java - 减少方法中返回语句的数量

Question

我有一个 java 代码，其中在一个方法中有多个 return 语句。但是出于代码清理的目的，每个方法只能有一个返回语句。可以做些什么来克服这个问题。

这是我的代码中的一个方法:-

public ActionForward login(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception {

        // Kill any old sessions
        //request.getSession().invalidate();
        DynaValidatorForm dynaform = (DynaValidatorForm)form;

        // validate the form
        ActionErrors errors = form.validate(mapping, request);
        if(!errors.isEmpty()) {
            this.saveErrors(request, errors);
            return mapping.getInputForward();
        }

        // first check if token is set
        if(!isTokenValid(request, true)) {
            String errmsg="There was a problem with your login. Please close your browser then reopen it and try again. Make sure to click the Login button only ONCE.";
            request.setAttribute("errormessage", errmsg);
            saveToken(request);
            return mapping.findForward(ConstantLibrary.FWD_CONTINUE);
        }

        // check the form for input errors
        String errmsg = checkInput(form);
        if (errmsg != null) {
            request.setAttribute("errormessage", errmsg);
            saveToken(request);
            return mapping.findForward(ConstantLibrary.FWD_CONTINUE);
        }

        // no input errors detected
        String resumekey = null;
        // check for valid login
        ObjectFactory objFactory = ObjectFactory.getInstance();
        DataAccessor dataAccessor = objFactory.getDataAccessor();

        request.setCharacterEncoding("UTF-8");
        String testcode = dynaform.getString("testcode").trim();
        String studentname =  dynaform.getString("yourname").trim();


        String password = dynaform.getString("password").trim();

        // 4/3/07 - passwords going forward are ALL lower case
        if (!CaslsUtils.isEmpty(password)) {
            password = password.toLowerCase();
        }

        try{
               resumekey = new String(studentname.getBytes("ISO-8859-1"),"UTF-8");

            } catch (Exception e) {
                log_.error("Error converting item content data to UTF-8 encoding. ",e);
            }

        String hashWord = CaslsUtils.encryptString(password);
        // Make sure this is short enough to fit in the db
        if (hashWord.length() > ConstantLibrary.MAX_PASSWORD_LENGTH) {
            hashWord = hashWord.substring(0, ConstantLibrary.MAX_PASSWORD_LENGTH);
        }

        Login login = dataAccessor.getLogin(testcode, hashWord, false);

        if (login == null || !login.getUsertype().equals(Login.USERTYPE_SUBJECT)) {
            request.setAttribute("errormessage", "Incorrect test code or password.");
            saveToken(request);
            return mapping.findForward(ConstantLibrary.FWD_CONTINUE);
        }

        // Check if the login has expired
        if (login.getLoginexpires() != null && login.getLoginexpires().before(new Date())) {
            request.setAttribute("errormessage", "Your login has expired.");
            saveToken(request);
            return mapping.findForward(ConstantLibrary.FWD_CONTINUE);
        }

        // Check if the password has expired
        if (login.getPasswordexpires() != null && login.getPasswordexpires().before(new Date())) {
            request.setAttribute("errormessage", "Your login password has expired.");
            saveToken(request);
            return mapping.findForward(ConstantLibrary.FWD_CONTINUE);
        }

        HttpSession session = request.getSession();
        session.setAttribute(ConstantLibrary.SESSION_LOGIN, login);
        session.setAttribute(ConstantLibrary.SESSION_STUDENTNAME, studentname);
        List<Testtaker> testtakers = null;
        try {
            //invalidate the old session if the incoming user is already logged in.
            synchronized(this){
            invalidateExistingSessionOfCurrentUser(request, studentname, testcode); 
            testtakers = dataAccessor.getTesttakersByResumeKey(studentname, login);// Adding this code to call getTesttakersByResumeKey instead of getTesttakers to improve the performance of the application during student login
            }
        } catch (Exception e) {
            log.error("Exception when calling getTesttakers");
            CaslsUtils.outputLoggingData(log_, request);
            throw e;
        }
        session = request.getSession();
        if(testtakers!=null)
        {
        if(testtakers.size() == 0) {
            // new student -> start fresh
            log_.debug("starting a fresh test");

            // if this is a demo test, skip the consent pages and dump them directly to the select test page
            if (login.getTestengine().equals(Itemmaster.TESTENGINE_DEMO)) {
                return mapping.findForward("continue-panel");
            }
        }
            // send them to fill out the profile

