Add a ParamConverterProvider for java.util.Optional parameters

Signed-off-by: Jorge Bescos Gascon <jorge.bescos.gascon@oracle.com>

Author: jbescos

core-common/src/main/java/org/glassfish/jersey/internal/inject/ParamConverters.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012, 2019 Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, 2021 Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2018 Payara Foundation and/or its affiliates.
  *
  * This program and the accompanying materials are made available under the
@@ -21,21 +21,23 @@
 import java.lang.reflect.Constructor;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
+import java.lang.reflect.ParameterizedType;
 import java.lang.reflect.Type;
 import java.security.AccessController;
 import java.text.ParseException;
 import java.util.Date;
+import java.util.Optional;
 
+import javax.inject.Inject;
+import javax.inject.Singleton;
 import javax.ws.rs.ProcessingException;
 import javax.ws.rs.WebApplicationException;
 import javax.ws.rs.ext.ParamConverter;
 import javax.ws.rs.ext.ParamConverterProvider;
 
-import javax.inject.Singleton;
-
+import org.glassfish.jersey.internal.LocalizationMessages;
 import org.glassfish.jersey.internal.util.ReflectionHelper;
 import org.glassfish.jersey.message.internal.HttpDateFormat;
-import org.glassfish.jersey.internal.LocalizationMessages;
 
 /**
  * Container of several different {@link ParamConverterProvider param converter providers}
@@ -247,6 +249,59 @@ public String toString(final T value) throws IllegalArgumentException {
         }
     }
 
+    /**
+     * Provider of {@link ParamConverter param converter} that produce the Optional instance
+     * by invoking {@link AggregatedProvider}.
+     */
+    @Singleton
+    public static class OptionalProvider implements ParamConverterProvider {
+
+        // Delegates to this provider when the type of Optional is extracted.
+        private final AggregatedProvider aggregated;
+
+        @Inject
+        public OptionalProvider(AggregatedProvider aggregated) {
+            this.aggregated = aggregated;
+        }
+
+        @Override
+        public <T> ParamConverter<T> getConverter(Class<T> rawType, Type genericType, Annotation[] annotations) {
+            return (rawType != Optional.class) ? null : new ParamConverter<T>() {
+
+                @Override
+                public T fromString(String value) {
+                    if (value == null) {
+                        return (T) Optional.empty();
+                    } else {
+                        ParameterizedType parametrized = (ParameterizedType) genericType;
+                        Type type = parametrized.getActualTypeArguments()[0];
+                        T val = aggregated.getConverter((Class<T>) type, type, annotations).fromString(value.toString());
+                        if (val != null) {
+                            return (T) Optional.of(val);
+                        } else {
+                            /*
+                             *  In this case we don't send Optional.empty() because 'value' is not null.
+                             *  But we return null because the provider didn't find how to parse it.
+                             */
+                            return null;
+                        }
+                    }
+                }
+
+                @Override
+                public String toString(T value) throws IllegalArgumentException {
+                    /*
+                     *  Unfortunately 'orElse' cannot be stored in an Optional. As only one value can
+                     *  be stored, it makes no sense that 'value' is Optional. It can just be the value.
+                     *  We don't fail here but we don't process it.
+                     */
+                    return null;
+                }
+            };
+        }
+
+    }
+
     /**
      * Aggregated {@link ParamConverterProvider param converter provider}.
      */
@@ -267,7 +322,8 @@ public AggregatedProvider() {
                     new TypeValueOf(),
                     new CharacterProvider(),
                     new TypeFromString(),
-                    new StringConstructor()
+                    new StringConstructor(),
+                    new OptionalProvider(this)
             };
         }
 

tests/e2e-server/src/test/java/org/glassfish/jersey/tests/e2e/server/OptionalParamConverterTest.java

@@ -0,0 +1,99 @@
+/*
+ * Copyright (c) 2021 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0, which is available at
+ * http://www.eclipse.org/legal/epl-2.0.
+ *
+ * This Source Code may also be made available under the following Secondary
+ * Licenses when the conditions for such availability set forth in the
+ * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
+ * version 2 with the GNU Classpath Exception, which is available at
+ * https://www.gnu.org/software/classpath/license.html.
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
+ */
+
+package org.glassfish.jersey.tests.e2e.server;
+
+import java.util.List;
+import java.util.Optional;
+
+import javax.ws.rs.GET;
+import javax.ws.rs.Path;
+import javax.ws.rs.QueryParam;
+import javax.ws.rs.core.Application;
+import javax.ws.rs.core.Response;
+
+import org.glassfish.jersey.server.ResourceConfig;
+import org.glassfish.jersey.test.JerseyTest;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class OptionalParamConverterTest extends JerseyTest {
+
+    private static final String PARAM_NAME = "paramName";
+
+    @Path("/OptionalResource")
+    public static class OptionalResource {
+
+        @GET
+        @Path("/fromString")
+        public Response fromString(@QueryParam(PARAM_NAME) Optional<String> data) {
+            return Response.ok(data.orElse("")).build();
+        }
+
+        @GET
+        @Path("/fromInteger")
+        public Response fromInteger(@QueryParam(PARAM_NAME) Optional<Integer> data) {
+            return Response.ok(data.orElse(0)).build();
+        }
+
+        @GET
+        @Path("/fromList")
+        public Response fromList(@QueryParam(PARAM_NAME) List<Optional<Integer>> data) {
+            StringBuilder builder = new StringBuilder("");
+            for (Optional<Integer> val : data) {
+                builder.append(val.orElse(0));
+            }
+            return Response.ok(builder.toString()).build();
+        }
+    }
+
+    @Override
+    protected Application configure() {
+        return new ResourceConfig(OptionalResource.class);
+    }
+
+    @Test
+    public void fromOptionalStr() {
+        Response empty = target("/OptionalResource/fromString").request().get();
+        Response notEmpty = target("/OptionalResource/fromString").queryParam(PARAM_NAME, "anyValue").request().get();
+        assertEquals(200, empty.getStatus());
+        assertEquals("", empty.readEntity(String.class));
+        assertEquals(200, notEmpty.getStatus());
+        assertEquals("anyValue", notEmpty.readEntity(String.class));
+    }
+
+    @Test
+    public void fromOptionalInt() {
+        Response empty = target("/OptionalResource/fromInteger").request().get();
+        Response notEmpty = target("/OptionalResource/fromInteger").queryParam(PARAM_NAME, 1).request().get();
+        assertEquals(200, empty.getStatus());
+        assertEquals(Integer.valueOf(0), empty.readEntity(Integer.class));
+        assertEquals(200, notEmpty.getStatus());
+        assertEquals(Integer.valueOf(1), notEmpty.readEntity(Integer.class));
+    }
+
+    @Test
+    public void fromOptionalList() {
+        Response empty = target("/OptionalResource/fromList").request().get();
+        Response notEmpty = target("/OptionalResource/fromList").queryParam(PARAM_NAME, 1)
+                .queryParam(PARAM_NAME, 2).request().get();
+        assertEquals(200, empty.getStatus());
+        assertEquals("", empty.readEntity(String.class));
+        assertEquals(200, notEmpty.getStatus());
+        assertEquals("12", notEmpty.readEntity(String.class));
+    }
+}