Defining a Standalone Main Method

Overview

In the case of a standalone deployment, the application developer to creates, configures and starts a CamelContext instance (which encapsulates the core of the router functionality). For this purpose, you should define a main() method that performs the following key tasks:

Create a CamelContext instance.
Add components to the CamelContext instance.
Add RouteBuilder objects to the CamelContext instance.
Start the CamelContext instance, so that it activates the routing rules you defined.

Example of a standalone main method

Example 1.1 shows the standard outline of a standalone main() method, which is defined in an example class, CamelJmsToFileExample. This example shows how to initialize and activate a CamelContext instance.

Example 1.1. Standalone Main Method

package org.apache.camel.example.jmstofile;

import javax.jms.ConnectionFactory;

import org.apache.activemq.ActiveMQConnectionFactory;
import org.apache.camel.CamelContext;
import org.apache.camel.CamelTemplate;
import org.apache.camel.Exchange;
import org.apache.camel.Processor;
import org.apache.camel.builder.RouteBuilder;
import org.apache.camel.component.jms.JmsComponent;
import org.apache.camel.impl.DefaultCamelContext;

public final class CamelJmsToFileExample {

    private CamelJmsToFileExample() {        
    }
    
    public static void main(String args[]) throws Exception { 
        CamelContext context = new DefaultCamelContext(); 

        // Add components to the CamelContext. 
        // ... (not shown)

        // Add routes to the CamelContext. 
        // ... (not shown)

        // Start the context.
        context.start(); 

        // End of main thread.
    }
}

The code in Example 1.1 does the following:

	Define a static `main()` method to serve as the entry point for running the standalone router.
	Instantiates a `CamelContext` instance explicitly. There is just one implementation of `CamelContext` currently available, the `DefaultCamelContext` class.
	Adds any components that are required to the `CamelContext` (see Adding Components to the Camel Context).
	Adds the `RouteBuilder` objects to the `CamelContext` (see Adding RouteBuilders to the CamelContext).
	The `CamelContext.start()` method creates a new thread and starts to process incoming messages using the registered routing rules. If the main thread now exits, the `CamelContext` sub-thread remains active and continues to process messages. Typically, you can stop the router by typing Ctrl+C in the window where you launched the router application (or by sending a `kill` signal in UNIX). If you want more control over stopping the router process, you can use the `CamelContext.stop()` method in combination with an instrumentation library (such as JMX).