org.jboss.resteasy.core.NoMessageBodyWriterFoundFailure: Could not find MessageBodyWriter for response object of type

Question

I develop REST-service with undertow+resteasy+ajckson, when I run this with IDEA, everything is OK, but when I create "fat-jar" with gradle or maven I get error during GET query:

org.jboss.resteasy.core.NoMessageBodyWriterFoundFailure: Could not find MessageBodyWriter for response object of type at org.jboss.resteasy.core.ServerResponseWriter.writeNomapResponse(ServerResponseWriter.java:67) at org.jboss.resteasy.core.SynchronousDispatcher.writeResponse(SynchronousDispatcher.java:448) at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:397) at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:200) at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.service(ServletContainerDispatcher.java:220) at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:56) at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:51) at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)

I could create jar without error with gradle build and debug my service in IDEA.

My gradle file:

apply plugin: 'application'
apply plugin: 'java'

sourceCompatibility = 1.8
targetCompatibility = 1.8

mainClassName = 'example.json.RestServer'

jar {
    manifest {
        attributes 'Implementation-Title': 'Rest-server',
                'Implementation-Version': '0.1',
                'Main-Class': 'example.json.RestServer'
    }
    from {
        configurations.compile.collect { it.isDirectory() ? it : zipTree(it) }
    }
}

repositories {
    jcenter()
}

dependencies {
    compile 'io.undertow:undertow-core:1.4.0.Final'
    compile 'io.undertow:undertow-servlet:1.4.0.Final'

    compile 'org.jboss.resteasy:jaxrs-api:3.0.12.Final'
    compile 'org.jboss.resteasy:resteasy-undertow:3.0.12.Final'
    compile 'org.jboss.resteasy:resteasy-jackson-provider:3.0.12.Final'

    testCompile 'junit:junit:4.12'
}

My source:

@Path("calculator")
public class Calculator {
    @GET
    @Path("squareRoot")
    @Produces(MediaType.APPLICATION_JSON)
    public Response squareRoot(@QueryParam("input") double input){
        Result result = new Result("Square Root");
        result.setInput(input);
        result.setOutput(Math.sqrt(result.getInput()));
        return Response.status(200).entity(result).build();
    }

Answer 1

Try to change your last code spinet like below because The anonymous GenericEntity subclass is required to supply the correct type information (otherwise erased by the compiler) for the writer.

@Path("calculator")
    public class Calculator {
        @GET
        @Path("squareRoot")
        @Produces(MediaType.APPLICATION_JSON)
        public Response squareRoot(@QueryParam("input") double input){
            Result result = new Result("Square Root");
            result.setInput(input);
            result.setOutput(Math.sqrt(result.getInput()));
    return Response.ok(
            new GenericEntity<Result >(result)
             )
        }

more explanation is here JAX-RS NoMessageBodyWriterFoundFailure