关于JSP中的文件上传和下载操作
先分析一下上传文件的流程
1-先通过前段页面中的选择文件选择要上传的图片
index.jsp
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"
contentType="text/html; charset=UTF-8"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head> <title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="content-type" content="text/html;charset=utf-8">
<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"> <script type="text/javascript" src="js/jquery.min.js"></script>
<script type="text/javascript" src="js/common.js"></script>
<script type="text/javascript" src="js/ajaxfileupload.js"></script> </head> <body>
<input type="file" value="上传" name="inputImage" id="inputImage">
<input type="button" value="上传" id="upload"> <a id="downLoad">下载</a>
</body>
</html>
2-点击提交按钮，通过ajax的文件上传访问服务器端
common.js
var path = (function() {
//获取当前网址
var curWwwPath = window.document.location.href;
//获取主机地址之后的目录
var pathName = window.document.location.pathname;
var pos = curWwwPath.indexOf(pathName);
//获取主机地址
var localhostPath = curWwwPath.substring(0, pos);
//获取带"/"的项目名
var projectName = pathName.substring(0, pathName.substr(1).indexOf('/') + 1);
return {
curWwwPath: curWwwPath,
pathName: pathName,
localhostPath: localhostPath,
projectName: projectName,
//部署路径
deployPath: localhostPath + projectName
};
})();
// 文件下载
$("a[id=downLoad]").click(function(){
window.location.href=path.deployPath+"/fileDown";
}); // 文件上传
$("input[id=upload]").click(function() {
$.ajaxFileUpload( {
url : path.deployPath + "/fileUp", // 处理页面的绝对路径
fileElementId : "inputImage", //file空间的id属性
dataType : "json",
success : function(data) {
alert("上传成功");
}
});
});
3-服务器端响应保存或者下载
保存上传文件的FileUpload.java
import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import java.util.UUID; import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; import net.sf.json.JSONArray; import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload; import com.stu.util.HttpUtil; /**
* 文件名称： com.stu.fileupload.FileUpload.java<br/>
* 初始作者： Administrator<br/>
* 创建日期： 2018-1-31<br/>
* 功能说明： 文件上传 <br/>
* =================================================<br/>
* 修改记录：<br/>
* 修改作者 日期 修改内容<br/>
* ================================================<br/>
* Copyright (c) 2010-2011 .All rights reserved.<br/>
*/
public class FileUpload extends HttpServlet { private static final long serialVersionUID = 1L; @Override
protected void service(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException { // 获取到当前服务器所在的路径
String serverPath = req.getSession().getServletContext().getRealPath("/"); // 设置保存上传文件的路径
String saveDirPath = serverPath + "img"; File saveDirPathFileObj = new File(saveDirPath);
// 如果当用来存放文件的目录不存在时，要创建该目录
if (!saveDirPathFileObj.exists()) {
saveDirPathFileObj.mkdirs();
} // 创建一个解析器工厂
DiskFileItemFactory factory = new DiskFileItemFactory(); // 设置工厂的缓存区大小
factory.setSizeThreshold(5 * 1024); // 文件上传的解析器(文件上传对象)
ServletFileUpload upload = new ServletFileUpload(factory); // 设置上传文件的最大值
upload.setSizeMax(3 * 1024 * 1024); // 设置编码格式
upload.setHeaderEncoding("UTF-8"); try {
// 上传以后的文件名
List<String> uploadFileNames = new ArrayList<String>(); List<FileItem> fileItems = upload.parseRequest(req);
System.out.println(fileItems);
for (FileItem file : fileItems) {
// 新的文件名
String saveFileName = UUID.randomUUID().toString().replace("-", "");
// 文件的后缀
String oldFileName = new String(file.getName().getBytes(),
"UTF-8");
