Java抛出错误的异常

Question

I have created 2 custom exceptions to handle creating and persisting new users to a DB. The email (username) is the unique ID so if an email is duplicated an exception should be thrown since the unique ID already exists. I'm also doing a password confirmation match. This confirmation match also will throw a custom exception of passwords don't match. These 2 piece work correctly independently of each other, however, when I put everything together and test, if a password confirmation fails its throwing the username already exists exception instead of passwords do not match exception. Why?

I've tried reordering the code but that doesn't seem to matter. I also tried if/else rather then just if but got the same results

        //Username(email) must be unique
        try {
            //password and confirm password must match
            if (!newGcUser.getPassword().equals(newGcUser.getConfirmPassword())) {
                throw new PasswordMatchException("password and confirm password does not match");
            } 
                //if passwords match - persist to DB
                newGcUser.setPassword(bCryptPasswordEncoder.encode(newGcUser.getPassword()));
                //Do NOT persist or show the confirm Password
                newGcUser.setConfirmPassword("");
                //set user
                newGcUser.setName(newGcUser.getUsername());
                return userRepository.save(newGcUser);

        } catch (Exception e) {
            throw new UsernameAlreadyExistsException("Username: '" + newGcUser.getUsername() + "' already exists.");
        }

    } 

I'm using Postman to test. If I test an email I know isn't registered and mismatch the passwords I get the UsernameAlreadyExistsException message instead of the PasswordMatchException

Answer 1

This happens because your try {} catch (Exception e) {} block is catching the exception you're throwing within the block, throw the exception outside the try catch block and it should work catch :

    // password and confirm password must match
    if (!newGcUser.getPassword().equals(newGcUser.getConfirmPassword())) {
        throw new PasswordMatchException("password and confirm password does not match");
    }

    // Username(email) must be unique
    try {
        // if passwords match - persist to DB
        newGcUser.setPassword(bCryptPasswordEncoder.encode(newGcUser.getPassword()));
        // Do NOT persist or show the confirm Password
        newGcUser.setConfirmPassword("");
        // set user
        newGcUser.setName(newGcUser.getUsername());
        return userRepository.save(newGcUser);

    } catch (Exception e) {
        throw new UsernameAlreadyExistsException("Username: '" + newGcUser.getUsername() + "' already exists.");
    }

(or catch a less generic exception eg the exception which is thrown from userRepository.save and rethrow it, then it will only catch that exception rather than all)

Answer 2

This is happening because your PasswordMatchException extends Exception and your catch block is catching it and throwing a UsernameAlreadyExistsException .

Reducing your code down to illustrate my point:

try {
     throw new PasswordMatchException();
} catch(Exception e) {
     throw new UsernameAlreadyExistsException();
}

Without knowing more about what kinds of exceptions your code can throw, you probably have two solutions:

1) Catch something more specific than Exception .

2) Move the password check outside your try/catch block.

Answer 3

Advise to break into different methods and make it modular:

private void matchPassword(..newGcUser..) throws PasswordMatchException{
// password and confirm password must match
    if (!newGcUser.getPassword().equals(newGcUser.getConfirmPassword())) {
        throw new PasswordMatchException("password and confirm password does not match");
    }
}

Method to persist should catch the specific exception:

// Username(email) must be unique
try {
    // if passwords match - persist to DB
   ...
    return userRepository.save(newGcUser);

} catch (DataIntegrityViolationException e) {
    throw new UsernameAlreadyExistsException("Username: '" + newGcUser.getUsername() + "' already exists.");
}