Spring MVC how to display data from database into a table

For the starters:

@RequestMapping(value = "task", method = RequestMethod.GET)
public String taskList(Map<String, Object> model) {
        model.put("task", taskRepository.findAll());
        return "/tasks/list";
  }

You should return some object you have created instead of String value. Let's asume you want to transfer two fields to you page lets name them field1 and field2. Now create your Data Transfer Object:

public class MyEntityDto{
  private String filed1;
  private String field2;
  //Getter and setter method
  .
  .
  .
}

Now your controller should look something like this:

@Autowired
SomeSevice someService;

@RequestMapping(value = "task", method = RequestMethod.GET)
@ResponseBody 
public List<MyEntityDto> taskList(Map<String, Object> model) {
    List<MyEntityDto> dtoList = someService.findALl();
    return dtoList;
  }

Your service from the other hand should look something like this:

@Service
public class SomeService(){
  @Autowired 
  TaskRepository taskRepository;

  public List<MyEntityDto> findAll(){
    return assemblyTasks(taskRepository.findAll());//TODO implement method assemblyTasks
  }
}

Notice that I put your repository usage into the service.This is the way it supposed to be done. You should use services in order to fetch data from your database and than you want to return your data using specificlly design for that purpose object - Data Transfer Object. I leave the implementation of assemblyTask method to you. What you need to do there is to assign fields you want to pass from entity to view through your dto object. Generally you would want to have an assembler class for every DTO object but for the sake of simplicity I introduced the idea by using method. If you want to read more about DTO, view this post: getting-value-of-invalid-field-after-methodargumentnotvalidexception

If you are completely new to the Spring world I recommend also find some basics web tutorials, for example here: gonetoseries