复习struts2+jsp上传文件

<form action="upload" id="upForm" method="post">
<input type="file" id="att" name="attachment" accept="img/jpeg">
<input type="submit" value="ok">
</form>

package action;
public Class UploadAction extends ActionSupport(){
private File attachment;
private String attachmentContentType;
private String attachmentFileName;
public File getAttachment() {
return attachment;
}
public void setAttachment(File attachment) {
this.attachment = attachment;
}
public String getAttachmentContentType() {
return attachmentContentType;
}
public void setAttachmentContentType(String attachmentContentType) {
this.attachmentContentType = attachmentContentType;
}
public String getAttachmentFileName() {
return attachmentFileName;
}
public void setAttachmentFileName(String attachmentFileName) {
this.attachmentFileName = attachmentFileName;
}
public String upload(){
String realpath=ServletActionContext.getServletContext().getRealPath("/");
FileInputStream fis=new FileInputStream(attachment);
FileOutputStream fos=new FileOutputStream(realpath+"/upload/x.jpg");
IOUtils.copy(fis, fos);
fos.flush();
fos.close();
fis.close();
return null;
}
}

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
"http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
<constant name="struts.multipart.maxSize" value="1048576"></constant>
<package name="struts2" namespace="/" extends="struts-default">
<action name="upload" class="action.UploadAction" method="upload">
</package>
</struts>