正文
Java Struts文件上传和下载详解
提示：扫一扫查出行【扫一扫了解最新限行尾号】
复制提示
Struts2文件上传
Struts 2框架提供了内置支持处理文件上传使用基于HTML表单的文件上传。上传一个文件时，它通常会被存储在一个临时目录中，他们应该由Action类进行处理或移动到一个永久的目录，以确保数据不丢失。
请注意，服务器有一个安全策略可能会禁止写到目录以外的临时目录和属于web应用的目录。
在Struts中的文件上传是通过预先定义的拦截文件上传拦截器这是可通过org.apache.struts2.interceptor.FileUploadInterceptor类的defaultStack中的一部分。仍然可以使用在struts.xml中设置各种参数，我们将在下面看到。
视图文件index.jsp<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@ taglib prefix="s" uri="/struts-tags"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <base href="<%=basePath%>"> <title>My JSP 'index.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css"> --> </head> <body> <form action="Upload.action" method="post" enctype="multipart/form-data"> <label for="myFile">你要上传的文件</label> <input type="file" name="myFile" /><br> <input type="submit" value="上传"/> </form> </body></html>
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@ taglib prefix="s" uri="/struts-tags"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <base href="<%=basePath%>"> <title>My JSP 'index.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css"> --> </head> <body> <form action="Upload.action" method="post" enctype="multipart/form-data"> <label for="myFile">你要上传的文件</label> <input type="file" name="myFile" /><br> <input type="submit" value="上传"/> </form> </body></html>
在上面的例子中值得注意几点说明。首先，表单的enctype属性设置为multipart/ form-data。这应该是设置为使得处理文件上传文件上传。下一个点值得注意的是表单的 action方法上传和文件上传字段的名称 – myFile。我们需要这些信息创建操作方法和struts配置。
接下来让我们创建一个简单的 jsp 文件的success.jsp 结果显示我们的文件上传的情况下成功。
<%@ page language="java" contentType="text/html; charset=UTF-8"pageEncoding="UTF-8"%><%@ taglib prefix="s" uri="/struts-tags"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd"><html><head><title>文件上传</title></head><body>成功</body></html>
创建action类： 处理上传文件package com.oumyye.FileUpload;import java.io.File;import java.io.IOException;import org.apache.commons.io.FileUtils;import com.opensymphony.xwork2.ActionSupport;public class FileUploadAction extends ActionSupport{ private File myFile; private String myFileContentType; private String myFileFileName; private String destPath; /** * */ private static final long serialVersionUID = 1L; @Override public String execute() throws Exception { // TODO Auto-generated method stub destPath = "e:/upload/"; try{ System.out.println("Src File name: " + myFile); System.out.println("我的文件名"+myFileFileName); System.out.println("我的文件类型"+ myFileContentType); File destFile = new File(destPath, myFileFileName); FileUtils.copyFile(myFile, destFile); }catch(IOException e){ e.printStackTrace(); return ERROR; } return SUCCESS; } public File getMyFile() { return myFile; } public void setMyFile(File myFile) { this.myFile = myFile; } public String getMyFileContentType() { return myFileContentType; } public void setMyFileContentType(String myFileContentType) { this.myFileContentType = myFileContentType; } public String getMyFileFileName() { return myFileFileName; } public void setMyFileFileName(String myFileFileName) { this.myFileFileName = myFileFileName; } public String getDestPath() { return destPath; } public void setDestPath(String destPath) { this.destPath = destPath; } public static long getSerialversionuid() { return serialVersionUID; }}
配置文件：
package com.oumyye.FileUpload;import java.io.File;import java.io.IOException;import org.apache.commons.io.FileUtils;import com.opensymphony.xwork2.ActionSupport;public class FileUploadAction extends ActionSupport{ private File myFile; private String myFileContentType; private String myFileFileName; private String destPath; /** * */ private static final long serialVersionUID = 1L; @Override public String execute() throws Exception { // TODO Auto-generated method stub destPath = "e:/upload/"; try{ System.out.println("Src File name: " + myFile); System.out.println("我的文件名"+myFileFileName); System.out.println("我的文件类型"+ myFileContentType); File destFile = new File(destPath, myFileFileName); FileUtils.copyFile(myFile, destFile); }catch(IOException e){ e.printStackTrace(); return ERROR; } return SUCCESS; } public File getMyFile() { return myFile; } public void setMyFile(File myFile) { this.myFile = myFile; } public String getMyFileContentType() { return myFileContentType; } public void setMyFileContentType(String myFileContentType) { this.myFileContentType = myFileContentType; } public String getMyFileFileName() { return myFileFileName; } public void setMyFileFileName(String myFileFileName) { this.myFileFileName = myFileFileName; } public String getDestPath() { return destPath; } public void setDestPath(String destPath) { this.destPath = destPath; } public static long getSerialversionuid() { return serialVersionUID; }}
