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is it possible to return "if condition satisfies return a list else return an error message" using a java method

I know that in Java a method can return only one return type... But if there is any possiblity to this, kindly let me know. From the below method I am trying to return a list if condition satisfies else i am trying to return an error message.
Here is my code:
#RequestMapping(value = "/getcompanies", method = RequestMethod.POST)
public List<CompanyMaster> getCompanies(#RequestBody UserDetails user) {
String OrgLoginId = user.getOrgLoginId();
String password = user.getuPassword();
String checkLoginId = null;
String uPassword = null;
String encPassword = null;
String loginId = null;
String checkAuthorized = null;
// String loginId=userService.getLoginId(OrgLoginId);
List<Object[]> CheckIdPassword = userService.checkLoginId(OrgLoginId);
List<Object[]> results = CheckIdPassword;
for (Object[] obj : results) {
checkLoginId = obj[0].toString();
if (null == obj[1]) {
uPassword = "";
} else {
uPassword = obj[1].toString();
}
loginId = obj[2].toString();
}
checkAuthorized = loginId.substring(0, 3);
if (null != password) {
MD5 md5 = new MD5();
encPassword = md5.getPassword(password);
}
if (checkLoginId == null) {
return "Incorrect loginId..Please enter valid loginId";
} else if (encPassword.equals(uPassword)) {
if (checkAuthorized.equals("STE")) {
List<CompanyMaster> companyList = userService.getCompanyList(OrgLoginId);
return companyList;
} else {
return "You are not Authorized";
}
} else {
return "Incorrect Password";
}

Yes its possible, create a custom Exception say 'MyAppException' and throw that exception with the error message you want.
Write your logic in a try{}catch block and throw the exception in catch so that the response has the error message
public List<CompanyMaster> getCompanies(#RequestBody UserDetails user) throws MyAppppException
{
try
{
//your logic which throws error
return companyList;
}
catch( final MyAppException we )
{
throw new MyAppException("User not found", HttpStatus.NOT_FOUND);
}
}
Refer this link
https://www.codejava.net/java-core/exception/how-to-create-custom-exceptions-in-java

You can achieve this by creating a new presenter Class which contains List and status of type String and change the return type of getCompanies method to presenter class like
public CompaniesPresenter getCompanies()
And your CompaniesPresenter class should look like
public class CompaniesPresenter {
private List<CompanyMaster> companyMaster;
private string status;
//default constructor
public CompaniesPresenter(){
}
//parameterized constructor to return only string in exception case
public CompaniesPresenter(Stirng status){
this.status = status;
}
//parametirized constructor to return success case
public CompaniesPresenter(List<CompanyMaster> companyMaster, Stirng status){
this.companyMaster = companyMaster;
this.status = status;
}
//getters and setters
}
This is how your updated method lokks like
#RequestMapping(value = "/getcompanies", method = RequestMethod.POST)
public CompaniesPresenter getCompanies(#RequestBody UserDetails user) {
String OrgLoginId = user.getOrgLoginId();
String password = user.getuPassword();
String checkLoginId = null;
String uPassword = null;
String encPassword = null;
String loginId = null;
String checkAuthorized = null;
// String loginId=userService.getLoginId(OrgLoginId);
List<Object[]> CheckIdPassword = userService.checkLoginId(OrgLoginId);
List<Object[]> results = CheckIdPassword;
for (Object[] obj : results) {
checkLoginId = obj[0].toString();
if (null == obj[1]) {
uPassword = "";
} else {
uPassword = obj[1].toString();
}
loginId = obj[2].toString();
}
checkAuthorized = loginId.substring(0, 3);
if (null != password) {
MD5 md5 = new MD5();
encPassword = md5.getPassword(password);
}
if (checkLoginId == null) {
return new CompaniesPresenter("Incorrect loginId..Please enter valid loginId");
} else if (encPassword.equals(uPassword)) {
if (checkAuthorized.equals("STE")) {
List<CompanyMaster> companyList = userService.getCompanyList(OrgLoginId);
return new CompaniesPresenter(companyList,"success");
} else {
return new CompaniesPresenter("You are not Authorized");
}
} else {
return new CompaniesPresenter("Incorrect Password");
}
This is not tested please make sure for any compilation errors

vavr's Either class would be a good choice.

