Jersey Sub-Resource Locators Error

问题

I'm trying to get the JSR-311 plugin working with Grails 2.3.7. I'm using version 0.10, because I think 0.11 requires Grails 2.4.

I've used the generate-resource command to create an end point for my domain class Product. Two resource classes are created, ProductCollectionResource and ProductResource. I've tweaked them a bit, but essentially they look like this:

ProductCollectionResource

@Path('/api/products')
@Consumes(['application/json'])
@Produces(['application/json'])
class ProductCollectionResource {

    def productResourceService

    @Path('{id}')
    @GET
    ProductResource getResource(@PathParam('id') Long id) {
        new ProductResource(productResourceService: productResourceService, id:id)
    }

    @GET
    Response readAll(@QueryParam("max") Integer max, @QueryParam("offset") Integer offset) {
        ok productResourceService.readAll(max, offset)
    }
}

ProductResource

@Consumes(['application/json'])
@Produces(['application/json'])
class ProductResource {

    def productResourceService
    def id

    @GET
    Response read() {
        ok productResourceService.read(id)
    }
}

The readAll method in ProductCollectionResource works fine - when I hit it, I get back a list of products, however when I try to access a specific product by id (on /api/products/123), I get the following error:

Caused by MessageException: A message body writer for Java class com.myapp.ProductResource, and Java type class com.myapp.ProductResource, and MIME media type application/json was not found
->>  285 | write              in com.sun.jersey.spi.container.ContainerResponse
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
|   1479 | _handleRequest     in com.sun.jersey.server.impl.application.WebApplicationImpl
|   1391 | handleRequest . .  in     ''
|   1381 | handleRequest      in     ''
|    416 | service . . . . .  in com.sun.jersey.spi.container.servlet.WebComponent
|    538 | service            in com.sun.jersey.spi.container.servlet.ServletContainer
|    716 | service . . . . .  in     ''
|    193 | process            in org.grails.jaxrs.web.JaxrsContext$JaxrsServiceImpl
|     45 | handle . . . . . . in org.grails.jaxrs.JaxrsController
|    195 | doFilter           in grails.plugin.cache.web.filter.PageFragmentCachingFilter
|     63 | doFilter . . . . . in grails.plugin.cache.web.filter.AbstractFilter
|    150 | invoke             in net.bull.javamelody.JspWrapper
|    285 | invoke . . . . . . in net.bull.javamelody.JdbcWrapper$DelegatingInvocationHandler
|    198 | doFilter           in net.bull.javamelody.MonitoringFilter
|    176 | doFilter . . . . . in     ''
|     67 | doFilter . . . . . in     ''
|     53 | doFilter           in grails.plugin.springsecurity.web.filter.GrailsAnonymousAuthenticationFilter
|     82 | doFilter           in grails.plugin.springsecurity.web.authentication.logout.MutableLogoutFilter
|     63 | doFilter . . . . . in com.odobo.grails.plugin.springsecurity.rest.RestLogoutFilter
|     46 | doFilterInternal   in org.grails.jaxrs.web.JaxrsFilter
|     82 | doFilter . . . . . in com.brandseye.cors.CorsFilter
|   1145 | runWorker          in java.util.concurrent.ThreadPoolExecutor
|    615 | run . . . . . . .  in java.util.concurrent.ThreadPoolExecutor$Worker
^    744 | run                in java.lang.Thread

So it looks like it's trying to marshall my ProductResource class to JSON, which I think isn't really what I want. I think it should be invoking the ProductResource.read() method, and marshalling the returned value from that method to JSON.

回答1:

I have no experience in Grails whatsoever, but from a pure Jersey standpoint, look at what you got here

@Path('{id}')
@GET
ProductResource getResource(@PathParam('id') Long id) {

This is resource method (endpoint). So the ProductsResource will be treated as the response body, just like any other resource method.

You seem to be trying to use the sub-resource locator functionality, forwarding to the ProductsResource class. For that to work, the sub-resource locator (getResource) should not have an @HttpMethod annotation. That's one of the factors that differentiates a resource method from a sub-resource locator.

So just remove the @GET from the getResource method. The @GET is already established by the read() method in the ProductsResource, which is what will be called.

For more information, see the documentation for Sub-Resource Locators

来源：https://stackoverflow.com/questions/30275284/jersey-sub-resource-locators-error

标签

json

grails

jersey