This project is a collection of Value Objects that encourages the use of strong typed identifiers. It also provides integrations for serialization libraries such as Jackson.
Imagine a service or repository, and you want to query an entity with two distinct IDs. Let's say they're both UUIDs. There's no other possibility than to differentiate between the IDs via the name of the argument.
public Entity query(UUID fooId, UUID barId) {
...
}There are three options to minimize the risk to confound the arguments of the method above.
- Be perfect and make no mistakes
- Verify the correctness with tests
- Change code design
- Use different argument types
Although I'd recommend option 1 and 2, it's never a bad idea to be extra sure and avoid misuse from the start. Strong typing and extensive use of Value Objects helps to improve readability and encourages self documenting code.
The library can be used as is, but the real benefits only come when you derive the identifier for each domain entity. Let's assume you hava an entity called Person. Your code could read something like this.
public class Person {
private final Person.Id id;
private String name;
// constructor, getter and setter omitted for brevity
public static final class Id extends UuidIdentifier {
public Id(UUID value) {
super(value);
}
}
}None of the modules below will ship transitive dependencies. Unless you are using a Spring Boot Starter Parent, you want to make sure to include the dependencies yourself.
The API module contains the core code base. Other modules are built on top of
the API. The usage is pretty self-explanatory. It contains the identifier,
factories and basic subtypes. The Identifiable interface is for convenience
may be implemented by any domain entities.
<dependency>
<groupId>de.vinado.lib</groupId>
<artifactId>identifier-api</artifactId>
<version>2.0.1</version>
</dependency>This module contains JSON deserializers for all generic base identifiers and a generic serializer that delegates to the ID value's serializer. Their purpose is to unwrap the value object into a plain JSON value. So the JSON tree stays clean and familiar to existing APIs (or at least to you and your OCDs).
If you want to derive from a basic identifier, you also need to implement a custom deserializer. The following example shows the amount of work that is necessary. Not much right?
@JsonDeserialize(using = Id.Deserializer.class)
public final class Id extends UuidIdentifier {
public Id(UUID value) {
super(value);
}
private static final class Deserializer extends UuidIdentifierDeserializer<Id> {
private Deserializer() {
super(Id::new);
}
}
}<dependency>
<groupId>de.vinado.lib</groupId>
<artifactId>identifier-jackson</artifactId>
<version>2.0.1</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>${jackson.version}</version>
</dependency>The Spring module contains generic identifier (reading) converters. They are capable of converting any compatible value to the corresponding identifier and subtypes. This is especially useful for Spring Web applications and you want to query resources by their identifier, like the following example shows.
@GetMapping("/{id}")
public ResponseEntity<Person> retrieve(@PathVariable Person.Id id) {
...
}The identifier instantiation is performed via Java reflection. Therefor subtypes must provide an accessible constructor that takes exactly on argument of the type the identifier encapsulates.
<dependency>
<groupId>de.vinado.spring</groupId>
<artifactId>identifier-convert</artifactId>
<version>2.0.1</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${spring.version}</version>
</dependency>In case you wish to integrate strong typed identifiers into your Spring Boot application you may want to use the zero-conf Spring Boot Starter.
<dependency>
<groupId>de.vinado.boot</groupId>
<artifactId>identifier-spring-boot-starter</artifactId>
<version>2.0.1</version>
</dependency>Apache License 2.0 - Vinado - Built with ❤️ in Dresden