The usage of custom exception is most reasonable solution. However, creating custom exception for just one case is not ideal always.
Another solution is to return empty List from your method, check if the List is empty in your servlet (or wherever you are invoking this method from), and show error message there.
It seems like you want to return multiple error messages for different cases. In this case, custom exception is recommended solution. If you don't like custom exceptions, you can return List<Object> and populate error message as the first element in the list. In the place where this List is obtained, check if the first element is instanceOf String or CompanyMaster. Based on what it is, you can perform your operations. This is a weird but possible solution (only if you don't like custom exceptions).

You need to understand the problem first. You are mixing two things here, first authorization, does the user has correct privileges to get company details, second giving the company details itself. Let's understand the first problem when a user tries to access "/getcompanies" endpoint will you let him in if does not have access, in REST world your security model should take care of it. I would use spring security to achieve this. My recommendation would be to explore on "interceptor" and solve the problem of invalid user. This will make your other problem easy as your "/getcompanies" endpoint can focus only on getting the details and return it (SRP).

Spring - in controller I find data from database, but I can't delete these data from database

According to the logic of the application, I have a controller to remove the recycle bin. By the link we get the session id, by it we search for the user in the database and delete all the invoices associated with it.
#RequestMapping(path="/basket/del/{sessId}", method=RequestMethod.DELETE, produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
public BasketListReply delAllProducts(#PathVariable String sessId){
BasketListReply rep = new BasketListReply();
try {
//check if session exist
List<Long> delList = userService.findInvoiceBySessionId(sessId);
//delList contain list of invoices id to delete
if(delList != null) {
for(int i=0;i<delList.size();i++){
invoiceService.delInvoice(delList.get(i));
}
}
}catch(Exception e){
rep.retcode = -1;
rep.error_message = e.getMessage();
}
return rep;
}
With method findInvoiceBySessionId() I get list of invoices from collection () to delete.
public List findInvoiceBySessionId(String sessId) throws Exception{
List list = new ArrayList();
List<Appuser> users = findUserBySessionId(sessId);
if(!users.isEmpty()) {
//if exist, then extract invoices for this user
Appuser u = users.get(0);
List<Invoice> invoices = (List<Invoice>)u.getInvoiceCollection();
for(Invoice inv:invoices) {
list.add(inv.getOrderId());
}
}
return list;
}
Method delInvoice() I use to delete invoice from repository.
public void delInvoice(Long orderId){
if(invoiceRepository.findOne(orderId) == null) {
return;
}
invoiceRepository.delete(orderId);
}
File Appuser.java (field that contain collection of Invoices):
#OneToMany(cascade = CascadeType.ALL, mappedBy = "userId")
private Collection<Invoice> invoiceCollection;
Did I understand correctly that I can not in one controller and extract data from the database via JPA and delete the same data ... since the deletion should go in a separate transaction.
Or am I doing something wrong?
When I delete the data by redirecting the request to the controller to delete the data, everything works fine.

