message: Could not find MessageBodyWriter for response object of type: java.util.ArrayList of media type: application/json
Description: The server encountered an internal error (Could not find MessageBodyWriter for response object of type: java.util.ArrayList of media type: application/json) that prevented it from fulfilling this request
@GET
@Path("/{userName}/questions")
//@Produces("application/json")
public Response getUserQuestions(@PathParam("userName") String userName){
UserDAO userDAO = new UserDAO();
List<Question> questions = userDAO.getUserQuestionsByUserName(userName);
GenericEntity<List<Question>> entity = new GenericEntity<List<Question>>(questions){};
return Response.status(200).entity(entity).type(MediaType.APPLICATION_JSON).build();
}
I have got the resteasy jackson provider in the classpath. Tried changing the return type form ArrayList
to List
, then wrapping it in GenericEntity
based on resteasy response , but still getting the same issue.
Running on tomcat7.
Thanks.
我通过在类路径中添加resteasy-jackson-provider.jar解决了这个异常。请参阅https://bitbucket.org/arcbees/gaestudio/issue/2/need-resteasy-jackson-provider-on
finally solved it using the Gson library
instead of relying on json. did not wrap in Generic Entity either. Here is the code that works
@GET
@Path("/{userName}/questions")
public Response getUserQuestions(@PathParam("userName") String userName){
UserDAO userDAO = new UserDAO();
List<Question> questions = userDAO.getQuestionsByUserName(userName);
Gson gson = new GsonBuilder().setExclusionStrategies(new UserQuestionsExclStrat()).create(); //.serializeNulls()
String json = gson.toJson(questions);
System.out.println(json);
return Response.status(200).entity(json).build();
}
Had to use the exclusion strategy to avoid cyclic reference. here is the link for that: stackoverflow error during json conversion (hibernate bi-directional mapping)
通过在ArrayList中使用的类中添加@XMLRootElement来解决相同的问题
By adding this dependency I was able to solve this issue.
<dependency>
<groupId>org.glassfish.jersey.media</groupId>
<artifactId>jersey-media-json-jackson</artifactId>
<version>2.10.1</version>
</dependency>
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