[英]Uploading image using Struts 2
我想要做的是使用此 JSP 文件上传图像:
<%@ page contentType="text/html; charset=UTF-8"%>
<%@ taglib prefix="s" uri="/struts-tags"%>
<html>
<head>
<title>Upload User Image</title>
</head>
<body>
<h2>Struts2 File Upload & Save Example</h2>
<s:actionerror />
<s:form action="imageinsert.action" method="post" enctype="multipart/form-data">
<td>Image : </td><td><input type="file" name="Image"></td>
<s:submit value="Upload" align="center" />
</s:form>
</body>
</html>
动作类如下:
public class InsertImageBean extends ActionSupport{
private static final long serialVersionUID = 1L;
private File Image;
private String myFileContentType;
private String myFileFileName;
public String execute()
{
/* Copy file to a safe location */
InsertImage.save(this);
return SUCCESS;
}
public File getMyFile() {
return Image;
}
public void setMyFile(File myFile) {
this.Image = myFile;
}
public String getMyFileContentType() {
return myFileContentType;
}
public void setMyFileContentType(String myFileContentType) {
this.myFileContentType = myFileContentType;
}
public String getMyFileName() {
return myFileFileName;
}
public void setMyFileName(String myFileFileName) {
this.myFileFileName = myFileFileName;
}
}
bean类如下:
public class InsertImage {
public static int save(InsertImageBean iib) {
try{
String filepath = "D:/TEAMWORK/NaTelangana/WebContent/Images";
File image = iib.getMyFile();
String myfilename = iib.getMyFileName();
System.out.println("Src File name: " + iib.getMyFileName());
System.out.println("Dst File name: " + myfilename);
File destFile = new File(filepath, myfilename); // Null pointer exception is thrown here
FileUtils.copyFile(image, destFile);
System.out.println(System.getProperty("user.dir") );
if(image.renameTo(new File(filepath)))
System.out.println("File is moved successful!");
else
System.out.println("Failed to move!");
}catch(Exception e){
e.printStackTrace();
}
return 0;
}
}
问题是,在上面的程序中,我在靠近这一行的程序中得到一个NullPointerException
:
File destFile = new File(filepath, myfilename);
问题是在 bean 文件中没有接收到发送的输入。 我该如何纠正这个错误?
这是我得到的错误:
java.lang.NullPointerException
at java.io.File.<init>(File.java:317)
at natelangana.com.InsertImage.save(InsertImage.java:23)
at bean.com.InsertImageBean.execute(InsertImageBean.java:26)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:440)
at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:279)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)Src File name: null
Dst File name: null
at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:163)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:249)
at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:122)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
at com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:148)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
at org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:93)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:306)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
at com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:89)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
at com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:128)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
at org.apache.struts2.interceptor.ProfilingActivationInterceptor.intercept(ProfilingActivationInterceptor.java:104)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:267)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
at com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:126)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
at com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:138)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
at com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:148)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
at org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
at com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:128)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:176)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:306)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:52)
at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:468)
at org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:395)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:562)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:395)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:250)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:188)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:744)
将输入名称更改为以小写字符开头:
<input type="file" name="image">
然后在 Action 中,您需要将 File 变量的名称添加到 contentType 和 FileName 字符串中,如下所示:
private File image; private String imageContentType; private String imageFileName; /* GETTERS AND SETTERS FOR ALL OF THEM */
您可能还对如何配置单个文件(以及整个请求)的最大大小、仅允许上传特定类型的文件或一次上传多个文件感兴趣。
编辑
你没有发布你的 struts.xml 和 web.xml 配置,而是 stacktrace 的那一行
在 org.apache.struts2.dispatcher。 FilterDispatcher .doFilter(FilterDispatcher.java:395)
揭示您使用了错误的 Filter 。
此外,文件上传拦截器似乎被配置为运行两次......这通常发生在以错误的方式配置它时,例如
<!-- WRONG -->
<interceptor-ref name="fileUpload">
<param name="maximumSize">2097152</param>
<param name="allowedTypes">
image/png,image/gif,image/jpeg,image/pjpeg
</param>
</interceptor-ref>
<interceptor-ref name="defaultStack" />
代替
<!-- RIGHT -->
<interceptor-ref name="defaultStack">
<param name="fileUpload.maximumSize">2097152</param>
<param name="fileUpload.allowedTypes">
image/png,image/gif,image/jpeg,image/pjpeg
</param>
</interceptor-ref>
再次,仔细检查您在 web.xml 和 struts.xml 中的配置,它会自动工作。
尝试使用<s:file name="Image"/>
标签而不是普通的<input/>
您可以从简单的文件上传示例开始,然后您可以查看上传文件的存储位置。 如果您设置了上传的文件名,则可以复制文件。 您可以在开始保存之前防止空指针异常。
if (myFileFileName != null)
InsertImage.save(this);
您还可以添加required
验证器,该验证器将在您的操作执行之前检查字段值。
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