com.google.gwt.user.server.rpc
Class RPC

java.lang.Object
  com.google.gwt.user.server.rpc.RPC

public final class RPC
extends java.lang.Object

Utility class for integrating with the RPC system. This class exposes methods for decoding of RPC requests, encoding of RPC responses, and invocation of RPC calls on service objects. The operations exposed by this class can be reused by framework implementors such as Spring and G4jsf to support a wide range of service invocation policies.

Canonical Example

The following example demonstrates the canonical way to use this class.

public String processCall(String payload) throws SerializationException {
  try {
    RPCRequest rpcRequest = RPC.decodeRequest(payload, this.getClass());
    return RPC.invokeAndEncodeResponse(this, rpcRequest.getMethod(),
        rpcRequest.getParameters());
  } catch (IncompatibleRemoteServiceException ex) {
    return RPC.encodeResponseForFailure(null, ex);
  }
}

Advanced Example

The following example shows a more advanced way of using this class to create an adapter between GWT RPC entities and POJOs.

public void doPost(HttpServletRequest httpRequest,
    HttpServletResponse httpResponse) {
  String payload = readPayloadAsUtf8(httpRequest);

  try {
    try {
      RPCRequest rpcRequest = RPC.decodeRequest(payload);

      Object targetInstance = getInstanceToHandleRequest(httpRequest,
          rpcRequest);

      Method targetMethod = maybeMapRequestedMethod(targetInstance,
          rpcRequest.getMethod());

      Object[] targetParameters = maybeMapParameters(rpcRequest.getParameters());

      try {
        Object result = targetMethod.invoke(targetInstance, targetParameters);

        result = maybeMapResult(rpcRequest.getMethod(), result);

        /*
         * Encode the object that will be given to the client code's
         * AsyncCallback::onSuccess(Object) method.
         */
        String encodedResult = RPC.encodeResponseForSuccess(
            rpcRequest.getMethod(), result);

        sendResponseForSuccess(httpResponse, encodedResult);
      } catch (IllegalArgumentException e) {
        SecurityException securityException = new SecurityException(
            "Blocked attempt to invoke method " + targetMethod);
        securityException.initCause(e);
        throw securityException;
      } catch (IllegalAccessException e) {
        SecurityException securityException = new SecurityException(
            "Blocked attempt to access inaccessible method "
                + targetMethod
                + (targetInstance != null ? " on target " + targetInstance
                    : ""));
        securityException.initCause(e);
        throw securityException;
      } catch (InvocationTargetException e) {
        Throwable cause = e.getCause();

        Throwable mappedThrowable = maybeMapThrowable(cause,
            rpcRequest.getMethod());

        /*
         * Encode the exception that will be passed back to the client's
         * client code's AsyncCallback::onFailure(Throwable) method.
         */
        String failurePayload = RPC.encodeResponseForFailure(
            rpcRequest.getMethod(), mappedThrowable);

        sendResponseForFailure(httpResponse, failurePayload);
      }
    } catch (IncompatibleRemoteServiceException e) {
      sendResponseForFailure(httpResponse, RPC.encodeResponseForFailure(null,
          e));
    }
  } catch (Throwable e) {
    /*
     * Return a generic error which will be passed to the client code's
     * AsyncCallback::onFailure(Throwable) method.
     */
    sendResponseForGenericFailure(httpResponse);
  }
}

Method Summary

static RPCRequest	decodeRequest(java.lang.String encodedRequest) Returns an RPCRequest that is built by decoding the contents of an encoded RPC request.
static RPCRequest	decodeRequest(java.lang.String encodedRequest, java.lang.Class type) Returns an RPCRequest that is built by decoding the contents of an encoded RPC request and optionally validating that type can handle the request.
static RPCRequest	decodeRequest(java.lang.String encodedRequest, java.lang.Class type, SerializationPolicyProvider serializationPolicyProvider) Returns an RPCRequest that is built by decoding the contents of an encoded RPC request and optionally validating that type can handle the request.
static java.lang.String	encodeResponseForFailure(java.lang.reflect.Method serviceMethod, java.lang.Throwable cause) Returns a string that encodes an exception.
static java.lang.String	encodeResponseForFailure(java.lang.reflect.Method serviceMethod, java.lang.Throwable cause, SerializationPolicy serializationPolicy) Returns a string that encodes an exception.
static java.lang.String	encodeResponseForSuccess(java.lang.reflect.Method serviceMethod, java.lang.Object object) Returns a string that encodes the object.
static java.lang.String	encodeResponseForSuccess(java.lang.reflect.Method serviceMethod, java.lang.Object object, SerializationPolicy serializationPolicy) Returns a string that encodes the object.
static SerializationPolicy	getDefaultSerializationPolicy() Returns a default serialization policy.
static java.lang.String	invokeAndEncodeResponse(java.lang.Object target, java.lang.reflect.Method serviceMethod, java.lang.Object[] args) Returns a string that encodes the result of calling a service method, which could be the value returned by the method or an exception thrown by it.
static java.lang.String	invokeAndEncodeResponse(java.lang.Object target, java.lang.reflect.Method serviceMethod, java.lang.Object[] args, SerializationPolicy serializationPolicy) Returns a string that encodes the result of calling a service method, which could be the value returned by the method or an exception thrown by it.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

decodeRequest

public static RPCRequest decodeRequest(java.lang.String encodedRequest)

Returns an RPCRequest that is built by decoding the contents of an encoded RPC request.

