Specification Api

Introduction

This is a simple library to handle generic search using Criteria/Specification API with JPA.

It generates a JPA Specification<T> with all criterias given a request object.

Entry point

SpecificationService is the entry point of the specification generator. The generated Specification<T> can be used with repository.findAll.

@Service
class Service {
    private final SpecificationService specificationService;
    // ...
    List<Entity> = repository.findAll(specificationService.generateSpecification(searchRequest));
    // ...
}    

Configuration

The SpecificationService bean only needs a JdbcTemplate

  @Bean
  public SpecificationService specificationService(JdbcTemplate jdbcTemplate) {
    return new SpecificationService(jdbcTemplate);
  }

The entity

Define the entity with usual JPA annotation

@Entity
@Table(name = "entity")
public class Entity {
   @Id
   private Integer entityId;
   // ...
}

Request object

This is the object containing all search parameters.

1. Use the annotation @SearchRequestObject for the object holding search values. This object typically comes from a HTTP request (request parameters or request body)
2. Use the annotation @SearchPath for each field of the request object to be mapped into a JPA Criteria.

@SearchRequestObject
public record SearchRequest(@SearchPath("path(name) like ?") Integer entityId) {}

Syntax

The @SearchPath annotation hold all information to generate a JPA criteria. These informations are a chain of operations to test a value with a field using a SQL like or equal.

1. Join
2. Values
   1. Simple values
   2. Operators
   3. Types
3. Json values

Validation

There is an optional bean to validate all expressions set with @SearchPath

  @Bean
  public SpecificationValidationService specificationValidationService(
      ResourceLoader resourceLoader) {
    return new SpecificationValidationService(resourceLoader) {
      @Override
      public String[] packagesToScan() {
        return new String[] {"package.that.contain.classes.annotated.with.SearchPath"};
      }
    };
  }

Json and Prostgres

Error handling

ParseException

SearchException