[原创]java WEB学习笔记72：Struts2 学习之路-- 文件的上传下载，及上传下载相关问题

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1.文件上传

　　1）表单需要注意三点：

　　　　　① 须把 HTML 表单的 enctype 属性设置为 multipart/form-data

　　　　 ②须把 HTML 表单的method 属性设置为 post

　　　　　③需添加 <input type=“file”> 字段.　

　　2）Struts2 的文件上传实际使用的是Common FileUpload 组件，导入jar包。commons-fileupload / commons-io

　　3）Struts2 进行文件上传需要使用FileUpload拦截器

　　4）基本的文件操作：直接在Action 中定义如下 3个属性，并提供对应的get / set方法

　　　　private File [fileFieldName]; //文件对应的file 对象

　　　　　private String [fileFieldName]ContentType; // 文件类型

　　　　　private String [fileFieldName]pptFileName; // 文件名

　　5）使用IO 流进行文件的上传

 <?xml version="1.0" encoding="UTF-8" ?>

 <!DOCTYPE struts PUBLIC

     "-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"

     "http://struts.apache.org/dtds/struts-2.3.dtd">

 <struts>

      <!-- 配置国际化资源文件 -->

      <constant name="strut2.custom.i18n.resouce" value="i18n"></constant>

      <constant name="struts.action.extension" value="action,do,"></constant>

      <package name="default" namespace="/" extends="struts-default">

          <action name="testUpload" class="com.jason.upload.app.UploadAction">

              <result>/sucess.jsp</result>

          </action>

      </package>

 </struts>

struts.xml

 <%@ 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>

 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

 <title>Insert title here</title>

 </head>

 <body>

     <s:form action="testUpload" method="post" enctype="multipart/form-data">

         <s:file name="ppt" label="PPTfile"></s:file>

         <s:textfield  name="pptDesc" label="PPTDesc"></s:textfield>

         <s:submit></s:submit>

     </s:form>

 </body>

 </html>

upload.jsp

 <%@ page language="java" contentType="text/html; charset=UTF-8"

     pageEncoding="UTF-8"%>

 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

 <html>

 <head>

 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

 <title>Insert title here</title>

 </head>

 <body>

     <h4> success page</h4>

 </body>

 </html>

sucess.jsp

 package com.jason.upload.app;

 import java.io.File;

 import java.io.FileInputStream;

 import java.io.FileOutputStream;

 import javax.servlet.Servlet;

 import javax.servlet.ServletContext;

 import org.apache.struts2.ServletActionContext;

 import com.opensymphony.xwork2.ActionSupport;

 public class UploadAction extends ActionSupport {

     /**

      * @Fields:serialVersionUID

      */

     private static final long serialVersionUID = 1L;

     private File ppt;

     private String pptContentType;

     private String pptFileName;

     public File getPpt() {

         return ppt;

     }

     public void setPpt(File ppt) {

         this.ppt = ppt;

     }

     public String getPptContentType() {

         return pptContentType;

     }

     public void setPptContentType(String pptContentType) {

         this.pptContentType = pptContentType;

     }

     public String getPptFileName() {

         return pptFileName;

     }

     public void setPptFileName(String pptFileName) {

         this.pptFileName = pptFileName;

     }

     @Override

     public String execute() throws Exception {

         ServletContext  servletContext = ServletActionContext.getServletContext();

         String dir = servletContext.getRealPath("/files/" + pptFileName);

         System.out.println(dir);

         FileOutputStream out = new FileOutputStream(dir);

         FileInputStream in = new FileInputStream(ppt);

         byte[] buffer = new byte[1024];

         int len = 0;

         while((len = in.read(buffer)) != -1){

             out.write(buffer, 0, len);

         }

           out.close();

           in.close();

         System.out.println(ppt);

         System.out.println(pptContentType);

         System.out.println(pptFileName);

         return SUCCESS;

