// The contents of this file are subject to the Mozilla Public License
// Version 1.1 (the "License"); you may not use this file except in
// compliance with the License. You may obtain a copy of the License
// at http://www.mozilla.org/MPL/
//
// Software distributed under the License is distributed on an "AS IS"
// basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
// the License for the specific language governing rights and
// limitations under the License.
//
// The Original Code is RabbitMQ.
//
// The Initial Developer of the Original Code is VMware, Inc.
// Copyright (c) 2007-2012 VMware, Inc. All rights reserved.
//
package com.rabbitmq.tools.jsonrpc;
import java.io.IOException;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeoutException;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.RpcClient;
import com.rabbitmq.client.ShutdownSignalException;
import com.rabbitmq.tools.json.JSONReader;
import com.rabbitmq.tools.json.JSONWriter;
/**
<a
href="http://json-rpc.org/wd/JSON-RPC-1-1-WD-20060807.html">JSON-RPC</a>
is a lightweight RPC mechanism using <a
href="http://www.json.org/">JSON</a> as a data language for
request and reply messages. It is rapidly becoming a
standard in web development, where it is used to make RPC
requests over HTTP. RabbitMQ provides an AMQP transport
binding for JSON-RPC in the form of
the <code>JsonRpcClient</code> class.
JSON-RPC services are self-describing - each service is able
to list its supported procedures, and each procedure
describes its parameters and types. An instance of
JsonRpcClient retrieves its service description using the
standard <code>system.describe</code> procedure when it is
constructed, and uses the information to coerce parameter
types appropriately. A JSON service description is parsed
into instances of <code>ServiceDescription</code>. Client
code can access the service description by reading the
<code>serviceDescription</code> field of
<code>JsonRpcClient</code> instances.
@see #call(String, Object[])
@see #call(String[])
*/
public class JsonRpcClient extends RpcClient implements InvocationHandler {
/** Holds the JSON-RPC service description for this client. */
private ServiceDescription serviceDescription;
/**
* Construct a new JsonRpcClient, passing the parameters through
* to RpcClient's constructor. The service description record is
* retrieved from the server during construction.
* @throws TimeoutException if a response is not received within the timeout specified, if any
*/
public JsonRpcClient(Channel channel, String exchange, String routingKey, int timeout)
throws IOException, JsonRpcException, TimeoutException
{
super(channel, exchange, routingKey, timeout);
retrieveServiceDescription();
}
public JsonRpcClient(Channel channel, String exchange, String routingKey)
throws IOException, JsonRpcException, TimeoutException
{
this(channel, exchange, routingKey, RpcClient.NO_TIMEOUT);
}
/**
* Private API - parses a JSON-RPC reply object, checking it for exceptions.
* @return the result contained within the reply, if no exception is found
* Throws JsonRpcException if the reply object contained an exception
*/
public static Object checkReply(Map<String, Object> reply)
throws JsonRpcException
{
if (reply.containsKey("error")) {
@SuppressWarnings("unchecked")
Map<String, Object> map = (Map<String, Object>) reply.get("error");
// actually a Map<String, Object>
throw new JsonRpcException(map);
}
Object result = reply.get("result");
//System.out.println(new JSONWriter().write(result));
return result;
}
/**
* Public API - builds, encodes and sends a JSON-RPC request, and
* waits for the response.
* @return the result contained within the reply, if no exception is found
* @throws JsonRpcException if the reply object contained an exception
* @throws TimeoutException if a response is not received within the timeout specified, if any
*/
public Object call(String method, Object[] params) throws IOException, JsonRpcException, TimeoutException
{
HashMap<String, Object> request = new HashMap<String, Object>();
request.put("id", null);
request.put("method", method);
request.put("version", ServiceDescription.JSON_RPC_VERSION);
request.put("params", (params == null) ? new Object[0] : params);
String requestStr = new JSONWriter().write(request);
try {
String replyStr = this.stringCall(requestStr);
@SuppressWarnings("unchecked")
Map<String, Object> map = (Map<String, Object>) (new JSONReader().read(replyStr));
return checkReply(map);
} catch(ShutdownSignalException ex) {
throw new IOException(ex.getMessage()); // wrap, re-throw
}
}
/**
* Public API - implements InvocationHandler.invoke. This is
* useful for constructing dynamic proxies for JSON-RPC
* interfaces.
*/
public Object invoke(Object proxy, Method method, Object[] args)
throws Throwable
{
return call(method.getName(), args);
}
/**
* Public API - gets a dynamic proxy for a particular interface class.
*/
public Object createProxy(Class<?> klass)
throws IllegalArgumentException
{
return Proxy.newProxyInstance(klass.getClassLoader(),
new Class[] { klass },
this);
}
/**
* Private API - used by {@link #call(String[])} to ad-hoc convert
* strings into the required data types for a call.
*/
public static Object coerce(String val, String type)
throws NumberFormatException
{
if ("bit".equals(type)) {
return Boolean.getBoolean(val) ? Boolean.TRUE : Boolean.FALSE;
} else if ("num".equals(type)) {
try {
return new Integer(val);
} catch (NumberFormatException nfe) {
return new Double(val);
}
} else if ("str".equals(type)) {
return val;
} else if ("arr".equals(type) || "obj".equals(type) || "any".equals(type)) {
return new JSONReader().read(val);
} else if ("nil".equals(type)) {
return null;
} else {
throw new IllegalArgumentException("Bad type: " + type);
}
}
/**
* Public API - as {@link #call(String,Object[])}, but takes the
* method name from the first entry in <code>args</code>, and the
* parameters from subsequent entries. All parameter values are
* passed through coerce() to attempt to make them the types the
* server is expecting.
* @return the result contained within the reply, if no exception is found
* @throws JsonRpcException if the reply object contained an exception
* @throws NumberFormatException if a coercion failed
* @throws TimeoutException if a response is not received within the timeout specified, if any
* @see #coerce
*/
public Object call(String[] args)
throws NumberFormatException, IOException, JsonRpcException, TimeoutException
{
if (args.length == 0) {
throw new IllegalArgumentException("First string argument must be method name");
}
String method = args[0];
int arity = args.length - 1;
ProcedureDescription proc = serviceDescription.getProcedure(method, arity);
ParameterDescription[] params = proc.getParams();
Object[] actuals = new Object[arity];
for (int count = 0; count < params.length; count++) {
actuals[count] = coerce(args[count + 1], params[count].type);
}
return call(method, actuals);
}
/**
* Public API - gets the service description record that this
* service loaded from the server itself at construction time.
*/
public ServiceDescription getServiceDescription() {
return serviceDescription;
}
/**
* Private API - invokes the "system.describe" method on the
* server, and parses and stores the resulting service description
* in this object.
* TODO: Avoid calling this from the constructor.
* @throws TimeoutException if a response is not received within the timeout specified, if any
*/
private void retrieveServiceDescription() throws IOException, JsonRpcException, TimeoutException
{
@SuppressWarnings("unchecked")
Map<String, Object> rawServiceDescription = (Map<String, Object>) call("system.describe", null);
serviceDescription = new ServiceDescription(rawServiceDescription);
}
}