为啥getFile()按照文档中的要求一直获取不到文件，返回空指针异常？


controller中的method

public void sceneFile() {

UploadFile aFile=getFile();

System.out.println(aFile.getFileName());

renderHtml("success");

}

前台的form

<form method="post" enctype="multipart/form-data" action="/backStage/sceneFile">

                        选择封面图片：

    <input type="file" class="form-control" id="image">

    <br>

    <input type="submit" class="form-control" name="submit" style="float: right;" /></form>


项目：JFinal

评论区

JFinal

2019-06-10 11:42

信息量不够，例如异常信息都没有
 回复

soarfly

2019-06-10 12:36

java.lang.NullPointerException
at com.ec.controller.BackStageController.sceneFile(BackStageController.java:41)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.jfinal.aop.Invocation.invoke(Invocation.java:74)
at com.jfinal.core.ActionHandler.handle(ActionHandler.java:81)
at com.jfinal.core.JFinalFilter.doFilter(JFinalFilter.java:89)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1634)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:533)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:146)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:548)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:257)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:1595)
at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:255)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1340)
at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:203)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:473)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:1564)
at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:201)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1242)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:144)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
at org.eclipse.jetty.server.Server.handle(Server.java:503)
at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:364)
at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:260)
at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:305)
at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:103)
at org.eclipse.jetty.io.ChannelEndPoint$2.run(ChannelEndPoint.java:118)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.runTask(EatWhatYouKill.java:333)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.doProduce(EatWhatYouKill.java:310)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.tryProduce(EatWhatYouKill.java:168)
at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.run(EatWhatYouKill.java:126)
at org.eclipse.jetty.util.thread.ReservedThreadExecutor$ReservedThread.run(ReservedThreadExecutor.java:366)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:765)
at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:683)
at java.lang.Thread.run(Thread.java:748)

补上异常信息（就是getFile()这个方法获取不到文件）
这是constant 的配置
//设置默认上传文件保存路径 getFile等使用
me.setBaseUploadPath("upload/temp/");
//设置上传最大限制尺寸
me.setMaxPostSize(1024*1024*10);
 回复

soarfly

2019-06-10 12:37

@JFinal
 回复

JFinal

2019-06-10 15:26

@soarfly 一定要先调用 getFile() 才能再调用其它 get 方法，如： getPara 之类的

如果有拦截器或者 Validator ，也要在其中先调用 getFile 方法，这个在文档中有过说明

最后，null pointer exception 可以很容易通过单步调试看一下是什么问题
 回复
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