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Reading attachments

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For example:

@POST
@Path("/books/jaxbjson")
@Produces("text/xml")
public Response addBookJaxbJson(
        @Multipart(value = "rootPart", type = "text/xml") Book2 b1,
        @Multipart(value = "book2", type = "application/json") Book b2) 
        throws Exception {
}

...

All attachment parts can be accessed as a list of Attachment with Attachment making it easy to deal with a given part:

@POST
public void addAttachments(List<Attachment> atts) throws Exception {
}

...

Similarly, the whole request body can be represented as a MultipartBody:

@POST
public void addAttachments(MultipartBody body) throws Exception {
body.getAllAtachments();
body.getRootAttachment();
}

When handling complex multipart/form-data submissions (such as those containing files) MultipartBody (and Attachment) need to be used directly. In simpler cases, when every form part can be captured by a String, the following code will suffice:

@POST
@Consumes("multipart/form-data")
public void addForm1(@FormParam("name") String title, @FormParam("id") Long id) throws Exception {
}

@POST
@Consumes("multipart/form-data")
public void addForm2(@FormParam("") BookBean book) throws Exception {
}

@POST
@Consumes("multipart/form-data")
public void addForm3(MultivaluedMap<String, String> formData) throws Exception {
}

When working with either List of Attachments or MultipartBody, one may want to process the individual parts with the help of some custom procedures. Starting from CXF 2.3.0 it is also possible to do the following:

@POST
public void addAttachments(MultipartBody body) throws Exception {
    Book book = body.getAttachmentObject("bookPart", Book.class);
}

@POST
public void addAttachments(List<Attachment> attachments) throws Exception {
    for (Attachment attachment : attachments) {
        Book book = attachment.getObject(Book.class);
    }  
}

...

When you write the code like this

@POST
@Path("/books/jaxbjson")
@Produces("text/xml")
public Response addBookJaxbJson(
        @Multipart("rootPart") Book2 b1,
        @Multipart("book2") Book b2)  {}

the runtime will return a 400 status if either "rootPart" or "book2" parts can not be found in the multipart payload.
Starting from 2.5.1 it is possible to request the runtime to report a null value in case of missing parts:

@POST
@Path("/books/jaxbjson")
@Produces("text/xml")
public Response addBookJaxbJson(
        @Multipart("rootPart") Book2 b1,
        @Multipart(value = "book2", required = false) Book b2) {}

...

On the server side it is sufficient to update the @Produces value for a given method:

public class Resource {
   private List<Book> books; 
   @Produces("multipart/mixed;type=text/xml")
   public List<Book> getBooksAsMultipart() {
      return booksList;
   }

   @Produces("multipart/mixed;type=text/xml")
   public Book getBookAsMultipart() {
      return booksList;
   }
}

...

When returning mixed multiparts containing objects of different types, you can either return a Map with the media type string value to Object pairs or MultipartBody:

public class Resource {
   private List<Book> books; 
   @Produces("multipart/mixed")
   public Map<String, Object> getBooks() {
      Map<String, Object> map = new LinkedHashMap<String, Object>();
      map.put("text/xml", new JaxbBook());
      map.put("application/json", new JSONBook());
      map.put("application/octet-stream", imageInputStream);
      return map;  
   } 

   @Produces("multipart/mixed")
   public MultipartBody getBooks2() {
      List<Attachment> atts = new LinkedList<Attachment>();
      atts.add(new Attachment("root", "application/json", new JSONBook()));
      atts.add(new Attachment("image", "application/octet-stream", getImageInputStream()));
      return new MultipartBody(atts, true);  
   }

}

...

You can also control the contentId and the media type of the root attachment by using a Multipart annotation:

public class Resource {
   @Produces("multipart/form-data")
   @Multipart(value = "root", type = "application/octet-stream") 
   public File testGetImageFromForm() {
      return getClass().getResource("image.png").getFile();
   }
}

...

On the client side multiparts can be written the same way. For example:

WebClient client = WebClient.create("http://books");
client.type("multipart/mixed").accept("multipart/mixed");
List<Attachment> atts = new LinkedList<Attachment>();
atts.add(new Attachment("root", "application/json", new JSONBook()));
atts.add(new Attachment("image", "application/octet-stream", getImageInputStream()));
List<Attachment> atts = client.postAndGetCollection(atts, Attachment.class);

...

When using proxies, a Multipart annotation attached to a method parameter can also be used to set the root contentId and media type. Proxies do not support at the moment multiple method parameters annotated with Multipart (as opposed to the server side) but only a single multipart parameter:

public class Resource {
    @Produces("multipart/mixed")
    @Consumes("multipart/form-data")
    @Multipart(value = "root", type = "application/octet-stream") 
    public File postGetFile(@Multipart(value = "root2", type = "application/octet-stream") File file) {}
}

A method-level Multipart annotation will affect the writing on the server side and the reading on the client side. A parameter-level Multipart annotation will affect writing on the client (proxy) side and reading on the server side. You don't have to use Multipart annotations.

Uploading files with Client API

At the moment the only way to upload a file is to use a MultipartBody, Attachment or File:

WebClient client = WebClient.create("http://books");t
client.type("multipart/form-data");
ContentDisposition cd = new ContentDisposition("attachment;filename=image.jpg");
Attachment att = new Attachment("root", imageInputStream, cd);
client.post(new MultipartBody(att));

// or just post the attachment if it's a single part request only
client.post(att);

// or just use a file
client.post(getClass().getResource("image.png").getFile());

...

