Chapter 20. Multipart Providers
RESTEasy has rich support for the
multipart/* and multipart/form-data MIME (Multipurpose Internet Mail Extension) types. The multipart MIME format passes lists of content bodies. Multiple content bodies are embedded in the one message. multipart/form-data is often found in web application HTML Form documents, and is generally used to upload files. The form-data format works like other multipart formats, except that each inlined piece of content has a name associated with it.
RESTEasy provides a custom API for reading and writing
multipart types, as well as marshalling arbitrary List (for any multipart type) and Map (multipart/form-data only) objects.
20.1. Input with multipart/mixed
When you write a JAX-RS service, RESTEasy provides an interface to let you read any
multipart MIME type: org.jboss.resteasy.plugins.providers.multipart.MultipartInput.
package org.jboss.resteasy.plugins.providers.multipart;
public interface MultipartInput
{
List<InputPart> getParts();
String getPreamble();
}
public interface InputPart
{
MultivaluedMap<String, String> getHeaders();
String getBodyAsString();
<T> T getBody(Class<T> type, Type genericType) throws IOException;
<T> T getBody(org.jboss.resteasy.util.GenericType<T> type) throws IOException;
MediaType getMediaType();
}
MultipartInput is a simple interface that lets you access each part of the multipart message. Each part is represented by an InputPart interface, and is associated with a set of headers. You can unmarshal a part by calling one of the getBody() methods. The Type genericType parameter can be null, but the Class type parameter must be set. RESTEasy locates a MessageBodyReader based on the media type of the part, and the type information you pass in. The following piece of code unmarshalls XML parts into a JAXB annotated class called Customer.
@Path("/multipart")
public class MyService
{
@PUT
@Consumes("multipart/mixed")
public void put(MultipartInput input)
{
List<Customer> customers = new ArrayList...;
for (InputPart part : input.getParts())
{
Customer cust = part.getBody(Customer.class, null);
customers.add(cust);
}
}
}
If you want to unmarshall a body part that is sensitive to generic type metadata, you can use the
org.jboss.resteasy.util.GenericType class, like so:
@Path("/multipart")
public class MyService
{
@PUT
@Consumes("multipart/mixed")
public void put(MultipartInput input)
{
for (InputPart part : input.getParts())
{
List<Customer> cust = part.getBody(new GenericType>List>Customer<<() {});
}
}
}
GenericType is required here because it is the only way to obtain generic type information at runtime.
