Adds REST controller/endpoints

src/main/java/com/nisum/learning/student/StudentService.java

-package com.nisum.learning.student;
-
-public class StudentService {
-
-}

src/main/java/com/nisum/learning/student/controller/StudentController.java

 package com.nisum.learning.student.controller;
 
 import com.nisum.learning.student.model.Student;
-import org.springframework.http.ResponseEntity;
+import com.nisum.learning.student.service.StudentService;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.http.HttpStatus;
 import org.springframework.web.bind.annotation.*;
-import org.springframework.web.reactive.function.client.WebClient;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
 @RestController
 @RequestMapping("/students")
 public class StudentController {
+    @Autowired
+    StudentService studentService;
+
+    //for demo/ref purposes
     public static void main(String[] args) {
         Flux<Integer> nums = Flux.just(1, 2, 3)/*.concatWith(Flux.error(new RuntimeException("Exception occurred")))*/;
         nums.log()
@@ -20,26 +25,27 @@ public class StudentController {
 
     @GetMapping()
     public Flux<Student> getAllStudents(){
-        return null;
+        return studentService.findAll();
     }
 
     @GetMapping("/{id}")
     public Mono<Student> getStudentById(@PathVariable int id){
-        return null;
+        return studentService.findById(id);
     }
 
     @PostMapping()
-    public ResponseEntity<Student> createStudent(@RequestBody Student newStudent){
-        return null;
+    @ResponseStatus(HttpStatus.CREATED)
+    public void createStudent(@RequestBody Student newStudent){
+        studentService.create(newStudent);
     }
 
     @PutMapping("/{id}")
-    public Mono<ResponseEntity<Student>> updateStudentById(@RequestBody Student newStudent){
-        return null;
+    public Mono<Student> updateStudentById(@RequestBody Student newStudent){
+        return studentService.update(newStudent);
     }
 
     @DeleteMapping("/{id}")
-    public Mono<ResponseEntity<Student>> deleteStudentById(@PathVariable int id){
-        return null;
+    public void deleteStudentById(@PathVariable int id){
+        studentService.deleteById(id);
     }
 }

src/main/java/com/nisum/learning/student/repository/StudentRepository.java

+package com.nisum.learning.student.repository;
+
+import com.nisum.learning.student.model.Student;
+import org.springframework.data.mongodb.repository.ReactiveMongoRepository;
+import org.springframework.stereotype.Repository;
+
+@Repository
+public interface StudentRepository extends ReactiveMongoRepository<Student, Integer> {
+}

src/main/java/com/nisum/learning/student/service/StudentService.java

+package com.nisum.learning.student.service;
+
+import com.nisum.learning.student.model.Student;
+import com.nisum.learning.student.repository.StudentRepository;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Service;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+
+@Service
+public class StudentService {
+    @Autowired
+    StudentRepository studentRepo;
+
+    public Flux<Student> findAll() {
+        return studentRepo.findAll();
+    }
+
+    public Mono<Student> findById(Integer id){
+        return studentRepo.findById(id);
+    }
+
+    public void create(Student newStudent){
+        studentRepo.save(newStudent).subscribe();
+    }
+
+    public Mono<Student> update(Student newStudent){
+        return studentRepo.save(newStudent);
+    }
+
+    public void deleteById(int id){
+        studentRepo.deleteById(id);
+    }
+}