java - JAX-RS MessageBodyReader

Question

我正在从提供者处了解 MessageBodyReader 方法的工作原理。我看到该方法返回一个对象，但我不确定如何从服务访问该对象。我能否得到有关如何从阅读器类返回对象的解释？这将帮助我为所有 DTO 应用阅读规则。提前致谢!

服务:

    @POST
    @Produces({ MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON })
    @Path("/CreateAccount")
    @Consumes({ MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON })
    public Response createAccount(@Context HttpServletRequest req) {
        
        String a = "Reader success? ";//Would to see that string here!
        return Response.ok().build();
    }

提供者:

@Provider
public class readerClass implements MessageBodyReader<Object>
{

@Override
public boolean isReadable(Class<?> paramClass, Type paramType,
        Annotation[] paramArrayOfAnnotation, MediaType paramMediaType) {
    // TODO Auto-generated method stub
    return true;
}

@Override
public Object readFrom(Class<Object> paramClass, Type paramType,
        Annotation[] paramArrayOfAnnotation, MediaType paramMediaType,
        MultivaluedMap<String, String> paramMultivaluedMap,
        InputStream paramInputStream) throws IOException,
        WebApplicationException {
    // TODO Auto-generated method stub
    
    return "Successfully read from a providers reader method";
}

}

Answer 1

你误解了 MessageBodyReader 的用途，它的用途如下:

Contract for a provider that supports the conversion of a stream to a Java type. To add a MessageBodyReader implementation, annotate the implementation class with @Provider. A MessageBodyReader implementation may be annotated with Consumes to restrict the media types for which it will be considered suitable

例子: 如果你有一个用例，你得到了除 xml/json 之外的自定义格式，你想提供你自己的 UnMarshaller，你可以使用 messagebody reader

    @Provider
    @Consumes("customformat")
    public class CustomUnmarshaller implements MessageBodyReader {

        @Override
        public boolean isReadable(Class aClass, Type type, Annotation[] annotations, MediaType mediaType) {
            return true;
        }


        @Override
        public Object readFrom(Class aClass, Type type, Annotation[] annotations, MediaType mediaType, MultivaluedMap multivaluedMap, InputStream inputStream) throws IOException, WebApplicationException {
            Object result = null;
            try {
                result = unmarshall(inputStream, aClass); // un marshall custom format to java object here
            } catch (Exception e) {
                e.printStackTrace();
            }

            return result;


}
}

在网络服务中你可以像..一样使用它

    @POST    
    @Path("/CreateAccount")
    @Consumes("custom format")
    public Response createAccount(@Context HttpServletRequest req,Account acc) {

        saveAccount(acc); // here acc object is returned from your custom unmarshaller 
        return Response.ok().build();
    }

更多信息: Custom Marshalling/UnMarshalling Example , Jersy Entity Providers Tutorial