feat(validate): Add ValidationError, ValidationException, Validator interface

Author: thced

src/main/java/com/retailsvc/http/ValidationException.java

@@ -0,0 +1,16 @@
+package com.retailsvc.http;
+
+import com.retailsvc.http.validate.ValidationError;
+
+public final class ValidationException extends RuntimeException {
+  private final ValidationError error;
+
+  public ValidationException(ValidationError error) {
+    super(error.pointer() + " [" + error.keyword() + "] " + error.message());
+    this.error = error;
+  }
+
+  public ValidationError error() {
+    return error;
+  }
+}

src/main/java/com/retailsvc/http/validate/ValidationError.java

@@ -0,0 +1,4 @@
+package com.retailsvc.http.validate;
+
+public record ValidationError(
+    String pointer, String keyword, String message, Object rejectedValue) {}

src/main/java/com/retailsvc/http/validate/Validator.java

@@ -0,0 +1,8 @@
+package com.retailsvc.http.validate;
+
+import com.retailsvc.http.spec.schema.Schema;
+
+public interface Validator {
+  /** Throws ValidationException on first failure. */
+  void validate(Object value, Schema schema, String pointer);
+}

src/test/java/com/retailsvc/http/ValidationExceptionTest.java

@@ -0,0 +1,16 @@
+package com.retailsvc.http;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import com.retailsvc.http.validate.ValidationError;
+import org.junit.jupiter.api.Test;
+
+class ValidationExceptionTest {
+  @Test
+  void carriesError() {
+    ValidationError e = new ValidationError("/x", "type", "expected string", null);
+    ValidationException ex = new ValidationException(e);
+    assertThat(ex.error()).isSameAs(e);
+    assertThat(ex.getMessage()).contains("/x").contains("type").contains("expected string");
+  }
+}