ERROR: cannot execute UPDATE in a read-only transaction

I getting
ERROR: cannot execute UPDATE in a read-only transaction
in the following method at the line with user.update() call:
User user;
try {
user = User.finder.where().eq("phoneNumber", PhoneHelper.normalizePhoneNumber(phoneNumber)).findUnique();
} catch (NumberFormatException e) {
final ErrorMessage errorMessage = new ErrorMessage("Invalid phone number");
errorMessage.addField("phoneNumber");
return badRequest(Json.toJson(errorMessage));
}
...
some checks
...
final String newApiKey;
try {
newApiKey = UUID.randomUUID().toString();
user.addApiKey(newApiKey);
if (!isDemoUser(phoneNumber)) user.setSecurityCode(null);
user.update();
} catch (Exception e) {
Logger.warn("Can't create session", e);
return internalServerError(Json.toJson(new ErrorMessage("Can't create api_key. Please contact service administrator")));
}
return ok(Json.toJson(new ApiKey(newApiKey)));
What could be a reason of this error? I didn't set readOnly value of the transaction to 'true' by myself in this method. Please point me at the direction to search.
User it's just an entity:
#Entity
#Table(name = "userr")
public class User extends Model {
...fields...
public static Finder<Long, User> finder = new Finder<>(User.class);
}
Version of Ebean ORM is
"org.avaje.ebeanorm" % "avaje-ebeanorm" % "6.10.4"

It was just a missing #Transactional on service layer in my case..

JPA conditional insertion

I have a Java Spring based web application and I want to insert a record to a table only if the table does not contain any rows that are "similar" (according to some specific, irrelevant criteria) to the new row.
Because this is a multi-threaded environment, I cannot use a SELECT+INSERT two-step combination as it would expose me to a race condition.
The same question was first asked and answered here and here several years ago. Unfortunately, the questions have got only a little attention and the provided answer is not sufficient to my needs.
Here's the code I currently have and it's not working:
#Component("userActionsManager")
#Transactional
public class UserActionsManager implements UserActionsManagerInterface {
#PersistenceContext(unitName = "itsadDB")
private EntityManager manager;
#Resource(name = "databaseManager")
private DB db;
...
#SuppressWarnings("unchecked")
#Override
#PreAuthorize("hasRole('ROLE_USER') && #username == authentication.name")
public String giveAnswer(String username, String courseCode, String missionName, String taskCode, String answer) {
...
List<Submission> submissions = getAllCorrectSubmissions(newSubmission);
List<Result> results = getAllCorrectResults(result);
if (submissions.size() > 0
|| results.size() > 0) throw new SessionAuthenticationException("foo");
manager.persist(newSubmission);
manager.persist(result);
submissions = getAllCorrectSubmissions(newSubmission);
results = getAllCorrectResults(result);
for (Submission s : submissions) manager.lock(s, LockModeType.OPTIMISTIC_FORCE_INCREMENT);
for (Result r : results ) manager.lock(r, LockModeType.OPTIMISTIC_FORCE_INCREMENT);
manager.flush();
...
}
#SuppressWarnings("unchecked")
private List<Submission> getAllCorrectSubmissions(Submission newSubmission) {
Query q = manager.createQuery("SELECT s FROM Submission AS s WHERE s.missionTask = ?1 AND s.course = ?2 AND s.user = ?3 AND s.correct = true");
q.setParameter(1, newSubmission.getMissionTask());
q.setParameter(2, newSubmission.getCourse());
q.setParameter(3, newSubmission.getUser());
return (List<Submission>) q.getResultList();
}
#SuppressWarnings("unchecked")
private List<Result> getAllCorrectResults(Result result) {
Query q = manager.createQuery("SELECT r FROM Result AS r WHERE r.missionTask = ?1 AND r.course = ?2 AND r.user = ?3");
q.setParameter(1, result.getMissionTask());
q.setParameter(2, result.getCourse());
q.setParameter(3, result.getUser());
return (List<Result>) q.getResultList();
}
...
}
According to the answer provided here I am supposed to somehow use OPTIMISTIC_FORCE_INCREMENT but it's not working. I suspect that the provided answer is erroneous so I need a better one.
edit:
Added more context related code. Right now this code still has a race condition. When I make 10 simultaneous HTTP POST requests approximately 5 rows will get erroneously inserted. Other 5 requests are rejected with HTTP error code 409 (conflict). The correct code would guarantee that only 1 row would get inserted to the database no matter how many concurrent requests I make. Making the method synchronous is not a solution since the race condition still manifests for some unknown reason (I tested it).

