Understanding the Web Resource Classes for the Storage-Service Example

The first resource class, com.sun.jersey.samples.storageservice.resources.ContainersResource, provides metadata information on the containers. This resource references the ContainerResource resource using the @Path annotation declared on the ContainersResource.getContainerResource method. The following code is extracted from ContainersResource.java:

@Path("/containers")
@Produces("application/xml")
public class ContainersResource {
    @Context UriInfo uriInfo;
    @Context Request request;
    
    @Path("{container}")
    public ContainerResource getContainerResource(@PathParam("container")
        String container) {
        return new ContainerResource(uriInfo, request, container);
    }
    
    @GET
    public Containers getContainers() {
        System.out.println("GET CONTAINERS");
        
        return MemoryStore.MS.getContainers();
    }    
}

Another resource class , com.sun.jersey.samples.storageservice.resources.ContainerResource, provides for reading, creating, and deleting of containers. You can search for items in the container using a URI query parameter. The resource dynamically references the ItemResource resource class using the getItemResource method that is annotated with @Path. The following code is extracted from ContainerResource.java:

@Produces("application/xml")
public class ContainerResource {
    @Context UriInfo uriInfo;
    @Context Request request;
    String container;
    
    ContainerResource(UriInfo uriInfo, Request request, String container) {
        this.uriInfo = uriInfo;
        this.request = request;
        this.container = container;
    }
    
    @GET
    public Container getContainer(@QueryParam("search") String search) {
        System.out.println("GET CONTAINER " + container + ", search = " + search);

        Container c = MemoryStore.MS.getContainer(container);
        if (c == null)
            throw new NotFoundException("Container not found");
        
        
        if (search != null) {
            c = c.clone();
            Iterator<Item> i = c.getItem().iterator();
            byte[] searchBytes = search.getBytes();
            while (i.hasNext()) {
                if (!match(searchBytes, container, i.next().getName()))
                    i.remove();
            }
        }
        
        return c;
    }    

    @PUT
    public Response putContainer() {
        System.out.println("PUT CONTAINER " + container);
        
        URI uri =  uriInfo.getAbsolutePath();
        Container c = new Container(container, uri.toString());
        
        Response r;
        if (!MemoryStore.MS.hasContainer(c)) {
            r = Response.created(uri).build();
        } else {
            r = Response.noContent().build();
        }
        
        MemoryStore.MS.createContainer(c);
        return r;
    }
    
    @DELETE
    public void deleteContainer() {
        System.out.println("DELETE CONTAINER " + container);
        
        Container c = MemoryStore.MS.deleteContainer(container);
        if (c == null)
            throw new NotFoundException("Container not found");
    } 
    
    
    @Path("{item: .+}")
    public ItemResource getItemResource(@PathParam("item") String item) {
        return new ItemResource(uriInfo, request, container, item);
    }
    
    private boolean match(byte[] search, String container, String item) {
        byte[] b = MemoryStore.MS.getItemData(container, item);
        
        OUTER: for (int i = 0; i < b.length - search.length; i++) {
             for (int j = 0; j < search.length; j++) {
                if (b[i + j] != search[j])
                    continue OUTER;
            }
            
            return true;
        }
        
        return false;
    }
}

The last resource class discussed in this sample, com.sun.jersey.samples.storageservice.resources.ItemResource, provides for reading, creating, updating, and deleting of an item. The last modified time and entity tag are supported in that it conditionally returns content only if the browser or proxy has an older version of the content. The following code is extracted from ItemResource.java:

public class ItemResource {
    UriInfo uriInfo;
    Request request;
    String container;
    String item;
    
    public ItemResource(UriInfo uriInfo, Request request,
            String container, String item) {
        this.uriInfo = uriInfo;
        this.request = request;
        this.container = container;
        this.item = item;
    }
    
    @GET
    public Response getItem() {
        System.out.println("GET ITEM " + container + " " + item);
        
        Item i = MemoryStore.MS.getItem(container, item);
        if (i == null)
            throw new NotFoundException("Item not found");
        Date lastModified = i.getLastModified().getTime();
        EntityTag et = new EntityTag(i.getDigest());
        ResponseBuilder rb = request.evaluatePreconditions(lastModified, et);
        if (rb != null)
            return rb.build();
            
        byte[] b = MemoryStore.MS.getItemData(container, item);
        return Response.ok(b, i.getMimeType()).
                lastModified(lastModified).tag(et).build();
    }    
    
    @PUT
    public Response putItem(
            @Context HttpHeaders headers,
            byte[] data) {
        System.out.println("PUT ITEM " + container + " " + item);
        
        URI uri = uriInfo.getAbsolutePath();
        MediaType mimeType = headers.getMediaType();
        GregorianCalendar gc = new GregorianCalendar();
        gc.set(GregorianCalendar.MILLISECOND, 0);
        Item i = new Item(item, uri.toString(), mimeType.toString(), gc);
        String digest = computeDigest(data);
        i.setDigest(digest);
        
        Response r;
        if (!MemoryStore.MS.hasItem(container, item)) {
            r = Response.created(uri).build();
        } else {
            r = Response.noContent().build();
        }
        
        Item ii = MemoryStore.MS.createOrUpdateItem(container, i, data);
        if (ii == null) {
            // Create the container if one has not been created
            URI containerUri = uriInfo.getAbsolutePathBuilder().path("..").
                    build().normalize();
            Container c = new Container(container, containerUri.toString());
            MemoryStore.MS.createContainer(c);
            i = MemoryStore.MS.createOrUpdateItem(container, i, data);
            if (i == null)
                throw new NotFoundException("Container not found");
        }
        
        return r;
    }    
    
    @DELETE
    public void deleteItem() {
        System.out.println("DELETE ITEM " + container + " " + item);
        
        Item i = MemoryStore.MS.deleteItem(container, item);
        if (i == null) {
            throw new NotFoundException("Item not found");
        }
    }
    
    
    private String computeDigest(byte[] content) {
        try {
            MessageDigest md = MessageDigest.getInstance("SHA");
            byte[] digest = md.digest(content);
            BigInteger bi = new BigInteger(digest);
            return bi.toString(16);
        } catch (Exception e) {
            return "";
        }
    }
}

The mapping of the URI path space is shown in the following table.