JSONRPC 2.0 Server

JSON-RPC 2.0 Server
Simple and efficient Java framework for processing
JSON-RPC 2.0 requests and notifications
No complicated J2EE and Spring stuff,
just POJOs
With message context passing
1. Simple server framework for processing JSON-RPC 2.0 requests
This is a simple and easy to understand "old-school" Java framework for processing JSON-RPC 2.0 requests and notifications. It consists of just 2 classes and 2 interfaces. You can use it as a starting point to write your own JSON-RPC 2.0 web services, HTTP servlet based or otherwise. Proven in several enterprise-grade applications, such as the Json2Ldap directory web service.
2. How does it work?
The JSON-RPC 2.0 server framework represents the classical handler pattern:
Implement request and / or notification handlers for the various expected JSON-RPC 2.0 messages. A handler may process one or more request / notification methods identified by their name.
Create a new Dispatcher and register the handlers with it.
Pass the received JSON-RPC 2.0 requests and notifications to the Dispatcher.process(...) method. Then, if the message is a request, return the resulting JSON-RPC 2.0 response back to the client.
The server framework requires the sister JSON-RPC 2.0 Base package to represent JSON-RPC 2.0 request, notification and response messages. If you indend to do low-level JSON entity work you also need to get the JSON Smart toolkit package.
3. Example
Here is an example program which demonstrates processing of three JSON-RPC 2.0 request methods:
"echo" Echoes the first parameter value back to the client.
"getDate" Returns the current date.
"getTime" Returns the current time.
Note that the handlers here are implemented as static nested classes. In real life applications it may be more suitable to declare the handlers as regular classes within their own source files.
// The JSON-RPC 2.0 Base classes that define the 
// JSON-RPC 2.0 protocol messages
import com.thetransactioncompany.jsonrpc2.*;

// The JSON-RPC 2.0 server framework package
import com.thetransactioncompany.jsonrpc2.server.*;

import java.text.*;
import java.util.*;


/**
 * Demonstration of the JSON-RPC 2.0 Server framework usage. The request
 * handlers are implemented as static nested classes for convenience, but in 
 * real life applications may be defined as regular classes within their old 
 * source files.
 *
 * @author Vladimir Dzhuvinov
 * @version 2011-03-05
 */ 
public class Example {


    // Implements a handler for an "echo" JSON-RPC method
    public static class EchoHandler implements RequestHandler {
	

        // Reports the method names of the handled requests
        public String[] handledRequests() {
		
            return new String[]{"echo"};
        }
		
		
         // Processes the requests
         public JSONRPC2Response process(JSONRPC2Request req, MessageContext ctx) {
			
             if (req.getMethod().equals("echo")) {
				
                 // Echo first parameter
				
                 List params = (List)req.getParams();
	 
	         Object input = params.get(0);
	 
	         return new JSONRPC2Response(input, req.getID());
            }
            else {
	
                // Method name not supported
				
                return new JSONRPC2Response(JSONRPC2Error.METHOD_NOT_FOUND, req.getID());
	    }
        }
    }
	
	
    // Implements a handler for "getDate" and "getTime" JSON-RPC methods
    // that return the current date and time
    public static class DateTimeHandler implements RequestHandler {
	
	
        // Reports the method names of the handled requests
	public String[] handledRequests() {
	
	    return new String[]{"getDate", "getTime"};
	}
	
	
	// Processes the requests
	public JSONRPC2Response process(JSONRPC2Request req, MessageContext ctx) {
	
	    if (req.getMethod().equals("getDate")) {
	    
	        DateFormat df = DateFormat.getDateInstance();
		
		String date = df.format(new Date());
		
		return new JSONRPC2Response(date, req.getID());

            }
            else if (req.getMethod().equals("getTime")) {
	    
	        DateFormat df = DateFormat.getTimeInstance();
		
		String time = df.format(new Date());
		
		return new JSONRPC2Response(time, req.getID());
            }
	    else {
	    
	        // Method name not supported
		
		return new JSONRPC2Response(JSONRPC2Error.METHOD_NOT_FOUND, req.getID());
            }
        }
    }
    
    
    public static void main(String[] args) {
	
        // Create a new JSON-RPC 2.0 request dispatcher
	Dispatcher dispatcher =  new Dispatcher();
	
	
	// Register the "echo", "getDate" and "getTime" handlers with it
	dispatcher.register(new EchoHandler());
	dispatcher.register(new DateTimeHandler());
	
	
	// Simulate an "echo" JSON-RPC 2.0 request
	List echoParam = new LinkedList();
	echoParam.add("Hello world!");
	
