 * InvocationTargetException or false otherwise. NOTE we do not check that the
	 * type is serializable here. We assume that it must be otherwise the
	 * application would never have been allowed to run.
	 * 
	 * @param serviceIntfMethod
	 * @param e
	 * @return is expected exception
	 */
	private boolean isExpectedException(Method serviceIntfMethod, Throwable cause) {
		assert (serviceIntfMethod != null);
		assert (cause != null);

		Class[] exceptionsThrown = serviceIntfMethod.getExceptionTypes();
		if (exceptionsThrown.length <= 0) {
			// The method is not specified to throw any exceptions
			//
			return false;
		}

		Class causeType = cause.getClass();

		for (int index = 0; index < exceptionsThrown.length; ++index) {
			Class exceptionThrown = exceptionsThrown[index];
			assert (exceptionThrown != null);

			if (exceptionThrown.isAssignableFrom(causeType)) {
				return true;
			}
		}

		return false;
	}

	private final Map<String, Class> knownImplementedInterfacesMap = new HashMap<String, Class>();

	private void registerImplementedRemoteServiceInterface(Object delegate) {
		this.knownImplementedInterfacesMap.clear();
		if (delegate != null) {
			Class cls = delegate.getClass();
			if (cls.isInterface()) {
				addImplementedRemoteServiceInterfaceRecursive(cls);
			} else {
				while (cls != null) {
					Class[] intfs = cls.getInterfaces();
					for (int i = 0; i < intfs.length; i++) {
						addImplementedRemoteServiceInterfaceRecursive(intfs[i]);
					}

					// we look in the superclass
					cls = cls.getSuperclass();
				}
			}
		}
	}

	private void addImplementedRemoteServiceInterfaceRecursive(Class intfToCheck) {
		assert (intfToCheck.isInterface());

		if (RemoteService.class.equals(intfToCheck))
			return;

		if (RemoteService.class.isAssignableFrom(intfToCheck)) {
			this.knownImplementedInterfacesMap.put(intfToCheck.getName(), intfToCheck);
		}

		Class[] intfs = intfToCheck.getInterfaces();
		for (int i = 0; i < intfs.length; i++) {
			addImplementedRemoteServiceInterfaceRecursive(intfs[i]);
		}
	}

	private Class getImplementedRemoteServiceInterface(String intfName) {
		return this.knownImplementedInterfacesMap.get(intfName);
	}

	private String readPayloadAsUtf8(HttpServletRequest request) throws IOException, ServletException {
		int contentLength = request.getContentLength();
		if (contentLength == -1) {
			// Content length must be known.
			throw new ServletException("Content-Length must be specified");
		}

		String contentType = request.getContentType();
		boolean contentTypeIsOkay = false;
		// Content-Type must be specified.
		if (contentType != null) {
			// The type must be plain text.
			if (contentType.startsWith("text/plain")) {
				// And it must be UTF-8 encoded (or unspecified, in which case we assume
				// that it's either UTF-8 or ASCII).
				if (contentType.indexOf("charset=") == -1) {
					contentTypeIsOkay = true;
				} else if (contentType.indexOf("charset=utf-8") != -1) {
					contentTypeIsOkay = true;
				}
			}
		}
		if (!contentTypeIsOkay) {
			throw new ServletException(
					"Content-Type must be 'text/plain' with 'charset=utf-8' (or unspecified charset)");
		}
		InputStream in = request.getInputStream();
		try {
			byte[] payload = new byte[contentLength];
			int offset = 0;
			int len = contentLength;
			int byteCount;
			while (offset < contentLength) {
				byteCount = in.read(payload, offset, len);
				if (byteCount == -1) {
					throw new ServletException("Client did not send " + contentLength + " bytes as expected");
				}
				offset += byteCount;
				len -= byteCount;
			}
			return new String(payload, "UTF-8");
		} finally {
			if (in != null) {
				in.close();
			}
		}
	}

	/**
	 * Called when the machinery of this class itself has a problem, rather than
	 * the invoked third-party method. It writes a simple 500 message back to the
	 * client.
	 */
	private void respondWithFailure(HttpServletResponse response, Throwable caught) {
		ServletContext servletContext = getServletContext();
		servletContext.log("Exception while dispatching incoming RPC call", caught);
		try {
			response.setContentType("text/plain");
			response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
			response.getWriter().write(GENERIC_FAILURE_MSG);
		} catch (IOException e) {
			servletContext.log("sendError() failed while sending the previous failure to the client", caught);
		}
	}

	private void writeResponse(HttpServletRequest request, HttpServletResponse response, String responsePayload)
			throws IOException {

		byte[] reply = responsePayload.getBytes(CHARSET_UTF8);
		String contentType = CONTENT_TYPE_TEXT_PLAIN_UTF8;

