Spring boot web app gives 500 internal server error instead 404 not found

Question

How can i get 404 error when theres no student with a given id?

MY Controller:

    @GetMapping("/students/{stu_id}")  
    private Student_Information getInfo(@PathVariable("stu_id") String stu_id){
        Student_Information student = studentInformationService.getStudentById(stu_id);
        if(student == null) {
            throw new StudentNotFoundException("id"+stu_id);
        }
        return student;
    } 

MY Exception class:

    @ResponseStatus(HttpStatus.NOT_FOUND)
    public class StudentNotFoundException extends RuntimeException {
        
        public StudentNotFoundException(String message) {
            super(message);
        }
    }

What i got in POSTMAN: { "timestamp": "2021-03-21T20:50:15.072+00:00", "status": 500, "error": "Internal Server Error", "message": "", "path": "/students/stud231" }

Error from java:

java.util.NoSuchElementException: No value present
    at java.util.Optional.get(Optional.java:135) ~[na:1.8.0_251]
    at com.example.demo.services.StudentInformationService.getStudentById(StudentInformationService.java:17) ~[classes/:na]
    at com.example.demo.controllers.AppController.getInfo(AppController.java:32) ~[classes/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_251]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_251]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_251]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_251]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:197) ~[spring-web-5.3.4.jar:5.3.4]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:141) ~[spring-web-5.3.4.jar:5.3.4]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106) ~[spring-webmvc-5.3.4.jar:5.3.4]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:894) ~[spring-webmvc-5.3.4.jar:5.3.4]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.4.jar:5.3.4]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.4.jar:5.3.4]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1060) ~[spring-webmvc-5.3.4.jar:5.3.4]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:962) ~[spring-webmvc-5.3.4.jar:5.3.4]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.4.jar:5.3.4]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.3.4.jar:5.3.4]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:626) ~[tomcat-embed-core-9.0.43.jar:4.0.FR]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.4.jar:5.3.4]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) ~[tomcat-embed-core-9.0.43.jar:4.0.FR]
    at ...

Answer 1

That happens because the Optional returned by: repository.findById(id) can return an empty, so if you call get() on it it will throw a java.util.NoSuchElementException.

You can fix that with something like: repository.findById(id).orElseGet(null) or repository.findById(id).orElseGet(new Student_Information()).

4XX error code is related to client side mistakes and you should not return this as a best practice. You can return 200 Ok with empty response.

Because the resource is available but the record for path variable doesn't exist so it will not be a good choice to return 404 here.