     }

 }

UploadAction.java

2.相关问题

　　1）一次性上传过个文件？

　　　若传递多个文件，则上述3个属性，可以改为list类型，多个文件的name 属性需要一致

 <s:form action="testUpload" method="post" enctype="multipart/form-data">

         <s:file name="ppt" label="PPTfile"></s:file>

         <s:textfield  name="pptDesc[0]" label="PPTDesc"></s:textfield>

         <s:file name="ppt" label="PPTfile"></s:file>

         <s:textfield  name="pptDesc[1]" label="PPTDesc"></s:textfield>

         <s:file name="ppt" label="PPTfile"></s:file>

         <s:textfield  name="pptDesc[2]" label="PPTDesc"></s:textfield>

         <s:file name="ppt" label="PPTfile"></s:file>

         <s:textfield  name="pptDesc[3]" label="PPTDesc"></s:textfield>

         <s:submit></s:submit>

     </s:form>

     private List<File> ppts;

     private String pptContentType;

     private String pptFileName;

　　2）对上传文件的限制？例如扩展名，内容类型，上传文件的大小？如果出错，显示错误消息？消息可以定制?

Interceptor parameters: 

•maximumSize (optional) - the maximum size (in bytes) that the interceptor will allow a file reference to be set on the action. Note, this is not related to the various properties found in struts.properties. Default to approximately 2MB.



默认文件的最大值2M，上传的单个文件

•allowedTypes (optional) - a comma separated list of content types (ie: text/html) that the interceptor will allow a file reference to be set on the action. If none is specified allow all types to be uploaded.

允许上传的文件类型，多个使用 ',' 分割

•allowedExtensions (optional) - a comma separated list of file extensions (ie: .html) that the interceptor will allow a file reference to be set on the action. If none is specified allow all extensions to be uploaded.

允许的上传文件的类型，多个使用 ‘ , ’分割

定制文件上传错误消息

This interceptor will add several field errors, assuming that the action implements ValidationAware. These error messages are based on several i18n values stored in struts-messages.properties, a default i18n file processed for all i18n requests. You can override the text of these messages by providing text for the following keys: 

•struts.messages.error.uploading - a general error that occurs when the file could not be uploaded
文件上传出错的消息

•struts.messages.error.file.too.large - occurs when the uploaded file is too large

文件超过最大值的消息

•struts.messages.error.content.type.not.allowed - occurs when the uploaded file does not match the expected content types specified

文件内容不合法的消息

•struts.messages.error.file.extension.not.allowed - occurs when the uploaded file does not match the expected file extensions specified
文件扩展名不合法的消息

可以参考 org.apache.struts2. 下的 struts-message.properties ，可提供更多的定制信息

在 org.apache.struts2. 下的 default.properties 中有对文件上传总的大小的限制。可以使用常量的方式，修改限制：struts.multipart.maxSize = ?

  1 <!-- 配置国际化资源文件 -->

  2      <constant name="strut2.custom.i18n.resouce" value="i18n"></constant>

  3

  4      <constant name="struts.action.extension" value="action,do,"></constant>

  5

  6      <package name="default" namespace="/" extends="struts-default">

  7

  8          <interceptors>

  9              <interceptor-stack name="jasonStack">

 10                  <interceptor-ref name="defaultStack">

 11                      <param name="fileUpload.maximumSize">2000</param>

 12                      <param name="fileUpload.allowedTypes">text/html,text/xml</param>

 13                      <param name="fileUpload.allowedExtensions">html,ppt,xml</param>

 14                  </interceptor-ref>

 15              </interceptor-stack>

 16          </interceptors>

 17

 18

 19          <default-interceptor-ref name="jasonStack"></default-interceptor-ref>

