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Understanding Apache Camel Interceptors Using Example | JavaInUse

Understanding Apache Camel Interceptors

The intercept feature in Camel supports intercepting Exchanges while they are en route. We have overhauled the Intercept in Camel 2.0 so the following information is based on Camel 2.0. Camel supports three kinds of interceptors:
  • intercept that intercepts each and every processing step while routing an Exchange in the route.
  • interceptFrom that intercepts incoming Exchange in the route.
  • interceptSendToEndpoint that intercepts when an Exchange is about to be sent to the given Endpoint.
For this tutorial we will be taking reference of the Apache Camel+ JMS tutorial we had implemented before. 
Apache Camel - Table of Contents

File Transfer Using Java DSL Apache Camel
Apache Camel Java DSL + Spring Integration Hello World Example
Apache Camel Exception Handling Using Simple Example
Apache Camel Redelivery policy using example
Integrate Apache Camel and ActiveMQ
EIP patterns using Apache Camel
Apache Camel Tutorial- Integrate Spring Boot+ Apache Camel
Apache Camel Tutorial- Integrate with MySQL DB using SQL query
Apache Camel + Spring + ActiveMQ + JBoss Fuse 
Apache Camel EIP - Splitter and Aggregator pattern
Apache Camel Unit Testing 
Apache Camel + Spring + Quartz Hello World Example 
Camel application deployment on JBoss Fuse 
Apache Camel + Apache CXF SOAP Webservices
Apache Camel + JAX-RS REST Webservice
Apache Camel + CXFRS REST Webservice 
Apache Camel Routing Slip EIP Pattern
Apache Camel Dynamic Router Pattern
Apache Camel Load Balancer EIP Pattern
Apache Camel Interceptors
Apache Camel + Kafka Hello World Example
Apache Camel - Marshalling/Unmarshalling XML/JSON Data Example
Calling and Consuming Webservices using Apache Camel
Apache Camel Tutorial - Send SMTP Email Using Gmail
Apache Camel Tutorial - SEDA component Hello World Example
Spring Boot + Apache Camel + RabbitMQ - Hello World Example
Apache Camel Tutorial - Idempotent Consumer using MemoryIdempotentRepository and FileIdempotentRepository
Spring Boot + Apache Camel JDBC component + MySQL - Hello World Example 
Spring Boot + Apache Camel SQL component + MySQL - Hello World Example
Spring Boot + Apache Camel SQL component + Transaction Management Example

Lets Begin

We will create Eclipse maven project as follows-

Apache Camel Interceptor Tutorial
Our pom file will be as follows-
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.javainuse</groupId>
	<artifactId>camel-load-balancer</artifactId>
	<version>0.0.1-SNAPSHOT</version>

	<dependencies>
		<dependency>
			<groupId>org.apache.camel</groupId>
			<artifactId>camel-core</artifactId>
			<version>2.13.0</version>
		</dependency>
		<dependency>
			<groupId>org.apache.camel</groupId>
			<artifactId>camel-jms</artifactId>
			<version>2.14.1</version>
		</dependency>

		<dependency>
			<groupId>org.apache.activemq</groupId>
			<artifactId>activemq-camel</artifactId>
			<version>5.7.0</version>
		</dependency>

		<dependency>
			<groupId>org.apache.activemq</groupId>
			<artifactId>activemq-broker</artifactId>
			<version>5.10.1</version>
		</dependency>

		<dependency>
			<groupId>org.apache.activemq</groupId>
			<artifactId>activemq-client</artifactId>
			<version>5.10.1</version>
		</dependency>
		<dependency>
			<groupId>org.apache.activemq</groupId>
			<artifactId>activemq-pool</artifactId>
			<version>5.10.1</version>
		</dependency>
	</dependencies>
</project>

  • Intercept that intercepts each and every processing step while routing an Exchange in the route


    Apache Camel Interceptor Example
    Define the route. 



package com.javainuse;

import org.apache.camel.Exchange;
import org.apache.camel.Processor;
import org.apache.camel.builder.RouteBuilder;

public class SimpleRouteBuilder extends RouteBuilder {

	int count;

	@Override
	public void configure() throws Exception {

		intercept().process(new Processor() {
			public void process(Exchange exchange) {
				count++;
				System.out.println("interceptor called " + count + " times " + exchange.getIn().getBody());

			}
		});
		from("file:C:/inbox?noop=true").split().tokenize("\n").to("jms:queue:javainuse1").to("jms:queue:javainuse2");
	}

}
When Camel is started, it creates a CamelContext object that contains the definition of the Route to be started. Below we create default camel context and load the routes created in SimpleRouteBuilder. 
package com.javainuse;

import javax.jms.ConnectionFactory;
import org.apache.activemq.ActiveMQConnectionFactory;
import org.apache.camel.CamelContext;
import org.apache.camel.component.jms.JmsComponent;
import org.apache.camel.impl.DefaultCamelContext;

public class MainApp {

    public static void main(String[] args) {
        SimpleRouteBuilder routeBuilder = new SimpleRouteBuilder();
        CamelContext ctx = new DefaultCamelContext();
        ConnectionFactory connectionFactory = new ActiveMQConnectionFactory("tcp://0.0.0.0:61616");
        //define the jms component
        ctx.addComponent("jms", JmsComponent.jmsComponentAutoAcknowledge(connectionFactory));
        try {
            ctx.addRoutes(routeBuilder);
            ctx.start();
            Thread.sleep(5 * 60 * 1000);
            ctx.stop();
        }
        catch (Exception e) {
            e.printStackTrace();
        }

