Java以struts2为例介绍如何实现图片上传
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2024-03-07 21:33:21
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...
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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