如何解决 Java - JSP Wrong Class Cast？
如何解决 Java - JSP Wrong Class Cast？
提问于 2018-08-02 01:15:43
我有一个非常奇怪的错误，似乎是JSPRuntime或反射API的一个错误，以下是我的代码：
public class LB {
private ArrayList<Class> classes = new ArrayList<>();
public ArrayList<Class> getClasses() {
return classes;
}
public void setClasses(ArrayList<Class> classes) {
this.classes = classes;
}
}
public enum Class {
EINSBHIT("1BHIT"),
EINSAHIT("1AHIT"),
ZWEIBHIT("2BHIT"),
ZWEIAHIT("2AHIT"),
DREIBHIT("3BHIT"),
DREIAHIT("3AHIT");
private final String id;
private Class(String id) {
this.id = id;
}
public String getId() {
return id;
}
@Override
public String toString() {
return id;
}
public static Class getByName(String name) {
for (Class c : values())
if(c.getId().equals(name))
return c;
return null;
}
}所以我有一个JSP页面，需要ArrayList：
ArrayList<LB> dayLbs = LBManager.getDayLbs(d);
for(LB lb : dayLbs){
System.out.println("Entry Class : "lb.getClasses().get(0).getClass());
ArrayList<Class> classes = lb.getClasses();
for(Object c : classes){
System.out.println("Entry class : "+c.getClass());
}
} And honestly this code doesnt makes sense right? Yes you are right! But listen why i changed the code to this.
代码的输出如下：
List Class : class java.util.ArrayList
Entry class : class java.lang.String
Entry class : class java.lang.String
Entry class : class java.lang.String
List Class : class java.util.ArrayList
Entry class : class java.lang.String
Entry class : class java.lang.String如果我写：for(Class c : classes){虽然没有出现编译器错误，但是如果我调用页面，就会得到：
org.apache.jasper.JasperException: An exception occurred processing JSP page /assets/comps/eintragung.jsp at line 66
63: lbloop:for(LB lb : dayLbs){
64: System.out.println("List Class : "+lb.getClasses().getClass());
65: ArrayList<Class> classes = lb.getClasses();
66: for(Class c : classes){
67: System.out.println("Entry class : "+c.getClass());
68: if(c.toString().equals(css.getId())){
69: java.lang.ClassCastException: java.lang.String cannot be cast to com.lb.logic.Class
org.apache.jsp.assets.comps.eintragung_jsp._jspService(eintragung_jsp.java:24
2)该如何解决呢？
<%@page import="java.io.IOException"%>
<%@page import="com.lb.logic.student.DayPlan"%>
<%@page import="com.lb.logic.student.WeekPlan"%>
<%@page import="com.lb.utilitys.TimeManager"%>
<%@page import="com.lb.threads.EMailSenderSceduler"%>
<%@page import="com.lb.utilitys.LBManager"%>
<%@page import="com.lb.logic.lb.LB"%>
<%@page import="com.lb.logic.student.Student"%>
<%@page import="com.lb.inet.logic.CookieManager"%>
<%@page import="com.lb.logic.Lesson"%>
<%@page import="java.io.File"%>
<%@page import="java.io.FileFilter"%>
<%@page import="com.niton.media.filesystem.Directory"%>
<%@page import="java.util.ArrayList"%>
<%@page import="de.codeschnipsel.simple.mail.Email"%>
<%@page import="java.util.Locale"%>
<%@page import="com.lb.logic.Day"%>
<%@page import="java.util.Calendar"%>
<%@page import="java.util.GregorianCalendar"%>
<%@page import="com.lb.logic.Class"%>
<%@page import="com.lb.inet.logic.AccountManager"%>
<%
System.out.println("Eintragung.jsp request");
request.setCharacterEncoding("UTF-8");
%>
<%
Student s = CookieManager.getSession(request);
if (s == null) {
System.out.println("Redirect : 25");
response.sendRedirect("index.jsp?page=login&msg=Anmeldungs-cookie%20ungültig!");
%>
<meta http-equiv="refresh" content="0; url=index.jsp?page=login&msg=Anmeldungs-cookie%20ungültig!">