    }
}
Next run the MainApp class as a java application. We can see the output as follows-
Apache Camel Interceptor

  • InterceptFrom that intercepts incoming Exchange in the route


    Apache Camel Interceptor Incoming Request
    Define the route. 
    package com.javainuse;

import org.apache.camel.Exchange;
import org.apache.camel.Processor;
import org.apache.camel.builder.RouteBuilder;

public class SimpleRouteBuilder extends RouteBuilder {

	int count;

	@Override
	public void configure() throws Exception {
	
		interceptFrom("*")
		.process(new Processor() {
			public void process(Exchange exchange) {
				count++;
				System.out.println("interceptor called " + count + " times " + exchange.getIn().getBody());

			}
		});

		from("file:C:/inbox?noop=true").split().tokenize("\n").to("jms:queue:javainuse1");
		from("jms:queue:javainuse1").to("jms:queue:javainuse2");
		from("jms:queue:javainuse2").to("jms:queue:javainuse3");
		
	}

}
    When Camel is started, it creates a CamelContext object that contains the definition of the Route to be started. Below we create default camel context and load the routes created in SimpleRouteBuilder. 
    package com.javainuse;

import javax.jms.ConnectionFactory;
import org.apache.activemq.ActiveMQConnectionFactory;
import org.apache.camel.CamelContext;
import org.apache.camel.component.jms.JmsComponent;
import org.apache.camel.impl.DefaultCamelContext;

public class MainApp {

    public static void main(String[] args) {
        SimpleRouteBuilder routeBuilder = new SimpleRouteBuilder();
        CamelContext ctx = new DefaultCamelContext();
        ConnectionFactory connectionFactory = new ActiveMQConnectionFactory("tcp://0.0.0.0:61616");
        //define the jms component
        ctx.addComponent("jms", JmsComponent.jmsComponentAutoAcknowledge(connectionFactory));
        try {
            ctx.addRoutes(routeBuilder);
            ctx.start();
            Thread.sleep(5 * 60 * 1000);
            ctx.stop();
        }
        catch (Exception e) {
            e.printStackTrace();
        }

    }
}
    Next run the MainApp class as a java application. We can see the output as follows-
    Apache Camel Interceptor Run

  • InterceptSendToEndpoint that intercepts when an Exchange is about to be sent to the given Endpoint


    Apache Camel Exchange
    Define the route. 
    package com.javainuse;

import org.apache.camel.Exchange;
import org.apache.camel.Processor;
import org.apache.camel.builder.RouteBuilder;

public class SimpleRouteBuilder extends RouteBuilder {

	int count;

	@Override
	public void configure() throws Exception {

		interceptSendToEndpoint("jms:queue:javainuse2").process(new Processor() {
			public void process(Exchange exchange) {
				count++;
				System.out.println("interceptor called "+ count +" times "+exchange.getIn().getBody());
				
			}
		});
		
		from("file:C:/inbox?noop=true").split().tokenize("\n").to("jms:queue:javainuse1");
		from("jms:queue:javainuse1").to("jms:queue:javainuse2");
	}

}
    When Camel is started, it creates a CamelContext object that contains the definition of the Route to be started. Below we create default camel context and load the routes created in SimpleRouteBuilder. 
    package com.javainuse;

import javax.jms.ConnectionFactory;
import org.apache.activemq.ActiveMQConnectionFactory;
import org.apache.camel.CamelContext;
import org.apache.camel.component.jms.JmsComponent;
import org.apache.camel.impl.DefaultCamelContext;

public class MainApp {

    public static void main(String[] args) {
        SimpleRouteBuilder routeBuilder = new SimpleRouteBuilder();
        CamelContext ctx = new DefaultCamelContext();
        ConnectionFactory connectionFactory = new ActiveMQConnectionFactory("tcp://0.0.0.0:61616");
        //define the jms component
        ctx.addComponent("jms", JmsComponent.jmsComponentAutoAcknowledge(connectionFactory));
        try {
            ctx.addRoutes(routeBuilder);
            ctx.start();
            Thread.sleep(5 * 60 * 1000);
            ctx.stop();
        }
        catch (Exception e) {
            e.printStackTrace();
        }

    }
}
    Next run the MainApp class as a java application. We can see the output as follows-
    Apache Camel Intercpetor Output

    • Download Source Code

    Download it - Apache Camel Interceptor Example 

    See Also
    
Spring Boot Hello World Application- Create simple controller and jsp view using Maven
Spring Boot Tutorial-Spring Data JPA
Spring Boot + Simple Security Configuration
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Spring Boot + ActiveMQ Hello world Example
Spring Boot + Swagger Example Hello World Example
Spring Boot + Swagger- Understanding the various Swagger Annotations
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