Improvements from Review

Author: KarstenSchnitter

cf-java-logging-support-servlet/src/main/java/com/sap/hcp/cf/logging/servlet/filter/AddHttpHeadersToLogContextFilter.java

@@ -6,6 +6,7 @@
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
+import java.util.Objects;
 import java.util.stream.Stream;
 
 import javax.servlet.http.HttpServletRequest;
@@ -53,8 +54,8 @@ public AddHttpHeadersToLogContextFilter(HttpHeader... headers) {
     public AddHttpHeadersToLogContextFilter(List<? extends HttpHeader> list, HttpHeader... custom) {
         Stream<HttpHeader> allHeaders = Stream.concat(list.stream(), Arrays.stream(custom));
         this.headers = unmodifiableList(allHeaders.filter(HttpHeader::isPropagated).collect(toList()));
-        this.fields = unmodifiableList(headers.stream().map(HttpHeader::getField).filter(f -> f != null).collect(
-                                                                                                                 toList()));
+        this.fields = unmodifiableList(headers.stream().map(HttpHeader::getField).filter(Objects::nonNull).collect(
+                                                                                                                   toList()));
     }
 
     @Override

cf-java-logging-support-servlet/src/main/java/com/sap/hcp/cf/logging/servlet/filter/CompositeFilter.java

@@ -2,7 +2,6 @@
 
 import java.io.IOException;
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
@@ -18,31 +17,35 @@
  * <p>
  * The {@link CompositeFilter} allows to group several servlet {@link Filter}
  * into one. This is used to allow customizable filters and provide a backwards
- * compatible {@link RequestLoggingFilter}.
+ * compatible {@link RequestLoggingFilter}. The {@link FilterConfig} is
+ * forwarded to all filters, that are grouped. This may lead to
+ * incompatibilities between those shared configurations.
  * </p>
  * 
  * <p>
  * You can easily create a subclass of {@link CompositeFilter} and add all the
  * filters from com.sap.hcp.cf.logging.servlet.filter you wish. You can even
- * bring your own filters.
+ * bring your own filters. Make sure, there are no incompatible
+ * {@link FilterConfig} initializations.
  * </p>
  */
 public class CompositeFilter implements Filter {
 
-    private List<? extends Filter> filters;
+    private final List<Filter> filters;
 
     public CompositeFilter(Filter... filters) {
-        this.filters = Arrays.asList(filters);
-    }
-
-    public void setFilters(List<? extends Filter> filters) {
-        this.filters = new ArrayList<>(filters);
+        this.filters = new ArrayList<>(filters.length);
+        Collections.addAll(this.filters, filters);
     }
 
     public List<? extends Filter> getFilters() {
         return Collections.unmodifiableList(filters);
     }
 
+    /**
+     * Forwards the {@link FilterConfig} to all grouped filters. Be care to use
+     * only filters, that are compatible to each other.
+     */
     @Override
     public void init(FilterConfig config) throws ServletException {
         for (Filter filter: this.filters) {

cf-java-logging-support-servlet/src/main/java/com/sap/hcp/cf/logging/servlet/filter/GenerateRequestLogFilter.java

@@ -26,8 +26,8 @@
 
 public class GenerateRequestLogFilter extends AbstractLoggingFilter {
 
-    private static final String WRAP_RESPONSE_INIT_PARAM = "wrapResponse";
-    private static final String WRAP_REQUEST_INIT_PARAM = "wrapRequest";
+    public static final String WRAP_RESPONSE_INIT_PARAM = "wrapResponse";
+    public static final String WRAP_REQUEST_INIT_PARAM = "wrapRequest";
 
     private final RequestRecordFactory requestRecordFactory;
 

cf-java-logging-support-servlet/src/main/java/com/sap/hcp/cf/logging/servlet/filter/RequestLoggingFilter.java

@@ -44,6 +44,24 @@
  */
 public class RequestLoggingFilter extends CompositeFilter {
 
+    /**
+     * This is no longer used.
+     */
+    @Deprecated
+    public static final String LOG_PROVIDER = "[SERVLET]";
+
+    /**
+     * Please use {@link GenerateRequestLogFilter#WRAP_RESPONSE_INIT_PARAM}.
+     */
+    @Deprecated
+    public static final String WRAP_RESPONSE_INIT_PARAM = "wrapResponse";
+
+    /**
+     * Please use {@link GenerateRequestLogFilter#WRAP_REQUEST_INIT_PARAM}.
+     */
+    @Deprecated
+    public static final String WRAP_REQUEST_INIT_PARAM = "wrapRequest";
+
     public RequestLoggingFilter() {
         super(new AddVcapEnvironmentToLogContextFilter(), new AddHttpHeadersToLogContextFilter(),
               new CorrelationIdFilter(), new DynamicLogLevelFilter(), new GenerateRequestLogFilter());