Tag Archives: Java

Problem with Spring Boot Starter Web and FasterXML Jackson dependency

While working with Spring Boot and developing a combined REST/JSON & SOAP/XML (not sexy, I know) API I was able to build & compile but on runtime I had this error:

Error starting ApplicationContext. To display the auto-configuration report re-run your application with 'debug' enabled.
ERROR 2145 --- [ main] o.s.boot.SpringApplication : Application startup failed
org.springframework.context.ApplicationContextException: Unable to start embedded container; nested exception is org.springframework.boot.context.embedded.EmbeddedServletContainerException: Unable to start embedded Tomcat
at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.onRefresh( ...........
Caused by: java.lang.NoClassDefFoundError: com/fasterxml/jackson/databind/exc/InvalidDefinitionException

So Spring uses Jackson and the Jackson library is composed of three components: Jackson Databind, Core, and Annotation. I did not add anything specific to my maven pom.xml for Jackson so the dependency got inherited somewhere. So after some Google jobs I figured out the spring-boot-starter-parent uses some older FasterXML/Jackson libs which seem to screw things up.

jvzoggel$ mvn dependency:tree -Dincludes=com.fasterxml.jackson.*

[INFO] --- maven-dependency-plugin:2.10:tree (default-cli) @ springboot ---
[INFO] nl.rubix.api:springboot:jar:0.0.1-SNAPSHOT
[INFO] \- org.springframework.boot:spring-boot-starter-web:jar:1.5.10.RELEASE:compile
[INFO] \- com.fasterxml.jackson.core:jackson-databind:jar:2.8.10:compile
[INFO] +- com.fasterxml.jackson.core:jackson-annotations:jar:2.8.0:compile
[INFO] \- com.fasterxml.jackson.core:jackson-core:jar:2.8.10:compile

So by overriding the dependency in my pom.xml I could make sure a newer version of Jackson was used:

<!-- Jackson due to SpringBootStarterParent dependency problems -->

Problem solved.




1 Comment

Posted by on 04-02-2018 in Uncategorized


Tags: , ,

How to set the default Java version in IntelliJ IDE projects

When working in a Java environment with multiple developers using their own IDE preference I often get error like this opening a project with IntelliJ: “@Override is not allowed when implementing interface method”. Since I’m not a Java dev fulltime I tend to forget this stuff, so basically this is a reminder for myself …

Basically IntelliJ thinks the project is Java 1.5 by default so while my console / mvn build works perfectly due to using Java 8 the IDE thinks differently.


Project Language

File > Project Structure > Project > Language level

Module Language

If your project has multiple modules check that they inherit the project language, or when needed, set the correct non-default on the module

File > Project Structure > Module > Language level


Right Click module > Open Module Settings 

Java Compiler for Default Projects

While your at it, set this value as a default for new projects as well

File > Other Settiings > Default Settings > Build, Execution, Deployment > Compiler > Java Compiler > Project Bytecode version


Leave a comment

Posted by on 16-01-2018 in Uncategorized


Tags: ,

Publishing Apache Avro messages on a Apache Kafka topic

In earlier posts I played around with both Apache Avro and Apache Kafka. The next goal was naturally to combine both and start publishing binary Apache Avro data on a Apache Kafka topic.


Generating Java from the Avro schema

I use the  Avro schema “location.avsc” from my earlier post.

$ java -jar avro-tools-1.8.1.jar compile schema location.avsc .

Which results in the for our project.

* Autogenerated by Avro
package nl.rubix.avro;

import org.apache.avro.specific.SpecificData;
// ... and more stuff

Make sure we have the maven dependencies right in our pom.xml:


We can now use the Location object in Java to build our binary Avro message

public ByteArrayOutputStream GenerateAvroStream() throws IOException
    // Schema
    String schemaDescription = Location.getClassSchema().toString();
    Schema s = Schema.parse(schemaDescription);
    System.out.println("Schema parsed: " + s);

    // Encode the data using JSON schema and embed the schema as metadata along with the data.
    ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
    DatumWriter<GenericRecord> writer = new GenericDatumWriter<GenericRecord>(s);
    DataFileWriter<GenericRecord> dataFileWriter = new DataFileWriter<GenericRecord>(writer);
    dataFileWriter.create(s, outputStream);

    // Build AVRO message
    Location location = new Location();
    location.setVehicleId(new org.apache.avro.util.Utf8("VHC-001"));
    location.setTimestamp(System.currentTimeMillis() / 1000L);
    System.out.println("Message location " + location.toString());

    System.out.println("Encode outputStream: " + outputStream);

    return outputStream;

When we have our byteArrayOutput stream we can start publishing it on a Apache Kafka topic.