Unfortunately after several days of research I was unable to find a short and simple solution to my problem. Since my time budget is not unlimited I had to come up with a workaround. Call it a kludge if you may.
Since the whole HTTP request is a transaction, it will be rolled back at the sight of any conflicts. I am using this for my advantage by locking a special entity within the context of the whole HTTP request. Should multiple HTTP requests be received at the same time, all but one will result in some PersistenceException.
In the beginning of the transaction I am checking whether no other correct answers have been submitted yet. During that check the lock is already effective so no race condition could happen. The lock is effective until the answer is submitted. This basically simulates a critical section as a SELECT+INSERT two step query on the application level (in pure MySQL I would have used the INSERT IF NOT EXISTS construct).
This approach has some drawbacks. Whenever two students submit an answer at the same time, one of them will be thrown an exception. This is sort of bad for performance and bandwidth because the student who received HTTP STATUS 409 has to resubmit their answer.
To compensate the latter, I am automatically retrying to submit the answer on the server side a couple of times between randomly chosen time intervals. See the according HTTP request controller code is below:
#Controller
#RequestMapping("/users")
public class UserActionsController {
#Autowired
private SessionRegistry sessionRegistry;
#Autowired
#Qualifier("authenticationManager")
private AuthenticationManager authenticationManager;
#Resource(name = "userActionsManager")
private UserActionsManagerInterface userManager;
#Resource(name = "databaseManager")
private DB db;
.
.
.
#RequestMapping(value = "/{username}/{courseCode}/missions/{missionName}/tasks/{taskCode}/submitAnswer", method = RequestMethod.POST)
public #ResponseBody
Map<String, Object> giveAnswer(#PathVariable String username,
#PathVariable String courseCode, #PathVariable String missionName,
#PathVariable String taskCode, #RequestParam("answer") String answer, HttpServletRequest request) {
init(request);
db.log("Submitting an answer to task `"+taskCode+"` of mission `"+missionName+
"` in course `"+courseCode+"` as student `"+username+"`.");
String str = null;
boolean conflict = true;
for (int i=0; i<10; i++) {
Random rand = new Random();
int ms = rand.nextInt(1000);
try {
str = userManager.giveAnswer(username, courseCode, missionName, taskCode, answer);
conflict = false;
break;
}
catch (EntityExistsException e) {throw new EntityExistsException();}
catch (PersistenceException e) {}
catch (UnexpectedRollbackException e) {}
try {
Thread.sleep(ms);
} catch(InterruptedException ex) {
Thread.currentThread().interrupt();
}
}
if (conflict) str = userManager.giveAnswer(username, courseCode, missionName, taskCode, answer);
if (str == null) db.log("Answer accepted: `"+answer+"`.");
else db.log("Answer rejected: `"+answer+"`.");
Map<String, Object> hm = new HashMap<String, Object>();
hm.put("success", str == null);
hm.put("message", str);
return hm;
}
}
If for some reason the controller is unable to commit the transaction 10 times in a row then it will try one more time but will not attempt to catch the possible exceptions. When an exception is thrown on the 11th try then it will be processed by the global exception controller and the client will receive HTTP STATUS 409. The global exception controller is defined below.
#ControllerAdvice
public class GlobalExceptionController {
#Resource(name = "staticDatabaseManager")
private StaticDB db;
#ExceptionHandler(SessionAuthenticationException.class)
#ResponseStatus(value=HttpStatus.FORBIDDEN, reason="session has expired") //403
public ModelAndView expiredException(HttpServletRequest request, Exception e) {
ModelAndView mav = new ModelAndView("exception");
mav.addObject("name", e.getClass().getSimpleName());
mav.addObject("message", e.getMessage());
return mav;
}
#ExceptionHandler({UnexpectedRollbackException.class,
EntityExistsException.class,
OptimisticLockException.class,
PersistenceException.class})
