除了更改
saveDir（实际上是不必要和危险的）之外，您还没有遵循Action类中的约定：私有变量的名称必须与其Getter和Setter的名称匹配；最后，在页面中，您通过指向私有变量而不是setter来使名称不匹配。更改为：
public class UploadAction extends ActionSupport{ private File upload; private String uploadFileName; private String uploadContentType; public void setUpload(File upload){ this.upload=upload; } public void setUploadContentType(String uploadContentType){ this.uploadContentType=uploadContentType; } public void setUploadFileName(String uploadFileName){ this.uploadFileName=uploadFileName; } @Override public String execute(){ if(upload==null) { System.out.println("No file...."); } System.out.println(uploadContentType); System.out.println(uploadFileName); return SUCCESS; }}JSP
<s:form action="upload" method="post" enctype="multipart/form-data"> <input type="file" name="upload" id="uploadfile" /> <input type="submit" id="submit" /></s:form>
