Tasks_To_Do

Tasks to do

OK, let´s start with the workshop. First of all, we need the basic structure for this workshop. Please clone the basic structure from the given link to the git - repo.

LINK TO REPO FOR THE EVENT

compile the first class

• add to the project

JUnit5

• add the dependencies to the projects
• create some tests into the class called HelloWorldServiceTest
• let the mvn clean test run inside the docker container
• check the coverage report

Mutation testing

• create the mutation coverage report
• check the coverage report

Start coding

We are now ready to work with the different jdk´s in parallel.

core-frp-since08

FunctionalInterfaces - Basics

Optional

Result

Exceptions / CheckedFunctions

Functions - Basics

Task

Extract the logic from and formulate it generic;

jdk08 - Refactoring to functional

v001

1. Replace all anonymous classes with lambda expression.

2. Replace for-loops with Streams

3. create an interface with the name ImageFunctions

4. transform the oo style ImageUtils to a functional style ImageFunctions

   • byte[] failedImage(String imageID) to Function<String, byte[]> failedImage()
   • replace the usage of the method failedImage with the function
   • convert methods for filename creation into functions
   • convert imageAsStreamRessouce into a function and replace the usage
   • convert ImageUtils into ImageFunctions completely including usage

5. refactor the filter classes to functions

   • create an interface called FilterFunctions
   • create Function<BufferedImage, byte[]> toByteArray() to extract repetitive code from filters
   • create Function<byte[], BufferedImage> toBufferedImage() to extract the image read
     • use the function toBufferedImage
     • remove the try catch block, exception will lead to a failed image
   • convert all filter classes to filter functions at FilterFunctions
   • convert method imagePanel -> function imagePanel
   • move factory function into ImagePanel (static)
   • create Function<String, StreamResource> imageAsStreamRessouceNonCached()

6. start using Result<T>, Case, data classes and checked functions

   • switch Info to extends Sext<String, String, Boolean, Boolean, Boolean, Boolean>
   • convert the thumbnail creation to a functional style based on Case and Result
   • convert if - blocks for image creation into a functional style
     • don´t optimize, write it clean even if you are calculating something twice
   • use now Memoizing to remove unnecessary calculation for example done by filters (grayscale/points/..)

7. compare your result with others, start discussing

jdk09 - Refactoring to functional - reactive

v001 - functional reactive

1. first refactorings

   • replace all if statements inside the stream int ?: statements if possible

   • extract the part that is building the transformation function

     • use the functions from the functional JDK8 version
     • extract a function that will build the transformation function
     • build first the function that will use grayscale/pointerize and rotate
     • add a curried version of the resize function
     • decide what will be the right input Type
     • move the method for creating the transformation function into the interface FilterFunctions
     • reuse or create new a Function to read the Image itself from HDD

   • extract the CPU and IO intensive parts into a Function that will transform into a CompletableFuture

2. serverless monolith

   • create the following modules
   • init the monolith module fn init --runtime=java --name javaevents/frp-jdk09-monolith

core-frp-since10 ??

serverless-since09

ramp up FnProject

jdk10

Vaadin UI -> reduce code with var connect to FnProject

Fazit

FRP is possible since JDK8 JDK9 is not a big thing, maybe locale pub/sub JDK10 with var - good for oo style JDK11 will var for lambdas - good for FP style