JAX-RS with Kotlin MessageBodyWriter not found - rest

Question

I've implemented a JAX-RS resource (a) with Kotlin and (b) with Java. While the Java flavor works as expected, the Kotlin flavor fails with a
MessageBodyWriter not found for media type=application/json, type=class java.util.ArrayList, genericType=java.util.List<? extends ....Entry>.|#] exception.
This is my resource
#Path("demokotlin")
class DemoKotlinResource {
#GET
#Path("responseGenericEntityWithArrayList")
fun arrayList(): Response {
val list = arrayListOf(Entry("responseGenericEntityWithArrayList"))
val entity = object : GenericEntity<List<Entry>>(list) {}
return Response
.status(Response.Status.OK)
.entity(entity)
.type(MediaType.APPLICATION_JSON).build()
}
}
#XmlRootElement
#XmlAccessorType(XmlAccessType.FIELD)
open class Entry(val fieldName: String)
The integration test is essentially
private val client = ClientBuilder.newClient()
private val target = client.target("http://localhost:8080/xyz/resources/demokotlin")
#Test
fun responseGenericEntityWithArrayList() {
val response = target.path("responseGenericEntityWithArrayList").request(MediaType.APPLICATION_JSON).get()
assertThat("no ok status", response.status, equalTo(200))
val entity = response.readEntity(JsonArray::class.java)
assertThat(entity.getJsonObject(0).getString("fieldName"), equalTo("responseGenericEntityWithArrayList"))
assertThat(entity.toString(), equalTo("[{\"fieldName\":\"responseGenericEntityWithArrayList\"}]"))
}
The equivalent code in Java works fine while the shown code in Kotlin throws MessageBodyWriter not found for media type=application/json, type=class java.util.ArrayList, genericType=java.util.List<? extends ....Entry>.|#].
I am using Payara 4.1.2.172. Digging through some JAX-RS classes I found that the Java Code leads to
genericType=java.util.List<....Entry>
(without the ? extends) while the generic type info with Kotlin is
genericType=java.util.List<? extends ....Entry>
could that be the cause? If so, how can I fix this?
edit 2017-07-25 Here is the stack trace
#|2017-07-25T12:33:16.932+0000|INFO|Payara 4.1||_ThreadID=32;_ThreadName=http-thread-pool::http-listener-1(1);_TimeMillis=1500985996932;_LevelValue=800;|
javax.ws.rs.InternalServerErrorException: HTTP 500 Internal Server Error
at org.glassfish.jersey.server.internal.MappableExceptionWrapperInterceptor.aroundWriteTo(MappableExceptionWrapperInterceptor.java:90)
at org.glassfish.jersey.message.internal.WriterInterceptorExecutor.proceed(WriterInterceptorExecutor.java:162)
at org.glassfish.jersey.message.internal.MessageBodyFactory.writeTo(MessageBodyFactory.java:1130)
at org.glassfish.jersey.server.ServerRuntime$Responder.writeResponse(ServerRuntime.java:711)
at org.glassfish.jersey.server.ServerRuntime$Responder.processResponse(ServerRuntime.java:444)
at org.glassfish.jersey.server.ServerRuntime$Responder.process(ServerRuntime.java:434)
at org.glassfish.jersey.server.ServerRuntime$2.run(ServerRuntime.java:329)
at org.glassfish.jersey.internal.Errors$1.call(Errors.java:271)
at org.glassfish.jersey.internal.Errors$1.call(Errors.java:267)
at org.glassfish.jersey.internal.Errors.process(Errors.java:315)
at org.glassfish.jersey.internal.Errors.process(Errors.java:297)
at org.glassfish.jersey.internal.Errors.process(Errors.java:267)
at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:317)
at org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:305)
at org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:1154)
at org.glassfish.jersey.servlet.WebComponent.serviceImpl(WebComponent.java:473)
at org.glassfish.jersey.servlet.WebComponent.service(WebComponent.java:427)
at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:388)
at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:341)
at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:228)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1606)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:338)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.glassfish.tyrus.servlet.TyrusServletFilter.doFilter(TyrusServletFilter.java:305)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:250)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:256)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:654)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:593)
at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:155)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:371)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:238)
at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:466)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:169)
at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:206)
at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:180)
at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:235)
at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:284)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:201)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:133)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:112)
at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:539)
at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:593)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:573)
at java.lang.Thread.run(Thread.java:748)
Caused by: org.glassfish.jersey.message.internal.MessageBodyProviderNotFoundException: MessageBodyWriter not found for media type=application/json, type=class java.util.ArrayList, genericType=java.util.List<? extends com.github.reproducer.boundary.Entry>.
at org.glassfish.jersey.message.internal.WriterInterceptorExecutor$TerminalWriterInterceptor.aroundWriteTo(WriterInterceptorExecutor.java:247)
at org.glassfish.jersey.message.internal.WriterInterceptorExecutor.proceed(WriterInterceptorExecutor.java:162)
at org.glassfish.jersey.server.internal.JsonWithPaddingInterceptor.aroundWriteTo(JsonWithPaddingInterceptor.java:106)
at org.glassfish.jersey.message.internal.WriterInterceptorExecutor.proceed(WriterInterceptorExecutor.java:162)
at org.glassfish.jersey.server.internal.MappableExceptionWrapperInterceptor.aroundWriteTo(MappableExceptionWrapperInterceptor.java:86)
... 52 more
|#]
edit #2: working Java Code - should be quite similar to Kotlin variant
#Path("demojava")
public class DemoJavaResource {
#GET
#Path("responseGenericEntityWithArrayList")
public Response arrayList() {
final List<JEntry> list = new ArrayList<>();
list.add(new JEntry("responseGenericEntityWithArrayList"));
final GenericEntity<List<JEntry>> entity = new GenericEntity<List<JEntry>>(list) {};
return Response
.status(Response.Status.OK)
.entity(entity)
.type(MediaType.APPLICATION_JSON).build();
}
}
and JEntry
#XmlRootElement
#XmlAccessorType(XmlAccessType.FIELD)
class JEntry {
private String fieldName;
JEntry() { this(""); }
JEntry(final String responseGenericEntityWithArrayList) {
fieldName = responseGenericEntityWithArrayList;
}
public String getFieldName() { return fieldName; }
}

Answer 1

Because JAX-RS cannot encode ArrayList to JSON Array.
MessageBodyWriter is a handler to convert Java data type to output format, e.g. XML, JSON. JAX-RS has built-in MessageBodyWriter for major data type (include JAXB), however those does not include for ArrayList. Thus you need to create a custom MessageBodyWriter to accept ArrayList and encode to JSON.
But in this case, any custom MessageBodyWriter is not need. Instead of, you need to re-create Entry class. I'm sorry that I can't write Kotlin sample, but if it write using Java, it's following;
#Path("demokotlin")
public class DemoKotlinResource {
#GET
#Path("responseGenericEntityWithArrayList")
public Response arrayList() {
Entry entity = new Entry();
entity.fieldName.add("responseGenericEntityWithArrayList");
return Response
.status(Response.Status.OK)
.entity(entity)
.type(MediaType.APPLICATION_JSON).build();
}
}
#XmlRootElement
#XmlAccessorType(XmlAccessType.FIELD)
public class Entry {
public List<String> fieldName = new ArrayList<>();
}
And it translate to Kotlin, then it's maybe completed.