导致 NumberFormatException 的 Servlet 代码

Question

我的servlet代码，对于使用Java，JSP和MySQL的基于表单的在线预订系统，一直在"int customer"开头的行中抛出NumberFormatException。除了这里，我的代码没有其他问题。

java.lang.NumberFormatException：对于输入字符串："null">

如果我检查空字符串或空字符串，我得到的只是错误。

if (submit.equals("add booking")) {        
                int customerID = Integer.parseInt(request.getParameter("customerID").trim());
                int routeID = Integer.parseInt(request.getParameter("routeID").trim());
                String sailing = request.getParameter("sailing").trim();
                int noAdults = Integer.parseInt(request.getParameter("noAdults").trim());
                int noChildren = Integer.parseInt(request.getParameter("noChildren").trim());
                String otherinfo = request.getParameter("otherinfo").trim();
                if (sailing.equalsIgnoreCase("")) {
                    url = "/scotiavalidation.jsp";
                } else {
                    bookingManager.addBooking(customerID, routeID, sailing, noAdults, noChildren, otherinfo);
                    int bookingID = 0;
                    bookingID = bookingManager.getBookingIdByAdd(bookingID);
                    request.setAttribute("bookingID", bookingID);
                    url = "/bookingConfirmation.jsp";
                }

我知道我需要在某个地方尝试捕获块，但我无法弄清楚。任何人都可以提出解决方案吗？我的 Glassfish 4.1.1 输出如下所示：

Warning:   StandardWrapperValve[BookingServlet]: Servlet.service() for servlet BookingServlet threw exceptionjava.lang.NumberFormatException: For input string: "null"
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
at java.lang.Integer.parseInt(Integer.java:580)
at java.lang.Integer.parseInt(Integer.java:615)
at controller.BookingServlet.processRequest(BookingServlet.java:46)
at controller.BookingServlet.doGet(BookingServlet.java:161)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:687)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:318)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673)
at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:416)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:283)
at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:459)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:167)
at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:206)
at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:180)
at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:235)
at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:283)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:200)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:132)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:111)
at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:536)
at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:591)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:571)
at java.lang.Thread.run(Thread.java:745)

我正在"我的 JSP 页面"中使用会话。这是一个片段：

<form name="addBookingForm" action="BookingServlet">
                <table cellspacing="8" border="0">
                    <tr>
                        <td align="left"><p><label for="customerID">Customer No:</label></p></td>
                        <td><p><%= session.getAttribute("customerID")%></p></td>
                    </tr>
                    <tr>
                        <td align="left"><p><label for="routeID">Cruise No:</label></p></td>
                        <td><select name="routeID" id="routeID" value="">
                                <option selected></option>
                                <option>322</option>
                                <option>323</option>
                                <option>324</option>
                            </select></td>
                    </tr>

Answer 1

Integer.parseInt(value( .in here 值可能无法解析为 int。最好先验证用户输入，以检查这是否是数值，然后再逐步转换为 int。

您可以使用Apache Commons Lang 3.5 NumberUtils.isCreatable或StringUtils.isNumeric。

执行验证

Answer 2

似乎您的 customerID 值以字符串"null"的形式返回。在强制转换之前需要验证。您还应该检查您的 JSP 为什么将 customerID 设置为"null"。您还需要签入您的 servlet。类似的东西

if (submit.equals("add booking")&&request.getParameter("customerID")!=null)

Answer 3

错误消息很清楚：

java.lang.NumberFormatException：对于输入字符串："null">

您正在将null值解析为数字。是否确定填充了整数参数？。

在调用Integer.parse或trim函数之前检查null指针。