Java以struts2为例介绍如何实现图片上传
投稿：mrr
这篇文章主要介绍了Java struts2中如何实现图片上传的相关资料,需要的朋友可以参考下
总的说图片上传有两种方式，一种是把图片文件写到数据库中，另一种是存到服务器文件目录中。写到数据库中的图片文件需要转换成二进制流的格式，占用数据库空间比较，适合少量图片的存储，比如说，系统中某些小图标，写到数据库中的优点是比较安全，不容易被用户不小心删除。
在struts2中实现(以图片上传为例)
1.FileUpload.jsp代码清单如下:
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%> <%@ taglib prefix="s" uri="/struts-tags" %> <html> <head> <title>The FileUplaodDemo In Struts2</title> </head> <body> <s:form action="fileUpload" method="post" enctype="multipart/form-data" namespace="/"> <s:file name="myFile" label="MyFile" ></s:file> <s:textfield name="caption" label="Caption"></s:textfield> <s:submit label="提交"></s:submit> </s:form> </body> </html>
2.ShowUpload.jsp的功能清单如下:
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%> <%@ taglib prefix="s" uri="/struts-tags" %> <html> <head> <title>ShowUpload</title> </head> <body> <div style ="padding: 3px; border: solid 1px #cccccc; text-align: center" > <img src ="UploadImages/<s:property value ="imageFileName"/> "/> <br /> <s:property value ="caption"/> </div > </body> </html>
3.FileUploadAction.java的代码清单如下 :
package com.chris;
import java.io.*;
import java.util.Date;
import org.apache.struts2.ServletActionContext;
import com.opensymphony.xwork2.ActionSupport;
public class FileUploadAction extends ActionSupport{
private static final long serialVersionUID = 572146812454l ;
private static final int BUFFER_SIZE = 16 * 1024 ;
//注意，文件上传时<s:file/>同时与myFile，myFileContentType,myFileFileName绑定
//所以同时要提供myFileContentType,myFileFileName的set方法
private File myFile; //上传文件
private String contentType;//上传文件类型
private String fileName; //上传文件名
private String imageFileName;
private String caption;//文件说明，与页面属性绑定
public void setMyFileContentType(String contentType) {
System.out.println("文件类型 : " + contentType);
this .contentType = contentType;
}
public void setMyFileFileName(String fileName) {
System.out.println("文件名称 : " + fileName);
this .fileName = fileName;
}
public void setMyFile(File myFile) {
this .myFile = myFile;
}
public String getImageFileName() {
return imageFileName;
}
public String getCaption() {
return caption;
}
public void setCaption(String caption) {
this .caption = caption;
}
private static void copy(File src, File dst) {
try {
InputStream in = null ;
OutputStream out = null ;
try {
in = new BufferedInputStream( new FileInputStream(src), BUFFER_SIZE);
out = new BufferedOutputStream( new FileOutputStream(dst), BUFFER_SIZE);
byte [] buffer = new byte [BUFFER_SIZE];
while (in.read(buffer) > 0 ) {
out.write(buffer);
}
} finally {
if ( null != in) {
in.close();
}
if ( null != out) {
out.close();
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
private static String getExtention(String fileName) {
int pos = fileName.lastIndexOf(".");
return fileName.substring(pos);
}
@Override
public String execute() {
imageFileName = new Date().getTime() + getExtention(fileName);
File imageFile = new File(ServletActionContext.getServletContext().getRealPath("UploadImages" ) + "/" + imageFileName);
copy(myFile, imageFile);
return SUCCESS;
}
}
注:此时仅为方便实现Action所以继承ActionSupport,并Overrider execute()方法
在struts2中任何一个POJO都可以作为Action
4.struts.xml清单如下:
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN" "http://struts.apache.org/dtds/struts-2.0.dtd"> <struts> <package name="example" namespace="/" extends="struts-default"> <action name="fileUpload" class="com.chris.FileUploadAction"> <interceptor-ref name="fileUploadStack"/> <result>/ShowUpload.jsp</result> </action> </package> </struts>
5.web.xml清单如下:
<?xml version="1.0" encoding="UTF-8"?> <web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"> <filter > <filter-name > struts-cleanup </filter-name > <filter-class > org.apache.struts2.dispatcher.ActionContextCleanUp </filter-class > </filter > <filter-mapping > <filter-name > struts-cleanup </filter-name > <url-pattern > /* </url-pattern > </filter-mapping > <filter> <filter-name>struts2</filter-name> <filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class> </filter> <filter-mapping> <filter-name>struts2</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <welcome-file-list> <welcome-file>Index.jsp</welcome-file> </welcome-file-list> </web-app>
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