Merge pull request #1063 from yanmxa/br_mqtt_stru

Fix the `content-type` issue for the MQTT protocol

Author: embano1

protocol/mqtt_paho/v2/message.go

@@ -17,8 +17,7 @@ import (
 )
 
 const (
-	prefix      = "ce-"
-	contentType = "Content-Type"
+	prefix = "ce-"
 )
 
 var specs = spec.WithPrefix(prefix)
@@ -41,8 +40,7 @@ func NewMessage(msg *paho.Publish) *Message {
 	var f format.Format
 	var v spec.Version
 	if msg.Properties != nil {
-		// Use properties.User["Content-type"] to determine if message is structured
-		if s := msg.Properties.User.Get(contentType); format.IsFormat(s) {
+		if s := msg.Properties.ContentType; format.IsFormat(s) {
 			f = format.Lookup(s)
 		} else if s := msg.Properties.User.Get(specs.PrefixedSpecVersionName()); s != "" {
 			v = specs.Version(s)
@@ -88,14 +86,20 @@ func (m *Message) ReadBinary(ctx context.Context, encoder binding.BinaryWriter)
 			} else {
 				err = encoder.SetExtension(strings.TrimPrefix(userProperty.Key, prefix), userProperty.Value)
 			}
-		} else if userProperty.Key == contentType {
-			err = encoder.SetAttribute(m.version.AttributeFromKind(spec.DataContentType), string(userProperty.Value))
 		}
 		if err != nil {
 			return
 		}
 	}
 
+	contentType := m.internal.Properties.ContentType
+	if contentType != "" {
+		err = encoder.SetAttribute(m.version.AttributeFromKind(spec.DataContentType), contentType)
+		if err != nil {
+			return err
+		}
+	}
+
 	if m.internal.Payload != nil {
 		return encoder.SetData(bytes.NewBuffer(m.internal.Payload))
 	}

protocol/mqtt_paho/v2/message_test.go

@@ -32,7 +32,7 @@ func TestReadStructured(t *testing.T) {
 			msg: &paho.Publish{
 				Payload: []byte(""),
 				Properties: &paho.PublishProperties{
-					User: []paho.UserProperty{{Key: contentType, Value: event.ApplicationCloudEventsJSON}},
+					ContentType: event.ApplicationCloudEventsJSON,
 				},
 			},
 		},

protocol/mqtt_paho/v2/write_message.go

@@ -42,11 +42,9 @@ var (
 
 func (b *pubMessageWriter) SetStructuredEvent(ctx context.Context, f format.Format, event io.Reader) error {
 	if b.Properties == nil {
-		b.Properties = &paho.PublishProperties{
-			User: make([]paho.UserProperty, 0),
-		}
+		b.Properties = &paho.PublishProperties{}
 	}
-	b.Properties.User.Add(contentType, f.MediaType())
+	b.Properties.ContentType = f.MediaType()
 	var buf bytes.Buffer
 	_, err := io.Copy(&buf, event)
 	if err != nil {
@@ -85,15 +83,13 @@ func (b *pubMessageWriter) SetData(reader io.Reader) error {
 func (b *pubMessageWriter) SetAttribute(attribute spec.Attribute, value interface{}) error {
 	if attribute.Kind() == spec.DataContentType {
 		if value == nil {
-			b.removeProperty(contentType)
+			b.Properties.ContentType = ""
 		}
 		s, err := types.Format(value)
 		if err != nil {
 			return err
 		}
-		if err := b.addProperty(contentType, s); err != nil {
-			return err
-		}
+		b.Properties.ContentType = s
 	} else {
 		if value == nil {
 			b.removeProperty(prefix + attribute.Name())