java - Retrieving data from JSP-Class (MVC with Servlet) -

im working on school project me , group supposed build mvc-project have classes building , room. relation onetomany, building-(onetomany)-room. problem occurs when want search building name , later show rooms in building. can extract relevant data when run our servlet without our jsp, when start project running our searchbuilding.jsp can type building name, , when expected see connected rooms, instead message "java.lang.classcastexception: java.util.arraylist cannot cast org.ics.ejb.room". might bit messy code appreciate if me spot problem since im supposed show professor tomorrow.

this our code: building:

@entity     @table(name = "building")     public class building {     private string bname; private list<room> rooms; // building can have many rooms  @id @column(name = "bname") public string getbname() {     return bname; }  public void setbname(string bname) {     this.bname = bname; }  @onetomany(mappedby = "building", fetch = fetchtype.eager) public list<room> getrooms() {     return rooms; }  public void setrooms(list<room> rooms) {     this.rooms = rooms; }    

}

room:

@namedqueries({ @namedquery(name="room.findbybname",  query="select r room r r.bname :bname"), })  @entity @table(name = "room") public class room implements serializable { /**  *   */ private static final long serialversionuid = 1l; private roomid id; private string bname; private building building;  public string getbname() {     return bname; }  public void setbname(string bname) {     this.bname = bname; }  @id public roomid getid() {     return id; }  public void setid(roomid id) {     this.id = id; }  @manytoone @joincolumn(name = "bname", insertable = false, updatable = false) public building getbuilding() {     return this.building; }  public void setbuilding(building building) {     this.building = building; } } 

roomid:

@embeddable public class roomid implements serializable {  private string bname; private string rcode;  public roomid() { }  public roomid(string bname, string rcode) {     this.bname = bname;     this.rcode = rcode; }  @column(name = "bname", nullable = false) public string getbname() {     return bname; }  public void setbname(string bname) {     this.bname = bname; }  @column(name = "rcode", nullable = false) public string getrcode() {     return rcode; }  public void setrcode(string rcode) {     this.rcode = rcode; }  public boolean equals(object other) {     if ((this == other)) {         return true;     }      if ((other == null)) {         return false;     }      if (!(other instanceof roomid)) {         return false;     }      roomid castother = (roomid) other;      return ((this.getbname() == castother.getbname()) || (this.getbname() != null             && castother.getbname() != null &&      this.getbname().equals(castother.getbname())))              &&  ((this.getrcode() == castother.getrcode()) ||                                        (this.getrcode() != null               && castother.getrcode() != null &&              this.getrcode().equals(castother.getrcode()))); }  public int hashcode() {     return super.hashcode(); } 

}

buildingeao:

@stateless public class buildingeaoimpl implements buildingeaoimpllocal { @persistencecontext(unitname = "labejbsql") private entitymanager em;  public buildingeaoimpl() {     // todo auto-generated constructor stub }  public building findbybname(string bname) {     return em.find(building.class, bname); } } 

facade:

@stateless public class facade implements facaderemote, facadelocal { @ejb buildingeaoimpllocal buildingeao; @ejb roomeaoimpllocal roomeao;  public facade() {     // todo auto-generated constructor stub }  public list<room> findroomsbybname(string bname) {       return roomeao.findbybname(bname);       }  } 

servlet:

@webservlet("/testclientservlet") public class testclientservlet extends httpservlet { private static final long serialversionuid = 1l; @ejb private facadelocal facade;  /**  * @see httpservlet#httpservlet()  */ public testclientservlet() {     super();     // todo auto-generated constructor stub }  protected void service(httpservletrequest request,         httpservletresponse response) throws servletexception, ioexception {     printwriter out = response.getwriter();     out.println("<!doctype html><html><head>");     out.println("<title>lab1</title>");     out.println("<meta charset=\"iso-8859-1\">");     out.println("</head><body>");        /*//this works fine list<room> rooms = facade.findroomsbybname("ec2");     (room r : rooms) {         out.println("<h4>hittade: " + r.getid().getbname() + " "                 + r.getid().getrcode() + "</h4>");         out.println("</body></html>");     } }*/  protected void doget(httpservletrequest request,         httpservletresponse response) throws servletexception, ioexception {      printwriter out = response.getwriter();     out.println("testclientservlet-doget");     out.close();  }  protected void dopost(httpservletrequest request,         httpservletresponse response) throws servletexception, ioexception {      string url = null;     // hidden field     string operation = request.getparameter("operation");      if (operation.equals("showbuilding")) {         string bname = request.getparameter("txtbname");          list<room> r = facade.findroomsbybname(bname);         request.setattribute("rooms", r);         url = "/showbuilding.jsp";     } else if (operation.equals("searchbuilding")) {         system.out.println("testclientservlet-searchbuilding");         url = "/searchbuilding.jsp";     } else {         url = "/searchbuilding.jsp";     }     system.out.println(url);      requestdispatcher dispatcher = getservletcontext()             .getrequestdispatcher(url);     dispatcher.forward(request, response); } */ } 

searchbuilding.jsp:

<html>  <head>  <meta http-equiv="content-type" content="text/html; charset=iso- 8859-1">  <title>search building</title>  </head>  <body>  <form action="/buildroomclientproject/testclientservlet" method="post">   <table cellspacing="0" cellpadding="0" border="0" align="left">  <tr>  <td><h2>search building:</h2></td>  </tr>  <tr>  <td>   <input type= "text" name= "txtbname" size ="25" maxlength="25"> <input type="submit" name="submit" value="search" />  </td>  <td></td>  </tr>  </table>   <input name="operation" value="showbuilding" type="hidden">   </form>  </body>  </html>  

showbuilding.jsp:

<%@ page contenttype="text/html;charset=windows-1252"%>  <%@ page import = "org.ics.ejb.building" %>  <%@ page import = "org.ics.ejb.room" %>  <%@ page import = "org.ics.ejb.roomid" %>  <html>  <head>  <meta http-equiv="content-type" content="text/html; charset=iso-8859-1">  <title>  show building  </title>  </head>  <body>  <%  room r = (room)request.getattribute("rooms"); %> <% building b = (building)request.getattribute("building"); %> <% (int i=0; i<100; i++){ system.out.println(r.getbname() + " " + r.getid().getrcode()); }%>  <h2>  building:  </h2>  <p> <%= r.getid().getrcode()%> <%= b.getbname()%>  </p> <form action="/buildroomclientproject/testclientservlet" method="post">  <input type="submit" name="submit" value="tillbaka">  <input name="operation" value="searchbuilding" type="hidden">  </form>  </body>  </html> 

the "rooms" attribute being set arraylist of rooms in servlet. when trying in jsp, expecting single room. change

<%  room r = (room)request.getattribute("rooms"); %> 

to

<%  list<room> rooms = (list<room>)request.getattribute("rooms"); %> 

and iterate through each room.