<%
return;
} else {
Class css = s.getSchoolClass();
if (request.getParameter("msg") != null)
out.print("<script>alert(\"" + request.getParameter("msg") + "\");</script>");
%>
<div id="daybox">
<form action="Writer" method="post">
<%
request.setCharacterEncoding("UTF-8");
Day today = Day.getToday();
ArrayList<LB> todayLbs = LBManager.getTodayLbs();
boolean lbLeft = false;
int mins = TimeManager.getMinutesTill8();
for (LB l : todayLbs) {
if (!(l.getTable().getLessons(today).get(0).from - EMailSenderSceduler.minsBevore < mins)) {
lbLeft = true;
}
}
int index = today.getIndex();
WeekPlan studentsPlan = s.getThisWeek();
for (int i = 0; i < Day.SATURDAY.getDaysAfter().size(); i++) {
Day d = Day.SATURDAY.getDaysAfter().get(i);
DayPlan dayPlan = studentsPlan.get(d);
if (d == Day.SATURDAY || d == Day.SUNDAY) {
continue;
}
ArrayList<LB> dayLbs = LBManager.getDayLbs(d);
ArrayList<LB> dayClassLBs = new ArrayList<>();
lbloop:for(LB lb : dayLbs){
System.out.println("List Class : "+lb.getClasses().getClass());
ArrayList<Class> classes = lb.getClasses();
for(Class c : classes){
System.out.println("Entry class : "+c.getClass());
if(c.toString().equals(css.getId())){
dayClassLBs.add(lb);
continue lbloop;
}
}
}
%>
<div class="day">
<h1><%=d.name%></h1>
<h2>Vormittag</h2>
<h2>Nachmittag</h2>
<br> <span> <%
Calendar cal = GregorianCalendar.getInstance();
if (!lbLeft) {
cal.set(Calendar.DAY_OF_YEAR, (cal.get(Calendar.DAY_OF_YEAR) - index));
}
cal.set(Calendar.DAY_OF_YEAR, (cal.get(Calendar.DAY_OF_YEAR) + i));
out.print(cal.get(Calendar.DAY_OF_MONTH) + "." + (cal.get(Calendar.MONTH) + 1) + "."
+ cal.get(Calendar.YEAR));
%>
</span>
<select name="<%=d.name%>-morning">
<%
//Der Tag der momentanen Schleife ist vor heute -> nicht änderbar
boolean done = false;
if(d.isBevore(today)){
writeOverLB(dayPlan, dayClassLBs, out, d,false);
done = true;
}else{
//Der tag kommt noch eintragungsmöglichkeit
if(d == today){
int noonLBstart = 250;
for(LB lb : dayClassLBs)
if(lb.getTable().getLessons(d).get(0).from < 250){
noonLBstart = lb.getTable().getLessons(d).get(0).from;
}
if(noonLBstart-EMailSenderSceduler.minsBevore < TimeManager.getMinutesTill8()){
writeOverLB(dayPlan, dayClassLBs, out, d,true);
done = true;
}
}
if(!done){
%>
<option value="none">Nicht Eingetragen</option>
<%
for (LB lb : dayClassLBs) {
if (lb.getTable().getLessons(d).get(0).from < 250) {
boolean isIn = false;
for (Student sx : lb.getCurrentWeek().getRegistrations(d)) {
if (sx.getName().equals(s.getName()))
isIn = true;
}
out.print("<option value=\"" + lb.getName() + "\" "
+ (isIn ? "selected=\"selected\"" : "") + ">" + lb.getSubject().getName()
+ " - " + lb.getTeacher().name.split(" ")[1] + " "
+ lb.getCurrentWeek().getRegistrations(d).size() + "/" + lb.getCapacity() + "</option>");
}
}
}
}
%>
</select>
<select name="<%=d.name%>-afternoon">
<%
//Der Tag der momentanen Schleife ist vor heute -> nicht änderbar
if(d.isBevore(today)){
if(dayPlan.getAfterNoonLb().equals("none"))
out.print("<option selected=\"selected\"> Nicht eingetragen </option>");
else{
writeOverLB(dayPlan, dayClassLBs, out, d,false);
}
done = true;
}else{
//Der tag kommt noch eintragungsmöglichkeit
if(d == today){
int afternoonLBstart = 250;
for(LB lb : dayClassLBs)
if(lb.getTable().getLessons(d).get(0).from > 230){
