NEW BLOG! http://cleancode.consulting/

Dear Reader,

This Blog is closed and remains as an archive.

Please find our new Blog at http://cleancode.consulting/

How to create Nav with Angular + Angular Material

To setup a basic navigation in Angular Material, type the following command in your terminal (e.g. I am using WebStorm IDE):

$ ng generate @angular/material:material.nav -name=main-nav

This will create a component named main-nav with all basic elements, fully responsive and free to modify.

Find Color for CSS layout in Dreamweaver - Hex Value with Color Picker

If you need the color from an image, just 

• enter the color attribute in your CSS, e.g.

background-color: <type Ctrl + Enter> ;

• Choose the color-selection option, 
• choose Color picker and 
• place it above the image.
• Press Enter.

The value will appear in your CSS, e.g.: 

background-color: #25787F ;


Voilà!

RESTful Java Jersey JAX-RS Unit Test embedded Jetty Maven Webapp Download

HOWTO create a Java Webapp with JSON, REST and UNIT Test

RESTful Java Jersey JAX-RS Unit Test embedded Jetty Maven Webapp Download.

DOWNLOAD Source Code

Docker Compose Webapps Port Forwarding

Multiple Webapps Inside Docker Compose Setup

• Learn how to setup a custom network for your containers: container A talks to container B
• Learn how to run multiple webapps inside Docker containers on different ports with Docker Compose

Download complete source code here

• Create the network with $docker network create skynet
• Run with $docker-compose up
• Stop with $<Ctrl + C>
• Clean up from time to time (beware, network will be deleted as well) with $docker system prune -a -f
• access via http://localhost:8080/sample
• access via http://localhost:8081/sample

Docker How To Map Ports To Tomcat Application Server

How to map ports to your Tomcat application server in Docker.
Example uses Tomcat 7.
Adapt to your tomcat directory if using another version.

In Dockerfile:

#start Tomcat and map Port 8080 to Container Port 8080
RUN sed -i 's/port="8080"/port="8080"/' /opt/apache/tomcat/conf/server.xml

URL: http://localhost:8080



Example 8081:

#start Tomcat and map Port 8080 to Container Port 8081

RUN sed -i 's/port="8080"/port="8081"/' /opt/apache/tomcat/conf/server.xml

URL: http://localhost:8081

Docker - How to shrink large Docker Images.

Some images become very big - one reason being that multiple RUN commands will create a layer and keep the data there. No removal.

Example:

RUN unzip myfile.war  -d mynewdirectory/
RUN zip -r myfile.war mynewdirectory/
RUN mv myfile.war somedirectory

The myfile.war will be kept. It will not be deleted by the mv command.

Reason: Docker will create a layer for each RUN command.

Solution:

RUN unzip myfile.war  -d mynewdirectory/ &&\
    zip -r myfile.war mynewdirectory/ &&\
    mv myfile.war somedirectory

Keep everything in one layer by utilizing concatenation with '&&\'.

WARNING:
Docker is highly optimized and based on Checksums.
If everything is concatenated, building an image can take very long. 

Example: COPY or ADD will check wether a change in the underlying files or source code has been made and only execute if a change is detected.
Through concatenation, you reap Docker of the benefits regarding optimization (e.g. Checksums). No check. Everything is executed.

It is a good practice to keep this in mind when concatenating instrunctions.

How to make Virtualbox available on Windows via localhost

Sometimes fate forces us to work with Windows.
Because Linux is so good, we get a VirtualBox to emulate it.

How can we access a webapplication via localhost:8080 from the Windows machine inside of a Webbrowser?

VirtualBox Manager -> VM-Tools -> Settings -> Network -> Port Forwarding

Name: http8080 
Protocol: TCP
HostIP: empty
Host-Port: 8080
Guest-IP: empty
Guest-Port: 8080


Name: ssh 
Protocol: TCP
HostIP: 127.0.0.1
Host-Port: 2222
Guest-IP: empty
Guest-Port: 22

Howto create Docker Network with Docker Compose - Communication between Services inside of a Container

Create your network named 'yournetwork':

$ docker network create -d bridge yournetwork

You have created your own network now.
Verify it by typing

$network inspect yournetwork:

In the docker-compose.yml:

networks:
  yournetwork: #TODO remove this hard-coded network reference
    external:
      name: ${NETWORK}

  yourservice:
  container_name: "your-container-name"
    image: your-image-name:${TAG:-latest} #will pull the latest                                                #tagged image of yours
    ports:
    - 8080:8080 #example localhost:8080
    net: ${NETWORK}

Start it with:

$ NETWORK=yournetwork docker-compose-up

[Solution] Maven Proxy Issue - Maven not downloading artifacts - Maven behind Proxy

