diff --git a/lib/client-api/src/main/java/org/apache/olingo/client/api/ODataBatchConstants.java b/lib/client-api/src/main/java/org/apache/olingo/client/api/ODataBatchConstants.java
index df0c7fe67..a7e5be29c 100644
--- a/lib/client-api/src/main/java/org/apache/olingo/client/api/ODataBatchConstants.java
+++ b/lib/client-api/src/main/java/org/apache/olingo/client/api/ODataBatchConstants.java
@@ -21,31 +21,30 @@ package org.apache.olingo.client.api;
 /**
  * Constant values related to the OData protocol.
  */
-public class ODataBatchConstants {
+public interface ODataBatchConstants {
 
   /**
    * Batch item content type.
    */
-  public static final String ITEM_CONTENT_TYPE = "application/http";
+  String ITEM_CONTENT_TYPE = "application/http";
 
   /**
    * Boundary key.
    */
-  public static final String BOUNDARY = "boundary";
+  String BOUNDARY = "boundary";
 
   /**
    * Item content type.
    */
-  public static String ITEM_CONTENT_TYPE_LINE = "Content-Type: application/http";
+  String ITEM_CONTENT_TYPE_LINE = "Content-Type: application/http";
 
   /**
    * Item transfer encoding.
    */
-  public static String ITEM_TRANSFER_ENCODING_LINE = "Content-Transfer-Encoding: binary";
+  String ITEM_TRANSFER_ENCODING_LINE = "Content-Transfer-Encoding: binary";
 
   /**
    * Content id header name.
    */
-  public static String CHANGESET_CONTENT_ID_NAME = "Content-ID";
-
+  String CHANGESET_CONTENT_ID_NAME = "Content-ID";
 }
diff --git a/lib/client-api/src/main/java/org/apache/olingo/client/api/ODataClientBuilder.java b/lib/client-api/src/main/java/org/apache/olingo/client/api/ODataClientBuilder.java
index 99949776f..7ad81a4b0 100644
--- a/lib/client-api/src/main/java/org/apache/olingo/client/api/ODataClientBuilder.java
+++ b/lib/client-api/src/main/java/org/apache/olingo/client/api/ODataClientBuilder.java
@@ -21,6 +21,7 @@ package org.apache.olingo.client.api;
 import java.lang.reflect.Constructor;
 import java.lang.reflect.InvocationTargetException;
 
+import org.apache.olingo.commons.api.ODataRuntimeException;
 import org.apache.olingo.commons.api.edm.Edm;
 import org.apache.olingo.commons.api.format.ContentType;
 
@@ -99,6 +100,9 @@ public final class ODataClientBuilder {
     }
   }
 
+  /** Empty private constructor for static helper class */
+  private ODataClientBuilder() {}
+
   /**
    * Create an new ODataClient based on via system property ODATA_CLIENT_IMPL_SYS_PROPERTY
    * class name or if not net the default ODATA_CLIENT_IMPL_CLASS set class.
@@ -161,15 +165,19 @@ public final class ODataClientBuilder {
       Constructor<?> ctor = clazz.getConstructor(ctorParameterClasses);
       return typeOfClass.cast(ctor.newInstance(ctorParameters));
     } catch (ClassNotFoundException e) {
-      throw new RuntimeException("Requested class '" + className + "' could not be loaded.", e);
+      throw wrapException(className, e);
     } catch (InstantiationException e) {
-      throw new RuntimeException("Requested class '" + className + "' could not be loaded.", e);
+      throw wrapException(className, e);
     } catch (IllegalAccessException e) {
-      throw new RuntimeException("Requested class '" + className + "' could not be loaded.", e);
+      throw wrapException(className, e);
     } catch (NoSuchMethodException e) {
-      throw new RuntimeException("Requested class '" + className + "' could not be loaded.", e);
+      throw wrapException(className, e);
     } catch (InvocationTargetException e) {
-      throw new RuntimeException("Requested class '" + className + "' could not be loaded.", e);
+      throw wrapException(className, e);
     }
   }
+
+  private static ODataRuntimeException wrapException(String className, Exception e) {
+    return new ODataRuntimeException("Requested class '" + className + "' could not be loaded.", e);
+  }
 }
diff --git a/lib/client-api/src/main/java/org/apache/olingo/client/api/communication/request/invoke/EdmEnabledInvokeRequestFactory.java b/lib/client-api/src/main/java/org/apache/olingo/client/api/communication/request/invoke/EdmEnabledInvokeRequestFactory.java
index 5293f7dae..72ace1228 100644
--- a/lib/client-api/src/main/java/org/apache/olingo/client/api/communication/request/invoke/EdmEnabledInvokeRequestFactory.java
+++ b/lib/client-api/src/main/java/org/apache/olingo/client/api/communication/request/invoke/EdmEnabledInvokeRequestFactory.java
@@ -30,63 +30,63 @@ public interface EdmEnabledInvokeRequestFactory extends InvokeRequestFactory {
   /**
    * Gets an invoke request instance for the function import with the given name and no parameters.
    *
-   * @param <RES> OData domain object result, derived from return type defined in the function import
+   * @param <T> OData domain object result, derived from return type defined in the function import
    * @param functionImportName operation to be invoked
    * @return new {@link ODataInvokeRequest} instance.
    */
-  <RES extends ClientInvokeResult> ODataInvokeRequest<RES> getFunctionImportInvokeRequest(
+  <T extends ClientInvokeResult> ODataInvokeRequest<T> getFunctionImportInvokeRequest(
           String functionImportName);
 