afternoonLBstart = lb.getTable().getLessons(d).get(0).from;
}
if(afternoonLBstart-EMailSenderSceduler.minsBevore < TimeManager.getMinutesTill8()){
writeOverLB(dayPlan, dayClassLBs, out, d,false);
done = true;
}
}
if(!done){
%>
<option value="none">Nicht eingetragen</option>
<%
for (LB lb : dayClassLBs) {
if (lb.getTable().getLessons(d).get(0).from > 250) {
boolean isIn = false;
for (Student sx : lb.getCurrentWeek().getRegistrations(d)) {
if (sx.getName().equals(s.getName()))
isIn = true;
}
out.print("<option value=\"" + lb.getName() + "\" "
+ (isIn ? "selected=\"selected\"" : "") + ">" + lb.getSubject().getName()
+ " - " + lb.getTeacher().name.split(" ")[1] + " "
+ lb.getCurrentWeek().getRegistrations(d).size() + "/" + lb.getCapacity() + "</option>");
}
}
}
}
%>
</select>
</div>
<%
}
%>
<input type="submit" value="Eintragen">
</form>
</div>
<%
}
%>
<%!
public void writeOverLB(DayPlan dayPlan,ArrayList<LB> dayClassLBs,JspWriter out,Day d,boolean noon) throws IOException{
if(dayPlan.getNoonLb().equals("none"))
out.print("<option selected=\"selected\"> Nicht eingetragen </option>");
else{
LB lb = null;
for(LB dclb : dayClassLBs)
if(dclb.getName().equals(noon ? dayPlan.getNoonLb() : dayPlan.getAfterNoonLb()))
lb = dclb;
if(lb == null){
out.print("<option value=\"" + lb.getName() + "\" "
+ "selected=\"selected\">" + (noon ? dayPlan.getNoonLb() : dayPlan.getAfterNoonLb()) + "</option>");
}else
out.print("<option value=\"" + lb.getName() + "\" "
+ "selected=\"selected\">" + lb.getSubject().getName()
+ " - " + lb.getTeacher().name.split(" ")[1] + " "
+ lb.getCurrentWeek().getRegistrations(d).size() + "/" + lb.getCapacity() + "</option>");
}
}
%>
package com.lb.utilitys;
import java.util.ArrayList;
import com.lb.logic.Day;
import com.lb.logic.lb.LB;
import com.niton.media.filesystem.Directory;
public class LBManager {
private static ArrayList<LB> lbs;
public static ArrayList<LB> getAllLbs() {
if (lbs == null)
readAllLbs();
return lbs;
}
private static void readAllLbs() {
try {
Directory d = new Directory(System.getProperty("user.home")).addAndSaveDir("lbs");
ArrayList<Directory> all = d.getSubFolder();
lbs = new ArrayList<>();
for (Directory directory : all) {
LB lb = LB.read(directory);
lbs.add(lb);
}
} catch (Exception e) {
Log.log(e, "Fehler beim lesen der Lernbüros");
}
}
/**
* Filtert alle LBs von Heute Aus dem Array und gibt die Richtigen als
* {@link ArrayList} zurück
*
* @param all
* die Lernbüros aus denen die heutigen gefiltert werden sollen
* @return die Heutigen Lernbüros
*/
public static ArrayList<LB> getTodayLbs() {
return getDayLbs(TimeManager.getToday());
}
/**
* Filtert alle LBs von D Aus dem Array und gibt die Richtigen als
* {@link ArrayList} zurück
*
* @param d
* der zu filterte Tag
* @return die an diesem Tag stattfindenden Lernbüros
*/
public static ArrayList<LB> getDayLbs(Day d) {
ArrayList<LB> today = new ArrayList<>();
for (LB lb : lbs) {
if (lb.getTable().getLessons(d).size() > 0)
today.add(lb);
}
return today;
}
public static void saveAll() {
for (LB lb : lbs) {
try {
lb.save(new Directory(System.getProperty("user.home")));
} catch (Exception e) {
Log.log(e, "Error during saving LB");
}
}
}
public static LB getLB(String name) {
for (LB lb : lbs)
if(lb.getName().equals(name))
return lb;
return null;
}
}