 20          <action name="testUpload" class="com.jason.upload.app.UploadAction">

 21              <result>/sucess.jsp</result>

 22          </action>

 23

 24      </package>

 25

struts.xml

 struts.messages.error.uploading=\u6587\u4EF6\u4E0A\u4F20\u51FA\u9519\u7684\u6D88\u606F

 struts.messages.error.file.too.large=\u6587\u4EF6\u8D85\u8FC7\u6700\u5927\u503C\u7684\u6D88\u606F

 struts.messages.error.content.type.not.allowed=\u6587\u4EF6\u5185\u5BB9\u4E0D\u5408\u6CD5\u7684\u6D88\u606F

 struts.messages.error.file.extension.not.allowed=\u6587\u4EF6\u6269\u5C55\u540D\u4E0D\u5408\u6CD5\u7684\u6D88\u606F

i18n.properties

2.文件的下载

　　1）struts2 中使用 type="stream" 的result 进行下载即可：具体细节 /struts-2.3.15.3-all/struts-2.3.15.3/docs/WW/docs/stream-result.html

　　2）Struts 专门为文件下载提供了一种 Stream 结果类型. 在使用一个 Stream 结果时, 不必准备一个 JSP 页面.

　　3）Stream 结果类型可以设置如下参数:(以下参数可以在Action中以 getter 方法的方式提供)

　　　　 - contentType：被下载的文件的 MIME 类型。默认值为 text/plain

　　　　 - contentLength：被下载的文件的大小，以字节为单位

　　　　 - contentDisposition：可以设置下载文件名的ContentDispositon 响应头，默认值为 inline，通常设置为如下格式： attachment;filename="document.pdf".

　　　　 - inputName：Action 中提供的文件的输入流。默认值为 inputStream

　　　　 - bufferSize：文件下载时缓冲区的大小。默认值为 1024

　　　　 - allowCaching ：文件下载时是否允许使用缓存。默认值为 true

　　　　 - contentCharSet：文件下载时的字符编码。

4）Stream 结果类型的参数可以在 Action 以属性的方式覆盖

download.jsp

 <%@ page language="java" contentType="text/html; charset=UTF-8"

     pageEncoding="UTF-8"%>

 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

 <html>

 <head>

 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

 <title>Insert title here</title>

 </head>

 <body>

     <a href="testDownload">Down Load</a>

 </body>

 </html>

DownLoadAction.java
 对于

contentType

contentLength

contentDisposition

inputStream
我们需要在对应的Action 中声明一个变量 且提供 getter方法

 package com.jason.upload.app;

 import java.io.FileInputStream;

 import java.io.InputStream;

 import javax.servlet.ServletContext;

 import org.apache.struts2.ServletActionContext;

 import com.opensymphony.xwork2.ActionSupport;

 public class DownLoadAction extends ActionSupport {

     /**

      * @Fields:serialVersionUID

      */

     private static final long serialVersionUID = 1L;

     private String contentType;

     private long contentLength;

     private String contentDisposition;

     private InputStream inputStream;

     public String getContentDisposition() {

         return contentDisposition;

     }

     public long getContentLength() {

         return contentLength;

     }

     public String getContentType() {

         return contentType;

     }

     public InputStream getInputStream() {

         return inputStream;

     }

     @Override

     public String execute() throws Exception {

         //1.确定各成员的值

         contentType = "text/html";

44         contentDisposition = "attachment;filename='a.html'";

45

46         ServletContext  servletContext = ServletActionContext.getServletContext();

47         String fileName = servletContext.getRealPath("/files/a.html");

48         inputStream = new FileInputStream(fileName);

49         contentLength = inputStream.available();

         return super.execute();

     }

 }

struts.xml

 <?xml version="1.0" encoding="UTF-8" ?>

 <!DOCTYPE struts PUBLIC

     "-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"

     "http://struts.apache.org/dtds/struts-2.3.dtd">

 <struts>

 <action name="testDownload" class="com.jason.upload.app.DownLoadAction">

              <result type="stream">

                  <param name="bufferSize">2048</param>

              </result>

          </action>

 </package>

 </struts>