Your settings.xml - mine is in etc/maven/settings.xml on Linux - must look like:

<?xml version="1.0" encoding="UTF-8"?>
<!--
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
under the License.
-->

<settings
xmlns="http://maven.apache.org/SETTINGS/1.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0                                              http://maven.apache.org/xsd/settings-1.0.0.xsd">

<pluginGroups>
</pluginGroups>

<proxies>
</proxies>

<servers>

<server>
<id>myRepository</id>
<username>your user</username>
<password>your pw</password>
<configuration>
<httpConfiguration>
<all>
<usePreemptive>true</usePreemptive>
</all>
<settings>
</settings>
</httpConfiguration>
</configuration>
</server>

</servers>

<mirrors>

<mirror>
<id>myRepository</id>
<name>Proxy for XY</name>
<url>http://<maven proxy url></url>
<mirrorOf>*,!sonar</mirrorOf>
</mirror>
</mirrors>

<profiles>

</profiles>

</settings>

DOCKER - No Space Left on Device // How to clean Docker on Linux

Sometimes Docker will simply claim to much space. Time for a clean up ;)

docker system prune -a -f

Attention: if your network is not in the default, this command will eventually erase your subnet immediately.

Intellij Order Of Imports

IntelliJ sometimes changes the appearance of imports in the code on checkout when organizing imports.

To control that, one can adjust the settings:

Settings -> Editor -> Code Style -> Java -> Layout static imports separately

Change the order as you need, IntelliJ will sort the imports accordingly.

Getting Gradle Dependencies in IntelliJ IDEA

Gradle Project Import

1. Import the project as a Gradle project from within Idea.
2. When you add a dependency you need to open the Gradle window and perform a refresh

Gradle Wrapper

1. IntelliJ will ask you to auto-import Gradle in some cases. This can be done.
2. Gradle Wrapper - many environments will use this wrapper to maintain the same standard between the different environments and stages. How to:

Ctrl + Shift + Alt + S → Import Module → Import Module from external model → Choose Gradle → 

For Gradle Home: Use gradle 'wrapper' task configuration.

Kafka vs. MQ + JMS - Difference Apache Kafka and MQ, RabbitMQ, ActiveMQ, JMS

Kafka is a messaging system. From the ground up it has been designed to provide high throughput, fast performance, scalability and high availability.
Here are the basics:

• Producers of the messages publishes to the Topics
• Consumers subscribes to the Topics
• Messages are array of bytes. They can be JSON objects, Strings etc
• Topics are logs of messages
• Kafka is run as a Cluster of servers each of which is called a Broker

1. Kafka has no P2P model. Message order will remain.

In Kafka there is no concept of Queue and hence no send or receive for putting/getting messages from the queue. Publish-subscribe is the only paradigm available as a messaging model. Producers of the messages Publisha message to the Topic and Consumer receives messages by Subscribing to the topic. This publish-subscribe paradigm is very similar between MQ/JMS and Kafka - the difference is under the covers that we will discuss next.

2. Message Persistence

Typical JMS providers (IBM MQ, Rabbit MQ, Active MQ ..) implement the topics in a such way that the messages published to the topic are sent to a common storage (memory or/and persistent store) from where they are picked up by the subscribers. In MQ/JMS systems once the message is read it is removed from the storage and is no more available. Kafka retains the messages even after all the subscribers have read the message. The rentention period is a configurable parameter.

In a typical MQ/JMS consumer implementation, the message is deleted by the messaging system on receiving an ACK/Commit. If for some reason the message gets processed but fails before the ACK/Commit, it would lead to message being read more than once. This problem has been addressed by Kafka by way of message retention and state management based on the consumer offset.

3. Topic partitioning

Kafka has implemented the topics as partitioned logs. A partition is an ordered, immutable sequence of messages that is continually appended to. This is similar to database log, for that reason the partition is also referred to as the commit-log. This is one of the biggest difference between MQ/JMS and Kafka. The partitioning of the topic leads to its high throughput (and parallelism). 

·         Partitions for the same topic are distributed across multiple brokers in the cluster

·         Partitions are replicated across multiple servers; number of replicas is a configurable parameter

·         Each Partition has one server as a leader and a number of servers as followers

·         Each Server acts a leader for some of its partitions and as a follower for some other

·         The Producers are responsible for choosing which message to assign to which partition within the topic based on key assigned to message.

5. Message sequencing

In MQ/JMS there is no gurantee that the messages will be received in a sequence in which they were sent. In Kafka though the sequence is maintained at a partition level. In other words if the topic is configured with a single partition then the messages are received in the same order that they were sent in. 

