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java - 使用 Struts 文件上传时出现 NullPointerException

转载 作者:行者123 更新时间:2023-12-01 10:34:19 24 4
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我正在按照此处的示例 What is a NullPointerException, and how do I fix it?

在这个例子中,使用了拦截器fileUpload和basicStack

 <action name="upload" class="com.rwy.demo.action.UploadFile">
<interceptor-ref name="basicStack">
<interceptor-ref name="fileUpload">
<param name="allowedTypes">image/jpeg,image/gif</param>
</interceptor-ref>
<result name="success">/success.jsp</result>
<result name="error">/error.jsp</result>
</action>

运行这个例子后,我得到了一个 NullPointerException 。当我删除这些拦截器时(我知道没有指定拦截器时将使用 defaultStack ),它工作得很好。我认为问题是拦截器 params 没有正确使用/引用

  <action name="upload" class="com.rwy.demo.action.UploadFile">
<result name="success">/success.jsp</result>
<result name="error">/error.jsp</result>
</action>

但是,在 basicStack 中,包含 params。因此,表单中的参数没有传递给action,导致此异常

如有任何回应,我们将不胜感激。

以下是完整的堆栈跟踪:

java.lang.NullPointerException
java.io.File.<init>(File.java:317)
com.rwy.demo.action.UploadFile.execute(UploadFile.java:24)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.lang.reflect.Method.invoke(Method.java:497)
ognl.OgnlRuntime.invokeMethod(OgnlRuntime.java:891)
ognl.OgnlRuntime.callAppropriateMethod(OgnlRuntime.java:1293)
ognl.ObjectMethodAccessor.callMethod(ObjectMethodAccessor.java:68)
com.opensymphony.xwork2.ognl.accessor.XWorkMethodAccessor.callMethodWithDebugInfo(XWorkMethodAccessor.java:117)
com.opensymphony.xwork2.ognl.accessor.XWorkMethodAccessor.callMethod(XWorkMethodAccessor.java:108)
ognl.OgnlRuntime.callMethod(OgnlRuntime.java:1369)
ognl.ASTMethod.getValueBody(ASTMethod.java:90)
ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212)
ognl.SimpleNode.getValue(SimpleNode.java:258)
ognl.Ognl.getValue(Ognl.java:494)
ognl.Ognl.getValue(Ognl.java:458)
com.opensymphony.xwork2.ognl.OgnlUtil$2.execute(OgnlUtil.java:309)
com.opensymphony.xwork2.ognl.OgnlUtil.compileAndExecute(OgnlUtil.java:340)
com.opensymphony.xwork2.ognl.OgnlUtil.getValue(OgnlUtil.java:307)
com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:423)
com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:287)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:250)
org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:326)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
org.apache.struts2.interceptor.DeprecationInterceptor.intercept(DeprecationInterceptor.java:41)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:138)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:229)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:229)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:73)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
org.apache.struts2.interceptor.DateTextFieldInterceptor.intercept(DateTextFieldInterceptor.java:125)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:91)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:171)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:189)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244)
org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:54)
org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:564)
org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:81)
org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:99)
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212)
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616)
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:521)
org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1096)
org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:674)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1500)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1456)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
java.lang.Thread.run(Thread.java:745)

最佳答案

我刚刚发现问题所在。问题在于拦截器的顺序。下面的代码工作正常:

    <action name="upload" class="com.rwy.demo.action.UploadFile">
<interceptor-ref name="fileUpload">
<param name="allowedTypes">image/jpeg,image/gi,text/html</param>
</interceptor-ref>
<interceptor-ref name="basicStack"/>
<result name="success">/success.jsp</result>
<result name="error">/error.jsp</result>
</action>

关于java - 使用 Struts 文件上传时出现 NullPointerException,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/34870161/

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