public void ProduceKafkaByte()
        // Get the Apache AVRO message
        ByteArrayOutputStream data = GenerateAvroStream();
        System.out.println("Here comes the data: " + data);

        // Start KAFKA publishing
        Properties props = new Properties();
        props.put("bootstrap.servers", "localhost:9092");
        props.put("serializer.class", "kafka.serializer.StringEncoder");
        props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
        props.put("value.serializer", "org.apache.kafka.common.serialization.ByteArraySerializer");

        KafkaProducer<String, byte[]> messageProducer = new KafkaProducer<String, byte[]>(props);
        ProducerRecord<String, byte[]> producerRecord = null;
        producerRecord = new ProducerRecord<String, byte[]>("test","1",data.toByteArray());
    catch(IOException ex)
        System.out.println ("Well this error happened: " + ex.toString());

When we subscribe on our topic we can see the bytestream cruising by:

INFO Processed session termination for sessionid: 0x157d8bec7530002 (org.apache.zookeeper.server.PrepRequestProcessor)
Objavro.schema#####ype":"record","name":"Location","namespace":"nl.rubix.avro","fields":[{"name":"vehicle_id","type":"string","doc":"id of the vehicle"},{"name":"timestamp","type":"long","doc":"time in seconds"},{"name":"latitude","type":"double"},{"name":"longtitude","type":"double"}],"doc:":"A schema for vehicle movement events"}##<##O#P#######HC-001#ڲ#
=######@#####;@##<##O#P#######016-10-18 19:06:24,005] INFO Expiring session 0x157d8bec7530005, timeout of 30000ms exceeded (org.apache.zookeeper.server.ZooKeeperServer)
[2016-10-18 19:06:24,005] INFO Processed session termination for sessionid: 0x157d8bec7530005 (org.apache.zookeeper.server.PrepRequestProcessor)

All code available in github here.

Leave a comment

Posted by on 19-10-2016 in Uncategorized


Tags: , , , , , , ,

Getting started with Apache Kafka

Apache Kafka is a publish-subscribe messaging solution rethought as a distributed commit log.


The original use case for Kafka was to be able to rebuild a user activity tracking pipeline as a set of real-time publish-subscribe feeds. This means site activity (page views, searches, or other actions users may take) is published to central topics with one topic per activity type. These feeds are available for subscription for a range of use cases including real-time processing, real-time monitoring, and loading into Hadoop or offline data warehousing systems for offline processing and reporting.

Some use cases for Kafka are stream processing, event sourcing, metrics and all other (large sets of) data that go from publisher to 1-n subscriber(s). A single Kafka broker can handle hundreds of megabytes of reads and writes per second from thousands of clients making it a very efficient (and also easy to scale) high volume messaging solution.

So actually Kafka is a good alternative for any more traditional (JMS / MQ) message broker. Message brokers are used for a variety of reasons (to decouple processing from data producers, to buffer unprocessed messages, etc). In comparison to most messaging systems Kafka has better throughput, built-in partitioning, replication, and fault-tolerance which makes it a good solution for large scale message processing applications. And this all, is free.

Getting Started

The Kafka website has an excellent quickstart tutorial here. Download the latest version here and work through the tutorial to send and receive your first messages from console.

Playing around with Java

First we create a test topic.

bin/ –create –zookeeper localhost:2181 –replication-factor 1 –partitions 1 –topic testIteration
Created topic “testIteration”.

The earlier versions of Kafka came with default serializer but that created lot of confusion. With 0.8.2, you would need to pick a serializer yourself from StringSerializer or ByteArraySerializer that comes with API or build your own. Since both our key and value in the example will be a string, we use the StringSerializer.

Use the following Apache Kafka library as a Maven dependency (pom.xml).


The following lines of code produces / publishes 10 messages on the Kafka Topic.

public void ProduceIteration()
int amountMessages = 10; // 10 is enough for the demo

Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092");
props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
props.put("serializer.class", "kafka.serializer.StringEncoder");
props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");

org.apache.kafka.clients.producer.Producer<String, String> producer = new KafkaProducer<String, String>(props);

for(int i = 1; i <= amountMessages; i++)
ProducerRecord<String, String> data = new ProducerRecord<String, String>("testIteration", Integer.toString(i), Integer.<em>toString</em>(i));
System.out.println ("Publish message " + Integer.toString(i) + " - " + data);


The messages can be received from the topic:

jvzoggel$ bin/ –zookeeper localhost:2181 –topic testIteration –property print.key=true –property print.timestamp=true

