SmartConstraints

SmartContraints is a Java annotation processor that collects validation constraints from your entities and generates corresponding composed constraints annotations. Then, they can easily be used on your DTO's properties.

SmartConstraints is a Work In Progress. Stay tuned for incoming release on maven central :-)

Example

With given entity:

public class AddressEntity {

    @NotNull
    @Size(min = 5, max = 5)
    private String zipCode;

}

Without SmartConstraints

Your DTO would need to repeat constraints, like:

public class AddressDto {

    @NotNull
    @Size(min = 5, max = 5)
    private String zipCode;

}

• ❌ You repeat yourself
• ❌ If your constraintes have to change, your Entity and your DTO can become out of sync if you forget to update one of them

Alternatively, you could write by hand a composed contraint annotation. That's what SmartConstraints does for you automatically.

With SmartConstraints

You could simply write:

public class AddressDto {

    @ValidZipCode
    private String zipCode;

}

• ✅ DRY, and readable
• ✅ (Almost) no extra work
• ✅ Constraints are always in sync

Under the hood

SmartConstraints generates composed constraint annotations by analysing your entities.

@Generated
class Address_Constraints {

    
    @jakarta.validation.constraints.NotNull()   
    @jakarta.validation.constraints.Size(min = 5, max = 5)
    @Target({METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @jakarta.validation.Constraint(validatedBy = {})
    public @interface ValidZipCode {
        String message() default "{my.package.Address_Constraints.message}";
        Class<?>[] groups() default { };
        Class<? extends jakarta.validation.Payload>[] payload() default { };
    }

}

Of course, you can write them by yourself. SmartConstraints simply saves you from writing some boilerplate code.

Maven How-To

Define a property to define SmartConstraints version:

   <properties>
        <smartconstraints.version>0.5.1</smartconstraints.version>
    </properties>

Add the smartconstraints-annotation as a provided dependency to your project. (Not required at runtime)

    <dependencies>
        <dependency>
            <groupId>eu.aronnax.smartconstraints</groupId>
            <artifactId>smartconstraints-annotation</artifactId>
            <version>${smartconstraints.version}</version>
            <scope>provided</scope>
        </dependency>
    </dependencies>

Add the smartconstraints-annotationprocessor as a maven-compiler-plugin annotationProcessor:

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <annotationProcessorPaths>
                        <path>
                            <groupId>eu.aronnax.smartconstraints</groupId>
                            <artifactId>smartconstraints-annotationprocessor</artifactId>
                            <version>${smartconstraints.version}</version>
                        </path>
                    </annotationProcessorPaths>
                </configuration>
            </plugin>
        </plugins>
    </build>

Add the @CopyJavaxConstraints or @CopyJakartaConstraints annotation on a package-info.java in your project, where composed annotations will be generated. Add the from attribute and specify the package where your entities are located.

Run your build :-)

You can now use annotations like : @Address_Constraints.ValidStreetName (use a static import to shorten it as @ValidStreetName) on your DTOs that aggregates validation constraints from original field, without any runtime dependency to AddressEntity.

Notes

SmartContraints as been designed as a tool to help adoption of CleanArchitecture principles.

SmartConstraints also works with source entities located in third party libraries.

Requirements

Your project must be at least a Java 17 project.

Your project must use javax.validation.constraints.* or jakarta.validation.constraints.* annotations.

Roadmap

1.1

• Support multi-round annotation processor

1.0 (2023)

• Additional testing

0.6 (2023-07)

• Support validation groups

0.5 (2023-04-24)

• Also support jakarta constraints

0.4 (2023-02-24)

• Support javax constraints

Contribute

Project is still in alpha stage. Any contribution is welcome.

To build project : mvn clean install