要進行struts2文件上傳，我們需要寫一個action類，類中需要定義一個需要上傳的文件變量，即 PRivate File upFile;

      action類中代碼如下：

package struts.action;import java.io.File;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import javax.servlet.ServletContext;import org.apache.struts2.ServletActionContext;import com.opensymphony.xwork2.ActionSupport;public class FileUploadDemo extends ActionSupport {	private File upFile;	private String uploadPath;	private String upFileContentType;// 文件類型	private String upFileFileName; // 文件名	public File getUpFile() {		return upFile;	}	public void setUpFile(File upFile) {		this.upFile = upFile;	}	public String getUploadPath() {		return uploadPath;	}	public void setUploadPath(String uploadPath) {		this.uploadPath = uploadPath;	}	public String getUpFileContentType() {		return upFileContentType;	}	public void setUpFileContentType(String upFileContentType) {		this.upFileContentType = upFileContentType;	}	public String getUpFileFileName() {		return upFileFileName;	}	public void setUpFileFileName(String upFileFileName) {		this.upFileFileName = upFileFileName;	}	@Override	public String execute() throws Exception {		ServletContext context = ServletActionContext.getServletContext();		String realPath = context.getRealPath(uploadPath);		InputStream is = null;		OutputStream os = null;		try {			is = new FileInputStream(upFile);			File file=new File(realPath+"/"+upFileFileName);			os = new FileOutputStream(file);			int len = 0;			byte[] buf = new byte[2048];			while ((len = is.read(buf)) > 0) {				os.write(buf, 0, len);			}		} catch (IOException e) {			e.printStackTrace();		} finally {			if (is != null)				is.close();			if (os != null)				os.close();		}		return SUCCESS;	}}      其中定義的upFileContentType和upFileFileName字段的前綴upFile必須是定義的文件File的變量名upFile。
      action類中的uploadPath在struts2.xml文件中可以定義如下：
<action name="FileUploadDemo" class="struts.action.FileUploadDemo"			method="execute">		<param name="uploadPath">/upload</param>		<result name="success">/demo.jsp</result>	</action>        這樣，我們就可以在action類中直接使用uploadPath，賦值即為upload。
        上傳頁面代碼如下：
<form name="uploadForm" id="uploadForm" enctype="multipart/form-data" method="post" action="FileUploadDemo.ac" >	<input name="upFile" type="file"/>	<input type="submit"  value="上傳"/></form>        在頁面中
enctype="multipart/form-data" method="post"
為必須項，否則無法進行文件的上傳。
        當缺少 method="post" 屬性時，會報錯如下：
Struts Problem ReportStruts has detected an unhandled exception:Messages: 	No result defined for action struts.action.FileUploadDemo and result inputFile: 	file:/D:/Eclipse/Workspace/CombOfThreeFrameWorks/WebRoot/WEB-INF/classes/struts.xmlLine number: 	22Column number: 	21
        可以定義struts.properties文件
struts.multipart.saveDir=D://Eclipse//Workspace//CombOfThreeFrameWorks        該文件定義為upFile文件上傳后的臨時存放路徑。
        注：在實際的操作中發現，我們可以不用在action類中定義upFileContentType和upFileFileName字段，可以根據需要自己添加。