System.out.println("oldFileName" + oldFileName);
String fileType = oldFileName.substring(oldFileName.lastIndexOf("."));
// 新的文件路径
String saveFilePath = saveDirPath + File.separator
+ saveFileName + fileType;
uploadFileNames.add(saveFileName + fileType);
// 保存上传的文件
file.write(new File(saveFilePath));
}
System.out.println(uploadFileNames);
HttpUtil.setAttribute(req, "urls", uploadFileNames);
res.setContentType("application/json;charset=utf-8");
PrintWriter pw = res.getWriter();
pw.print(JSONArray.fromObject(uploadFileNames));
} catch (FileUploadException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
} }
下载文件的FileDownload.java
import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import java.util.UUID; import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; import net.sf.json.JSONArray; import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload; import com.stu.util.HttpUtil; /**
* 文件名称： com.stu.fileupload.FileUpload.java<br/>
* 初始作者： Administrator<br/>
* 创建日期： 2018-1-31<br/>
* 功能说明： 文件上传 <br/>
* =================================================<br/>
* 修改记录：<br/>
* 修改作者 日期 修改内容<br/>
* ================================================<br/>
* Copyright (c) 2010-2011 .All rights reserved.<br/>
*/
public class FileUpload extends HttpServlet { private static final long serialVersionUID = 1L; @Override
protected void service(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException { // 获取到当前服务器所在的路径
String serverPath = req.getSession().getServletContext().getRealPath("/"); // 设置保存上传文件的路径
String saveDirPath = serverPath + "img"; File saveDirPathFileObj = new File(saveDirPath);
// 如果当用来存放文件的目录不存在时，要创建该目录
if (!saveDirPathFileObj.exists()) {
saveDirPathFileObj.mkdirs();
} // 创建一个解析器工厂
DiskFileItemFactory factory = new DiskFileItemFactory(); // 设置工厂的缓存区大小
factory.setSizeThreshold(5 * 1024); // 文件上传的解析器(文件上传对象)
ServletFileUpload upload = new ServletFileUpload(factory); // 设置上传文件的最大值
upload.setSizeMax(3 * 1024 * 1024); // 设置编码格式
upload.setHeaderEncoding("UTF-8"); try {
// 上传以后的文件名
List<String> uploadFileNames = new ArrayList<String>(); List<FileItem> fileItems = upload.parseRequest(req);
System.out.println(fileItems);
for (FileItem file : fileItems) {
// 新的文件名
String saveFileName = UUID.randomUUID().toString().replace("-", "");
// 文件的后缀
String oldFileName = new String(file.getName().getBytes(),
"UTF-8");
System.out.println("oldFileName" + oldFileName);
String fileType = oldFileName.substring(oldFileName.lastIndexOf("."));
// 新的文件路径
String saveFilePath = saveDirPath + File.separator
+ saveFileName + fileType;
uploadFileNames.add(saveFileName + fileType);
// 保存上传的文件
file.write(new File(saveFilePath));
}
System.out.println(uploadFileNames);
HttpUtil.setAttribute(req, "urls", uploadFileNames);
res.setContentType("application/json;charset=utf-8");
PrintWriter pw = res.getWriter();
pw.print(JSONArray.fromObject(uploadFileNames));
} catch (FileUploadException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
} }
这里面用到了一个HttpUtil类，代码如下：
import javax.servlet.FilterConfig;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession; /**
* 文件名称＿com.niit.model2.util.Httputil.java</br>
* 初始作逯ܿAdministrator</br>
* 创建日期＿2018-1-23</br>
* 功能说明＿这里用一句话描述这个类的作用--此句话需删除 <br/>
* =================================================<br/>
* 修改记录＿br/>
* 修改作迠日期 修改内容<br/>
* ================================================<br/>
