Applicators · Lesson 3

Data Visualization

Interactive lessons: REST APIs, Spring Boot CRUD, search, filtering, pagination, and data queries.

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1 — REST APIs & CRUD with Mock Database

What this shows: Experiment with a live mock REST API. Send POST, GET, PUT, DELETE requests to create, read, update, and remove company records.

Response 
Send a request to see the response here.

2 — Query Methods & Company Builder

What this shows: Practice Spring Data JPA derived queries, and build company records with sample data.

Derived Query Practice

Write a method signature to find companies with size greater than a minimum:

Show Hint

Use Spring Data naming: findBy<Field>GreaterThan(param)

Company Builder


        

      

    

  


  
  

    

      
3 — Search & Data Filtering

      
What this shows: Build query filters using derived queries, JPQL, and Specifications.

      
Query Builder

      

        

          

          
          

          
          

          
          

          
          

        

        

          
          
SELECT c FROM Company c

          
          
Specification.where(null)

        

      

      
Learning Recap

      

        

          
Derived Queries

          
Simple
findByLocation(..)

          
Multi-field
findByLocationAndIndustry(..)

          
Compare
findBySizeGreaterThan(..)

          
Like
findByNameContaining(..)

        

        

          
JPQL & Native

          
Filter
WHERE c.size > :min

          
Join
JOIN c.skills s

          
Projection
SELECT new DTO(..)

        

        

          
Specifications

          
Chain
where(a).and(b)

          
Optional
return null to skip

          
Flexible
Best for dynamic filters

        

      

    

  


  
  

    

      
4 — Pagination & Sorting

      
What this shows: See how Pageable works with sorting, limiting, and page navigation.

      

        

          
          
          
          
          
          
          

          
        

        

          
          
Click Apply Pagination to see results.

        

      

      
Pageable Example Code

      
// Repository method
Page<Company> findAll(Pageable pageable);

// Service usage
Pageable paging = PageRequest.of(0, 10, Sort.by("size").descending());
Page<Company> page = repo.findAll(paging);

    

  


  
  

    

      
5 — Scenario Checker & Quick Quiz

      
What this shows: Real-world scenarios and a quick knowledge check.

      
Scenario Checker

      

        

          
          
          
          
          

        

        

          
Select a scenario and approach, then click Check.

        

      

      
Exit Quiz

      

      

        
        
        
      

    

  


  
  

    

      
6 — Completion Checklist & Export

      
What this shows: Self-assessment and exportable progress summary.

      

        

          
Self-Assessment

          

          

        

        

          
Notes

          
          

        

      

    

  


  

    
    

      
      
    

  











      


      
      
      

      
      

        

          

          
          

          
          

          
            
            
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