   /**
    * Gets an invoke request instance for the function import with the given name and matching parameter names.
    *
-   * @param <RES> OData domain object result, derived from return type defined in the function import
+   * @param <T> OData domain object result, derived from return type defined in the function import
    * @param functionImportName operation to be invoked
    * @param parameters parameters to pass to operation import invocation
    * @return new {@link ODataInvokeRequest} instance.
    */
-  <RES extends ClientInvokeResult> ODataInvokeRequest<RES> getFunctionImportInvokeRequest(
+  <T extends ClientInvokeResult> ODataInvokeRequest<T> getFunctionImportInvokeRequest(
           String functionImportName, Map<String, ClientValue> parameters);
 
   /**
    * Gets an invoke request instance for the action import with the given name.
    *
-   * @param <RES> OData domain object result, derived from return type defined in the action import
+   * @param <T> OData domain object result, derived from return type defined in the action import
    * @param actionImportName operation to be invoked
    * @return new {@link ODataInvokeRequest} instance.
    */
-  <RES extends ClientInvokeResult> ODataInvokeRequest<RES> getActionImportInvokeRequest(
+  <T extends ClientInvokeResult> ODataInvokeRequest<T> getActionImportInvokeRequest(
           String actionImportName);
 
   /**
    * Gets an invoke request instance for the action import with the given name.
    *
-   * @param <RES> OData domain object result, derived from return type defined in the action import
+   * @param <T> OData domain object result, derived from return type defined in the action import
    * @param actionImportName operation to be invoked
    * @param parameters parameters to pass to operation import invocation
    * @return new {@link ODataInvokeRequest} instance.
    */
-  <RES extends ClientInvokeResult> ODataInvokeRequest<RES> getActionImportInvokeRequest(
+  <T extends ClientInvokeResult> ODataInvokeRequest<T> getActionImportInvokeRequest(
           String actionImportName, Map<String, ClientValue> parameters);
 
   /**
    * Gets an invoke request instance for the function bound to given URI (no parameters).
    *
-   * @param <RES> OData domain object result
+   * @param <T> OData domain object result
    * @param bindingParameterURI binding parameter URI
    * @param functionName operation to be invoked
    * @param bindingParameterTypeName binding parameter type full qualified name
    * @param isBindingParameterCollection whether binding parameter is collection
    * @return new {@link ODataInvokeRequest} instance.
    */
-  <RES extends ClientInvokeResult> ODataInvokeRequest<RES> getBoundFunctionInvokeRequest(
+  <T extends ClientInvokeResult> ODataInvokeRequest<T> getBoundFunctionInvokeRequest(
           URI bindingParameterURI, FullQualifiedName functionName, FullQualifiedName bindingParameterTypeName,
           Boolean isBindingParameterCollection);
 
   /**
    * Gets an invoke request instance for the function bound to given URI (with parameters).
    *
-   * @param <RES> OData domain object result
+   * @param <T> OData domain object result
    * @param bindingParameterURI binding parameter URI
    * @param functionName operation to be invoked
    * @param bindingParameterTypeName binding parameter type full qualified name
@@ -94,28 +94,28 @@ public interface EdmEnabledInvokeRequestFactory extends InvokeRequestFactory {
    * @param parameters parameters to pass to function invocation
    * @return new {@link ODataInvokeRequest} instance.
    */
-  <RES extends ClientInvokeResult> ODataInvokeRequest<RES> getBoundFunctionInvokeRequest(
+  <T extends ClientInvokeResult> ODataInvokeRequest<T> getBoundFunctionInvokeRequest(
           URI bindingParameterURI, FullQualifiedName functionName, FullQualifiedName bindingParameterTypeName,
           Boolean isBindingParameterCollection, Map<String, ClientValue> parameters);
 