            // check for custom profiles
            String[] surveynames = new String[4];
            List<Logingroup> logingroups = dataAccessor.getLoginGroupsByLogin(login.getLoginid());
            for(Logingroup logingroup : logingroups) {
                Groupmaster group = logingroup.getGroupmaster();
                log_.debug(String.format("group: {groupid: %d, grouptype: %s, groupname: %s}", new Object[] {group.getGroupid(), group.getGrouptype(), group.getName()}));
                Set<Groupsurvey> surveys = group.getGroupsurveys();
                if(surveys.size() > 0) {
                    // grab the first (and only) one
                    Groupsurvey survey = surveys.toArray(new Groupsurvey[0])[0];
                    if(group.getGrouptype().equalsIgnoreCase(Groupmaster.GROUPTYPE_CLASS)) {
                        surveynames[0] = survey.getSurveyname();
                    } else if (group.getGrouptype().equalsIgnoreCase(Groupmaster.GROUPTYPE_SCHOOL)){
                        surveynames[1] = survey.getSurveyname();
                    } else if (group.getGrouptype().equalsIgnoreCase(Groupmaster.GROUPTYPE_DISTRICT)){
                        surveynames[2] = survey.getSurveyname();
                    } else if (group.getGrouptype().equalsIgnoreCase(Groupmaster.GROUPTYPE_STATE)){
                        surveynames[3] = survey.getSurveyname();
                    }
                }
            }

            // match the most grandular survey
            for(int i=0; i < surveynames.length; ++i) {
                if(surveynames[i] != null) {
                    saveToken(request);
                    return mapping.findForward("student-profile-"+surveynames[i]);
                }
            }
            // no custom profile, send them to the default
            saveToken(request);
            return mapping.findForward("student-profile");
        }

        // get the set of availible panels
        Set<Panel> availiblePanels = dataAccessor.getAvailiblePanels(login, studentname);
        if(availiblePanels.size() == 0) {
            // no panels availible.  send to all done!
            log_.debug(String.format("No panels availible for Login:%s with resumekey:%s", login.toString(), studentname));
            session.setAttribute("logoutpage", true);
            resetToken(request);
            return mapping.findForward("continue-alldone");
        }
        //Eventum #427 - Prevent test takers from retaking a finished test.
        TestSubjectResult testSubjecResult=dataAccessor.getTestSubjectResult(login, resumekey);
        if(testSubjecResult != null){
            if(testSubjecResult.getRdscore() != null && testSubjecResult.getWrscore() != null && testSubjecResult.getLsscore() != null && testSubjecResult.getOlscore() != null){
                if(testSubjecResult.getRdscore().getFinishtime() != null && testSubjecResult.getWrscore().getFinishtime() != null && testSubjecResult.getLsscore().getFinishtime() != null && testSubjecResult.getOlscore().getFinishtime() != null){
                    log_.debug(String.format("Already completed all the Skill Tests.", login.toString(), studentname));
                    session.setAttribute("logoutpage", true);
                    resetToken(request);
                    return mapping.findForward("continue-alldone");
                }
            }
        }
        // get a list of resumeable testtakers
        List<Testtaker> resumeableTesttakers = new ArrayList<Testtaker>();
        for(Testtaker testtaker : testtakers) {
            if(testtaker.getPhase().equals(ConstantLibrary.PHASE_GOODBYE)) {
                // testtaker is done with test.  skip.
                continue;
            }
            if(testtaker.getCurrentpanelid() == null) {
                // testtaker is the profile testtaker
                continue;
            }
            resumeableTesttakers.add(testtaker);
        }
        // sort them from least recent to latest
        Collections.sort(resumeableTesttakers, new Comparator<Testtaker>() {
            @Override
            public int compare(Testtaker o1, Testtaker o2) {
                // TODO Auto-generated method stub
                //return 0;
                return new CompareToBuilder()
                    .append(o1.getLasttouched(), o2.getLasttouched())
                    .toComparison();
            }
        });

        if(resumeableTesttakers.size() == 0 && availiblePanels.size() > 0) {
            // nobody is resumeable but there are panels left to take
            // send them to the panel choice
            // TODO: This is probably a misuse of Struts.
            log_.info("No resumeable testtakers. Sending to panel select");
            saveToken(request);
            ActionForward myForward = (new ActionForward("/do/capstartpanel?capStartPanelAction=retest&lasttesttakerid="
                    + testtakers.get(0).getTesttakerid(), true));
            return myForward;// mapping.findForward(ConstantLibrary.FWD_CONTINUE + "-panel");
        } else {
            // grab the one most recently created and take their test
            log_.info(String.format("Resuming with choice of %d testtakers", resumeableTesttakers.size()));
            // we're forwarding to resume at this point, so we should do the some of the initialization
            // that would have happened if we were still using getTesttaker() instead of getTesttakers() above.

            session.setAttribute(ConstantLibrary.SESSION_LOGIN, login);
            session.setAttribute(ConstantLibrary.SESSION_TESTTAKER, resumeableTesttakers.get(resumeableTesttakers.size()-1));
            saveToken(request);
            return mapping.findForward(ConstantLibrary.FWD_RESUME);
        }

    }

Answer 1

将每个方法的多个返回更改为单个返回语句是不值得的。实际上，这会不必要地增加将结果存储在局部变量中然后最终返回的负担，

ActionForward result = null;
//scenario 1 
result = ... 
//scenario 2
result = ...
//scenario 3
result = ...
//finally
return result;

希望这对我有帮助，但是，这对我来说意义不大