Java 从JSP类检索数据（带Servlet的MVC）_Java_Jsp_Search_Servlets_Model View Controller

Java 从JSP类检索数据（带Servlet的MVC）

java jsp search servlets model-view-controller

Java 从JSP类检索数据（带Servlet的MVC）,java,jsp,search,servlets,model-view-controller,Java,Jsp,Search,Servlets,Model View Controller,我现在正在做一个学校的项目，我和我的团队应该在那里建设一个MVC项目，我们有教室和教室。这个关系是一间一间的，正在建一间一间的房间。当我们要搜索建筑名称并稍后显示该建筑中的所有房间时，就会出现问题。当我们在没有jsp的情况下运行servlet时，我们可以提取相关数据，但是当我们通过运行searchBuilding.jsp启动项目时，我们只能键入建筑名称，当我们希望看到连接的房间时，我们反而会得到消息 “java.lang.ClassCastException:java.util.ArrayL

我现在正在做一个学校的项目，我和我的团队应该在那里建设一个MVC项目，我们有教室和教室。这个关系是一间一间的，正在建一间一间的房间。当我们要搜索建筑名称并稍后显示该建筑中的所有房间时，就会出现问题。当我们在没有jsp的情况下运行servlet时，我们可以提取相关数据，但是当我们通过运行searchBuilding.jsp启动项目时，我们只能键入建筑名称，当我们希望看到连接的房间时，我们反而会得到消息 “java.lang.ClassCastException:java.util.ArrayList不能强制转换为org.ics.ejb.Room”。可能所有的代码都有点混乱，但如果有人能帮我发现问题，我会非常感激，因为我明天应该把这个给我的教授看

这是我们的代码：建筑：

@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;
}

室友：

@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();
}

}

建筑EAO：

@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);
}
}

正面：

@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); 
     }
 }

@无状态
公共类Facade实现FacadeMote、FacadeLocal{
@EJB
BuildingEAO本地BuildingEAO；
@EJB
RoomEAO本地RoomEAO；
公共立面（）{
//TODO自动生成的构造函数存根
}
公共列表FindRoomByName（字符串bname）{
返回房间ao.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 PERFECTLY FINE
List<Room> rooms = facade.findRoomsByBname("EC2");
    for (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;
    // Get 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);
}
*/
}

@WebServlet（“/TestClientServlet”）
公共类TestClientServlet扩展了HttpServlet{
私有静态最终长serialVersionUID=1L；
@EJB
私人立面；
/**
*@参见HttpServlet#HttpServlet（）
*/
公共TestClientServlet（）{
超级（）；
//TODO自动生成的构造函数存根
}
受保护的无效服务（HttpServletRequest），
HttpServletResponse响应）引发ServletException，IOException{
PrintWriter out=response.getWriter（）；
out.println（“”）；
out.println（“Lab1”）；
out.println（“”）；
out.println（“”）；
/*//这个很好用
列表房间=facade.findRoomsByBname（“EC2”）；
用于（r室：房间）{
out.println（“Hittade:+r.getId（）.getbname（）+”）
+r.getId（）.getrcode（）+“”）；
out.println（“”）；
}
}*/
受保护的无效数据集（HttpServletRequest请求，
HttpServletResponse响应）引发ServletException，IOException{
PrintWriter out=response.getWriter（）；
out.println（“TestClientServlet-doGet”）；
out.close（）；
}
受保护的void doPost（HttpServletRequest请求，
HttpServletResponse响应）引发ServletException，IOException{
字符串url=null；
//获取隐藏字段
字符串操作=request.getParameter（“操作”）；
if（操作等于（“展示建筑”））{
字符串bname=request.getParameter（“txtBname”）；
List r=facade.findRoomsByBname（bname）；
request.setAttribute（“房间”，r）；
url=“/ShowBuilding.jsp”；
}else if（operation.equals（“searchbuilding”））{
System.out.println（“TestClientServlet searchbuilding”）；
url=“/SearchBuilding.jsp”；
}否则{
url=“/SearchBuilding.jsp”；
}
System.out.println（url）；
RequestDispatcher dispatcher=getServletContext（）
.getRequestDispatcher（url）；
转发（请求、响应）；
}
*/
}

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>

<%@ 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"); %>
<% for (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>


搜索大楼
搜索大楼：

SHOWBUILDING.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>

<%@ 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"); %>
<% for (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>


展览大楼
“rooms”属性被设置为servlet中房间的ArrayList。但是，当您试图在jsp中获取它时，您期望的是一个单人房间。
改变


到


然后遍历每个房间
<%  List<Room> rooms = (List<Room>)request.getAttribute("rooms"); %>