大家好,我有一个讲师为实验室分配导师的网站,目前,我有一个导师列表,可以单击分配,然后将用户带到另一个带有下拉框的页面,他们可以选择哪个实验室他们希望辅导老师教书。应该将实验室的ID和用户的ID提交到数据库。
当前,当用户获得教师列表时,他们单击名为“分配”的链接,该链接将教师ID放在url中,然后,他们具有一个可以选择的教师列表,一旦我选择了教师,然后单击“提交”,我就会得到以下错误。
描述服务器遇到内部错误(),导致服务器无法满足此请求。
exception
java.lang.NumberFormatException: null
java.lang.Integer.parseInt(Unknown Source)
java.lang.Integer.parseInt(Unknown Source)
TutorAssign.doPost(TutorAssign.java:97)
javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
sendBack方法正在运行,但doPost没有运行,它指向我获取请求参数为null的行-
int user_id = Integer.parseInt(request.getParameter("id"));
我怎样才能解决这个问题?我将包括整个servlet以便进行更好的说明
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
/**
* Servlet implementation class TutorAssign
*/
@WebServlet("/TutorAssign")
public class TutorAssign extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public TutorAssign() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
sendBack(request, response);
}
private void sendBack(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
HttpSession session = request.getSession(true);
//Set data you want to send back to the request (will be forwarded to the page)
//Can set string, int, list, array etc.
int user_id = Integer.parseInt((String)request.getParameter("id"));
String sql = "SELECT l.id,s.name,l.day,l.time,l.room" +
" FROM subject s, lab l " +
" WHERE s.user_id="+(Integer)session.getAttribute("id");
try{
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/wae","root","");
System.out.println("got a hj");
System.out.println(session.getAttribute("id"));
Statement stmt = con.createStatement();
ResultSet res = stmt.executeQuery(sql);
System.out.println(res);
ArrayList<String> list1 = new ArrayList<String>();
ArrayList<String> list2 = new ArrayList<String>();
if (res.next()){
do{
list1.add(res.getString(1));
list2.add(res.getString(2)+" "+res.getString(3)+" "+res.getString(4)+" "+res.getString(5));
}while(res.next());
System.out.println("Outside");
String[] arr1 = list1.toArray(new String[list1.size()]);
String[] arr2 = list2.toArray(new String[list2.size()]);
System.out.println(list1);
request.setAttribute("res1", arr1);
request.setAttribute("res2", arr2);
request.setAttribute("user_id", user_id);
}
}catch (SQLException e) {
}
catch (Exception e) {
}
//Decides what page to send the request data to
RequestDispatcher view = request.getRequestDispatcher("TutorAssign.jsp");
//Forward to the page and pass the request and response information
view.forward(request, response);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
int user_id = Integer.parseInt((String)request.getParameter("id"));
System.out.println(user_id);
int lab_id = 0;
System.out.println("I got a blow job");
String message = null;
try {
Class.forName("com.mysql.jdbc.Driver");
Connection con =
DriverManager.getConnection("jdbc:mysql://localhost:3306/wae","root","");
System.out.println("got connection");
System.out.println(user_id);
Statement s = con.createStatement();
String sql = "INSERT INTO user_lab" +
" (user_id, lab_id)" +
" VALUES" +
" ('" + user_id + "'," +
" '" + lab_id + "')";
System.out.println(sql);
int i = s.executeUpdate(sql);
if (i==1) {
message = "Successfully assigned a tutor.";
response.sendRedirect("Lecturer_labs");
}
s.close();
con.close();
}
catch (SQLException e) {
message = "Error." + e.toString();
boolean error = true;
}
catch (Exception e) {
message = "Error." + e.toString();
boolean error = true;
}
if (message!=null) {
PrintWriter out = response.getWriter();
out.println("<B>" + message + "</B><BR>");
out.println("<HR><BR>");
}
}
// TODO Auto-generated method stub
}
这是我的jsp代码
<form name ="TutorAssign" ACTION="TutorAssign" method="post">
<input type="hidden" name="user_id" value="user_id"/>
<select name="lab_id">
<%
for(int i=0; i<list1.length;i++)
{
out.println("<option value="+list1[i]+"> "+list2[i]+" </option>");
} %>
</select>
<input type=SUBMIT value="Submit" name="Submit" />
</form>
最佳答案
问题在这里:
<form name ="TutorAssign" ACTION="TutorAssign" method="post">
<select name="labs">
<%
for(int i=0; i<list1.length;i++)
{
out.println("<option value="+list1[i]+"> "+list2[i]+" </option>");
} %>
</select>
进一步来说:
<select name="labs">
如果将名称更改为
id
或使用request.getParameter("labs")
,则可能会得到所需的内容。