JSON Serialization in Server Plugin

[Constantin Mitocaru]

I have not found a solid solution on stackoverflow nor here yet.

I developed a Server plugin and installed it on neo4j server.

The rest works fine if it returns primitives.

However when it gets to this method:

@GET

@Path("/dum")

@Produces({MediaType.APPLICATION_JSON})

public RestResponse<Pair<String,String>> dumDum() {

return RestResponse.success("Ok", Pair.of("dum", "dum"));

}

throws this error

SEVERE: A message body writer for Java class com.mycomp.rest.RestResponse, and Java type com.mycomp.rest.RestResponse<com.mycomp.commons.Pair<java.lang.String, java.lang.String>>, and MIME media type application/json was not found

Mar 24, 2015 11:19:41 AM com.sun.jersey.spi.container.ContainerResponse write

SEVERE: The registered message body writers compatible with the MIME media type are:

*/* ->

  com.sun.jersey.core.impl.provider.entity.FormProvider

  com.sun.jersey.core.impl.provider.entity.StringProvider

  com.sun.jersey.core.impl.provider.entity.ByteArrayProvider

  com.sun.jersey.core.impl.provider.entity.FileProvider

  com.sun.jersey.core.impl.provider.entity.InputStreamProvider

  com.sun.jersey.core.impl.provider.entity.DataSourceProvider

  com.sun.jersey.core.impl.provider.entity.XMLJAXBElementProvider$General

  com.sun.jersey.core.impl.provider.entity.ReaderProvider

  com.sun.jersey.core.impl.provider.entity.DocumentProvider

  com.sun.jersey.core.impl.provider.entity.StreamingOutputProvider

  com.sun.jersey.core.impl.provider.entity.SourceProvider$SourceWriter

  com.sun.jersey.server.impl.template.ViewableMessageBodyWriter

  com.sun.jersey.core.impl.provider.entity.XMLRootElementProvider$General

  com.sun.jersey.core.impl.provider.entity.XMLListElementProvider$General

Mar 24, 2015 11:19:41 AM com.sun.jersey.spi.container.ContainerResponse logException

SEVERE: Mapped exception to response: 500 (Internal Server Error)

javax.ws.rs.WebApplicationException: com.sun.jersey.api.MessageException: A message body writer for Java class com.mycomp.rest.RestResponse, and Java type com.mycomp.rest.RestResponse<com.mycomp.commons.Pair<java.lang.String, java.lang.String>>, and MIME media type application/json was not found

at com.sun.jersey.spi.container.ContainerResponse.write(ContainerResponse.java:285)

at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1437)

at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1349)

at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1339)

at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:416)

at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:537)

at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:699)

at javax.servlet.http.HttpServlet.service(HttpServlet.java:848)

at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:698)

at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:505)

at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:211)

at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1096)

at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:432)

at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:175)

at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1030)

at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:136)

at org.eclipse.jetty.server.handler.HandlerList.handle(HandlerList.java:52)

at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)

at org.eclipse.jetty.server.Server.handle(Server.java:445)

at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:268)

at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:229)

at org.eclipse.jetty.io.AbstractConnection$ReadCallback.run(AbstractConnection.java:358)

at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:601)

at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:532)

at java.lang.Thread.run(Thread.java:745)

Caused by: com.sun.jersey.api.MessageException: A message body writer for Java class com.mycomp.rest.RestResponse, and Java type com.mycomp.rest.RestResponse<com.mycomp.commons.Pair<java.lang.String, java.lang.String>>, and MIME media type application/json was not found

... 25 more

One solution i found was to use genson. It works BUT it breaks the functionality of the regular neo4j endpoint db/data/. So the genson solution ain't gonna fly.

Under a normal web app I would add this in web.xml

<init-param>

<param-name>com.sun.jersey.api.json.POJOMappingFeature</param-name>

<param-value>true</param-value>

</init-param>

But here I do NOT have a web.xml to alter.

Please let me know my options

[Michael Hunger]

Is your Pair serializable, i.e. a POJO?

Otherwise you can just create a Map or List of Map of Lists.

Michael

--
You received this message because you are subscribed to the Google Groups "Neo4j" group.
To unsubscribe from this group and stop receiving emails from it, send an email to neo4j+un...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

[Jim Webber]

Hi Constantin,

I think this is a Jersey thing.

It means that natively Jersey (which is the REST library that Neo4j server uses) doesn't know how to serialise your Pair<> type.

You have to register a serializer with Jersey, or since it'll end up as a string anyway just serialise it manually in that dumDum() method.

Jim

[Martin Uhlir]

Add jersey-json library along with your plugin (thus adding it to the classpath of the neo4j server) and annotate the object/class which you return from your method Pair.of("dum", "dum") with the annotation @XmlRootElement (javax.xml.bind.annotation.XmlRootElement).