#ResponseStatus(value=HttpStatus.CONFLICT, reason="conflicting requests") //409
public ModelAndView conflictException(HttpServletRequest request, Exception e) {
ModelAndView mav = new ModelAndView("exception");
mav.addObject("name", e.getClass().getSimpleName());
mav.addObject("message", e.getMessage());
synchronized (db) {
db.setUserInfo(request);
db.log("Conflicting "+request.getMethod()+" request to "+request.getRequestURI()+" ("+e.getClass().getSimpleName()+").", Log.LVL_SECURITY);
}
return mav;
}
//ResponseEntity<String> customHandler(Exception ex) {
// return new ResponseEntity<String>("Conflicting requests, try again.", HttpStatus.CONFLICT);
//}
}
Finally, the giveAnswer method itself utilizes a special entity with a primary key lock_addCorrectAnswer. I lock that special entity with the OPTIMISTIC_FORCE_INCREMENT flag which makes sure that no two transactions can have overlapping execution times for the giveAnswer method. The respective code can be seen below:
#Component("userActionsManager")
#Transactional
public class UserActionsManager implements UserActionsManagerInterface {
#PersistenceContext(unitName = "itsadDB")
private EntityManager manager;
#Resource(name = "databaseManager")
private DB db;
.
.
.
#SuppressWarnings("unchecked")
#Override
#PreAuthorize("hasRole('ROLE_USER') && #username == authentication.name")
public String giveAnswer(String username, String courseCode, String missionName, String taskCode, String answer) {
.
.
.
if (!userCanGiveAnswer(user, course, missionTask)) {
error = "It is forbidden to submit an answer to this task.";
db.log(error, Log.LVL_MAJOR);
return error;
}
.
.
.
if (correctAnswer) {
.
.
.
addCorrectAnswer(newSubmission, result);
return null;
}
newSubmission = new Submission(user, course, missionTask, answer, false);
manager.persist(newSubmission);
return error;
}
private void addCorrectAnswer(Submission submission, Result result) {
String var = "lock_addCorrectAnswer";
Global global = manager.find(Global.class, var);
if (global == null) {
global = new Global(var, 0);
manager.persist(global);
manager.flush();
}
manager.lock(global, LockModeType.OPTIMISTIC_FORCE_INCREMENT);
manager.persist(submission);
manager.persist(result);
manager.flush();
long submissions = getCorrectSubmissionCount(submission);
long results = getResultCount(result);
if (submissions > 1 || results > 1) throw new EntityExistsException();
}
private long getCorrectSubmissionCount(Submission newSubmission) {
Query q = manager.createQuery("SELECT count(s) FROM Submission AS s WHERE s.missionTask = ?1 AND s.course = ?2 AND s.user = ?3 AND s.correct = true");
q.setParameter(1, newSubmission.getMissionTask());
q.setParameter(2, newSubmission.getCourse());
q.setParameter(3, newSubmission.getUser());
return (Long) q.getSingleResult();
}
private long getResultCount(Result result) {
Query q = manager.createQuery("SELECT count(r) FROM Result AS r WHERE r.missionTask = ?1 AND r.course = ?2 AND r.user = ?3");
q.setParameter(1, result.getMissionTask());
q.setParameter(2, result.getCourse());
q.setParameter(3, result.getUser());
return (Long) q.getSingleResult();
}
}
It is important to note that the entity Global has to have a version annotation in its class for the OPTIMISTIC_FORCE_INCREMENT to work (see code below).
#Entity
#Table(name = "GLOBALS")
public class Global implements Serializable {
.
.
.
#Id
#Column(name = "NAME", length = 32)
private String key;
#Column(name = "INTVAL")
private int intVal;
#Column(name = "STRVAL", length = 4096)
private String strVal;
#Version
private Long version;
.
.
.
}
Such an approach can be optimized even further. Instead of using the same lock name lock_addCorrectAnswer for all giveAnswer calls, I could generate the lock name deterministically from the name of the submitting user. For example, if the student's username is Hyena then the primary key for the lock entity would be lock_Hyena_addCorrectAnswer. That way multiple students could submit answers at the same time without receiving any conflicts. However, if a malicious user spams the HTTP POST method for submitAnswer 10x in parallel they will be prevented by the this locking mechanism.