可以使用恒定的标签在应用程序 struts.xml文件，像我一样改变要上传的文件的最大大小。让我们有我们的在struts.xml如下：
<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.1//EN" "http://struts.apache.org/dtds/struts-2.1.dtd"><struts> <constant name="struts.devMode" value="false" /> <!-- 指定每次请求到达，重新加载资源文件 --> <constant name="struts.i18n.reload" value="true" /> <!-- 指定每次配置文件更改后，自动重新加载 --> <constant name="struts.configuration.xml.reload" value="true" /> <!-- 把主题配置为simple --> <constant name="struts.ui.theme" value="simple" /> <!-- 指定允许上传的文件最大字节数。默认值是2097152(2M) --> <constant name="struts.multipart.maxSize" value="10701096" /><!--文件上传--> <package name="upload" namespace="/" extends="struts-default"> <action name="Upload" class="com.oumyye.FileUpload.FileUploadAction"> <result name="success">/success.jsp</result> <result name="input">/index.jsp</result> </action><!--文件下载--> <action name="FileDownload" class="com.oumyye.action.FileDownload"> <result name="success" type="stream"> <param name="contentType">text/plain</param> <param name="contentDisposition">attachment;fileName="${fileName}"</param> <param name="inputName">downloadFile</param> <param name="bufferSize">1024</param> </result> </action> </package></struts>
以下是web.xml文件中的内容,与Struts2的基本配置一样
<?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0"> <display-name>Struts2_1000_FileUpload</display-name> <filter> <filter-name>struts2</filter-name> <filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class> </filter> <filter-mapping> <filter-name>struts2</filter-name> <url-pattern>*.action</url-pattern> </filter-mapping></web-app>
上述代码即可完成文件上传
文件下载视图文件filedownload.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <base href="<%=basePath%>"> <title>文件下载</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css"> --> </head> <body> <h2>文件下载内容：</h2><br/> Dream.jpg:<a href="FileDownload.action">点击下载</a><br/> </body></html>
创建action类： 处理上传文件，package com.oumyye.action;import java.io.InputStream;import org.apache.struts2.ServletActionContext;import com.opensymphony.xwork2.ActionSupport;//文件下载public class FileDownload extends ActionSupport{ private String fileName; public String getFileName() { return fileName; } public void setFileName(String fileName) { this.fileName = fileName; } //返回一个输入流，作为一个客户端来说是一个输入流，但对于服务器端是一个 输出流 public InputStream getDownloadFile() throws Exception { this.fileName = "hello.jpg" ; //获取资源路径 return ServletActionContext.getServletContext().getResourceAsStream("upload/"+this.fileName) ; } @Override public String execute() throws Exception { return SUCCESS; }}
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <base href="<%=basePath%>"> <title>文件下载</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css"> --> </head> <body> <h2>文件下载内容：</h2><br/> Dream.jpg:<a href="FileDownload.action">点击下载</a><br/> </body></html>
package com.oumyye.action;import java.io.InputStream;import org.apache.struts2.ServletActionContext;import com.opensymphony.xwork2.ActionSupport;//文件下载public class FileDownload extends ActionSupport{ private String fileName; public String getFileName() { return fileName; } public void setFileName(String fileName) { this.fileName = fileName; } //返回一个输入流，作为一个客户端来说是一个输入流，但对于服务器端是一个 输出流 public InputStream getDownloadFile() throws Exception { this.fileName = "hello.jpg" ; //获取资源路径 return ServletActionContext.getServletContext().getResourceAsStream("upload/"+this.fileName) ; } @Override public String execute() throws Exception { return SUCCESS; }}
配置文件同上
下载时可能会出现错误
Can not find a java.io.InputStream with the name [downloadFile] in the invocation stack. Check the <param name="inputName"> tag specified for this action.
可能的原因：
1.文件路径不对，根本就没有取到文件。这种情况下，可以将获得InputStream的那条语句放在system.out.println()中输出一下，若为null，那就是路径不对了，或者说得准确些就根本没有找到文件。
2.在action中没有写配置文件中”<param name=”inputName”>”后面属性的那个get方法.