* Copyright (c) 2010-2011 .All rights reserved.<br/>
*/
public class HttpUtil { private HttpUtil() { } /**
* 方法描述: [用于向不同的作用域存放属性]</br>
* 初始作迺 Administrator<br/>
* 创建日期: 2018-1-23-上午11:24:45<br/>
* 弿Nj版本: 2.0.0<br/>
* =================================================<br/>
* 修改记录＿br/>
* 修改作迠日期 修改内容<br/>
* ================================================<br/>
* void
*/
public static void setAttribute(Object scopeObj, String name, Object value) { if (scopeObj instanceof HttpServletRequest) {
((HttpServletRequest) scopeObj).setAttribute(name, value);
}
if (scopeObj instanceof HttpSession) {
((HttpSession) scopeObj).setAttribute(name, value);
}
if (scopeObj instanceof ServletContext) {
((ServletContext) scopeObj).setAttribute(name, value);
}
} /**
* 方法描述: [获取作用域中指定名称的属性思</br>
* 初始作迺 Administrator<br/>
* 创建日期: 2018-1-23-上午11:29:17<br/>
* 弿Nj版本: 2.0.0<br/>
* =================================================<br/>
* 修改记录＿br/>
* 修改作迠日期 修改内容<br/>
* ================================================<br/>
*
* @param scopeObj
* @param name
* @return
* Object
*/
public static Object getAttribute(Object scopeObj, String name) { if (scopeObj instanceof HttpServletRequest) {
return ((HttpServletRequest) scopeObj).getAttribute(name);
}
if (scopeObj instanceof HttpSession) {
return ((HttpSession) scopeObj).getAttribute(name);
}
if (scopeObj instanceof ServletContext) {
return ((ServletContext) scopeObj).getAttribute(name);
}
return null;
} /**
* 方法描述: [获取上下文对象的方法]</br>
* 初始作迺 Administrator<br/>
* 创建日期: 2018-1-23-上午11:31:26<br/>
* 弿Nj版本: 2.0.0<br/>
* =================================================<br/>
* 修改记录＿br/>
* 修改作迠日期 修改内容<br/>
* ================================================<br/>
*
* @return
* ServletContext
*/
public static ServletContext getServletContext(Object sourceObj) { if (sourceObj instanceof HttpServletRequest) {
return ((HttpServletRequest) sourceObj).getSession().getServletContext();
}
if (sourceObj instanceof ServletConfig) {
return ((ServletConfig) sourceObj).getServletContext();
}
if (sourceObj instanceof FilterConfig) {
return ((FilterConfig) sourceObj).getServletContext();
}
return null;
} /**
* 方法描述: [获取项目的实际路径]</br>
* 初始作迺 Administrator<br/>
* 创建日期: 2018-1-23-上午11:45:47<br/>
* 弿Nj版本: 2.0.0<br/>
* =================================================<br/>
* 修改记录＿br/>
* 修改作迠日期 修改内容<br/>
* ================================================<br/>
*
* @param req
* @return
* String
*/
public static String getContextPath(HttpServletRequest req) { return req.getContextPath();
}
}
当然，代码编辑好了也不要忘了在 WebRoot/WEB-INF/web.xml 中添加新建的Servlet，就是刚刚的两个Java文件啦
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list> <!-- 文件上传 -->
<servlet>
<servlet-name>fileUpload</servlet-name>
<servlet-class>com.stu.fileupload.FileUpload</servlet-class>
</servlet> <servlet-mapping>
<servlet-name>fileUpload</servlet-name>
<url-pattern>/fileUp</url-pattern>
</servlet-mapping> <!-- 文件下载 -->
<servlet>
<servlet-name>fileDownload</servlet-name>
<servlet-class>com.stu.fileupload.FileDownload</servlet-class>
</servlet> <servlet-mapping>
<servlet-name>fileDownload</servlet-name>
<url-pattern>/fileDown</url-pattern>
</servlet-mapping>
</web-app>
这样的话就可以运行啦。
TIP: 不要忘记相关的jar包和 js 包哦
在 WebRoot / WEB-INF / lib 下，有 commons-fileupload.jar 和 commons-io.jar ，另外 json-lib-x.x.x-jdkxx.jar 包是用来把上传的返回数据修改为JSON格式的
在 WebRoot / js 下，导入 jquery.js , common.js , ajaxfileupload.js