package com.lb.logic.lb;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import javax.crypto.BadPaddingException;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
import com.lb.logic.Class;
import com.lb.logic.Subject;
import com.lb.logic.Teacher;
import com.niton.media.crypt.SimpleAES;
import com.niton.media.filesystem.Directory;
import com.niton.media.filesystem.NFile;
import com.niton.media.json.JsonArray;
import com.niton.media.json.JsonObject;
/**
* Eine Klasse die ein Lernbüro repräsentiert<br>
* sie speichert die einzelnen Stundenblöcke und die dafür eingetragenen
* Schüler!
*
* @author NilsBrugger, Max Frühmann
* @serial Serializable
*/
public class LB {
public static LB read(Directory parent) throws IOException, ClassNotFoundException, InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidAlgorithmParameterException, IllegalBlockSizeException, BadPaddingException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
LB lb = new LB();
readData(parent,lb);
readTimetable(parent,lb);
NFile keyFile = new NFile(parent, "key", "store");
// SecretKey key = (SecretKey) keyFile.readData();
// keyFile.getInputStream().close();
// keyFile.delete();
SecretKey key = null;
readCurrent(parent,lb,key);
readOldRegistrations(parent,lb,key);
return lb;
}
private static void readCurrent(Directory d, LB lb, SecretKey key) throws InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidAlgorithmParameterException, IllegalBlockSizeException, ClassNotFoundException, BadPaddingException, IOException {
NFile cur = new NFile(d, "current", "data");
// lb.setCurrentWeek((WeekRegistrations) SimpleAES.decryptObject((SealedObject) cur.readData(), key));
lb.setCurrentWeek((WeekRegistrations) cur.readData());
}
private static void readData(Directory d, LB lb) throws IOException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
NFile dataFile = new NFile(d, "data", "json");
JsonObject data = (JsonObject) dataFile.readJson();
data.read(lb);
}
private static void readOldRegistrations(Directory d, LB lb, SecretKey key) throws InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidAlgorithmParameterException, IllegalBlockSizeException, ClassNotFoundException, BadPaddingException, IOException {
d = d.addDir("old");
ArrayList<WeekRegistrations> weeks = new ArrayList<>();
for (NFile weekRegistration : d.getSubFiles()) {
if(weekRegistration.getAbsolutePath().endsWith(".data")) {
// weeks.add((WeekRegistrations) SimpleAES.decryptObject((SealedObject) weekRegistration.readData(), key));
weeks.add((WeekRegistrations) weekRegistration.readData());
}
}
lb.setWeeks(weeks);
}
@SuppressWarnings("unchecked")
private static void readTimetable(Directory d, LB lb) throws IOException, ClassNotFoundException {
NFile tableFile = new NFile(d, "timetable", "json");
Timetable tt = new Timetable();
tt.read((JsonArray<JsonObject>) tableFile.readJson());
lb.setTable(tt);
}
/**
* Der gegenstand der unterrichtet wird
*/
private Subject subject;
/**
* Maximale Kapazität des Raumes
*/
private int capacity = 20;
/**
* Der Lehrer der dieses LB betreuen wird
*/
private Teacher teacher;
/**
* Klassen mit Zugriff auf dieses Lernbüro
*/
private ArrayList<Class> classes = new ArrayList<>();
private transient Timetable table;
private transient ArrayList<WeekRegistrations> weeks = new ArrayList<>();