	JSONRPC2Request req = new JSONRPC2Request("echo", echoParam, "req-id-01");
	System.out.println("Request: \n" + req);
	
	JSONRPC2Response resp = dispatcher.process(req, null);
	System.out.println("Response: \n" + resp);
	
	// Simulate a "getDate" JSON-RPC 2.0 request
	req = new JSONRPC2Request("getDate", "req-id-02");
	System.out.println("Request: \n" + req);
	
	resp = dispatcher.process(req, null);
	System.out.println("Response: \n" + resp);
	
	// Simulate a "getTime" JSON-RPC 2.0 request
	req = new JSONRPC2Request("getTime", "req-id-03");
	System.out.println("Request: \n" + req);
	
	resp = dispatcher.process(req, null);
	System.out.println("Response: \n" + resp);
    }
}
The resulting console output:
Request: 
{"id":"req-id-01","method":"echo","params":["Hello world!"],"jsonrpc":"2.0"}
Response: 
{"id":"req-id-01","result":"Hello world!","jsonrpc":"2.0"}

Request: 
{"id":"req-id-02","method":"getDate","jsonrpc":"2.0"}
Response: 
{"id":"req-id-02","result":"Mar 5, 2011","jsonrpc":"2.0"}

Request: 
{"id":"req-id-03","method":"getTime","jsonrpc":"2.0"}
Response: 
{"id":"req-id-03","result":"3:20:47 PM","jsonrpc":"2.0"}
You can download the complete Java example from here.
4. Request + notification context info
The framework also includes a MessageContext class to allow passing of important context information about the processed request or notification to the handler.
The client's host name.
The client's IP address.
Whether the request / notification was transmitted securely (e.g. via HTTPS).
The client X.509 certificate principal, if authenticated.
5. Reporting request execution time
Since version 1.4 the Dispatcher is able to report request processing time in millisecond precision. Reporting is enabled by the Dispatcher.reportProcTime() method.
Once request execution time reporting is turned on, the dispatcher will append a non-standard "xProcTime" attribute to the resulting JSON-RPC 2.0 response.
Example:
{ 
   "result"    : "xyz",
   "id"        : 1,
   "jsonrpc"   : "2.0",
   "xProcTime" : "189 us"
}
The client can then parse the "xProcTime" attribute. Processing time reporting can be useful when measuring performance of JSON-RPC 2.0 web services and comparing hosting / cloud providers.
6. JavaDoc documentation
The JSON-RPC 2.0 Server source comes with extensive documentation in the form of JavaDocs. A copy of the docs is available for browsing online.
7. Download
The JSON-RPC 2.0 Server package comes with an Apache 2.0 open source license.
Download now JSON-RPC 2.0 Server
Write to me if you have questions or comments about the JSON-RPC 2.0 Server software. For general questions go to the JSON-RPC forum.
You may also want to have a look at the companion JSON-RPC 2.0 Shell product, a must have tool for developers undertaking serious JSON-RPC 2.0 work.
8. Change log
version 1.0 (2010-05-18)
First release.
version 1.1 (2010-10-10)
Renames class RequestInfo to RequestContext.
version 1.2 (2010-11-23)
Renames package.
Removes dependency on org.apache.commons.lang.
version 1.3 (2011-03-05)
Major API naming changes.
Adds support for handling JSON-RPC 2.0 notifications.
Allows for undefined (null) message context arguments in Dispatcher.dispatch() and {Request|Notification}Handler.process() methods.
version 1.4 (2011-07-11)
Raises minimal JSON-RPC 2.0 Base requirement to version 1.19.
Adds support for reporting request processing time by adding a non-standard "_procTime" attribute to the JSON-RPC 2.0 response.
version 1.4.1 (2011-07-15)
Renames the non-standard processing time attribute to "xProcTime".
Documentation improvements.
version 1.5 (2012-02-20)
Fixes a bug in MessageContext getter method for java.security.Principal.
MessageContext allows storing of multiple java.security.Principal identities.
Updates JSON-RPC 2.0 Base JAR to 1.25 (JSON Smart 1.1).
version 1.5.1 (2012-04-03)
Updates JSON-RPC 2.0 Base JAR to 1.25.1 (JSON Smart 1.1.1).
version 1.6 (2012-07-14)
Adds minimal MessageContext constructor.
Updates JSON-RPC 2.0 Base JAR to 1.27.
version 1.7 (2012-08-27)
Dispatcher implements RequestHandler and Notification handler; deprecates Dispatcher.dispatch(...) methods.