下面是我将如何修复这一问题的报告我已经尝试在doPost上返回requestdispatcher有人能解释一下发生了什么吗？我只是在数据库中插入了参数。我的代码出了什么问题？感谢
type Exception report
message Cannot forward after response has been committed
description The server encountered an internal error that prevented it from fulfilling this request.
exception
java.lang.IllegalStateException: Cannot forward after response has been committed
EventHandler.InsertEvent.doPost(InsertEvent.java:75)
javax.servlet.http.HttpServlet.service(HttpServlet.java:646)
javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
SERVLET
package EventHandler;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
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;
@WebServlet("/AddEvent")
public class InsertEvent extends HttpServlet {
String title,description, founder, time, date, location, payment;
int price = 0;
int bank = 0;
String query;
Connection conn;
Statement stmt;
ResultSet rs;
DatabaseConnection dbconn;
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html");
try{
title = request.getParameter("title");
description = request.getParameter("description");
founder = request.getParameter("founder");
time = request.getParameter("time");
date = request.getParameter("date");
location = request.getParameter("location");
payment = request.getParameter("payment");
price = Integer.parseInt(request.getParameter("price"));
bank = Integer.parseInt(request.getParameter("bank"));
System.out.println(title);
System.out.println(description);
System.out.println(founder);
System.out.println(time);
System.out.println(date);
System.out.println(location);
System.out.println(payment);
System.out.println(price);
System.out.println(bank);
conn = dbconn.setConnection();
stmt = conn.createStatement();
query = "insert into event_list values('"+title+"','"+description+"','"+founder+"','"+time+"','"+date+"','"+location+"','"+payment+"',"+price+","+bank+")";
int i = stmt.executeUpdate(query);
}catch(Exception e){
request.setAttribute("Error", e);
RequestDispatcher rd = request.getRequestDispatcher("error.jsp");
rd.forward(request, response);
}finally{
RequestDispatcher rd = request.getRequestDispatcher("CreateEvent.jsp");
rd.forward(request, response);
}
}
}
DBCONNECTION
package EventHandler;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
public class DatabaseConnection {
Connection conn;
Statement stmt;
ResultSet rs;
String url = "jdbc:mysql://localhost:3306/form";
String driver = "com.mysql.jdbc.Driver";
String userName = "root";
String password = "Incorrect00!";
public DatabaseConnection(){
}
public Connection setConnection(){
try{
Class.forName(driver);
conn = DriverManager.getConnection(url, userName, password);
}catch(Exception e){
}
return conn;
}
public ResultSet getResult(String sql, Connection conn){
this.conn = conn;
try{
stmt = conn.createStatement();
rs = stmt.executeQuery(sql);
}catch (Exception e){
}
return rs;
}
}
JSP
<html>
<head>
<title>Create An event</title>
<script src="js/jquery.js"></script>
<script src="js/bootstrap.min.js"></script>
<script src="js/bootstrap-datetimepicker.min.js"></script>
<script src="js/CreateEvent.js"></script>
<link href="css/bootstrap.css" rel="stylesheet" type="text/css"/>
<link href="css/bootstrap-datetimepicker.min.css" rel="stylesheet" type="text/css"/>
</head>
<body>
<form method="post" action="AddEvent" >
<br>
Title: <input type="text" name="title" ><br><br>
Event Founder: <input type="text" name="founder" ><br><br>
Description: <textarea name="description" ></textarea><br><br>
Time:
<input type='text' class="form-control" name="time" />
Day:
<input type='text' class="form-control" data-date-format="YYYY/MM/DD" name="date"/>
Where: <input type="text" name="location"> <br>
Include Payment? <br>
<input type="radio" name="payment" id="showprice" value="yes">Yes<br>
<input type="radio" name="payment" value="no">No<br>
<div id="price">
Price: <input type="text" value="0" name="price">
<br>
Bank Account Number : <input type="text" name="bank" value="0">
</div>
<input type="submit" value="Finish" class="btn btn-success"/>
</form>
<a href="/EventPlannerV3">Show List</a>
</body>
</html>
问题是您要调用请求调度程序两次。
}catch(Exception e){
request.setAttribute("Error", e);
RequestDispatcher rd = request.getRequestDispatcher("error.jsp");
rd.forward(request, response);
}finally{
RequestDispatcher rd = request.getRequestDispatcher("CreateEvent.jsp");
rd.forward(request, response);
}
你的程序正在捕获一个异常，然后它也在执行最后一行——在你已经转发了请求之后，你不能转发它。
明智地使用.forward()方法。另外，如果同一类中有多个转发，也不要忘记添加return语句。阅读此处并https://stackoverflow.com/questions/19619949/how-does-function-terminate-with-requestdispatcher-forward。
catch(Exception e){
request.setAttribute("Error", e);
RequestDispatcher rd = request.getRequestDispatcher("error.jsp");
rd.forward(request, response);
return;
}finally{
RequestDispatcher rd = request.getRequestDispatcher("CreateEvent.jsp");
rd.forward(request, response);
return;
}
从而重置程序控制，而不是执行其他块。您在finally()中使用了RequestDispatcher，因此它将始终独立于您的错误执行。试着以明智的方式使用finally。
我应该在什么时候使用Java中的finally块'；s try catch finally
为什么我需要使用finally来关闭资源？
希望这能有所帮助！！