fix: Add Content-Type header to push notification requests (#489)

Set `Content-Type: application/json` header when sending push
notifications
to prevent `415 Unsupported Media Type` errors. The request was
previously
defaulting to `application/octet-stream`.

Updates tests to verify that the `Content-Type` header is always present
in push notification requests, regardless of whether authentication
token is included.

Fixes: #486
Signed-off-by: Jeff Mesnil <[email protected]>

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- [X] Ensure the tests pass
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Fixes #486 🦕

Signed-off-by: Jeff Mesnil <[email protected]>

Author: jmesnil

extras/push-notification-config-store-database-jpa/src/test/java/io/a2a/extras/pushnotificationconfigstore/database/jpa/JpaPushNotificationConfigStoreTest.java

@@ -1,5 +1,7 @@
 package io.a2a.extras.pushnotificationconfigstore.database.jpa;
 
+import static io.a2a.client.http.A2AHttpClient.APPLICATION_JSON;
+import static io.a2a.client.http.A2AHttpClient.CONTENT_TYPE;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertInstanceOf;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
@@ -235,6 +237,7 @@ public void testSendNotificationSuccess() throws Exception {
         // Mock successful HTTP response
         when(mockHttpClient.createPost()).thenReturn(mockPostBuilder);
         when(mockPostBuilder.url(any(String.class))).thenReturn(mockPostBuilder);
+        when(mockPostBuilder.addHeader(CONTENT_TYPE, APPLICATION_JSON)).thenReturn(mockPostBuilder);
         when(mockPostBuilder.body(any(String.class))).thenReturn(mockPostBuilder);
         when(mockPostBuilder.post()).thenReturn(mockHttpResponse);
         when(mockHttpResponse.success()).thenReturn(true);
@@ -245,6 +248,7 @@ public void testSendNotificationSuccess() throws Exception {
         ArgumentCaptor<String> bodyCaptor = ArgumentCaptor.forClass(String.class);
         verify(mockHttpClient).createPost();
         verify(mockPostBuilder).url(config.url());
+        verify(mockPostBuilder).addHeader(CONTENT_TYPE, APPLICATION_JSON);
         verify(mockPostBuilder).body(bodyCaptor.capture());
         verify(mockPostBuilder).post();
 

http-client/src/main/java/io/a2a/client/http/A2AHttpClient.java

@@ -7,6 +7,9 @@
 
 public interface A2AHttpClient {
 
+    String CONTENT_TYPE= "Content-Type";
+    String APPLICATION_JSON= "application/json";
+
     GetBuilder createGet();
 
     PostBuilder createPost();

server-common/src/main/java/io/a2a/server/tasks/BasePushNotificationSender.java

@@ -1,5 +1,7 @@
 package io.a2a.server.tasks;
 
+import static io.a2a.client.http.A2AHttpClient.APPLICATION_JSON;
+import static io.a2a.client.http.A2AHttpClient.CONTENT_TYPE;
 import static io.a2a.common.A2AHeaders.X_A2A_NOTIFICATION_TOKEN;
 import jakarta.enterprise.context.ApplicationScoped;
 import jakarta.inject.Inject;
@@ -90,6 +92,7 @@ private boolean dispatchNotification(Task task, PushNotificationConfig pushInfo)
         try {
             postBuilder
                     .url(url)
+                    .addHeader(CONTENT_TYPE, APPLICATION_JSON)
                     .body(body)
                     .post();
         } catch (IOException | InterruptedException e) {

server-common/src/test/java/io/a2a/server/tasks/InMemoryPushNotificationConfigStoreTest.java

@@ -1,5 +1,7 @@
 package io.a2a.server.tasks;
 