   /**
    * Gets an invoke request instance for the action bound to given URI (no parameters).
    *
-   * @param <RES> OData domain object result
+   * @param <T> OData domain object result
    * @param bindingParameterURI binding parameter URI
    * @param actionName operation to be invoked
    * @param bindingParameterTypeName binding parameter type full qualified name
    * @param isBindingParameterCollection whether binding parameter is collection
    * @return new {@link ODataInvokeRequest} instance.
    */
-  <RES extends ClientInvokeResult> ODataInvokeRequest<RES> getBoundActionInvokeRequest(
+  <T extends ClientInvokeResult> ODataInvokeRequest<T> getBoundActionInvokeRequest(
           URI bindingParameterURI, FullQualifiedName actionName, FullQualifiedName bindingParameterTypeName,
           Boolean isBindingParameterCollection);
 
   /**
    * Gets an invoke request instance for the action bound to given URI (with parameters).
    *
-   * @param <RES> OData domain object result
+   * @param <T> OData domain object result
    * @param bindingParameterURI binding parameter URI
    * @param actionName operation to be invoked
    * @param bindingParameterTypeName binding parameter type full qualified name
@@ -123,7 +123,7 @@ public interface EdmEnabledInvokeRequestFactory extends InvokeRequestFactory {
    * @param parameters parameters to pass to function invocation
    * @return new {@link ODataInvokeRequest} instance.
    */
-  <RES extends ClientInvokeResult> ODataInvokeRequest<RES> getBoundActionInvokeRequest(
+  <T extends ClientInvokeResult> ODataInvokeRequest<T> getBoundActionInvokeRequest(
           URI bindingParameterURI, FullQualifiedName actionName, FullQualifiedName bindingParameterTypeName,
           Boolean isBindingParameterCollection, Map<String, ClientValue> parameters);
 
diff --git a/lib/client-api/src/main/java/org/apache/olingo/client/api/communication/request/invoke/InvokeRequestFactory.java b/lib/client-api/src/main/java/org/apache/olingo/client/api/communication/request/invoke/InvokeRequestFactory.java
index 7a3f3014f..21388ea5b 100644
--- a/lib/client-api/src/main/java/org/apache/olingo/client/api/communication/request/invoke/InvokeRequestFactory.java
+++ b/lib/client-api/src/main/java/org/apache/olingo/client/api/communication/request/invoke/InvokeRequestFactory.java
@@ -36,57 +36,57 @@ public interface InvokeRequestFactory {
    * This method is mainly meant for internal usage, but defined for generic calls from proxy; normally, one of other
    * methods should be used instead.
    *
-   * @param <RES> OData domain object result
+   * @param <T> OData domain object result
    * @param method HTTP invocation method
    * @param uri invocation URI
    * @param resultRef reference Class for result
    * @param parameters parameters to pass to function invocation
    * @return new {@link ODataInvokeRequest} instance.
    */
-  <RES extends ClientInvokeResult> ODataInvokeRequest<RES> getInvokeRequest(
-          HttpMethod method, URI uri, Class<RES> resultRef, Map<String, ClientValue> parameters);
+  <T extends ClientInvokeResult> ODataInvokeRequest<T> getInvokeRequest(
+          HttpMethod method, URI uri, Class<T> resultRef, Map<String, ClientValue> parameters);
 
   /**
    * Gets an invoke request instance for the function bound to given URI (no parameters).
    *
-   * @param <RES> OData domain object result
+   * @param <T> OData domain object result
    * @param uri invocation URI
    * @param resultRef reference Class for result
    * @return new {@link ODataInvokeRequest} instance.
    */
-  <RES extends ClientInvokeResult> ODataInvokeRequest<RES> getFunctionInvokeRequest(URI uri, Class<RES> resultRef);
+  <T extends ClientInvokeResult> ODataInvokeRequest<T> getFunctionInvokeRequest(URI uri, Class<T> resultRef);
 
