Use the nullValueCheckStrategy = NullValueCheckStrategy.ALWAYS) on the mapping property you want to be checked. In this snippet you can see a PostalAdress entity is mapped to an entity of the same type, but the id is overwritten only when it is present in the source:

import java.time.LocalDateTime;

import org.mapstruct.Mapper;
import org.mapstruct.Mapping;
import org.mapstruct.NullValueCheckStrategy;

import com.example.entity.PostalAddress;

@Mapper(
    componentModel = "cdi",
    imports = {LocalDateTime.class})
public interface PostalAddressEntity2EntityMapperService {

  @Mapping(source = "id", target = "id", nullValueCheckStrategy = NullValueCheckStrategy.ALWAYS)
  PostalAddress toPostalAddressntityToPostalAddressEntity(
      PostalAddress PostalAddress);
}

This will generate something similar with the following

package com.example.entitytoentity;

import com.example.entity.PostalAddress;
import java.time.LocalDateTime;
import javax.annotation.processing.Generated;
import javax.enterprise.context.ApplicationScoped;

@Generated(
    value = "org.mapstruct.ap.MappingProcessor",
    date = "2021-09-01T14:28:11+0200",
    comments = "version: 1.4.2.Final, compiler: javac, environment: Java 11.0.12 (Azul Systems, Inc.)"
)
@ApplicationScoped
public class PostalAddressEntity2EntityMapperServiceImpl implements PostalAddressEntity2EntityMapperService {

    @Override
    public PostalAddress toPostalAddressEntity(PostalAddress PostalAddress) {
        if ( PostalAddress == null ) {
            return null;
        }

        PostalAddress PostalAddress1 = new PostalAddress();

        if ( PostalAddress.getId() != null ) {
            PostalAddress1.setId( PostalAddress.getId() );
        }
        PostalAddress1.setStreeNo( PostalAddress.getStreetNo() );
        PostalAddress1.setStreet( PostalAddress.getStreet() );
        PostalAddress1.setMainAdress( PostalAddress.getMainAdress() );

        return PostalAddress1;
    }
}

Reference - https://mapstruct.org/documentation/stable/api/org/mapstruct/NullValueCheckStrategy.html

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A basic introduction in Rust, with code snippets taken from the The Rust Programming Language and Rust by Example books, to present in a 40 minutes slot.

You can execute most of the snippets directly on Rust Playground

• Hello world!
• Println macro
• Variables
  • Mutability
  • Variables Scope
• Primitives
  • Scalar Types
  • Compound Types
  • Snippet example
  • Tuples
• Functions
• Ownership
• Stack & Heap
  • Ownership rules
  • Take ownership - snippet
• Structs
• Traits
• Enums
• Control flow
  • Unconditional loop
  • Ranges
• Collections
  • Vectors
  • Hashmaps
• Generics
• Rust Module System

What is the order in which the following texts are logged via console.log ?

console.log('1 - start');
setTimeout(() => console.log('2 - setTimeout1'), 0);
Promise.resolve('Success')
    .then(()=> console.log('3 - promise1'))
    .then(()=> console.log('4 - promise2'));
setTimeout(() => console.log('5 - setTimeout2'), 0);
console.log('6 - end');

Output

1 - start// statement is executed directly in the script (first "Run script" task)
5 - end // part of the first "Run script" task gets executed too
3 - promise1 // placed in microTasks queue and executed between tasks, after first "Run script" task is ready
4 - promise2 // microtask added  during previous microtask execution  and executed immediately
2 - setTimeout1 // callback execution scheduled in another task in the "macroTasks" queue (also task queue), executed in the next interation of the event-loop
5 - setTimeout2 // callback execution scheduled in another task in the task queue, executed in the next iteration of event-loop

Reference - https://developer.mozilla.org/en-US/docs/Web/API/HTML_DOM_API/Microtask_guide/In_depth

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First with “normal” functions:

//closures and higher order function
function salute(salutation) {
  return function(firstName) {
    return function(lastName) {
      console.log(`hi ${salutation} ${firstName} ${lastName}`)
    }
  }
}

salute('Mr.')('John')('Wick')

//output
hi Mr. John Wick

The shorter variant with arrow functions:

const saluteArrowFunction = (salutation) => (firstName) => (lastName) => console.log(`hi ${salutation} ${firstName} ${lastName}`);

saluteArrowFunction ('Mr.')('Johnny')('Cage')

//output
hi Mr. Johnny Cage

Reference - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Functions

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Via hoisting, memory is allocated to the variable var1, but it is not initialised by the time the closure is executed

function one() {
  function two() {
    console.log(`closure var1 - ${var1}`);
  }

  three();
  var var1 = 'var1';
}

one();

//output
hoisting var1 - undefined

But if we use setTimeout(), by the time callback closure function is executed var1 will have been initialised and its value is printed:

function one() {
 setTimeout(function() {
  console.log(`closure var1 - ${var1}`);
 }, 0);
  var var1 = 'var1';
}

one();

//output
closure var1 - var1

Reference - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Closures

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