一丶先引入上传下载的lib
二丶上传的的servlet
package com.test.action;
import java.io.file;
import java.io.fileoutputstream;
import java.io.ioexception;
import java.io.inputstream;
import java.io.outputstream;
import java.util.list;
import javax.servlet.servletexception;
import javax.servlet.annotation.webservlet;
import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
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;
@webservlet("/upload")
public class fileuploadaction extends httpservlet {
private static final long serialversionuid = 1l;
protected void dopost(httpservletrequest request,
httpservletresponse response) throws servletexception, ioexception {
// 设置编码
request.setcharacterencoding("utf-8");
//对提交的数据进行处理，保存上传文件
boolean success = processupload(request);
if(success){
//获取表单text控件的值
string account = request.getattribute("account").tostring();
system.out.println(account);
//获取文件上传的原始名称
string filename = request.getattribute("upfile").tostring();
system.out.println(filename);
//获取文件上传后，服务器上保存的名字
string filenameserver = request.getattribute("upfileserver").tostring();
system.out.println(filenameserver);
request.setattribute("upfile", filenameserver);
request.setattribute("message", "上传成功");
}
request.getrequestdispatcher("/upload.jsp").forward(request, response);
}
private boolean processupload(httpservletrequest request) {
boolean success = true;
string message = null;
// 获取文件需要上传到的路径
string path = request.getservletcontext().getrealpath("/upload");
system.out.println(path);
// 如果此文件夹不存在，则构造此文件夹
file f = new file(path);
if (!f.exists()) {
f.mkdir();
}
// 构造出文件工厂，用于存放jsp页面中传递过来的文件
diskfileitemfactory factory = new diskfileitemfactory();
// 设置上传文件的保存路径
factory.setrepository(f);
// 设置缓存大小，如果文件大于缓存大小时，则先把文件放到缓存中
factory.setsizethreshold(1 * 1024 * 1024);
servletfileupload upload = new servletfileupload(factory);
// 设置可以上传文件大小的上界20mb
upload.setsizemax(20 * 1024 * 1024);
try {
// 可以上传多个文件
list list = (list) upload.parserequest(request);
for (fileitem item : list) {
// 获取表单的属性名字
string name = item.getfieldname();
if (item.isformfield()) {
string value = item.getstring();
//解决乱码问题
value = new string(value.getbytes("iso-8859-1"),"utf-8");
request.setattribute(name, value);
} else {
// 获得文件类型
string contenttype = item.getcontenttype();
// 获得文件大小
long filesize = item.getsize();
// 获取路径名
string value = item.getname();
// 索引到最后一个反斜杠
int start = value.lastindexof("\\");
// 截取 上传文件的 字符串名字，加1是 去掉反斜杠，
string filename = value.substring(start + 1);
if (filename != null && !filename.trim().equals("")) {
// 如果上传的文件不是图片，那么不上传
string allimgext = ".jpg|.jpeg|.gif|.bmp|.png|";
string extname = filename.substring(filename.indexof("."), filename.length());
if (allimgext.indexof(extname + "|") == -1) {
message = "该文件类型不允许上传。请上传 " + allimgext
+ " 类型的文件，当前文件类型为" + extname;
success = false;
break;
}
request.setattribute(name, filename);
// 随机数产生名称
string newname = system.currenttimemillis() + extname;
request.setattribute(name + "server", newname);
// 将文件保存到服务器中
inputstream in = item.getinputstream();
// 原文件名
// outputstream out = new fileoutputstream(new file(path, filename));
// 随机数文件名
outputstream out = new fileoutputstream(new file(path,
newname));
int length = 0;
byte[] buf = new byte[1024];
while ((length = in.read(buf)) != -1) {
out.write(buf, 0, length);
}
in.close();
out.close();
}
}
}
} catch (fileuploadexception e) {
message = "文件的内容过大，请上传小于20mb的文件" ;
success = false;
e.printstacktrace();
} catch (ioexception e) {
success = false;
e.printstacktrace();
}
request.setattribute("message", message);
return success;
}
}
三丶下载的servlet
package com.test.action;
import java.io.file;
import java.io.fileinputstream;
import java.io.ioexception;
import java.io.outputstream;
import javax.servlet.servletexception;
import javax.servlet.annotation.webservlet;
import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
@webservlet("/download")
public class filedownloadaction extends httpservlet {
private static final long serialversionuid = 1l;
protected void doget(httpservletrequest request,
httpservletresponse response) throws servletexception, ioexception {
string id = request.getparameter("id");
// 根据主键读取文件的真实名字 + 服务器上的名字
processdownload("1444442288605.png", "腾讯.png", request, response);
}
private boolean processdownload(string filename, string savename,
httpservletrequest request, httpservletresponse response) {
boolean success = true;
// 获取文件下载所在的路径
string path = request.getservletcontext().getrealpath("/upload");
file fileload = new file(path, filename); // 下载文件
long filelength = fileload.length(); // 文件大小
byte[] buffer = new byte[1024]; // 缓冲字节数组
try {
response.reset();
response.setheader("content-disposition", "attachment;filename=\""
+ new string(savename.getbytes("gb2312"), "iso-8859-1") + "\"");
response.setcontenttype("application/octet-stream");
response.setheader("content_length", string.valueof(filelength));
outputstream os = response.getoutputstream();
fileinputstream in = new fileinputstream(fileload);
int hasread = 0;
while ((hasread = in.read(buffer)) != -1) {
os.write(buffer, 0, hasread);
}
os.flush();
os.close();
in.close();
} catch (ioexception e) {
success = false;
e.printstacktrace();
}
return success;
}
}
以上所述是小编给大家介绍的javaweb中上传和下载文件实例代码，希望对大家有所帮助
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