Spring MVC, attempting to edit but creating new objects

I have an MVC app that is creating new offices instead of updating them on when using an edit form. Please help me understand why this is happening.
Search method that populates the search results:
#RequestMapping(value = "/searchResults", method = RequestMethod.POST)
public ModelAndView search(#RequestParam String searchCriteria, HttpServletRequest request) {
List<Office> offices = officeServiceImpl.search(searchCriteria);
return new ModelAndView("searchResults", "offices", offices);
}
Here's what the link to the edit form looks like on the search results page:
Edit Office
Here is the Controller's edit GET method that populates the form with the existing Office:
#RequestMapping(value = "/{officeId}/edit", method = RequestMethod.GET)
#Transactional(noRollbackFor=NoResultException.class)
public ModelAndView initUpdateOfficeForm(
#PathVariable("officeId") Long officeId, Model model) {
Office office = officeServiceImpl.find(officeId);
//prepareEditFormModelAndView(office) just converts some objects to strings for typeahead form population
return prepareEditFormModelAndView(office);
}
Here is the edit POST method:
#RequestMapping(value = "/{officeId}/edit", method = RequestMethod.POST)
public ModelAndView processUpdateOfficeForm(#ModelAttribute("office") #Valid Office office,
BindingResult result, SessionStatus status) {
if (! "united states of america".equals(office.getFolderStrings().toLowerCase())) {
//This portion of code converts the typeahead strings to objects
result = tryCountries(office, result);
result = tryDepartments(office, result);
result = tryEmployees(office, result);
}
if (result.hasErrors()) {
return prepareEditFormModelAndView(office);
} else {
officeServiceImpl.save(office);
status.setComplete();
return new ModelAndView("editResult", "office", office);
}
}
officeServiceImpl calls officeRepositoryImpl method save which looks like:
#Override
public Office save(Office office) {
em.merge(office);
em.flush();
return office;
}
Thanks
Edit: Adding prepareEditFormModelAndView(office), This method attempts to build strings from associated objects:
#Transactional(noRollbackFor={NoResultException.class, IndexOutOfBoundsException.class})
private ModelAndView prepareEditFormModelAndView(Office office) {
String departmentStrings = "";
String employeeStrings = "";
List<OOM> officeOOMs = new ArrayList<OOM>();
StringBuilder sb = new StringBuilder();
try {
officeOOMs = oomServiceImpl.getOOMsForCurrentOffice(office.getId());
} catch (NoResultException e) {
officeOOMs = null;
}
for (OOM o : officeOOMs) {
try {
Employee tempEmployee = employeeServiceImpl.find(o
.getEmployeeId());
sb.append(tempEmployee.getDisplayName() + ", ");
} catch (NoResultException e) {
sb.append("Not found in system");
}
}
employeeStrings = sb.toString();
if ((! "".equals(office.getDepartmentStringsOnForm())) && office.getDepartmentStringsOnForm() != null) {
departmentStrings = office.getDepartmentStringsOnForm();
}
String folderStrings = "";
try {
folderStrings = kmlFolderServiceImpl.getInternationalOfficeString(office.getId());
LOGGER.info("Folder Strings: " + folderStrings);
} catch (NoResultException e) {
folderStrings = "";
LOGGER.info("Folder Strings: " + "no result");
}
boolean isInternational = office.isInternational();
ModelAndView result = new ModelAndView("editOfficeForm", "office", office);
result.addObject("departmentStrings", departmentStrings);
result.addObject("isInternational", isInternational);
result.addObject("folderStrings", folderStrings);
result.addObject("employeeStrings", employeeStrings);
return result;
}

I am adding a previous comment here, for better clarification. According to the OP the following fixes the problem:
When the ID is not in the form then when the model is posted back no ID is set to the entity making the persistence provider believe it is new entity.
Therefor the most obvious solution is to post the ID of the entity as well in the save operation (probably using a hidden field).
Another solution would be to try to load the entity in the database based on some business key
to see if the entity is new or not.