[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
1 <?xml version="1.0" encoding="UTF-8" ?> 2 <!DOCTYPE struts PUBLIC 3 "-//Apache Software Foundation//DTD Struts Configuration 2.3//EN" 4 "http://struts.apache.org/dtds/struts-2.3.dtd"> 5 6 <struts> 7 8 9 <!-- 配置国际化资源文件 --> 10 <constant name="strut2.custom.i18n.resouce" value="i18n"></constant> 11 12 <constant name="struts.action.extension" value="action,do,"></constant> 13 <package name="default" namespace="/" extends="struts-default"> 14 15 <action name="testUpload" class="com.jason.upload.app.UploadAction"> 16 <result>/sucess.jsp</result> 17 </action> 18 19 </package> 20 21 </struts>
1 <%@ page language="java" contentType="text/html; charset=UTF-8" 2 pageEncoding="UTF-8"%> 3 <%@ taglib prefix="s" uri="/struts-tags" %> 4 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 5 <html> 6 <head> 7 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 8 <title>Insert title here</title> 9 </head> 10 <body> 11 12 <s:form action="testUpload" method="post" enctype="multipart/form-data"> 13 <s:file name="ppt" label="PPTfile"></s:file> 14 <s:textfield name="pptDesc" label="PPTDesc"></s:textfield> 15 16 <s:submit></s:submit> 17 </s:form> 18 19 20 </body> 21 </html>
1 <%@ page language="java" contentType="text/html; charset=UTF-8" 2 pageEncoding="UTF-8"%> 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 4 <html> 5 <head> 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 7 <title>Insert title here</title> 8 </head> 9 <body> 10 11 <h4> success page</h4> 12 </body> 13 </html>
1 package com.jason.upload.app; 2 3 import java.io.File; 4 import java.io.FileInputStream; 5 import java.io.FileOutputStream; 6 7 import javax.servlet.Servlet; 8 import javax.servlet.ServletContext; 9 10 import org.apache.struts2.ServletActionContext; 11 12 import com.opensymphony.xwork2.ActionSupport; 13 14 public class UploadAction extends ActionSupport { 15 16 /** 17 * @Fields:serialVersionUID 18 */ 19 private static final long serialVersionUID = 1L; 20 21 private File ppt; 22 private String pptContentType; 23 private String pptFileName; 24 25 26 public File getPpt() { 27 return ppt; 28 } 29 30 public void setPpt(File ppt) { 31 this.ppt = ppt; 32 } 33 34 public String getPptContentType() { 35 return pptContentType; 36 } 37 38 public void setPptContentType(String pptContentType) { 39 this.pptContentType = pptContentType; 40 } 41 42 public String getPptFileName() { 43 return pptFileName; 44 } 45 46 public void setPptFileName(String pptFileName) { 47 this.pptFileName = pptFileName; 48 } 49 50 51 @Override 52 public String execute() throws Exception { 53 54 ServletContext servletContext = ServletActionContext.getServletContext(); 55 56 String dir = servletContext.getRealPath("/files/" + pptFileName); 57 System.out.println(dir); 58 59 FileOutputStream out = new FileOutputStream(dir); 60 FileInputStream in = new FileInputStream(ppt); 61 62 byte[] buffer = new byte[1024]; 63 int len = 0; 64 while((len = in.read(buffer)) != -1){ 65 out.write(buffer, 0, len); 66 } 67 out.close(); 68 in.close(); 69 70 71 System.out.println(ppt); 72 System.out.println(pptContentType); 73 System.out.println(pptFileName); 74 return SUCCESS; 75 } 76 77 }
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
1 <s:form action="testUpload" method="post" enctype="multipart/form-data">
2 <s:file name="ppt" label="PPTfile"></s:file>
3 <s:textfield name="pptDesc[0]" label="PPTDesc"></s:textfield>
4
5 <s:file name="ppt" label="PPTfile"></s:file>
6 <s:textfield name="pptDesc[1]" label="PPTDesc"></s:textfield>