		if (acceptsGzipEncoding(request) && shouldCompressResponse(request, response, responsePayload)) {
			// Compress the reply and adjust headers.
			//
			ByteArrayOutputStream output = null;
			GZIPOutputStream gzipOutputStream = null;
			Throwable caught = null;
			try {
				output = new ByteArrayOutputStream(reply.length);
				gzipOutputStream = new GZIPOutputStream(output);
				gzipOutputStream.write(reply);
				gzipOutputStream.finish();
				gzipOutputStream.flush();
				response.setHeader(CONTENT_ENCODING, CONTENT_ENCODING_GZIP);
				reply = output.toByteArray();
			} catch (UnsupportedEncodingException e) {
				caught = e;
			} catch (IOException e) {
				caught = e;
			} finally {
				if (null != gzipOutputStream) {
					gzipOutputStream.close();
				}
				if (null != output) {
					output.close();
				}
			}

			if (caught != null) {
				getServletContext().log("Unable to compress response", caught);
				response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
				return;
			}
		}

		// Send the reply.
		//
		response.setContentLength(reply.length);
		response.setContentType(contentType);
		response.setStatus(HttpServletResponse.SC_OK);
		response.getOutputStream().write(reply);
	}

}

// delegate 用法参照 org.springframework.web.servlet.mvc.multiaction.MultiActionController

/*
  For GWT 1.4.60
*/
public class GwtRemoteServiceController extends RemoteServiceServlet implements
		Controller, ServletContextAware {
	private static final long serialVersionUID = 8175888785480720736L;

	private Object delegate;

	private ServletContext servletContext;

	@Override
	public void setServletContext(ServletContext servletContext) {
		this.servletContext = servletContext;
	}

	@Override
	public ServletContext getServletContext() {
		return servletContext;
	}

	@Override
	public ModelAndView handleRequest(HttpServletRequest request,
			HttpServletResponse response) throws Exception {
		super.doPost(request, response);
		return null;
	}

	@Override
	public String processCall(String payload) throws SerializationException {
		Object delegateToUse = this.delegate;
		if (delegateToUse == null) {
			return super.processCall(payload);
		} else {
			try {
				RPCRequest rpcRequest = RPC.decodeRequest(payload,
						delegateToUse.getClass(), this);
				return RPC.invokeAndEncodeResponse(delegateToUse, rpcRequest
						.getMethod(), rpcRequest.getParameters(), rpcRequest
						.getSerializationPolicy());
			} catch (IncompatibleRemoteServiceException ex) {
				getServletContext()
						.log(
								"An IncompatibleRemoteServiceException was thrown while processing this call.",
								ex);
				return RPC.encodeResponseForFailure(null, ex);
			}
		}
	}

	public Object getDelegate() {
		return delegate;
	}

	public void setDelegate(Object delegate) {
		this.delegate = delegate;
	}
}

开源真好:D

评论

3 楼 ccj 2008-04-25  

使用Gwt-SL整合效果很好.

2 楼 gwbasic 2008-03-25  

有新版本了,请参照论坛中的<<gwt spring 完美整合>>
http://www.iteye.com/topic/143455

delegate 用法参照 org.springframework.web.servlet.mvc.multiaction.MultiActionController

public class GwtRemoteServiceController extends RemoteServiceServlet implements
		Controller, ServletContextAware {
	private static final long serialVersionUID = 8175888785480720736L;

	private Object delegate;

	private ServletContext servletContext;

	@Override
	public void setServletContext(ServletContext servletContext) {
		this.servletContext = servletContext;
	}

	@Override
	public ServletContext getServletContext() {
		return servletContext;
	}

	@Override
	public ModelAndView handleRequest(HttpServletRequest request,
			HttpServletResponse response) throws Exception {
		super.doPost(request, response);
		return null;
	}

	@Override
	public String processCall(String payload) throws SerializationException {
		Object delegateToUse = this.delegate;
		if (delegateToUse == null) {
			return super.processCall(payload);
		} else {
			try {
				RPCRequest rpcRequest = RPC.decodeRequest(payload,
						delegateToUse.getClass(), this);
				return RPC.invokeAndEncodeResponse(delegateToUse, rpcRequest
						.getMethod(), rpcRequest.getParameters(), rpcRequest
						.getSerializationPolicy());
			} catch (IncompatibleRemoteServiceException ex) {
				getServletContext()
						.log(
								"An IncompatibleRemoteServiceException was thrown while processing this call.",
								ex);
				return RPC.encodeResponseForFailure(null, ex);
			}
		}
	}

	public Object getDelegate() {
		return delegate;
	}

	public void setDelegate(Object delegate) {
		this.delegate = delegate;
	}
}

1 楼 li_tieyang 2008-03-19  

ServerSerializationStreamReader streamReader = new ServerSerializationStreamReader(
serializableTypeOracle);
你用的GWT是什么版本,我用1.4.6的这句代码过不去.