JSTL使用的servlet

Question

檢索數據庫中的數據

你好，我是新來的Java編程

這裏我試圖檢索使用的servlet從數據庫中的數據，並顯示jsp頁面上。

請建議我

這裏是代碼

User.java

public class User { 

private String EventName; 
private String Location; 


public User(){} 

public User(String EventName,String Location){ 

this.EventName=EventName; 
this.Location=Location; 

} 


public String getEventName() 
{ 
    return (this.EventName); 
} 

public String getLocation() 
{ 
    return (this.Location); 
} 

public void setName(String EventName) 
{ 
    this.EventName=EventName; 
} 

public void setLoc(String Location) 
{ 
    this.Location=Location; 
} 

} 

retrieve.java

try{ 

     ArrayList<User> users = new ArrayList<User>(); 
     //List<String> users = new ArrayList<String>(); 
     while(rs.next()){ 
     User user = new User(); 
     String Name=rs.getString(9); 
     String Loc=rs.getString(7); 
     user.setName(Name); 
     user.setLoc(Loc); 
     users.add(user); 
    } 

    request.setAttribute("users", users); 
    RequestDispatcher view = request.getRequestDispatcher("Display.jsp"); 
    view.forward(request, response); 

}

display.jsp

<table> 
<c:forEach var="user" items="${users}"> 
<tr> 
<td><c:out value="${users.EventName}"/> </td> 
<td><c:out value="${users.Location}"/> </td> 
</tr> 
</c:forEach> 
</table> 

誤差如下

例外

org.apache.jasper.JasperException: java.lang.NumberFormatException: For input 
    string: "EventName" 
                         org.apache.jasper.servlet.JspServletWrapper.handleJspException 
    (JspServletWrapper.java:548) 
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:471) 
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:389) 
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:333) 
javax.servlet.http.HttpServlet.service(HttpServlet.java:722) 

org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter 
    (MonitorFilter.java:393) 
TicketPkg.Daily.processRequest(Daily.java:77) 
TicketPkg.Daily.doGet(Daily.java:97) 
javax.servlet.http.HttpServlet.service(HttpServlet.java:621) 
javax.servlet.http.HttpServlet.service(HttpServlet.java:722) 


    org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter 
    (MonitorFilter.java:393) 

    root cause 

    java.lang.NumberFormatException: For input string: "EventName" 
java.lang.NumberFormatException.forInputString(NumberFormatException.java:65) 
java.lang.Integer.parseInt(Integer.java:492) 
java.lang.Integer.parseInt(Integer.java:527) 
javax.el.ListELResolver.coerce(ListELResolver.java:173) 
javax.el.ListELResolver.getValue(ListELResolver.java:52) 
javax.el.CompositeELResolver.getValue(CompositeELResolver.java:67) 
org.apache.el.parser.AstValue.getValue(AstValue.java:169) 
org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:189) 

org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate 
    (PageContextImpl.java:985) 
org.apache.jsp.Daily_jsp._jspx_meth_c_005fout_005f0(Daily_jsp.java:266) 
org.apache.jsp.Daily_jsp._jspx_meth_c_005fforEach_005f0(Daily_jsp.java:229) 
org.apache.jsp.Daily_jsp._jspService(Daily_jsp.java:184) 
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) 
javax.servlet.http.HttpServlet.service(HttpServlet.java:722) 
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:433) 
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:389) 
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:333) 
javax.servlet.http.HttpServlet.service(HttpServlet.java:722) 

org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter 
    (MonitorFilter.java:393) 
TicketPkg.Daily.processRequest(Daily.java:77) 
TicketPkg.Daily.doGet(Daily.java:97) 
javax.servlet.http.HttpServlet.service(HttpServlet.java:621) 
javax.servlet.http.HttpServlet.service(HttpServlet.java:722) 

org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter 
    (MonitorFilter.java:393) 

    Thanks in advance 

Answer 1

實施例代碼SEE HERE

private void doProcess(HttpServletRequest request, HttpServletResponse response) 
      throws ServletException, IOException , SQLException{ 
     Connection conn = null; 
     Statement stmt = null; 
     ResultSet rs = null; 
     PrintWriter out = response.getWriter(); 
     try{ 
      Class.forName("com.mysql.jdbc.Driver").newInstance(); 

      System.out.println("Set connection : URL : jdbc:mysql://localhost:3306/mydatabase"); 
      conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydatabase","root","root"); 

      System.out.println("Create statement."); 
      stmt = conn.createStatement(); 

      ...... 
     }catch(Exception e){ 
      e.printStackTrace(); 
     }finally{ 
      if(stmt != null){ 
       stmt.close(); 
      } 
      if(conn != null){ 
       conn.close(); 
      } 
     } 
    }