+import static io.a2a.client.http.A2AHttpClient.APPLICATION_JSON;
+import static io.a2a.client.http.A2AHttpClient.CONTENT_TYPE;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertNull;
@@ -50,6 +52,7 @@ public void setUp() {
     private void setupBasicMockHttpResponse() throws Exception {
         when(mockHttpClient.createPost()).thenReturn(mockPostBuilder);
         when(mockPostBuilder.url(any(String.class))).thenReturn(mockPostBuilder);
+        when(mockPostBuilder.addHeader(CONTENT_TYPE, APPLICATION_JSON)).thenReturn(mockPostBuilder);
         when(mockPostBuilder.body(any(String.class))).thenReturn(mockPostBuilder);
         when(mockPostBuilder.post()).thenReturn(mockHttpResponse);
         when(mockHttpResponse.success()).thenReturn(true);
@@ -230,11 +233,7 @@ public void testSendNotificationSuccess() throws Exception {
         configStore.setInfo(taskId, config);
 
         // Mock successful HTTP response
-        when(mockHttpClient.createPost()).thenReturn(mockPostBuilder);
-        when(mockPostBuilder.url(any(String.class))).thenReturn(mockPostBuilder);
-        when(mockPostBuilder.body(any(String.class))).thenReturn(mockPostBuilder);
-        when(mockPostBuilder.post()).thenReturn(mockHttpResponse);
-        when(mockHttpResponse.success()).thenReturn(true);
+        setupBasicMockHttpResponse();
 
         notificationSender.sendNotification(task);
 

server-common/src/test/java/io/a2a/server/tasks/PushNotificationSenderTest.java

@@ -1,6 +1,9 @@
 package io.a2a.server.tasks;
 
+import static io.a2a.client.http.A2AHttpClient.APPLICATION_JSON;
+import static io.a2a.client.http.A2AHttpClient.CONTENT_TYPE;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.io.IOException;
@@ -158,7 +161,12 @@ private void testSendNotificationWithInvalidToken(String token, String testName)
         // Verify that no authentication header was sent (invalid token should not add header)
         assertEquals(1, testHttpClient.headers.size());
         Map<String, String> sentHeaders = testHttpClient.headers.get(0);
-        assertTrue(sentHeaders.isEmpty(), "No headers should be sent when token is invalid");
+        assertEquals(1, sentHeaders.size());
+        assertFalse(sentHeaders.containsKey(A2AHeaders.X_A2A_NOTIFICATION_TOKEN),
+                "X-A2A-Notification-Token header should not be sent when token is invalid");
+        // Content-Type header should always be present
+        assertTrue(sentHeaders.containsKey(CONTENT_TYPE));
+        assertEquals(APPLICATION_JSON, sentHeaders.get(CONTENT_TYPE));
     }
 
     private Task createSampleTask(String taskId, TaskState state) {
@@ -227,8 +235,13 @@ public void testSendNotificationWithTokenSuccess() throws InterruptedException {
         // Verify that the X-A2A-Notification-Token header is sent with the correct token
         assertEquals(1, testHttpClient.headers.size());
         Map<String, String> sentHeaders = testHttpClient.headers.get(0);
+        assertEquals(2, sentHeaders.size());
         assertTrue(sentHeaders.containsKey(A2AHeaders.X_A2A_NOTIFICATION_TOKEN));
         assertEquals(config.token(), sentHeaders.get(A2AHeaders.X_A2A_NOTIFICATION_TOKEN));
+        // Content-Type header should always be present
+        assertTrue(sentHeaders.containsKey(CONTENT_TYPE));
+        assertEquals(APPLICATION_JSON, sentHeaders.get(CONTENT_TYPE));
+
     }
 
     @Test
@@ -290,10 +303,10 @@ public void testSendNotificationHttpError() {
         String taskId = "task_send_http_err";
         Task taskData = createSampleTask(taskId, TaskState.COMPLETED);
         PushNotificationConfig config = createSamplePushConfig("http://notify.me/http_error", "cfg1", null);
-        
+
         // Set up the configuration in the store
         configStore.setInfo(taskId, config);
-        
+
         // Configure the test client to throw an exception
         testHttpClient.shouldThrowException = true;