   /**
    * Gets an invoke request instance for the function bound to given URI (with parameters).
    *
-   * @param <RES> OData domain object result
+   * @param <T> OData domain object result
    * @param uri invocation URI
    * @param resultRef reference Class for result
    * @param parameters parameters to pass to function invocation
    * @return new {@link ODataInvokeRequest} instance.
    */
-  <RES extends ClientInvokeResult> ODataInvokeRequest<RES> getFunctionInvokeRequest(
-          URI uri, Class<RES> resultRef, Map<String, ClientValue> parameters);
+  <T extends ClientInvokeResult> ODataInvokeRequest<T> getFunctionInvokeRequest(
+          URI uri, Class<T> resultRef, Map<String, ClientValue> parameters);
 
   /**
    * Gets an invoke request instance for the action bound to given URI (no parameters).
    *
-   * @param <RES> OData domain object result
+   * @param <T> OData domain object result
    * @param uri invocation URI
    * @param resultRef reference Class for result
    * @return new {@link ODataInvokeRequest} instance.
    */
-  <RES extends ClientInvokeResult> ODataInvokeRequest<RES> getActionInvokeRequest(URI uri, Class<RES> resultRef);
+  <T extends ClientInvokeResult> ODataInvokeRequest<T> getActionInvokeRequest(URI uri, Class<T> resultRef);
 
   /**
    * Gets an invoke request instance for the action bound to given URI (with parameters).
    *
-   * @param <RES> OData domain object result
+   * @param <T> OData domain object result
    * @param uri invocation URI
    * @param resultRef reference Class for result
    * @param parameters parameters to pass to action invocation
    * @return new {@link ODataInvokeRequest} instance.
    */
-  <RES extends ClientInvokeResult> ODataInvokeRequest<RES> getActionInvokeRequest(
-          URI uri, Class<RES> resultRef, Map<String, ClientValue> parameters);
+  <T extends ClientInvokeResult> ODataInvokeRequest<T> getActionInvokeRequest(
+          URI uri, Class<T> resultRef, Map<String, ClientValue> parameters);
 }
diff --git a/lib/client-api/src/main/java/org/apache/olingo/client/api/domain/ClientCollectionValue.java b/lib/client-api/src/main/java/org/apache/olingo/client/api/domain/ClientCollectionValue.java
index 8a0078efa..d5c6c9fbd 100644
--- a/lib/client-api/src/main/java/org/apache/olingo/client/api/domain/ClientCollectionValue.java
+++ b/lib/client-api/src/main/java/org/apache/olingo/client/api/domain/ClientCollectionValue.java
@@ -23,16 +23,16 @@ import java.util.Collection;
 /**
  * OData collection property value.
  * 
- * @param <OV> The actual ODataValue interface.
+ * @param <T> The actual ODataValue interface.
  */
-public interface ClientCollectionValue<OV extends ClientValue> extends ClientValue, Iterable<OV> {
+public interface ClientCollectionValue<T extends ClientValue> extends ClientValue, Iterable<T> {
 
   /**
    * Adds a value to the collection.
    * 
    * @param value value to be added.
    */
-  ClientCollectionValue<OV> add(ClientValue value);
+  ClientCollectionValue<T> add(ClientValue value);
 
   /**
    * Checks if collection is empty.
diff --git a/lib/client-api/src/main/java/org/apache/olingo/client/api/domain/ClientEntitySetIterator.java b/lib/client-api/src/main/java/org/apache/olingo/client/api/domain/ClientEntitySetIterator.java
index 376404ba5..64247c2d6 100644
--- a/lib/client-api/src/main/java/org/apache/olingo/client/api/domain/ClientEntitySetIterator.java
+++ b/lib/client-api/src/main/java/org/apache/olingo/client/api/domain/ClientEntitySetIterator.java
@@ -44,9 +44,9 @@ import org.slf4j.LoggerFactory;
  * <b>Please don't forget to call the <tt>close()>/</tt> method when not needed any more.</b>
  *
  * @param <E> concrete ODataEntity implementation
- * @param <ES> concrete ODataEntitySet implementation
+ * @param <T> concrete ODataEntitySet implementation
  */
-public class ClientEntitySetIterator<ES extends ClientEntitySet, E extends ClientEntity>
+public class ClientEntitySetIterator<T extends ClientEntitySet, E extends ClientEntity>
         implements Iterator<E> {
 
   /**
@@ -62,7 +62,7 @@ public class ClientEntitySetIterator<ES extends ClientEntitySet, E extends Clien
 
   private final ContentType contentType;
 
-  private ES entitySet;
+  private T entitySet;
 
   private final ByteArrayOutputStream osEntitySet;
 
