add a numeric rule

Co-author-by: Julian Gojani <julian@gojani.xyz>

Author: JWaldecker

src/main/java/org/javawebstack/validator/Validator.java

@@ -32,6 +32,7 @@ public class Validator {
         registerRuleType("ipv6", IPv6AddressRule.class);
         registerRuleType("int", IntegerRule.class);
         registerRuleType("integer", IntegerRule.class);
+        registerRuleType("numeric", NumericRule.class);
         registerRuleType("date", DateRule.class);
         registerRuleType("array", ArrayRule.class);
         registerRuleType("list", ArrayRule.class);

src/main/java/org/javawebstack/validator/rule/NumericRule.java

@@ -0,0 +1,29 @@
+package org.javawebstack.validator.rule;
+
+import org.javawebstack.abstractdata.AbstractElement;
+import org.javawebstack.validator.ValidationContext;
+
+import java.lang.reflect.Field;
+
+public class NumericRule implements ValidationRule {
+    @Override
+    public String validate(ValidationContext context, Field field, AbstractElement value) {
+        if (value == null)
+            return null;
+
+        float v;
+        if (value.isNumber())
+            v = value.number().floatValue();
+        else if (value.isString()) {
+            try {
+                v = Float.parseFloat(value.string());
+            } catch(NumberFormatException ex) {
+                return "Not a numeric value";
+            }
+        } else {
+            return "Not a numeric value";
+        }
+
+        return null;
+    }
+}