[RESTEASY-3390] Use the request entity parts if a multipart/form-data…

… request is sent and the injection parameter type is a string.

https://issues.redhat.com/browse/RESTEASY-3390
Signed-off-by: James R. Perkins <jperkins@redhat.com>

providers/multipart/src/test/java/org/jboss/resteasy/plugins/providers/multipart/MultipartEntityPartProviderTest.java

@@ -165,6 +165,61 @@ public void multiInjection() throws Exception {
         }
     }
 
+    /**
+     * Tests sending {@code multipart/form-data} content as a {@link EntityPart List<EntityPart>}. Three parts are sent
+     * and injected as {@link FormParam @FormParam} method parameters. Each part send is different and injected as a
+     * specific type.
+     * <p>
+     * The result from the REST endpoint is {@code multipart/form-data} content with a new name and the content for the
+     * injected field.
+     * </p>
+     *
+     * @throws Exception if an error occurs in the test
+     */
+    @Test
+    public void multiAllFilesInjection() throws Exception {
+        try (Client client = ClientBuilder.newClient()) {
+            final List<EntityPart> multipart = List.of(
+                    EntityPart.withName("entity-part")
+                            .fileName("file1.txt")
+                            .content("test entity part file1.txt")
+                            .mediaType(MediaType.TEXT_PLAIN_TYPE)
+                            .build(),
+                    EntityPart.withName("string-part")
+                            .fileName("file2.txt")
+                            .content("test string file2.txt")
+                            .mediaType(MediaType.TEXT_PLAIN_TYPE)
+                            .build(),
+                    EntityPart.withName("input-stream-part")
+                            .fileName("file3.txt")
+                            .content("test input stream file3.txt".getBytes(StandardCharsets.UTF_8))
+                            .mediaType(MediaType.APPLICATION_OCTET_STREAM_TYPE)
+                            .build());
+            try (
+                    Response response = client.target(INSTANCE.configuration()
+                            .baseUriBuilder()
+                            .path("test/multi-injected"))
+                            .request(MediaType.MULTIPART_FORM_DATA_TYPE)
+                            .post(Entity.entity(new GenericEntity<>(multipart) {
+                            }, MediaType.MULTIPART_FORM_DATA))) {
+                Assert.assertEquals(Response.Status.OK, response.getStatusInfo());
+                final List<EntityPart> entityParts = response.readEntity(new GenericType<>() {
+                });
+                if (entityParts.size() != 3) {
+                    final String msg = "Expected 3 entries got " +
+                            entityParts.size() +
+                            '.' +
+                            System.lineSeparator() +
+                            getMessage(entityParts);
+                    Assert.fail(msg);
+                }
+                checkEntity(entityParts, "received-entity-part", "test entity part file1.txt");
+                checkEntity(entityParts, "received-string", "test string file2.txt");
+                checkEntity(entityParts, "received-input-stream", "test input stream file3.txt");
+            }
+        }
+    }
+
     /**
      * Tests sending {@code multipart/form-data} content as a {@link EntityPart List<EntityPart>}. One part is sent
      * and injected as {@link FormParam @FormParam} method parameters. The same part should be injected in different

resteasy-core/src/main/java/org/jboss/resteasy/core/FormParamInjector.java

@@ -1,6 +1,8 @@
 package org.jboss.resteasy.core;
 
+import java.io.IOException;
 import java.io.InputStream;
+import java.io.UncheckedIOException;
 import java.lang.annotation.Annotation;
 import java.lang.reflect.AccessibleObject;
 import java.lang.reflect.Type;
@@ -11,6 +13,7 @@
 
 import jakarta.ws.rs.FormParam;
 import jakarta.ws.rs.core.EntityPart;
+import jakarta.ws.rs.core.MediaType;
 
 import org.jboss.resteasy.resteasy_jaxrs.i18n.Messages;
 import org.jboss.resteasy.spi.HttpRequest;
@@ -45,6 +48,17 @@ public Object inject(HttpRequest request, HttpResponse response, boolean unwrapA
         } else if (InputStream.class.isAssignableFrom(type)) {
             final Optional<EntityPart> part = request.getFormEntityPart(paramName);
             return part.map(EntityPart::getContent).orElse(null);
+        } else if (String.class.isAssignableFrom(type) &&
+        // request.getHttpHeaders().getMediaType() may return null, but the isCompatible handles this check
+                MediaType.MULTIPART_FORM_DATA_TYPE.isCompatible(request.getHttpHeaders().getMediaType())) {
+            final Optional<EntityPart> part = request.getFormEntityPart(paramName);
+            return part.map(p -> {
+                try {
+                    return p.getContent(String.class);
+                } catch (IOException e) {
+                    throw new UncheckedIOException(Messages.MESSAGES.unableToExtractParameter(paramName, null), e);
+                }
+            }).orElse(null);
         }
         List<String> list = request.getDecodedFormParameters().get(paramName);
         if (list != null && encode) {