@@ -118,7 +118,7 @@ public class ClientEntitySetIterator<ES extends ClientEntitySet, E extends Clien
       if (cached == null) {
         available = false;
         try {
-          entitySet = (ES) odataClient.getReader().
+          entitySet = (T) odataClient.getReader().
                   readEntitySet(new ByteArrayInputStream(osEntitySet.toByteArray()), contentType);
         } catch (final ODataDeserializerException e) {
           available = false;
diff --git a/lib/client-api/src/main/java/org/apache/olingo/client/api/domain/ClientItem.java b/lib/client-api/src/main/java/org/apache/olingo/client/api/domain/ClientItem.java
index 32dcdce0a..a50053a6e 100644
--- a/lib/client-api/src/main/java/org/apache/olingo/client/api/domain/ClientItem.java
+++ b/lib/client-api/src/main/java/org/apache/olingo/client/api/domain/ClientItem.java
@@ -45,7 +45,7 @@ public abstract class ClientItem {
   /**
    * OData item self link.
    */
-  protected URI link;
+  private URI link;
 
   /**
    * Constructor.
diff --git a/lib/client-api/src/main/java/org/apache/olingo/client/api/domain/ClientLink.java b/lib/client-api/src/main/java/org/apache/olingo/client/api/domain/ClientLink.java
index d4d6d23e7..530716509 100644
--- a/lib/client-api/src/main/java/org/apache/olingo/client/api/domain/ClientLink.java
+++ b/lib/client-api/src/main/java/org/apache/olingo/client/api/domain/ClientLink.java
@@ -31,11 +31,11 @@ public class ClientLink extends ClientItem implements ClientAnnotatable {
 
   public static class Builder {
 
-    protected URI uri;
+    private URI uri;
 
-    protected ClientLinkType type;
+    private ClientLinkType type;
 
-    protected String title;
+    private String title;
 
     public Builder setURI(final URI uri) {
       this.uri = uri;
@@ -88,17 +88,17 @@ public class ClientLink extends ClientItem implements ClientAnnotatable {
   /**
    * Link type.
    */
-  protected final ClientLinkType type;
+  private final ClientLinkType type;
 
   /**
    * Link rel.
    */
-  protected final String rel;
+  private final String rel;
 
   /**
    * ETag for media edit links.
    */
-  protected String mediaETag;
+  private String mediaETag;
 
   private final List<ClientAnnotation> annotations = new ArrayList<ClientAnnotation>();
 
@@ -112,8 +112,8 @@ public class ClientLink extends ClientItem implements ClientAnnotatable {
   public ClientLink(final URI uri, final ClientLinkType type, final String title) {
     super(title);
 
-    link = uri;
     this.type = type;
+    setLink(uri);
 
     switch (this.type) {
     case ASSOCIATION:
diff --git a/lib/client-api/src/main/java/org/apache/olingo/client/api/domain/ClientValue.java b/lib/client-api/src/main/java/org/apache/olingo/client/api/domain/ClientValue.java
index de778c53a..85bce73ea 100644
--- a/lib/client-api/src/main/java/org/apache/olingo/client/api/domain/ClientValue.java
+++ b/lib/client-api/src/main/java/org/apache/olingo/client/api/domain/ClientValue.java
@@ -55,10 +55,10 @@ public interface ClientValue {
   /**
    * Casts to collection value.
    * 
-   * @param <OV> The actual ODataValue interface.
+   * @param <T> The actual ODataValue interface.
    * @return collection value.
    */
-  <OV extends ClientValue> ClientCollectionValue<OV> asCollection();
+  <T extends ClientValue> ClientCollectionValue<T> asCollection();
 
   /**
    * Casts to complex value.
diff --git a/lib/client-api/src/main/java/org/apache/olingo/client/api/uri/FilterArgFactory.java b/lib/client-api/src/main/java/org/apache/olingo/client/api/uri/FilterArgFactory.java
index f03a78c6d..9a768b6cc 100644
--- a/lib/client-api/src/main/java/org/apache/olingo/client/api/uri/FilterArgFactory.java
+++ b/lib/client-api/src/main/java/org/apache/olingo/client/api/uri/FilterArgFactory.java
@@ -21,7 +21,7 @@ package org.apache.olingo.client.api.uri;
 
 public interface FilterArgFactory {
 
-  FilterArg _null();
+  FilterArg nullValue();
 
