Java 无法在数据库中插入字段

我是java web开发的新手。我正在尝试开发一个项目。我得到了SQLException错误

以下是我的servlet代码：

protected void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
    // TODO Auto-generated method stub
    res.setContentType("text/html");
    PrintWriter pw=res.getWriter();

    try {
        Class.forName("com.mysql.jdbc.Driver");
        Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/ocp2","root", "");
        ps=con.createStatement();
        RequestDispatcher rr;

        String courseid=req.getParameter("courseid");
        String coursename=req.getParameter("coursename");
        String s1=req.getParameter("sday");
        String s2=req.getParameter("smonth");
        String s3=req.getParameter("syear");
        String sdate=s1+'-'+s2+'-'+s3;
        String s4=req.getParameter("eday");
        String s5=req.getParameter("emonth");
        String s6=req.getParameter("eyear");
        String edate=s4+'-'+s5+'-'+s6;
        String duration=req.getParameter("duration");
        String fee=req.getParameter("fee");

        pw.println("insert into course values('"+courseid+"','"+coursename+"','"+sdate+"','"+edate+"','"+duration+"',"+fee+")");
        ps.executeUpdate("insert into course values('"+courseid+"','"+coursename+"','"+sdate+"','"+edate+"','"+duration+"',"+fee+")");
        con.commit();

        rr= req.getRequestDispatcher("incousuc.html");
        rr.forward(req,res);
    } catch(ClassNotFoundException e) {
        pw.println("exception"+e);
    } catch(SQLException e) {
        pw.println("SQL EXCEPTION");    
        pw.println("TRY AGAIN");
    } catch(Exception e) {
        pw.println("can't load driver"+e.getMessage());
    }
}

以下是我的HTML代码：

</table>
</td>

<td width="75%" align="center">
    <h2>New Course Details</h2>
    <form name="facreg" onsubmit="return check()" action="./inscourse" method="post">
        <table width="500" height="30" border="0">
            <tr>
                <td>
                    <center>courseid</center>
                </td>
                <td>
                    <input id="courseid" name="courseid" type="text" size="50" maxlength="100" value="">
                </td>
            </tr>
            <tr>
                <td>
                    <center>coursename</center>
                </td>
                <td>
                    <input id="couname" name="couname" type="text" size="50" maxlength="100" value="">
                </td>
            </tr>
            <tr>
                <td>StartingDate</td>
                <td>
                    <select name="sday" size="">
                        <option value=01>1</option>
                        <option value=02>2</option>
                        <option value=03>3</option>
                        <option value=04>4</option>
                        <option value=05>5</option>
                        <option value=06>6</option>
                        <option value=07>7</option>
                        <option value=08>8</option>
                        <option value=09>9</option>
                        <option value=10>10</option>
                        <option value=11>11</option>
                        <option value=12>12</option>
                        <option value=13>13</option>
                        <option value=14>14</option>
                        <option value=15>15</option>
                        <option value=16>16</option>
                        <option value=17>17</option>
                        <option value=18>18</option>
                        <option value=19>19</option>
                        <option value=20>20</option>
                        <option value=21>21</option>
                        <option value=22>22</option>
                        <option value=23>23</option>
                        <option value=24>24</option>
                        <option value=25>25</option>
                        <option value=26>26</option>
                        <option value=27>27</option>
                        <option value=28>28</option>
                        <option value=29>29</option>
                        <option value=30>30</option>
                        <option value=31>31</option>
                    </select>&nbsp;&nbsp;&nbsp;&nbsp;
                    <select name="smonth" size="">
                        <option value="Jan">Jan</option>
                        <option value="Feb">Feb</option>
                        <option value="Mar">Mar</option>
                        <option value="Apr">Apr</option>
                        <option value="May">May</option>
                        <option value="Jun">Jun</option>
                        <option value="Jul">Jul</option>
                        <option value="Aug">Aug</option>
                        <option value="Sep">Sep</option>
                        <option value="Oct">Oct</option>
                        <option value="Nov">Nov</option>
                        <option value="Dec">Dec</option>
                    </select>&nbsp;&nbsp;&nbsp;&nbsp;
                    <input id="syear" name="syear" type="text" size="8" maxlength="4" value="" onkeypress=checknumeric()>(yyyy)&nbsp;&nbsp;&nbsp;&nbsp;
                </td>
            </tr>
            <tr>
                <td>EndingDate</td>
                <td>
                    <select name="eday" size="">
                        <option value=01>1</option>
                        <option value=02>2</option>
                        <option value=03>3</option>
                        <option value=04>4</option>
                        <option value=05>5</option>
                        <option value=06>6</option>
                        <option value=07>7</option>
                        <option value=08>8</option>
                        <option value=09>9</option>
                        <option value=10>10</option>
                        <option value=11>11</option>
                        <option value=12>12</option>
                        <option value=13>13</option>
                        <option value=14>14</option>
                        <option value=15>15</option>
                        <option value=16>16</option>
                        <option value=17>17</option>
                        <option value=18>18</option>
                        <option value=19>19</option>
                        <option value=20>20</option>
                        <option value=21>21</option>
                        <option value=22>22</option>
                        <option value=23>23</option>
                        <option value=24>24</option>
                        <option value=25>25</option>
                        <option value=26>26</option>
                        <option value=27>27</option>
                        <option value=28>28</option>
                        <option value=29>29</option>
                        <option value=30>30</option>
                        <option value=31>31</option>
                    </select>&nbsp;&nbsp;&nbsp;&nbsp;
                    <select name="emonth" size="">
                        <option value="Jan">Jan</option>
                        <option value="Feb">Feb</option>
                        <option value="Mar">Mar</option>
                        <option value="Apr">Apr</option>
                        <option value="May">May</option>
                        <option value="Jun">Jun</option>
                        <option value="Jul">Jul</option>
                        <option value="Aug">Aug</option>
                        <option value="Sep">Sep</option>
                        <option value="Oct">Oct</option>
                        <option value="Nov">Nov</option>
                        <option value="Dec">Dec</option>
                    </select>&nbsp;&nbsp;&nbsp;&nbsp;
                    <input id="eyear" name="eyear" type="text" size="8" maxlength="4" value="" onkeypress=checknumeric()>(yyyy)&nbsp;&nbsp;&nbsp;&nbsp;
                </td>
            </tr>
            <tr>
                <td>
                    <center>duration</center>
                </td>
                <td>
                    <input id="duration" name="duration" type="text" size="50" maxlength="100" value="">
                </td>
            </tr>
            <tr>
                <td>
                    <center>Fee</center>
                </td>
                <td>
                    <input id="fee" name="fee" type="text" size="50" maxlength="100" value="" onkeypress="checknumeric()">
                </td>
            </tr>
            <tr>
                <td colspan=2>
                    <center>
                        <input name="submit" type="submit" value="SUBMIT">
                        <input name="reset" type="reset" value="RESET">
                </td>
            </tr>
        </table>
    </form>
</td>
</tr>
</table>