private transient WeekRegistrations currentWeek = new WeekRegistrations();
private String name;
public int getCapacity() {
return capacity;
}
public ArrayList<Class> getClasses() {
return classes;
}
public WeekRegistrations getCurrentWeek() {
return currentWeek;
}
public String getName() {
return name;
}
// public ArrayList<Student> getStudentsFor(Day d) {
// if (d == null)
// return null;
// switch (d) {
// case FRIDAY:
// return getStudentsOnFr();
// case MONDAY:
// return getStudentsOnMo();
// case THUESDAY:
// return getStudentsOnDi();
// case THURESDAY:
// return getStudentsOnDo();
// case WEDNESDAY:
// return getStudentsOnMi();
// case SATURDAY:
// case SUNDAY:
// return new ArrayList<>();
// default:
// return null;
// }
// }
public Subject getSubject() {
return subject;
}
public Timetable getTable() {
return table;
}
public Teacher getTeacher() {
return teacher;
}
public ArrayList<WeekRegistrations> getWeeks() {
return weeks;
}
public void save(Directory parent) throws Exception {
Directory d = parent.addAndSaveDir("lbs").addAndSaveDir(getName());
saveData(d);
saveTimetable(d);
SecretKey key = SimpleAES.generateKey(128);
NFile keyFile = new NFile(d, "key", "store");
keyFile.save();
keyFile.write(key);
saveCurrent(d,key);
saveOldRegistrations(d,key);
}
private void saveCurrent(Directory d,SecretKey key) throws IOException, InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidAlgorithmParameterException, IllegalBlockSizeException {
NFile cur = new NFile(d, "current", "data");
// cur.write(SimpleAES.encryptObject(currentWeek, key));
cur.write(currentWeek);
}
private void saveData(Directory d) throws Exception {
NFile dataFile = new NFile(d, "data", "json");
if(dataFile.exisits())
dataFile.delete();
dataFile.save();
JsonObject data = new JsonObject(this);
dataFile.write(data);
}
private void saveOldRegistrations(Directory d, SecretKey key) throws IOException, InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidAlgorithmParameterException, IllegalBlockSizeException {
d = d.addAndSaveDir("old");
int i = 0;
for (WeekRegistrations weekRegistrations : weeks) {
NFile nf = new NFile(d, "School Week "+i, "data");
// nf.write(SimpleAES.encryptObject(weekRegistrations,key));
nf.write(weekRegistrations);
}
}
private void saveTimetable(Directory d) throws IOException {
NFile tableFile = new NFile(d, "timetable", "json");
if(tableFile.exisits())
tableFile.delete();
tableFile.write(table.getJSON());
}
public void setCapacity(int capacity) {
this.capacity = capacity;
}
public void setClasses(ArrayList<Class> classes) {
this.classes = classes;
}
public void setCurrentWeek(WeekRegistrations currentWeek) {
this.currentWeek = currentWeek;
}
public void setName(String name) {
this.name = name;
}
public void setSubject(Subject subject) {
this.subject = subject;
}
public void setTable(Timetable table) {
this.table = table;
}
public void setTeacher(Teacher teacher) {
this.teacher = teacher;
}
public void setWeeks(ArrayList<WeekRegistrations> weeks) {
this.weeks = weeks;
}
public void newWeek() {
weeks.add(currentWeek);
currentWeek = new WeekRegistrations();
}
}回答 1
Stack Overflow用户
发布于 2018-08-02 10:35:20
如果你把它改为for(Class c : classes)，那么在这种情况下也应该将其更改为c.getId()，还有为什么要用c.toString()？应该用c.name()吧
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/-100001856
复制相关文章
相似问题
腾讯云开发者
