Extensible validator (#101)

Make RequestValidator <<extending-request-validator, extensible>> by introducing AbstractRequestValidator base class

Author: jpraet

belgif-rest-problem-validator/src/main/java/io/github/belgif/rest/problem/validation/AbstractRequestValidator.java

@@ -0,0 +1,10 @@
+package io.github.belgif.rest.problem.validation;
+
+public abstract class AbstractRequestValidatorExtensionA<SELF extends AbstractRequestValidatorExtensionA<SELF>>
+        extends AbstractRequestValidator<SELF> {
+
+    public SELF a() {
+        return getThis();
+    }
+
+}

belgif-rest-problem-validator/src/main/java/io/github/belgif/rest/problem/validation/RequestValidator.java

@@ -0,0 +1,10 @@
+package io.github.belgif.rest.problem.validation;
+
+public abstract class AbstractRequestValidatorExtensionB<SELF extends AbstractRequestValidatorExtensionB<SELF>>
+        extends AbstractRequestValidatorExtensionA<SELF> {
+
+    public SELF b() {
+        return getThis();
+    }
+
+}

belgif-rest-problem-validator/src/test/java/io/github/belgif/rest/problem/validation/AbstractRequestValidatorExtensionA.java

@@ -0,0 +1,5 @@
+package io.github.belgif.rest.problem.validation;
+
+public final class RequestValidatorExtensionA extends AbstractRequestValidatorExtensionA<RequestValidatorExtensionA> {
+
+}

belgif-rest-problem-validator/src/test/java/io/github/belgif/rest/problem/validation/AbstractRequestValidatorExtensionB.java

@@ -0,0 +1,5 @@
+package io.github.belgif.rest.problem.validation;
+
+public final class RequestValidatorExtensionB extends AbstractRequestValidatorExtensionB<RequestValidatorExtensionB> {
+
+}

belgif-rest-problem-validator/src/test/java/io/github/belgif/rest/problem/validation/RequestValidatorExtensionA.java

@@ -468,6 +468,20 @@ void chainingInvalid() {
                 InputValidationIssues.invalidEnterpriseNumber(BODY, "enterpriseNumber", "2111111112"));
     }
 
+    @Test
+    void extension() {
+        new RequestValidatorExtensionB()
+                .require(Input.body("test", "value"))
+                .b()
+                .a()
+                .validate();
+        new RequestValidatorExtensionB()
+                .a()
+                .b()
+                .require(Input.body("test", "value"))
+                .validate();
+    }
+
     private void assertValid(RequestValidator validator) {
         assertThatNoException().isThrownBy(validator::validate);
     }

belgif-rest-problem-validator/src/test/java/io/github/belgif/rest/problem/validation/RequestValidatorExtensionB.java

@@ -31,6 +31,10 @@ The library consists of these modules:
 
 === Version 0.7
 
+*belgif-rest-problem-validator:*
+
+* Make RequestValidator <<extending-request-validator, extensible>> by introducing AbstractRequestValidator base class
+
 *belgif-rest-problem-spring:*
 
 * Extract ProblemWebClientCustomizer to belgif-rest-problem-spring-boot-2 and belgif-rest-problem-spring-boot-3 to fix NoSuchMethodError compatibility issue
@@ -281,6 +285,33 @@ include::../../../belgif-rest-problem-validator/src/test/java/adoc/CodeSamples.j
 ----
 ====
 
+[discrete]
+[[extending-request-validator]]
+=== Extending the RequestValidator
+
+You may have a need to extend the RequestValidator with custom organization- or domain-specific validations. +
+This is possible by extending the AbstractRequestValidator base class.
+
+If in turn, you want your own validator implementation to be extensible as well, you can propagate the extensible fluent builder pattern as follows:
+
+[source,java]
+.Extensible request validator
+----
+ public abstract class AbstractMyRequestValidator<SELF extends AbstractMyRequestValidator<SELF>>
+         extends AbstractRequestValidator<SELF> {
+
+     public SELF something(Input<String> input) {
+         addValidator(new SomethingValidator(input));
+         return getThis();
+     }
+
+ }
+
+ public final class MyRequestValidator extends AbstractMyRequestValidator<MyRequestValidator> {
+
+ }
+----
+
 [[belgif-rest-problem-java-ee]]
 == belgif-rest-problem-java-ee