Improve AbstractLogginFilter and CompositeFilter

rename callbacks and improve javadoc
specify return type

Author: KarstenSchnitter

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

@@ -27,8 +27,8 @@ public void doFilter(ServletRequest request, ServletResponse response, FilterCha
      * Provides a default implementation for handling servlet requests already
      * cast to {@link HttpServletRequest} and {@link HttpServletResponse}.
      * Custom implementations of {@link AbstractLoggingFilter} should overwrite
-     * {@link #preProcess(HttpServletRequest, HttpServletResponse)} and/or
-     * {@link #postProcess(HttpServletRequest, HttpServletResponse)}.
+     * {@link #beforeFilter(HttpServletRequest, HttpServletResponse)} and/or
+     * {@link #cleanup(HttpServletRequest, HttpServletResponse)}.
      * 
      * @param request
      *            cast as {@link HttpServletRequest}
@@ -43,34 +43,36 @@ protected void doFilterRequest(HttpServletRequest request, HttpServletResponse r
                                                                                                                 throws IOException,
                                                                                                                 ServletException {
         try {
-            preProcess(request, response);
+            beforeFilter(request, response);
             chain.doFilter(request, response);
         } finally {
-            postProcess(request, response);
+            cleanup(request, response);
 
         }
     }
 
     /**
-     * Pre-process the request/response before it is passed along the filter
-     * chain.
+     * Processes the request/response before it is passed along the filter
+     * chain. Even if {@link #beforeFilter} fails, {@link #cleanup} will be
+     * executed.
      * 
      * @param request
      * @param response
-     * @throws IOException
      */
-    protected void preProcess(HttpServletRequest request, HttpServletResponse response) {
+    protected void beforeFilter(HttpServletRequest request, HttpServletResponse response) {
     }
 
     /**
-     * Post-process the request/response after it was handled by the filter
-     * chain. This is executed even in cases of failures during handling. Use
-     * this method to reset or clean-up state, e.g. MDC.
+     * Cleanup after the request/response was handled by the filter chain. This
+     * is executed even in cases of failures during handling or
+     * {@link #beforeFilter}. Use this method to reset or clean-up state, e.g.
+     * MDC. Be aware, that there may be partially initalized state from
+     * {@link #beforeFilter}.
      * 
      * @param request
      * @param response
      */
-    protected void postProcess(HttpServletRequest request, HttpServletResponse response) {
+    protected void cleanup(HttpServletRequest request, HttpServletResponse response) {
     }
 
     /**

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

@@ -59,7 +59,7 @@ public AddHttpHeadersToLogContextFilter(List<? extends HttpHeader> list, HttpHea
     }
 
     @Override
-    protected void preProcess(HttpServletRequest request, HttpServletResponse response) {
+    protected void beforeFilter(HttpServletRequest request, HttpServletResponse response) {
         for (HttpHeader header: headers) {
             String headerValue = HttpHeaderUtilities.getHeaderValue(request, header);
             if (header.getField() != null && headerValue != null) {
@@ -69,7 +69,7 @@ protected void preProcess(HttpServletRequest request, HttpServletResponse respon
     }
 
     @Override
-    protected void postProcess(HttpServletRequest request, HttpServletResponse response) {
+    protected void cleanup(HttpServletRequest request, HttpServletResponse response) {
         fields.forEach(LogContext::remove);
     }
 }

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

@@ -23,12 +23,12 @@
 public class AddVcapEnvironmentToLogContextFilter extends AbstractLoggingFilter {
 
     @Override
-    protected void preProcess(HttpServletRequest request, HttpServletResponse response) {
+    protected void beforeFilter(HttpServletRequest request, HttpServletResponse response) {
         LogContext.loadContextFields();
     }
 
     @Override
-    protected void postProcess(HttpServletRequest request, HttpServletResponse response) {
+    protected void cleanup(HttpServletRequest request, HttpServletResponse response) {
         LogContext.resetContextFields();
     }
 }

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

@@ -38,7 +38,7 @@ public CompositeFilter(Filter... filters) {
         Collections.addAll(this.filters, filters);
     }
 
-    public List<? extends Filter> getFilters() {
+    public List<Filter> getFilters() {
         return Collections.unmodifiableList(filters);
     }
 

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

@@ -35,7 +35,7 @@ public CorrelationIdFilter(HttpHeader correlationHeader) {
     }
 
     @Override
-    protected void preProcess(HttpServletRequest request, HttpServletResponse response) {
+    protected void beforeFilter(HttpServletRequest request, HttpServletResponse response) {
         String correlationId = determineCorrelationId(request);
         LogContext.add(correlationHeader.getField(), correlationId);
         addCorrelationIdHeader(response, correlationId);
@@ -60,7 +60,7 @@ private void addCorrelationIdHeader(HttpServletResponse response, String correla
     }
 
     @Override
-    protected void postProcess(HttpServletRequest request, HttpServletResponse response) {
+    protected void cleanup(HttpServletRequest request, HttpServletResponse response) {
         LogContext.remove(correlationHeader.getField());
     }
 

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

@@ -117,7 +117,7 @@ protected Optional<DynamicLogLevelProcessor> getProcessor() {
     }
 
     @Override
-    protected void preProcess(HttpServletRequest request, HttpServletResponse response) {
+    protected void beforeFilter(HttpServletRequest request, HttpServletResponse response) {
         getProcessor().ifPresent(processor -> extractHeader(request).ifPresent(processor::copyDynamicLogLevelToMDC));
     }
 
@@ -126,7 +126,7 @@ private Optional<String> extractHeader(HttpServletRequest request) {
     }
 
     @Override
-    protected void postProcess(HttpServletRequest request, HttpServletResponse response) {
+    protected void cleanup(HttpServletRequest request, HttpServletResponse response) {
         getProcessor().ifPresent(DynamicLogLevelProcessor::removeDynamicLogLevelFromMDC);
     }
 

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

@@ -25,7 +25,7 @@
 public class LogContextToRequestAttributeFilter extends AbstractLoggingFilter {
 
     @Override
-    protected void preProcess(HttpServletRequest request, HttpServletResponse response) {
+    protected void beforeFilter(HttpServletRequest request, HttpServletResponse response) {
         request.setAttribute(MDC.class.getName(), MDC.getCopyOfContextMap());
     }