   FilterArg add(FilterArg first, FilterArg second);
 
diff --git a/lib/client-core/src/main/java/org/apache/olingo/client/core/uri/FilterArgFactoryImpl.java b/lib/client-core/src/main/java/org/apache/olingo/client/core/uri/FilterArgFactoryImpl.java
index 02e9c63a9..d6996b2e0 100644
--- a/lib/client-core/src/main/java/org/apache/olingo/client/core/uri/FilterArgFactoryImpl.java
+++ b/lib/client-core/src/main/java/org/apache/olingo/client/core/uri/FilterArgFactoryImpl.java
@@ -25,7 +25,7 @@ import org.apache.olingo.client.api.uri.URIFilter;
 public class FilterArgFactoryImpl implements FilterArgFactory {
 
   @Override
-  public FilterArg _null() {
+  public FilterArg nullValue() {
     return new FilterConst("null");
   }
 
diff --git a/lib/commons-api/src/main/java/org/apache/olingo/commons/api/ODataPreferenceNames.java b/lib/commons-api/src/main/java/org/apache/olingo/commons/api/ODataPreferenceNames.java
index cdd489b04..28d152353 100644
--- a/lib/commons-api/src/main/java/org/apache/olingo/commons/api/ODataPreferenceNames.java
+++ b/lib/commons-api/src/main/java/org/apache/olingo/commons/api/ODataPreferenceNames.java
@@ -35,7 +35,7 @@ public enum ODataPreferenceNames {
 
   private final String preferenceName;
 
-  private ODataPreferenceNames(final String preferenceName) {
+  ODataPreferenceNames(final String preferenceName) {
     this.preferenceName = preferenceName;
   }
 
diff --git a/lib/server-api/src/main/java/org/apache/olingo/server/api/ODataLibraryException.java b/lib/server-api/src/main/java/org/apache/olingo/server/api/ODataLibraryException.java
index b6397021c..86125cd29 100644
--- a/lib/server-api/src/main/java/org/apache/olingo/server/api/ODataLibraryException.java
+++ b/lib/server-api/src/main/java/org/apache/olingo/server/api/ODataLibraryException.java
@@ -41,9 +41,9 @@ public abstract class ODataLibraryException extends ODataException {
   protected static final String DEFAULT_SERVER_BUNDLE_NAME = "server-core-exceptions-i18n";
 
   /** Key for the exception text in the resource bundle. */
-  public static interface MessageKey {
+  public interface MessageKey {
     /** Gets this key. */
-    public String getKey();
+    String getKey();
   }
 
   private MessageKey messageKey;
@@ -137,9 +137,9 @@ public abstract class ODataLibraryException extends ODataException {
   }
 
   /** Error message text and {@link Locale} used for it. */
-  public class ODataErrorMessage {
-    String message;
-    Locale locale;
+  public static class ODataErrorMessage {
+    private String message;
+    private Locale locale;
 
     public ODataErrorMessage(final String message, final Locale usedLocale) {
       this.message = message;
diff --git a/lib/server-api/src/main/java/org/apache/olingo/server/api/deserializer/batch/BatchOptions.java b/lib/server-api/src/main/java/org/apache/olingo/server/api/deserializer/batch/BatchOptions.java
index 0873e237c..98b0f10f1 100644
--- a/lib/server-api/src/main/java/org/apache/olingo/server/api/deserializer/batch/BatchOptions.java
+++ b/lib/server-api/src/main/java/org/apache/olingo/server/api/deserializer/batch/BatchOptions.java
@@ -24,7 +24,7 @@ package org.apache.olingo.server.api.deserializer.batch;
  * {@link org.apache.olingo.server.api.deserializer.FixedFormatDeserializer
  *  #parseBatchRequest(java.io.InputStream, String, BatchOptions)}
  */
-public class BatchOptions {
+public final class BatchOptions {
   private boolean isStrict = true;
   private String rawBaseUri = "";
   private String rawServiceResolutionUri = "";
diff --git a/lib/server-api/src/main/java/org/apache/olingo/server/api/prefer/PreferencesApplied.java b/lib/server-api/src/main/java/org/apache/olingo/server/api/prefer/PreferencesApplied.java
index 028d3b1a7..e97f8779e 100644
--- a/lib/server-api/src/main/java/org/apache/olingo/server/api/prefer/PreferencesApplied.java
+++ b/lib/server-api/src/main/java/org/apache/olingo/server/api/prefer/PreferencesApplied.java
@@ -19,9 +19,11 @@
 package org.apache.olingo.server.api.prefer;
 
 import java.util.Collections;
+import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.Locale;
 import java.util.Map;
+import java.util.Set;
 
 import org.apache.olingo.commons.api.ODataPreferenceNames;
 import org.apache.olingo.server.api.prefer.Preferences.Return;
@@ -31,8 +33,9 @@ import org.apache.olingo.server.api.prefer.Preferences.Return;
  * as described in <a href="https://www.ietf.org/rfc/rfc7240.txt">RFC 7240</a>.
  * There are named methods for preferences defined in the OData standard.
  */
-public class PreferencesApplied {
+public final class PreferencesApplied {
 