This method is equivalent to calling decodeRequest(String, Class) with null for the type parameter.

Parameters:

encodedRequest - a string that encodes the RemoteService interface, the service method to call, and the arguments to for the service method

Returns:

an RPCRequest instance

Throws:

IncompatibleRemoteServiceException - if any of the following conditions apply:

• if the types in the encoded request cannot be deserialized
• if the ClassLoader acquired from Thread.currentThread().getContextClassLoader() cannot load the service interface or any of the types specified in the encodedRequest
• the requested interface is not assignable to RemoteService
• the service method requested in the encodedRequest is not a member of the requested service interface
• the type parameter is not null and is not assignable to the requested RemoteService interface

decodeRequest

public static RPCRequest decodeRequest(java.lang.String encodedRequest,
                                       java.lang.Class type)

Returns an RPCRequest that is built by decoding the contents of an encoded RPC request and optionally validating that type can handle the request. If the type parameter is not null, the implementation checks that the type is assignable to the RemoteService interface requested in the encoded request string.

Invoking this method with null for the type parameter, decodeRequest(encodedRequest, null), is equivalent to calling decodeRequest(encodedRequest).

Parameters:

encodedRequest - a string that encodes the RemoteService interface, the service method, and the arguments to pass to the service method

type - if not null, the implementation checks that the type is assignable to the RemoteService interface encoded in the encoded request string.

Returns:

an RPCRequest instance

Throws:

java.lang.NullPointerException - if the encodedRequest is null

java.lang.IllegalArgumentException - if the encodedRequest is an empty string

IncompatibleRemoteServiceException - if any of the following conditions apply:

• if the types in the encoded request cannot be deserialized
• if the ClassLoader acquired from Thread.currentThread().getContextClassLoader() cannot load the service interface or any of the types specified in the encodedRequest
• the requested interface is not assignable to RemoteService
• the service method requested in the encodedRequest is not a member of the requested service interface
• the type parameter is not null and is not assignable to the requested RemoteService interface

decodeRequest

public static RPCRequest decodeRequest(java.lang.String encodedRequest,
                                       java.lang.Class type,
                                       SerializationPolicyProvider serializationPolicyProvider)

Returns an RPCRequest that is built by decoding the contents of an encoded RPC request and optionally validating that type can handle the request. If the type parameter is not null, the implementation checks that the type is assignable to the RemoteService interface requested in the encoded request string.

If the serializationPolicyProvider parameter is not null, it is asked for a SerializationPolicy to use to restrict the set of types that can be decoded from the request. If this parameter is null, then only subtypes of IsSerializable or types which have custom field serializers can be decoded.

Invoking this method with null for the type parameter, decodeRequest(encodedRequest, null), is equivalent to calling decodeRequest(encodedRequest).

Parameters:

encodedRequest - a string that encodes the RemoteService interface, the service method, and the arguments to pass to the service method

type - if not null, the implementation checks that the type is assignable to the RemoteService interface encoded in the encoded request string.

serializationPolicyProvider - if not null, the implementation asks this provider for a SerializationPolicy which will be used to restrict the set of types that can be decoded from this request

Returns:

an RPCRequest instance

Throws:

java.lang.NullPointerException - if the encodedRequest is null

java.lang.IllegalArgumentException - if the encodedRequest is an empty string

IncompatibleRemoteServiceException - if any of the following conditions apply:

• if the types in the encoded request cannot be deserialized
• if the ClassLoader acquired from Thread.currentThread().getContextClassLoader() cannot load the service interface or any of the types specified in the encodedRequest
• the requested interface is not assignable to RemoteService
• the service method requested in the encodedRequest is not a member of the requested service interface
• the type parameter is not null and is not assignable to the requested RemoteService interface

encodeResponseForFailure

public static java.lang.String encodeResponseForFailure(java.lang.reflect.Method serviceMethod,
                                                        java.lang.Throwable cause)
                                                 throws SerializationException

Returns a string that encodes an exception. If method is not null, it is an error if the exception is not in the method's list of checked exceptions.

