Chapter 1: Driver Setup, Ticket: Projection [Solved]

MongoDB University M220J: MongoDB for Java Developers
#1

I did Ticket: Projection, and my implementation of getMoviesByCountry method did work (it passed test)

Here is test code:

  @Test
  public void testFindMoviesByCountry() {
int expectedSize = 2;
// by the way Kosovo is Serbia
String country = "Kosovo";
Iterable<Document> cursor = dao.getMoviesByCountry(country);
int actualSize = 0;
for (Document d : cursor) {
  System.out.println(d);
  actualSize++;
}

Assert.assertEquals(
    "Unexpected number of returned movie documents. Check your query filter",
    expectedSize,
    actualSize);
  }

and here is my method:

  public List<Document> getMoviesByCountry(String... country) {

    //Bson queryFilter = new Document("countries", new Document("$all", Arrays.asList(country)));

    Bson queryFilter = all("countries", country);
    Bson projection = new Document("title",1).append("_id",0);
    //TODO> Ticket: Projection - implement the query and projection required by the unit test

    List<Document> movies = new ArrayList<>();


    moviesCollection.find(queryFilter).projection(projection).into(movies);

    return movies;
  }

After running application Im getting this error:

2019-04-14 03:13:56.293 ERROR 9196 --- [nio-5000-exec-8] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause

java.lang.NullPointerException: null
	at mflix.api.daos.MovieDocumentMapper.mapToMovieTitle(MovieDocumentMapper.java:25) ~[classes/:na]
	at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193) ~[na:1.8.0_171]
	at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1382) ~[na:1.8.0_171]
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481) ~[na:1.8.0_171]
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471) ~[na:1.8.0_171]
	at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708) ~[na:1.8.0_171]
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[na:1.8.0_171]
	at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499) ~[na:1.8.0_171]
	at mflix.api.services.MoviesService.getMoviesByCountry(MoviesService.java:98) ~[classes/:na]
	at mflix.api.controllers.MovieController.moviesByCountry(MovieController.java:72) ~[classes/:na]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_171]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_171]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_171]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_171]
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:209) ~[spring-web-5.0.7.RELEASE.jar:5.0.7.RELEASE]
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136) ~[spring-web-5.0.7.RELEASE.jar:5.0.7.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102) ~[spring-webmvc-5.0.7.RELEASE.jar:5.0.7.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:877) ~[spring-webmvc-5.0.7.RELEASE.jar:5.0.7.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:783) ~[spring-webmvc-5.0.7.RELEASE.jar:5.0.7.RELEASE]
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.0.7.RELEASE.jar:5.0.7.RELEASE]
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991) ~[spring-webmvc-5.0.7.RELEASE.jar:5.0.7.RELEASE]
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925) ~[spring-webmvc-5.0.7.RELEASE.jar:5.0.7.RELEASE]
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:974) ~[spring-webmvc-5.0.7.RELEASE.jar:5.0.7.RELEASE]
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:866) ~[spring-webmvc-5.0.7.RELEASE.jar:5.0.7.RELEASE]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:635) ~[tomcat-embed-core-8.5.31.jar:8.5.31]
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:851) ~[spring-webmvc-5.0.7.RELEASE.jar:5.0.7.RELEASE]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) ~[tomcat-embed-core-8.5.31.jar:8.5.31]

Any suggestions ?

#2

well I did find the error,

Bson projection = new Document("title",1).append("_id",0);

I thought we need to exclude _id, but that was mistake.

With correct projection it worked fine and I got validation code.

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