6. Message reads

The consumer of the messages in Kafka issues a fetch request to the broker leading the partition it wants to consume. As part of the fetch, consumer specifies the offset from which the message in the log is read from. This is very different from the MQ/JMS messaging system where First In First Out (FIFO) is the way messages are read off the queue/topic. The other thing that happens is that with offset based control, the consumer can re-read the same message which is not possible in MQ/JMS (yes you can do it with browse but that is not what it is intended for).

This rewinding mechanism can be very handy in some situation. E.g., if you received a batch of messages and processed it with buggy code, you may fix the code and re-run the processing on the messages by resetting the offset.

7. Load balancing

In the case of MQ/JMS the load balancing required messaging systems to be designed using some clustering mechanism and the onus of distributing the load across the cluster members was on the producer sending the messages. The Kafka nodes publish the metadata which tells the producer which servers are alive in the cluster, where the leader for the partitions are. This allows the client to send message to the appropriate server (and partition) thus distributing the message load across the cluster members.

8. Automatic failover & High availability

Traditional MQ/JMS implementations did not have the concept of message replication but some systems built it over a period of time; those replication features at most times were not leveraged in favor of simplicity. In Kafka, as decribed earlier the messages are replicated (leader-followers) for each topic's partitions across a configurable number of servers. This inherently leads to an architecture that provides automatic failover to replica thus leading to high availability.

Zookeeper

Zookeeper plays a central role in this replication mechanism. The follower servers maintain a session to zookeeper and respond to the heartbeat messages. The slaves/replicas continuously read messages from the leader as fast as they can as to not fall behind. The leader if discovers that the slave is lagging removes it as the replica; this is determined by way of configurable parameters. The message is considered committed when all replicas are in sync with the leader. This sync aspect is also configurable.

The state of the replication is managed by the leader server and leader may drop the replica/slave if the replica is lagging too far behind or is unresponsive.

My Advice to Founders + Anyone Starting Their Own Business

Here is my advice when you are about to start your own business.

No matter what business you start, at a certain level it is all the same. 

#1 Get a Coach

Look for someone who is able to help you out by giving advice to you. The best thing was if this person has already achieved what you want to achieve. For instance, my own Coach is successfully running multiple companies. It may cost you money but investing in yourself is the best thing you can do!

#2 Manage yourself as a boss and employee in one. 

Enjoy the freedom and flexibility regarding time, appointments and mindset - you are your own boss now. Because of this: negotiate clever and be tough as nails regarding your ressource planning, even more with yourself ;)

#3 Go with the flow 

It is easier for me to accept the limits or moods of my employees than accepting my own. But if I hit the floor because of sleep deprivation or anxiety, my business will go down, too. Thus: 

#4 Be kind to yourself

... as you do already have proven that you have the courage to walk your own path. Being kind to yourself will help you to not crack under the pressure. 

#5 Fun is the most important thing

Life is too short. Never forget that stress is a powerful force. Do always remember that fun is what this is about. The rest will follow - #lawOfAttraction . 

Wish you much success with your business and all the best! 

Tim

How to remove line breaks etc. in Java String

myString.trim()
.replace("\n", "")
.replace("\r", "")
.replace(System.getProperty("line.separator"), "");

Spring Security - get User Name

If you want to retrieve the name of  a logged in user, do this:

import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.security.core.userdetails.UserDetails;

private String getUserName() {

    Object principal = SecurityContextHolder
          .getContext()
          .getAuthentication()
          .getPrincipal();

    String userName;

    if (principal instanceof UserDetails) {
        userName = ((UserDetails)principal).getUsername();
    } else {
        userName = principal.toString();
    }
    return userName;
}

Recover and Restore System Properties with Java - JUnit and more - Free program

Sometimes it is necessary to change System Properties. Maybe for a Test or something else. This program and test will recover and restore the System Properties to their initial state.

The program and test may be used freely under GNU General Public License Version and is brought to you by Harder IT Consulting www.harder-it-consulting.de
  

Download here

Remove duplicates in list with Java > 8

    //remove duplicates from a list with Java 8 or greater     

    mylist.stream().distinct.collect(Collectors.toList())

Mock static methods with Mockito in Java (mock, static, method, java)

import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.BDDMockito;
import org.powermock.api.mockito.PowerMockito;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

@RunWith(PowerMockRunner.class)
@PrepareForTest(MyStatic.class)
...


@Test

public void someTest() {
    

    //given    

    PowerMockito.mockStatic(MyStatic.class);
    BDDMockito.given(MyStatic.someStaticMethod()).willReturn(...);

    //when
    ...

    //then     

    PowerMockito.verifyStatic();
    MyStatic.someStaticMethod();

    assertThat(//your further asserts....