[GitHub] [jena] kinow commented on a diff in pull request #1729: Allow for overriding the default dispatch choice

["kinow (via GitHub)" <gi...@apache.org>]

kinow commented on code in PR #1729:
URL: https://github.com/apache/jena/pull/1729#discussion_r1085904835


##########
jena-fuseki2/jena-fuseki-core/src/main/java/org/apache/jena/fuseki/server/Dispatcher.java:
##########
@@ -274,18 +316,23 @@ private static Endpoint chooseEndpoint(HttpAction action, DataService dataServic
         if ( ep != null )
             // Single dispatch, may not be valid.
             return ep;
+
         // No single direct dispatch. Multiple choices (different operation, same endpoint name)
-        // Work out which operation we are looking for.
-        Operation operation = chooseOperation(action);
-        ep = epSet.get(operation);
-        if ( ep == null ) {
-            if ( GSP_R.equals(operation) )
-                // If asking for GSP_R, and GSP_RW available, pass that back.
-                ep = epSet.get(GSP_RW);
-            else if ( GSP_RW.equals(operation) ) {
-                // If asking for GSP_RW, but only GSP_R available -> 405.
-                if ( epSet.contains(GSP_R) )
-                    ServletOps.errorMethodNotAllowed(action.getMethod());
+        // Work out which operation we are looking for based on SPARQL characteristics.
+        Operation operation = chooseOperation(action, epSet);
+
+     // Special case for GSP_R/GSP_RW

Review Comment:
   indentation



##########
jena-fuseki2/jena-fuseki-core/src/main/java/org/apache/jena/fuseki/server/DispatchFunction.java:
##########
@@ -0,0 +1,30 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.jena.fuseki.server;
+
+import org.apache.jena.fuseki.servlets.HttpAction;
+
+/**
+ * Select a operation based on the request ({@link HttpAction}) and the choices at

Review Comment:
   s/a operation/an operation? And missing newline at the end of the file?



##########
jena-fuseki2/jena-fuseki-core/src/main/java/org/apache/jena/fuseki/server/Dispatcher.java:
##########
@@ -395,27 +455,13 @@ private static void applyAuthentication(String user, DataService dataService, En
      * Assumes, and does not check, that the action is a GSP action.
      */
     private static Operation gspOperation(HttpAction action, HttpServletRequest request) {
-        // Check enabled.
-        if ( isReadMethod(request) )
-            return GSP_R;
-        else
-            return GSP_RW;
+        return isReadMethod(request) ? GSP_R : GSP_RW;
     }
 
     /**
-     * Determine the {@link Operation} for a Quads operation. (GSP, except on the
-     * whole dataset).
-     * <p>
-     * Assumes, and does not check, that the action is a Quads action.
+     * Return whether request method is a "read" (GET or HEAD) or "write", modifying
+     * (POST, PUT, DELETE, PATCH)

Review Comment:
   Out of curiosity, are the other methods (connect/trace/options) filtered by the web server, or further up/down the request chain?



##########
jena-fuseki2/jena-fuseki-core/src/main/java/org/apache/jena/fuseki/server/Dispatcher.java:
##########
@@ -370,8 +419,19 @@ private static Operation chooseOperation(HttpAction action) {
         }
 
         // ---- No registered content type, no query parameters.
-        // Plain HTTP operation on the dataset handled as quads or rejected.
-        return quadsOperation(action, request);
+        // Plain HTTP operation on the dataset.
+        DispatchFunction selectOperation = action.getDataService().getDefaultOperationChooser();
+        if ( selectOperation == null )
+            // Defaul is a quads operation.

