configuration validation

src/main/java/com/commafeed/CommaFeedConfiguration.java

@@ -6,11 +6,13 @@ import io.dropwizard.db.DataSourceFactory;
 import java.util.Date;
 
 import javax.validation.Valid;
+import javax.validation.constraints.Min;
 import javax.validation.constraints.NotNull;
 
 import lombok.Getter;
 
 import org.apache.commons.lang.time.DateUtils;
+import org.hibernate.validator.constraints.NotBlank;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
 
@@ -34,21 +36,30 @@ public class CommaFeedConfiguration extends Configuration {
 	@Getter
 	public static class ApplicationSettings {
 		@JsonProperty
+		@NotNull
+		@NotBlank
 		private String contextPath;
 
 		@JsonProperty
+		@NotNull
+		@NotBlank
 		private String publicUrl;
 
 		@JsonProperty
+		@NotNull
 		private boolean allowRegistrations;
 
 		@JsonProperty
 		private String googleAnalyticsTrackingCode;
 
 		@JsonProperty
+		@NotNull
+		@Min(1)
 		private int backgroundThreads;
 
 		@JsonProperty
+		@NotNull
+		@Min(1)
 		private int databaseUpdateThreads;
 
 		@JsonProperty
@@ -67,27 +78,38 @@ public class CommaFeedConfiguration extends Configuration {
 		private String smtpPassword;
 
 		@JsonProperty
+		@NotNull
 		private boolean heavyLoad;
 
 		@JsonProperty
+		@NotNull
 		private boolean pubsubhubbub;
 
 		@JsonProperty
+		@NotNull
 		private boolean imageProxyEnabled;
 
 		@JsonProperty
+		@NotNull
+		@Min(0)
 		private int queryTimeout;
 
 		@JsonProperty
+		@NotNull
+		@Min(0)
 		private int keepStatusDays;
 
 		@JsonProperty
+		@NotNull
+		@Min(0)
 		private int refreshIntervalMinutes;
 
 		@JsonProperty
+		@NotNull
 		private CacheType cache;
 
 		@JsonProperty
+		@NotNull
 		private String announcement;
 
 		public Date getUnreadThreshold() {