Parameters:

serviceMethod - the method that threw the exception, may be null

cause - the Throwable that was thrown

Returns:

a string that encodes the exception

Throws:

java.lang.NullPointerException - if the the cause is null

SerializationException - if the result cannot be serialized

UnexpectedException - if the result was an unexpected exception (a checked exception not declared in the serviceMethod's signature)

encodeResponseForFailure

public static java.lang.String encodeResponseForFailure(java.lang.reflect.Method serviceMethod,
                                                        java.lang.Throwable cause,
                                                        SerializationPolicy serializationPolicy)
                                                 throws SerializationException

Returns a string that encodes an exception. If method is not null, it is an error if the exception is not in the method's list of checked exceptions.

If the serializationPolicy parameter is not null, it is used to determine what types can be encoded as part of this response. If this parameter is null, then only subtypes of IsSerializable or types which have custom field serializers may be encoded.

Parameters:

serviceMethod - the method that threw the exception, may be null

cause - the Throwable that was thrown

serializationPolicy - determines the serialization policy to be used

Returns:

a string that encodes the exception

Throws:

java.lang.NullPointerException - if the the cause or the serializationPolicy are null

SerializationException - if the result cannot be serialized

UnexpectedException - if the result was an unexpected exception (a checked exception not declared in the serviceMethod's signature)

encodeResponseForSuccess

public static java.lang.String encodeResponseForSuccess(java.lang.reflect.Method serviceMethod,
                                                        java.lang.Object object)
                                                 throws SerializationException

Returns a string that encodes the object. It is an error to try to encode an object that is not assignable to the service method's return type.

Parameters:

serviceMethod - the method whose result we are encoding

object - the instance that we wish to encode

Returns:

a string that encodes the object, if the object is compatible with the service method's declared return type

Throws:

java.lang.IllegalArgumentException - if the result is not assignable to the service method's return type

java.lang.NullPointerException - if the service method is null

SerializationException - if the result cannot be serialized

encodeResponseForSuccess

public static java.lang.String encodeResponseForSuccess(java.lang.reflect.Method serviceMethod,
                                                        java.lang.Object object,
                                                        SerializationPolicy serializationPolicy)
                                                 throws SerializationException

Returns a string that encodes the object. It is an error to try to encode an object that is not assignable to the service method's return type.

If the serializationPolicy parameter is not null, it is used to determine what types can be encoded as part of this response. If this parameter is null, then only subtypes of IsSerializable or types which have custom field serializers may be encoded.

Parameters:

serviceMethod - the method whose result we are encoding

object - the instance that we wish to encode

serializationPolicy - determines the serialization policy to be used

Returns:

a string that encodes the object, if the object is compatible with the service method's declared return type

Throws:

java.lang.IllegalArgumentException - if the result is not assignable to the service method's return type

java.lang.NullPointerException - if the serviceMethod or the serializationPolicy are null

SerializationException - if the result cannot be serialized

getDefaultSerializationPolicy

public static SerializationPolicy getDefaultSerializationPolicy()

Returns a default serialization policy.

Returns:

the default serialization policy.

invokeAndEncodeResponse

public static java.lang.String invokeAndEncodeResponse(java.lang.Object target,
                                                       java.lang.reflect.Method serviceMethod,
                                                       java.lang.Object[] args)
                                                throws SerializationException

Returns a string that encodes the result of calling a service method, which could be the value returned by the method or an exception thrown by it.

This method does no security checking; security checking must be done on the method prior to this invocation.

Parameters:

target - instance on which to invoke the serviceMethod

serviceMethod - the method to invoke

args - arguments used for the method invocation

Returns:

a string which encodes either the method's return or a checked exception thrown by the method

Throws:

java.lang.SecurityException - if the method cannot be accessed or if the number or type of actual and formal arguments differ

SerializationException - if an object could not be serialized by the stream

UnexpectedException - if the serviceMethod throws a checked exception that is not declared in its signature

invokeAndEncodeResponse

public static java.lang.String invokeAndEncodeResponse(java.lang.Object target,
                                                       java.lang.reflect.Method serviceMethod,
                                                       java.lang.Object[] args,
                                                       SerializationPolicy serializationPolicy)
                                                throws SerializationException

Returns a string that encodes the result of calling a service method, which could be the value returned by the method or an exception thrown by it.

If the serializationPolicy parameter is not null, it is used to determine what types can be encoded as part of this response. If this parameter is null, then only subtypes of IsSerializable or types which have custom field serializers may be encoded.

This method does no security checking; security checking must be done on the method prior to this invocation.

Parameters:

target - instance on which to invoke the serviceMethod

serviceMethod - the method to invoke

args - arguments used for the method invocation

serializationPolicy - determines the serialization policy to be used

Returns:

a string which encodes either the method's return or a checked exception thrown by the method

Throws:

java.lang.NullPointerException - if the serviceMethod or the serializationPolicy are null

java.lang.SecurityException - if the method cannot be accessed or if the number or type of actual and formal arguments differ

SerializationException - if an object could not be serialized by the stream

UnexpectedException - if the serviceMethod throws a checked exception that is not declared in its signature