当我运行此代码时： 我得到了以下错误：

Jul 19, 2014 11:36:18 AM org.apache.catalina.loader.WebappClassLoader loadClass
INFO: Illegal access: this web application instance has been stopped already.  Could not load java.net.BindException.  The eventual following stack trace is caused by an error thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access, and has no functional impact.
java.lang.IllegalStateException
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1588)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1547)
    at com.mysql.jdbc.SQLError.createLinkFailureMessageBasedOnHeuristics(SQLError.java:1275)
    at com.mysql.jdbc.exceptions.jdbc4.CommunicationsException.<init>(CommunicationsException.java:60)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
    at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1118)
    at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:3321)
    at com.mysql.jdbc.MysqlIO.quit(MysqlIO.java:1667)
    at com.mysql.jdbc.ConnectionImpl.realClose(ConnectionImpl.java:4322)
    at com.mysql.jdbc.ConnectionImpl.cleanup(ConnectionImpl.java:1348)
    at com.mysql.jdbc.ConnectionImpl.finalize(ConnectionImpl.java:2679)
    at java.lang.System$2.invokeFinalize(Unknown Source)
    at java.lang.ref.Finalizer.runFinalizer(Unknown Source)
    at java.lang.ref.Finalizer.access$100(Unknown Source)
    at java.lang.ref.Finalizer$FinalizerThread.run(Unknown Source)
    Jul 19, 2014 11:36:18 AM org.apache.catalina.loader.WebappClassLoader loadClass
    INFO: Illegal access: this web application instance has been stopped already.  Could not load   com.mysql.jdbc.ProfilerEventHandlerFactory.  The eventual following stack trace is caused by an  error thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access, and has no functional impact.
    java.lang.IllegalStateException
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1588)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1547)
    at com.mysql.jdbc.ConnectionImpl.realClose(ConnectionImpl.java:4346)
    at com.mysql.jdbc.ConnectionImpl.cleanup(ConnectionImpl.java:1348)
    at com.mysql.jdbc.ConnectionImpl.finalize(ConnectionImpl.java:2679)
    at java.lang.System$2.invokeFinalize(Unknown Source)
    at java.lang.ref.Finalizer.runFinalizer(Unknown Source)
    at java.lang.ref.Finalizer.access$100(Unknown Source)
    at java.lang.ref.Finalizer$FinalizerThread.run(Unknown Source)

我的数据库也没有更新。

---

谁能告诉我我哪里做错了？我该怎么解决呢？

您的coursename值为空，您必须更改这行servlet代码

   String coursename=req.getParameter("coursename");

用这个

   String coursename=req.getParameter("couname");

---

检查您的html代码，您将得到原因

它显示SQLException。只是SQLException没有用处，请向我们显示它显示的消息。您可以将SQL Exception的catch块更改为pw.printlnSQL Exception+e.getMessage；然后把结果贴在这里？这将有助于人们理解什么是例外。我改变了。现在它显示为这样。。。信息：非法访问：此web应用程序实例已停止。无法加载com.mysql.jdbc.ProfilerEventHandlerFactory。最终的后续堆栈跟踪是由出于调试目的以及试图终止导致非法访问的线程而引发的错误引起的，没有任何功能影响。我最大胆的猜测是您正在尝试将字符串值设置为courseId。第一个值不应该用单引号括起来。insert语句中的最后两个字段也可能存在同样的问题。附言：不要只是改变打印行。将executeUpdate行更改为请停止在同一问题上发布三次，改为同样地编辑答案，因为您提供的任何新更新：-+1，但对于此答案，似乎这是正确的。@nIcEcOw感谢+1，我将在将来处理它