+  private static final Set<String> SAFE_PREFERENCE_NAMES = new HashSet<String>();
   private Map<String, String> applied;
 
   private PreferencesApplied() {
@@ -57,14 +60,7 @@ public class PreferencesApplied {
       final String key = entry.getKey();
       result.append(key);
       if (entry.getValue() != null) {
-        final boolean safe = ODataPreferenceNames.ALLOW_ENTITY_REFERENCES.toString().equals(key)
-            || ODataPreferenceNames.CALLBACK.toString().equals(key)
-            || ODataPreferenceNames.CONTINUE_ON_ERROR.toString().equals(key)
-            || ODataPreferenceNames.MAX_PAGE_SIZE.toString().equals(key)
-            || ODataPreferenceNames.TRACK_CHANGES.toString().equals(key)
-            || ODataPreferenceNames.RETURN.toString().equals(key)
-            || ODataPreferenceNames.RESPOND_ASYNC.toString().equals(key)
-            || ODataPreferenceNames.WAIT.toString().equals(key);
+        final boolean safe = isSafe(key);
         result.append('=')
             .append(safe ? "" : '"')
             .append(entry.getValue().replaceAll("\\\\|\"", "\\\\$0"))
@@ -74,6 +70,20 @@ public class PreferencesApplied {
     return result.toString();
   }
 
+  private boolean isSafe(String key) {
+    if(SAFE_PREFERENCE_NAMES.isEmpty()) {
+      SAFE_PREFERENCE_NAMES.add(ODataPreferenceNames.ALLOW_ENTITY_REFERENCES.toString());
+      SAFE_PREFERENCE_NAMES.add(ODataPreferenceNames.CALLBACK.toString());
+      SAFE_PREFERENCE_NAMES.add(ODataPreferenceNames.CONTINUE_ON_ERROR.toString());
+      SAFE_PREFERENCE_NAMES.add(ODataPreferenceNames.MAX_PAGE_SIZE.toString());
+      SAFE_PREFERENCE_NAMES.add(ODataPreferenceNames.TRACK_CHANGES.toString());
+      SAFE_PREFERENCE_NAMES.add(ODataPreferenceNames.RETURN.toString());
+      SAFE_PREFERENCE_NAMES.add(ODataPreferenceNames.RESPOND_ASYNC.toString());
+      SAFE_PREFERENCE_NAMES.add(ODataPreferenceNames.WAIT.toString());
+    }
+    return SAFE_PREFERENCE_NAMES.contains(key);
+  }
+
   @Override
   public String toString() {
     return toValueString();
diff --git a/lib/server-api/src/main/java/org/apache/olingo/server/api/processor/DefaultProcessor.java b/lib/server-api/src/main/java/org/apache/olingo/server/api/processor/DefaultProcessor.java
index c8481c56a..376315acc 100644
--- a/lib/server-api/src/main/java/org/apache/olingo/server/api/processor/DefaultProcessor.java
+++ b/lib/server-api/src/main/java/org/apache/olingo/server/api/processor/DefaultProcessor.java
@@ -19,6 +19,8 @@
 package org.apache.olingo.server.api.processor;
 
 import java.io.ByteArrayInputStream;
+import java.nio.charset.Charset;
+import java.util.Locale;
 