Review Comment:
   s/Defaul/Default



##########
jena-fuseki2/jena-fuseki-main/src/main/java/org/apache/jena/fuseki/main/sys/FusekiModules.java:
##########
@@ -38,35 +40,45 @@ public static void load() {
     }
 
     public static void reload() {
-        registry = ConcurrentHashMap.newKeySet();
+        registry = new ArrayList<>();
         subsystem = new Subsystem<FusekiModule>(FusekiModule.class);
         subsystem.initialize();
-        subsystem.forEach(registry::add);
+        synchronized(lock) {
+            subsystem.forEach(registry::add);
+        }
     }
 
     /** Add a code module */
     public static void add(FusekiModule module) {
-        load();
-        module.start();
-        registry.add(module);
+        synchronized(lock) {
+            load();
+            module.start();
+            registry.add(module);
+        }
     }
 
     /** Remove a code module */
     public static void remove(FusekiModule module) {
-        registry.remove(module);
-        module.stop();
+        synchronized(lock) {
+            registry.remove(module);
+            module.stop();
+        }
     }
 
     /** Test whether a code module is registered. */
     public static boolean contains(FusekiModule module) {
-        return registry.contains(module);
+        synchronized(lock) {
+            return registry.contains(module);
+        }
     }
 
     /*package*/ static void forEachModule(Consumer<FusekiModule> action) {
-        if ( registry == null )
-            load();
-        if ( registry == null || registry.isEmpty() )
-            return ;
-        registry.forEach(action);
+        synchronized(lock) {
+            if ( registry == null )
+                load();
+            if ( registry == null || registry.isEmpty() )

Review Comment:
   I think the `load()` call above means the `registry` cannot be null (it'll be at least an empty arraylist?)



##########
jena-fuseki2/jena-fuseki-core/src/main/java/org/apache/jena/fuseki/server/Dispatcher.java:
##########
@@ -42,13 +42,55 @@
 /**
  * Dispatch on registered datasets. This is the entry point into Fuseki for dataset
  * operations.
- *
- * Administration operations, and directly registered servlets and static content are
- * called through the usual web server process.
- *
- * HTTP Request URLs, after servlet context removed, take the form {@code /dataset} or {@code /dataset/service}.
- * The most general URL is {@code /context/dataset/service}.
- * The {@link DataAccessPointRegistry} maps {@code /dataset} to a {@link DataAccessPoint}.
+ * <p>
+ * Administration operations, and directly registered servlets and static content,
+ * are called through the usual web server process.
+ * <p>
+ * HTTP Request URLs, after servlet context removed, take the form {@code /dataset}
+ * or {@code /dataset/service}. The most general URL is
+ * {@code /context/dataset/service}. The {@link DataAccessPointRegistry} maps
+ * {@code /dataset} to a {@link DataAccessPoint} which is a name and a
+ * {@linkplain DataService}.
+ * <p>
+ * The dispatch process is:
+ * </p>
+ * <p>
+ * 1. {@linkplain Dispatcher#dispatch} calls
+ * {@linkplain Dispatcher#locateDataAccessPoint} to get the
+ * {@linkplain DataAccessPoint} and calls {@linkplain Dispatcher#process}.
+ * </p>
+ * <p>
+ * 2. {@linkplain Dispatcher#process} create the {@linkplain HttpAction} then calls
+ * {@linkplain Dispatcher#dispatchAction} which calls through to
+ * {@linkplain Dispatcher#chooseProcessor}.
+ * </p>
+ * <p>
+ * 3. {@linkplain Dispatcher#chooseProcessor} does some checking and calls
+ * {@linkplain Dispatcher#chooseEndpoint}.
+ * </p>
+ * <p>
+ * 4. {@linkplain Dispatcher#chooseEndpoint} looks at request, and determines the
+ * {@linkplain EndpointSet}.
+ * </p>
+ * <p>
+ * 5. If there isn't an {@linkplain EndpointSet}, the dispatch process returns.
+ * </p>
+ * <p>
+ * 6. If there is exactly one entry, this is the outcome.
+ * </p>
+ * <p>
+ * 7. If there are multiple choices , {@linkplain Dispatcher#chooseOperation} looks
+ * at request and decides which {@linkplain Operation} is being requested based on
+ * SPARQL operations signatures and Content-Type.
+ * </p>
+ * <p>
+ * 8.There is a default for dispatches with multiple choices that can't be separated
+ * by SPARQL signature. These have no regsitered Content-type and no query string.
+ * </p>
+ * <p>
+ * A choice by dispatch does not necessarily mean an operation is valid and will be
+ * executed. It may fail authentication or not have an registered handler.

Review Comment:
   s/an registered/a registered



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