7
8 <s:file name="ppt" label="PPTfile"></s:file>
9 <s:textfield name="pptDesc[2]" label="PPTDesc"></s:textfield>
10
11 <s:file name="ppt" label="PPTfile"></s:file>
12 <s:textfield name="pptDesc[3]" label="PPTDesc"></s:textfield>
13
14 <s:submit></s:submit>
15 </s:form>
1 private List<File> ppts;
2 private String pptContentType;
3 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 1 <!-- 配置国际化资源文件 --> 2 2 <constant name="strut2.custom.i18n.resouce" value="i18n"></constant> 3 3 4 4 <constant name="struts.action.extension" value="action,do,"></constant> 5 5 6 6 <package name="default" namespace="/" extends="struts-default"> 7 7 8 8 <interceptors> 9 9 <interceptor-stack name="jasonStack"> 10 10 <interceptor-ref name="defaultStack"> 11 11 <param name="fileUpload.maximumSize">2000</param> 12 12 <param name="fileUpload.allowedTypes">text/html,text/xml</param> 13 13 <param name="fileUpload.allowedExtensions">html,ppt,xml</param> 14 14 </interceptor-ref> 15 15 </interceptor-stack> 16 16 </interceptors> 17 17 18 18 19 19 <default-interceptor-ref name="jasonStack"></default-interceptor-ref> 20 20 <action name="testUpload" class="com.jason.upload.app.UploadAction"> 21 21 <result>/sucess.jsp</result> 22 22 </action> 23 23 24 24 </package> 25 25
1 struts.messages.error.uploading=\u6587\u4EF6\u4E0A\u4F20\u51FA\u9519\u7684\u6D88\u606F 2 struts.messages.error.file.too.large=\u6587\u4EF6\u8D85\u8FC7\u6700\u5927\u503C\u7684\u6D88\u606F 3 struts.messages.error.content.type.not.allowed=\u6587\u4EF6\u5185\u5BB9\u4E0D\u5408\u6CD5\u7684\u6D88\u606F 4 struts.messages.error.file.extension.not.allowed=\u6587\u4EF6\u6269\u5C55\u540D\u4E0D\u5408\u6CD5\u7684\u6D88\u606F
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
1 <%@ page language="java" contentType="text/html; charset=UTF-8"
2 pageEncoding="UTF-8"%>
3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
4 <html>
5 <head>
6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
7 <title>Insert title here</title>
8 </head>
9 <body>
10 <a href="testDownload">Down Load</a>
11 </body>
12 </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
1 package com.jason.upload.app;
2
3 import java.io.FileInputStream;
4 import java.io.InputStream;
5
6 import javax.servlet.ServletContext;
7
8 import org.apache.struts2.ServletActionContext;
9
10 import com.opensymphony.xwork2.ActionSupport;
11
12 public class DownLoadAction extends ActionSupport {
13
14 /**
15 * @Fields:serialVersionUID
16 */
17 private static final long serialVersionUID = 1L;
18
19 private String contentType;
20 private long contentLength;
21 private String contentDisposition;
22 private InputStream inputStream;
23
24 public String getContentDisposition() {
25 return contentDisposition;
26 }
27
28 public long getContentLength() {
29 return contentLength;
30 }
31
32 public String getContentType() {
33 return contentType;
34 }
35
36 public InputStream getInputStream() {
37 return inputStream;
38 }
39 @Override
40 public String execute() throws Exception {
41
42 //1.确定各成员的值
43 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();
50 return super.execute();
51 }
52
53 }
struts.xml
1 <?xml version="1.0" encoding="UTF-8" ?>
2 <!DOCTYPE struts PUBLIC
3 "-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
4 "http://struts.apache.org/dtds/struts-2.3.dtd">
5
6 <struts>
7 <action name="testDownload" class="com.jason.upload.app.DownLoadAction">
8 <result type="stream">
9 <param name="bufferSize">2048</param>
10 </result>
11 </action>
12 </package>
13
14 </struts>
