1 files changed, 146 insertions, 0 deletions
diff --git a/common-parameters/src/main/java/org/onap/policy/common/parameters/ValueValidator.java b/common-parameters/src/main/java/org/onap/policy/common/parameters/ValueValidator.java
new file mode 100644
index 00000000..faf41008
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+++ b/common-parameters/src/main/java/org/onap/policy/common/parameters/ValueValidator.java
@@ -0,0 +1,146 @@
+/*-
+ * ============LICENSE_START=======================================================
+ * ONAP
+ * ================================================================================
+ * Copyright (C) 2020-2021 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.common.parameters;
+
+import java.lang.annotation.Annotation;
+import java.util.ArrayList;
+import java.util.List;
+import lombok.AccessLevel;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+import lombok.Setter;
+import org.onap.policy.common.parameters.annotations.NotNull;
+
+/**
+ * Validator of a value.
+ * <p/>
+ * Note: this currently does not support Min/Max validation of "short" or "byte"; these
+ * annotations are simply ignored for these types.
+ */
+@NoArgsConstructor
+public class ValueValidator {
+
+    /**
+     * {@code True} if the value is allowed to be {@code null}, {@code false} otherwise.
+     * Subclasses are expected to set this, typically based on the validation annotations
+     * associated with the value.
+     */
+    @Getter
+    @Setter(AccessLevel.PROTECTED)
+    private boolean nullAllowed = true;
+
+    /**
+     * Predicates to invoke to validate an object.
+     * <p/>
+     * Note: each predicate is expected to return {@code true} if the next check is
+     * allowed to proceed, {@code false} otherwise. In addition, if {@link #nullAllowed}
+     * is {@code true}, then the predicates must be prepared to deal with a {@code null}
+     * Object as their input parameter.
+     */
+    protected List<Checker> checkers = new ArrayList<>(10);
+
+    /**
+     * Determines if the validator has anything to check.
+     *
+     * @return {@code true} if the validator is empty (i.e., has nothing to check)
+     */
+    public boolean isEmpty() {
+        return checkers.isEmpty();
+    }
+
+    /**
+     * Performs validation of a single field.
+     *
+     * @param result validation results are added here
+     * @param fieldName field whose value is being verified
+     * @param value value to be validated
+     */
+    protected void validateValue(BeanValidationResult result, String fieldName, Object value) {
+
+        if (value == null && isNullAllowed()) {
+            // value is null and null is allowed - just return
+            return;
+        }
+
+        for (Checker checker : checkers) {
+            if (!checker.test(result, fieldName, value)) {
+                // invalid - don't bother with additional checks
+                return;
+            }
+        }
+    }
+
+    /**
+     * Looks for an annotation at the class or field level. If an annotation is found at
+     * either the field or class level, then it adds a verifier to
+     * {@link ValueValidator#checkers}.
+     *
+     * @param annotClass class of annotation to find
+     * @param checker function to validate the value
+     */
+    public <T extends Annotation> void addAnnotation(Class<T> annotClass, Checker checker) {
+        var annot = getAnnotation(annotClass);
+        if (annot != null) {
+            checkers.add(checker);
+
+            if (annotClass == NotNull.class) {
+                setNullAllowed(false);
+            }
+        }
+    }
+
+    /**
+     * Looks for an annotation at the class or field level. If an annotation is found at
+     * either the field or class level, then it adds a verifier to
+     * {@link ValueValidator#checkers}.
+     *
+     * @param annotClass class of annotation to find
+     * @param checker function to validate the value
+     */
+    public <T extends Annotation> void addAnnotation(Class<T> annotClass, CheckerWithAnnot<T> checker) {
+        var annot = getAnnotation(annotClass);
+        if (annot != null) {
+            checkers.add((result, fieldName, value) -> checker.test(result, fieldName, annot, value));
+        }
+    }
+
+    /**
+     * Gets an annotation from the field or the class. The default method simply returns
+     * {@code null}.
+     *
+     * @param annotClass annotation class of interest
+     * @return the annotation, or {@code null} if neither the field nor the class has the
+     *         desired annotation
+     */
+    public <T extends Annotation> T getAnnotation(Class<T> annotClass) {
+        return null;
+    }
+
+    // functions to validate a value extracted from a field
+
+    public static interface Checker {
+        boolean test(BeanValidationResult result, String fieldName, Object value);
+    }
+
+    public static interface CheckerWithAnnot<T extends Annotation> {
+        boolean test(BeanValidationResult result, String fieldName, T annotation, Object value);
+    }
+}