better exception handling for runtime exceptions in the server handler

gradle.properties

@@ -1,6 +1,6 @@
 group = org.xbib
 name = netty-http
-version = 4.1.52.0
+version = 4.1.52.1
 
 gradle.wrapper.version = 6.4.1
 netty.version = 4.1.52.Final

netty-http-server-api/src/main/java/org/xbib/netty/http/server/api/Domain.java

@@ -19,4 +19,6 @@ public interface Domain<R extends EndpointResolver<?>> {
     Collection<? extends X509Certificate> getCertificateChain();
 
     void handle(ServerRequest.Builder serverRequestBuilder, ServerResponse.Builder serverResponseBuilder) throws IOException;
+
+    void handleAfterError(ServerRequest.Builder serverRequestBuilder, ServerResponse.Builder serverResponseBuilder, Throwable throwable);
 }

netty-http-server/src/main/java/org/xbib/netty/http/server/HttpServerDomain.java

@@ -21,6 +21,7 @@ import org.xbib.netty.http.server.endpoint.HttpEndpointResolver;
 import org.xbib.netty.http.server.api.Filter;
 import org.xbib.netty.http.server.security.CertificateUtils;
 import org.xbib.netty.http.server.security.PrivateKeyUtils;
+import org.xbib.netty.http.server.util.ExceptionFormatter;
 import javax.crypto.NoSuchPaddingException;
 import javax.net.ssl.TrustManagerFactory;
 import java.io.IOException;
@@ -40,12 +41,16 @@ import java.util.Collection;
 import java.util.List;
 import java.util.Objects;
 import java.util.ServiceLoader;
+import java.util.logging.Level;
+import java.util.logging.Logger;
 
 /**
  * The {@code HttpServerDomain} class represents a virtual server with a name.
  */
 public class HttpServerDomain implements Domain<HttpEndpointResolver> {
 
+    private static final Logger logger = Logger.getLogger(HttpServerDomain.class.getName());
+
     private final String name;
 
     private final HttpAddress httpAddress;
@@ -164,12 +169,20 @@ public class HttpServerDomain implements Domain<HttpEndpointResolver> {
         } else {
             if (serverResponseBuilder != null) {
                 serverResponseBuilder.setStatus(HttpResponseStatus.NOT_FOUND)
-                        .setContentType("text/plain")
+                        .setContentType("text/plain;charset=utf-8")
                         .build().write("no endpoint found to match request");
             }
         }
     }
 
+    @Override
+    public void handleAfterError(ServerRequest.Builder serverRequestBuilder, ServerResponse.Builder serverResponseBuilder, Throwable throwable) {
+        logger.log(Level.SEVERE, throwable.getMessage(), throwable);
+        serverResponseBuilder.setStatus(HttpResponseStatus.INTERNAL_SERVER_ERROR)
+                .setContentType("text/plain;charset=utf-8")
+                .build().write(ExceptionFormatter.format(throwable));
+    }
+
     @Override
     public String toString() {
         return name + " (" + httpAddress + ")";
@@ -335,7 +348,7 @@ public class HttpServerDomain implements Domain<HttpEndpointResolver> {
                     .addEndpoint(HttpEndpoint.builder()
                             .setPath(path)
                             .build())
-                    .setDispatcher(filter::handle)
+                    .setDispatcher(filter)
                     .build());
             return this;
         }
@@ -349,7 +362,7 @@ public class HttpServerDomain implements Domain<HttpEndpointResolver> {
                             .setPrefix(prefix)
                             .setPath(path)
                             .build())
-                    .setDispatcher(filter::handle)
+                    .setDispatcher(filter)
                     .build());
             return this;
         }
@@ -365,7 +378,7 @@ public class HttpServerDomain implements Domain<HttpEndpointResolver> {
                             .setPath(path)
                             .setMethods(Arrays.asList(methods))
                             .build())
-                    .setDispatcher(filter::handle)
+                    .setDispatcher(filter)
                     .build());
             return this;
         }

netty-http-server/src/main/java/org/xbib/netty/http/server/Server.java

@@ -207,9 +207,9 @@ public final class Server implements AutoCloseable {
     }
 
     public URL getBaseURL(HttpHeaders headers) {
-        String scheme = null;
+        String scheme;
-        String host = null;
+        String host;
-        String port = null;
+        String port;
         if (headers == null) {
             URL bindURL = serverConfig.getDefaultDomain().getHttpAddress().base();
             scheme = bindURL.getScheme();
@@ -258,7 +258,7 @@ public final class Server implements AutoCloseable {
     }
 
     public void handle(ServerRequest.Builder serverRequestBuilder,
-                       ServerResponse.Builder serverResponseBuilder) throws IOException {
+                       ServerResponse.Builder serverResponseBuilder) {
         URL baseURL = getBaseURL(serverRequestBuilder.getHeaders());
         serverRequestBuilder.setBaseURL(baseURL);
         Domain<? extends EndpointResolver<?>> domain = getDomain(baseURL);
@@ -266,8 +266,9 @@ public final class Server implements AutoCloseable {
             executor.submit(() -> {
                 try {
                     domain.handle(serverRequestBuilder, serverResponseBuilder);
-                } catch (IOException e) {
+                } catch (Throwable t) {
-                    executor.afterExecute(null, e);
+                    executor.afterExecute(null, t);
+                    domain.handleAfterError(serverRequestBuilder, serverResponseBuilder, t);
                 } finally {
                     serverRequestBuilder.release();
                 }
@@ -275,6 +276,8 @@ public final class Server implements AutoCloseable {
         } else {
             try {
                 domain.handle(serverRequestBuilder, serverResponseBuilder);
+            } catch (Throwable t) {
+                domain.handleAfterError(serverRequestBuilder, serverResponseBuilder, t);
             } finally {
                 serverRequestBuilder.release();
             }

netty-http-server/src/main/java/org/xbib/netty/http/server/util/ExceptionFormatter.java

@@ -0,0 +1,56 @@
+package org.xbib.netty.http.server.util;
+
+import java.io.PrintWriter;
+import java.io.StringWriter;
+
+/**
+ * Format exception messages and stack traces.
+ */
+public final class ExceptionFormatter {
+
+    private ExceptionFormatter() {
+    }
+
+    /**
+     * Format exception with stack trace.
+     *
+     * @param t the thrown object
+     * @return the formatted exception
+     */
+    public static String format(Throwable t) {
+        StringBuilder sb = new StringBuilder();
+        append(sb, t, 0, true);
+        return sb.toString();
+    }
+
+    /**
+     * Append Exception to string builder.
+     */
+    private static void append(StringBuilder sb, Throwable t, int level, boolean details) {
+        if (((t != null) && (t.getMessage() != null)) && (!t.getMessage().isEmpty())) {
+            if (details && (level > 0)) {
+                sb.append("\n\nCaused by\n");
+            }
+            sb.append(t.getMessage());
+        }
+        if (details) {
+            if (t != null) {
+                if ((t.getMessage() != null) && (t.getMessage().isEmpty())) {
+                    sb.append("\n\nCaused by ");
+                } else {
+                    sb.append("\n\n");
+                }
+            }
+            StringWriter sw = new StringWriter();
+            if (t != null) {
+                t.printStackTrace(new PrintWriter(sw));
+            }
+            sb.append(sw.toString());
+        }
+        if (t != null) {
+            if (t.getCause() != null) {
+                append(sb, t.getCause(), level + 1, details);
+            }
+        }
+    }
+}