DATAREST-797

stack trace.txt

org.springframework.http.converter.HttpMessageNotWritableException: Could not write content: [no message for java.lang.NullPointerException]; nested exception is com.fasterxml.jackson.databind.JsonMappingException: [no message for java.lang.NullPointerException]
	at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:272)
	at org.springframework.http.converter.AbstractGenericHttpMessageConverter.write(AbstractGenericHttpMessageConverter.java:100)
	at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:222)
	at org.springframework.web.servlet.mvc.method.annotation.HttpEntityMethodProcessor.handleReturnValue(HttpEntityMethodProcessor.java:183)
	at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:80)
	at org.springframework.data.rest.webmvc.ResourceProcessorHandlerMethodReturnValueHandler.handleReturnValue(ResourceProcessorHandlerMethodReturnValueHandler.java:174)
	at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:80)
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:126)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:817)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:731)
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:968)
	at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:870)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:844)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
	at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:87)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
	at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:121)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:522)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1095)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:672)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1500)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1456)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:745)
Caused by: com.fasterxml.jackson.databind.JsonMappingException: [no message for java.lang.NullPointerException]
	at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:141)
	at com.fasterxml.jackson.databind.ObjectWriter$Prefetch.serialize(ObjectWriter.java:1387)
	at com.fasterxml.jackson.databind.ObjectWriter.writeValue(ObjectWriter.java:889)
	at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:265)
	... 53 more
Caused by: java.lang.NullPointerException
	at org.springframework.data.rest.webmvc.mapping.LinkCollectingAssociationHandler.doWithAssociation(LinkCollectingAssociationHandler.java:101)
	at org.springframework.data.mapping.model.BasicPersistentEntity.doWithAssociations(BasicPersistentEntity.java:353)
	at org.springframework.data.rest.webmvc.json.PersistentEntityJackson2Module$LinkCollector.getLinksFor(PersistentEntityJackson2Module.java:643)
	at org.springframework.data.rest.webmvc.json.PersistentEntityJackson2Module$PersistentEntityResourceSerializer.serialize(PersistentEntityJackson2Module.java:170)
	at org.springframework.data.rest.webmvc.json.PersistentEntityJackson2Module$PersistentEntityResourceSerializer.serialize(PersistentEntityJackson2Module.java:128)
	at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:130)
	... 56 more

ValidateNPETestCase.java

package com.example;

import static org.hamcrest.CoreMatchers.*;
import static org.hamcrest.MatcherAssert.*;

import java.net.UnknownHostException;
import java.util.Set;

import javax.annotation.PreDestroy;

import lombok.Data;
import lombok.NoArgsConstructor;

import org.bson.types.ObjectId;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.test.SpringApplicationConfiguration;
import org.springframework.boot.test.TestRestTemplate;
import org.springframework.boot.test.WebIntegrationTest;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.SimpleMongoDbFactory;
import org.springframework.data.mongodb.core.mapping.DBRef;
import org.springframework.data.mongodb.core.mapping.Document;
import org.springframework.data.mongodb.repository.config.EnableMongoRepositories;
import org.springframework.data.repository.CrudRepository;
import org.springframework.data.repository.query.Param;
import org.springframework.data.rest.core.annotation.RepositoryRestResource;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import com.mongodb.MongoClient;

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = ValidateNPETestCase.Config.class)
@WebIntegrationTest
public class ValidateNPETestCase {

    private TestRestTemplate restTemplate = new TestRestTemplate();

    @Test
    public void test() throws Exception {

        ResponseEntity<String> create = restTemplate.postForEntity("http://localhost:8080/model", new Model("foo"),
                String.class);
        assertThat(create.getStatusCode(), is(HttpStatus.INTERNAL_SERVER_ERROR));
    }

    @RepositoryRestResource(path = "model")
    public interface ModelRepo extends CrudRepository<Model, ObjectId> {

        Model findByName(@Param("name") String name);
    }

    @Data
    @NoArgsConstructor
    @Document(collection = "model")
    public static class Model {

        @Id
        private ObjectId id;
        private String name;

        @DBRef
        private Object posts;

        public Model(String name) {
            this.name = name;
        }
    }


    @SpringBootApplication
    @Configuration
    @EnableMongoRepositories(considerNestedRepositories = true)
    static class Config {

        private MongoClient mongo;

        @Bean
        public SimpleMongoDbFactory mongoDbFactory(MongoClient mongo) throws Exception {
            return new SimpleMongoDbFactory(mongo, "playground");
        }

        @PreDestroy
        public void close() {
            if (this.mongo != null) {
                this.mongo.close();
            }
        }

        @Bean
        public MongoClient mongo() throws UnknownHostException {
            this.mongo = new MongoClient("localhost");
            return this.mongo;
        }
    }
}