One can use the following properties to set up folder, memory threshold and max size (from CXF 2.4.4 and 2.5) values when dealing with large attachments:

<beans>
  <jaxrs:server id="bookstore1">
     <jaxrs:properties>
         <entry key="attachment-directory" value="/temp/bookstore1"/>
         <!-- 200K-->
         <entry key="attachment-memory-threshold" value="404800"/>
         
         <entry key="attachment-max-size" value="404800"/>
     </jaxrs:properties>
  </jaxrs:server>  
</beans>

...

Note that if a given attachment exceeds the maximum size property (default is no-limit) then HTTP 413 status will be returned. For more information on these configuration properties, please see the documentation on Securing CXF Services.

Forms and multiparts

The Forms in HTML documents recommendation suggests that multipart/form-data requests should mainly be used to upload files.

...

For example this request can be handled by a method with the following signature:

@POST
@Path("/books/jsonform")
@Consumes("multipart/form-data")
public Response addBookJsonFromForm(Book b1)  {...}

Similarly, this request can be handled by a method with the following signature:

@POST
@Path("/books/jsonjaxbform")
@Consumes("multipart/form-data")
public Response addBookJaxbJsonForm(@Multipart("jsonPart") Book b1,
                                        @Multipart("jaxbPart") Book b2) {}

Note that once a request has more than two parts then one needs to start using @Mutipart@Multipart, the values can refer to either ContentId header or to ContentDisposition/name. Note that at the moment using @Multipart is preferred to using @FormParam unless a plain name/value submission is dealt with. The reason is that @Multipart can also specify an expected media type of the individual part and thus act similarly to a @Consume annotation.

...

Finally, multipart/form-data requests with multiple files (file uploads) can be supported too. For example, this request can be handled by a method with the signature like :

@POST
@Path("/books/filesform")
@Produces("text/xml")
@Consumes("multipart/form-data")
public Response addBookFilesForm(@Multipart("owner") String name,
                                 @Multipart("files") List<Book> books) {} 

...

Please note that using JAX-RS FormParams is recommended for dealing with plain application/www-url-encoded submissions consisting of name/value pairs only.

XOP support

CXF JAXRS clients and endpoints can support XML-binary Optimized Packaging (XOP).
What it means at a practical level is that a JAXB bean containing binary data is serialized using a multipart packaging, with the root part containing non-binary data only but also linking to co-located parts containing the actual binary payloads. Next it is deserialized into a JAXB bean on the server side.

Content-Disposition UTF-8 file names

Starting from CXF 3.0.4 it is possible to specify a Content-Disposition file names in a UTF-8 format, using a "filename*" Content-Disposition extension parameter as opposed to the "filename" one.

Please see RFC 6266 and this unit test for more information. 

Content-Type

If the content type (Content-Type) of the attachment is not set, it is assumed to be "application/octet-stream". This default could be overridden.

XOP support

CXF JAXRS clients and endpoints can support XML-binary Optimized Packaging (XOP).
What it means at a practical level is that a JAXB bean containing binary data is serialized using a multipart packaging, with the root part containing non-binary data only but also linking to co-located parts containing the actual binary payloads. Next it is deserialized into a JAXB bean on the server side.

If you'd like to experiment with XOP then you need to set an "mtom-enabled" property on CXF jaxrs endpoints and clients.
Please see JAXRSMultipartTest (testXopWebClient) and MultipartStore (addBookXop) for more details.

Multipart Filters

It is possible to intercept the attachment write or read process starting from CXF 3.1.12.

MultipartInputFilter and MultipartOutputFilter have been introduced. These filters can be used to modify the list of the attachment parts or customize some of the individual part's properties, example, replace the part input stream, etc.

These filters can be registered from JAX-RS 2.0 client or container request/response filters or CXF in/out interceptors. MultipartInputFilter can be added to the list of the input filters which is identified by a "multipart.input.filters" property on the current CXF message. Likewise, MultipartOutputFilter can be added to the list of the output filters which is identified by a "multipart.output.filters" property on the current CXF message.

Signing Multiparts

See this section for more informationIf you'd like to experiment with XOP then you need to set an "mtom-enabled" property on CXF jaxrs endpoints and clients.
Please see JAXRSMultipartTest (testXopWebClient) and MultipartStore (addBookXop) for more details.

Note about Struts

If you are using CXF and Struts2 within the same application and expecting CXF to process multipart/form-data payloads then you need to make sure Struts2 dispatcher is not consuming the request input stream.

One option is to let Struts2 handle URIs matching some specific patterns only, for example:

<web-app>
<filter>
      <filter-name>struts2</filter-name>
      <filter-class>
           org.apache.struts2.dispatcher.FilterDispatcher
       </filter-class>
   </filter>

   <filter-mapping>
       <filter-name>struts2</filter-name>
       <url-pattern>*.action</url-pattern>
   </filter-mapping>

   <filter-mapping>
       <filter-name>struts2</filter-name>
       <url-pattern>*.jsp</url-pattern>
   </filter-mapping>
</web-app>

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