CreateTime:1474354960268        1       1
CreateTime:1474354960284        2       2
CreateTime:1474354960284        3       3
CreateTime:1474354960285        4       4
CreateTime:1474354960285        5       5
CreateTime:1474354960285        6       6
CreateTime:1474354960285        7       7
CreateTime:1474354960285        8       8
CreateTime:1474354960285        9       9
CreateTime:1474354960285        10      10



Posted by on 20-09-2016 in Uncategorized


Tags: , , ,

How to Configure WebLogic Server to Send a Notification When Its Configuration is Changed

My former collegue, Java maven (no not that one, this one) and friend Pierluigi contacted me about my post regarding the Weblogic Security Audit Provider. As always Pier is very political correct ;)


To my positive surprise he found a great solution for the limitation of the security audit provider. He discovered a way to configure WebLogic server to send a notification when it’s configuration is changed [Knowledge Base ID 1377733.1].

Which is awesome if you have a large Oracle environment and maintenance team and want to keep track of all the changes. Wish we knew this last year at the huge envuironment I was working then.

His blogpost contains all the code, scripts, etc so go and check it out!!! :)

And to end with his favourite quote:

Failure is not an option


Leave a comment

Posted by on 21-02-2013 in Java, Oracle, Weblogic, WLST


Tags: , , , ,

Oracle ADF custom Validator for BSN check

In the Netherlands, all people of ages 14 and up receive a Burgerservicenummer (BSN) (Citizen’s Service Number). It is printed on driving licenses, passports and international ID cards, under the header Personal Number. The number is unique and may not contain any information about the person to whom it is assigned. (no information such as gender or date of birth, etc). (source: Wikipedia)

The BSN consists of 9 digits and uses an algorithm often called “the 11-check”. This 11-check algorithm works like this:

Let's say we perform the 11-check on BSN 123456782
1st digit = 1, 9 * 1 = 9
2nd digit = 2, 8 * 2 = 16
3rd digit = 3, 7 * 3 = 21
4th digit = 4, 6 * 4 = 24
5th digit = 5, 5 * 5 = 25
6th digit = 6, 4 * 6 = 24
7th digit = 7, 3 * 7 = 21
8th digit = 8, 2 * 8 = 16
9th digit = 2, -1 * 2 = -2 (last digit is not added but subtracted)

total: 154

Because 154 can be divided by 11 we can assume 123456782 is valid (154/11=14, no rest 0)

So let’s start with creating a custom Validator in our ADF project. This is excellent documented by Mohammed Jabr on his blog.

Create a Java class that implements the javax.faces.validator.Validator


Use the following code:

package nl.rubix;

import javax.faces.application.FacesMessage;
import javax.faces.component.UIComponent;
import javax.faces.context.FacesContext;
import javax.faces.validator.Validator;
import javax.faces.validator.ValidatorException;

public class BsnValidator implements Validator
 public BsnValidator()

public void validate(FacesContext facesContext, UIComponent uIComponent,
 Object object) throws ValidatorException
 String BSN = object.toString();
 if (BSN.length()==9)
 int checksum = 0;
 for(int i=0;i<8;i++)
 checksum = checksum + (Character.digit(BSN.charAt(i),10) * (9-i));
 checksum = checksum - Character.digit(BSN.charAt(8),10);
 // System.out.println("checksum total = " + checksum);
 // check Modulus for checksum
 if ( (checksum % 11 ) != 0)
 System.out.println("checksum / 11 is niet 0");
 FacesMessage fm = new FacesMessage("BSN fails 11-check");
 throw new ValidatorException(fm);
 // System.out.println("checksum works !!!");
 FacesMessage fm = new FacesMessage("BSN must be 9 digits");
 throw new ValidatorException(fm);

register the custom validator in your WEB-INF/faces-config.xml file


Configure the inputText to use the custom validator.


Go to the properties of your inputText and make sure you use the correct validatorID:

<af:inputText label="BSN:" id="it1">
 <f:validator validatorId="bsnvalidator"/>

And on runtime this is the result (in Dutch I know):


Leave a comment

Posted by on 10-01-2013 in ADF, Oracle


Tags: , ,

Get value from inputtext in Oracle ADF

No rockit science this blogpost for the ADF gurus out there, but since I’m the new kid in town regarding Oracle ADF I decided to note down some of the stuff I found very usefull.

In our Oracle BPM project we generate our human task screens, however the customer wants them heavy modifed and at one time we needed the value of a inputtext component which had no binding.

FacesContext facesContext = FacesContext.getCurrentInstance();
 UIViewRoot root = facesContext.getViewRoot();
 RichInputText inputText = (RichInputText)root.findComponent("it1");
 String myString = inputText.getValue().toString();

Where value “it1” is the ID of your inputText component

Reference and all credits:

1 Comment

Posted by on 19-12-2012 in Oracle


Tags: , ,