 import org.apache.olingo.commons.api.format.ContentType;
 import org.apache.olingo.commons.api.http.HttpHeader;
@@ -116,7 +118,7 @@ public class DefaultProcessor implements MetadataProcessor, ServiceDocumentProce
       // This should never happen but to be sure we have this catch here to prevent sending a stacktrace to a client.
       String responseContent =
           "{\"error\":{\"code\":null,\"message\":\"An unexpected exception occurred during error processing\"}}";
-      response.setContent(new ByteArrayInputStream(responseContent.getBytes()));
+      response.setContent(new ByteArrayInputStream(responseContent.getBytes(Charset.forName("utf-8"))));
       response.setStatusCode(HttpStatusCode.INTERNAL_SERVER_ERROR.getStatusCode());
       response.setHeader(HttpHeader.CONTENT_TYPE, ContentType.APPLICATION_JSON.toContentTypeString());
     }
diff --git a/lib/server-api/src/main/java/org/apache/olingo/server/api/processor/ErrorProcessor.java b/lib/server-api/src/main/java/org/apache/olingo/server/api/processor/ErrorProcessor.java
index 00058a697..c58d25dfe 100644
--- a/lib/server-api/src/main/java/org/apache/olingo/server/api/processor/ErrorProcessor.java
+++ b/lib/server-api/src/main/java/org/apache/olingo/server/api/processor/ErrorProcessor.java
@@ -36,6 +36,6 @@ public interface ErrorProcessor extends Processor {
    * @param serverError the server error
    * @param responseFormat requested content type after content negotiation
    */
-  public void processError(ODataRequest request, ODataResponse response, ODataServerError serverError,
+  void processError(ODataRequest request, ODataResponse response, ODataServerError serverError,
       ContentType responseFormat);
 }
diff --git a/lib/server-api/src/main/java/org/apache/olingo/server/api/serializer/PrimitiveSerializerOptions.java b/lib/server-api/src/main/java/org/apache/olingo/server/api/serializer/PrimitiveSerializerOptions.java
index aa88b66ac..3a507c649 100644
--- a/lib/server-api/src/main/java/org/apache/olingo/server/api/serializer/PrimitiveSerializerOptions.java
+++ b/lib/server-api/src/main/java/org/apache/olingo/server/api/serializer/PrimitiveSerializerOptions.java
@@ -22,7 +22,7 @@ import org.apache.olingo.commons.api.data.ContextURL;
 import org.apache.olingo.commons.api.edm.EdmProperty;
 
 /** Options for the OData serializer. */
-public class PrimitiveSerializerOptions {
+public final class PrimitiveSerializerOptions {
 
   private ContextURL contextURL;
   private Boolean isNullable;
diff --git a/lib/server-api/src/main/java/org/apache/olingo/server/api/serializer/ReferenceCollectionSerializerOptions.java b/lib/server-api/src/main/java/org/apache/olingo/server/api/serializer/ReferenceCollectionSerializerOptions.java
index b889595fa..2e979e694 100644
--- a/lib/server-api/src/main/java/org/apache/olingo/server/api/serializer/ReferenceCollectionSerializerOptions.java
+++ b/lib/server-api/src/main/java/org/apache/olingo/server/api/serializer/ReferenceCollectionSerializerOptions.java
@@ -22,7 +22,7 @@ import org.apache.olingo.commons.api.data.ContextURL;
 import org.apache.olingo.server.api.uri.queryoption.CountOption;
 
 /** Options for the OData serializer. */
-public class ReferenceCollectionSerializerOptions {
+public final class ReferenceCollectionSerializerOptions {
   private ContextURL contextURL;
   private CountOption count;
   
diff --git a/lib/server-api/src/main/java/org/apache/olingo/server/api/serializer/ReferenceSerializerOptions.java b/lib/server-api/src/main/java/org/apache/olingo/server/api/serializer/ReferenceSerializerOptions.java
index 0479ca4f3..189367a55 100644
--- a/lib/server-api/src/main/java/org/apache/olingo/server/api/serializer/ReferenceSerializerOptions.java
+++ b/lib/server-api/src/main/java/org/apache/olingo/server/api/serializer/ReferenceSerializerOptions.java
@@ -20,7 +20,7 @@ package org.apache.olingo.server.api.serializer;
 
 import org.apache.olingo.commons.api.data.ContextURL;
 
-public class ReferenceSerializerOptions {
+public final class ReferenceSerializerOptions {
   private ContextURL contextURL;
 
   /** Gets the {@link ContextURL}. */
diff --git a/lib/server-api/src/main/java/org/apache/olingo/server/api/uri/queryoption/SystemQueryOptionKind.java b/lib/server-api/src/main/java/org/apache/olingo/server/api/uri/queryoption/SystemQueryOptionKind.java
index 248790eea..77dfb842b 100644
--- a/lib/server-api/src/main/java/org/apache/olingo/server/api/uri/queryoption/SystemQueryOptionKind.java
+++ b/lib/server-api/src/main/java/org/apache/olingo/server/api/uri/queryoption/SystemQueryOptionKind.java
@@ -84,9 +84,9 @@ public enum SystemQueryOptionKind {
    */
   LEVELS("$level");
 
-  String syntax;
+  private String syntax;
 
-  private SystemQueryOptionKind(final String syntax) {
+  SystemQueryOptionKind(final String syntax) {
     this.syntax = syntax;
   }