java - 使用 java 的 MVC - 返回 NULL

Question

我正在尝试使用 jsp servlet 的 MVC。但无法通过 bean 从数据库返回值。

下面是我的代码:

JSP 页面:

        <c:forEach var="pro" items="list">
         <tr>        
            <td><c:out value="${pro.reqno}"></c:out></td>
            <td><c:out value="${pro.leave_Type}"></c:out></td>
            <td><c:out value="${pro.no_of_days}"></c:out></td>
            <td><c:out value="${pro.status}"></c:out></td>
            <td><c:out value="${pro.balanceUnits}"></c:out></td>
            <td><c:out value="${pro.totalUnits}"></c:out></td>
        </tr>
       </c:forEach>

Servlet:

            SummaryDetail summary=new SummaryDetail();
            ArrayList temp=new ArrayList();
            temp=summary.getSummary();
            request.setAttribute("list", temp);
            RequestDispatcher rd = request.getRequestDispatcher("JSP page");
            rd.forward(request, response);

DAO 类:

    public ArrayList<LeaveSummary> getSummary(){
    ArrayList<LeaveSummary> rowArray = new ArrayList<LeaveSummary>();
     try{
        LeaveSummary getValuesFromDb=new LeaveSummary();
        Connection con = ConnectionProvider.getCon();
        Statement stmt = con.createStatement();    
        ResultSet rs = stmt.executeQuery("SELECT REQNO,USERNAME,LEAVEUNITS,LEAVETYPE,STATUS,TOTALUNITS,BALANCEUNITS FROM leave_request");
        while(rs.next())
        {
          getValuesFromDb.setReqno(rs.getInt(1));
          getValuesFromDb.setUser_name(rs.getString(2));
          getValuesFromDb.setNo_of_days(rs.getInt(3));
          getValuesFromDb.setLeave_Type(rs.getString(4));
          getValuesFromDb.setStatus(rs.getString(5));
          getValuesFromDb.setTotalUnits(rs.getInt(6));
          getValuesFromDb.setBalanceUnits(rs.getInt(7));
          rowArray.add(getValuesFromDb);
        }
    }
   catch(Exception e)
           {}
    return rowArray;
    }

Bean 类:

public class LeaveSummary {

public int getBalanceUnits() {
    return balanceUnits;
}

public void setBalanceUnits(int balanceUnits) {
    this.balanceUnits = balanceUnits;
}

public String getLeave_Type() {
    return leave_Type;
}

public void setLeave_Type(String leave_Type) {
    this.leave_Type = leave_Type;
}

public int getNo_of_days() {
    return no_of_days;
}

public void setNo_of_days(int no_of_days) {
    this.no_of_days = no_of_days;
}

public int getReqno() {
    return reqno;
}

public void setReqno(int reqno) {
    this.reqno = reqno;
}

public String getStatus() {
    return status;
}

public void setStatus(String status) {
    this.status = status;
}

public int getTotalUnits() {
    return totalUnits;
}

public void setTotalUnits(int totalUnits) {
    this.totalUnits = totalUnits;
}

public String getUser_name() {
    return user_name;
}

public void setUser_name(String user_name) {
    this.user_name = user_name;
}
private int reqno;
private String leave_Type;
private int no_of_days; // represents no of days of leave that is LeaveUnits field in DB
private String user_name;
private int balanceUnits;
private String status;
private int totalUnits;



}

它确实打印了我的 JSP 中的任何值。请解释我的错误。提前致谢!!

Answer 1

我在 Controller servlet 方面犯了错误。

 try {
            List temp = summary.getSummary();
            request.setAttribute("list", temp);
            RequestDispatcher rd = request.getRequestDispatcher("JSP/login-success.jsp");
            rd.forward(request, response);
             }