Resolve "Create missing service classes"

Closes #16 (closed)

src/main/java/cz/muni/ics/kypo/training/adaptive/config/BeanValidationDeserializer.java

+package cz.muni.ics.kypo.training.config;
+
+import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.databind.DeserializationContext;
+import com.fasterxml.jackson.databind.deser.BeanDeserializer;
+import com.fasterxml.jackson.databind.deser.BeanDeserializerBase;
+
+import javax.validation.*;
+import java.io.IOException;
+import java.util.Set;
+
+public class BeanValidationDeserializer extends BeanDeserializer {
+
+    private final static ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
+    private final Validator validator = factory.getValidator();
+
+    public BeanValidationDeserializer(BeanDeserializerBase src) {
+        super(src);
+    }
+
+    @Override
+    public Object deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {
+        Object instance = super.deserialize(p, ctxt);
+        validate(instance);
+        return instance;
+    }
+
+    private void validate(Object instance) {
+        Set<ConstraintViolation<Object>> violations = validator.validate(instance);
+        if (!violations.isEmpty()) {
+            StringBuilder msg = new StringBuilder();
+            msg.append("JSON object is not valid. Reasons (").append(violations.size()).append("): ");
+            for (ConstraintViolation<Object> violation : violations) {
+                msg.append(violation.getMessage()).append(", ");
+            }
+            throw new ConstraintViolationException(msg.toString(), violations);
+        }
+    }
+}