文件上传的方法主要目前有两个常用的，一个是smartupload，一个是apache的commons fileupload.
我们这里主要介绍下第二个的用法，首先要上传文件，注意几个问题：
1 form表单内，要添加空间<input type="file" name="myfile">
2 form表单的内容格式要定义成multipart/form-data格式
3 需要类库：1 commons-io.jar 2commons-fileupload-1.3.1.jar
接下来我们看下用法。
首先阅读apache commons fileupload的官方文档可以发现下面几个常用的函数：
1 创建文件解析对象
2 进行文件解析后放在list中，因为这个类库支持多个文件上传，因此把结果会存在list中。
3 获取上传文件，进行分析（不是必须）
4 创建新对象，进行流拷贝
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file1 = new file(this.getservletcontext().getrealpath("attachment"),remotefile.getname());
file1.getparentfile().mkdirs();
file1.createnewfile();
inputstream ins = fileitem.getinputstream();
outputstream ous = new fileoutputstream(file1);
try{
byte[] buffer = new byte[1024];
int len = 0;
while((len = ins.read(buffer)) > -1)
ous.write(buffer,0,len);
out.println("以保存文件"+file1.getabsolutepath()+"<br/>");
}finally{
ous.close();
ins.close();
}
这样我们就完成了文件的上传。
fileupload.html
<form action="servlet/uploadservlet" method="post" enctype="multipart/form-data">
<div align="center">
<fieldset style="width:80%">
<legend>上传文件</legend><br/>
<div align="left">上传文件1</div>
<div align="left">
<input type="file" name="file1"/>
</div>
<div align="left">上传文件2</div>
<div align="left">
<input type="file" name="file2"/>
</div>
<div>
<div align='left'>上传文件说明1</div>
<div align='left'><input type="text" name="description1"/></div>
</div>
<div>
<div align='left'>上传文件说明2</div>
<div align='left'><input type="text" name="description2"/></div>
</div>
<div>
<div align='left'>
<input type='submit' value="上传文件"/>
</div>
</div>
</fieldset>
</div>
</form>
web.xml
<servlet> <servlet-name>uploadservlet</servlet-name> <servlet-class>com.test.hello.uploadservlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>uploadservlet</servlet-name> <url-pattern>/servlet/uploadservlet</url-pattern> </servlet-mapping>
uploadservlet.java
package com.test.hello;
import java.io.file;
import java.io.fileoutputstream;
import java.io.ioexception;
import java.io.inputstream;
import java.io.outputstream;
import java.io.printwriter;
import java.util.list;
import javax.servlet.servletexception;
import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
import org.apache.commons.fileupload.diskfileupload;
import org.apache.commons.fileupload.fileitem;
import org.apache.commons.fileupload.fileuploadexception;
public class uploadservlet extends httpservlet {
/**
* constructor of the object.
*/
public uploadservlet() {
super();
}
/**
* destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // just puts "destroy" string in log
// put your code here
}
/**
* the doget method of the servlet. <br>
*
* this method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws servletexception if an error occurred
* @throws ioexception if an error occurred
*/
public void doget(httpservletrequest request, httpservletresponse response)
throws servletexception, ioexception {
response.setcharacterencoding("utf-8");
response.getwriter().println("请以post方式上传文件");
}
/**
* the dopost method of the servlet. <br>
*
* this method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws servletexception if an error occurred
* @throws ioexception if an error occurred
*/
@suppresswarnings({ "unchecked", "deprecation" })
public void dopost(httpservletrequest request, httpservletresponse response)
throws servletexception, ioexception {
file file1 = null,file2=null;
string description1 = null,description2 = null;
response.setcharacterencoding("utf-8");
request.setcharacterencoding("utf-8");
response.setcontenttype("text/html");
printwriter out = response.getwriter();
diskfileupload diskfileupload = new diskfileupload();
try{
list<fileitem> list = diskfileupload.parserequest(request);
out.println("遍历所有的fileitem...<br/>");
for(fileitem fileitem : list){
if(fileitem.isformfield()){
if("description1".equals(fileitem.getfieldname())){
out.println("遍历到description1 ... <br/>");
description1 = new string(fileitem.getstring().getbytes(),"utf-8");
}
if("description2".equals(fileitem.getfieldname())){
out.println("遍历到description2 ... <br/>");
description2 = new string(fileitem.getstring().getbytes(),"utf-8");
}
}else{
if("file1".equals(fileitem.getfieldname())){
file remotefile = new file(new string(fileitem.getname().getbytes(),"utf-8"));
out.println("遍历到file1...<br/>");
out.println("客户端文件位置："+remotefile.getabsolutepath()+"<br/>");
file1 = new file(this.getservletcontext().getrealpath("attachment"),remotefile.getname());
file1.getparentfile().mkdirs();
file1.createnewfile();
inputstream ins = fileitem.getinputstream();
outputstream ous = new fileoutputstream(file1);
try{
byte[] buffer = new byte[1024];
int len = 0;
while((len = ins.read(buffer)) > -1)
ous.write(buffer,0,len);
out.println("以保存文件"+file1.getabsolutepath()+"<br/>");
}finally{
ous.close();
ins.close();
}
}
if("file2".equals(fileitem.getfieldname())){
file remotefile = new file(new string(fileitem.getname().getbytes(),"utf-8"));
out.println("遍历到file2...<br/>");
out.println("客户端文件位置："+remotefile.getabsolutepath()+"<br/>");
file2 = new file(this.getservletcontext().getrealpath("attachment"),remotefile.getname());
file2.getparentfile().mkdirs();
file2.createnewfile();
inputstream ins = fileitem.getinputstream();
outputstream ous = new fileoutputstream(file2);
try{
byte[] buffer = new byte[1024];
int len = 0;
while((len = ins.read(buffer)) > -1)
ous.write(buffer,0,len);
out.println("以保存文件"+file2.getabsolutepath()+"<br/>");
}finally{
ous.close();
ins.close();
}
}
}
out.println("request 解析完毕<br/><br/>");
}
}catch(fileuploadexception e){}
out.println("<!doctype html public \"-//w3c//dtd html 4.01 transitional//en\">");
out.println("<html>");
out.println(" <head><title>a servlet</title></head>");
out.println(" <body>");
if(file1 != null){
out.println("<div>");
out.println(" <div align='left'>file1;</div>");
out.println(" <div align='left'><a href='"+request.getcontextpath()+"/attachment/"+
file1.getname()+"'target=_blank>"+file1.getname()+"</a>");
out.println("</div>");
out.println("</div>");
}
if(file2 != null){
out.println("<div>");
out.println(" <div align='left'>file2;</div>");
out.println(" <div align='left'><a href='"+request.getcontextpath()+"/attachment/"+
file2.getname()+"'target=_blank>"+file2.getname()+"</a>");
out.println("</div>");
out.println("</div>");
}
out.println("<div>");
out.println(" <div align='left'>description1:</div>");
out.println(" <div align='left'>");
out.println(description1);
out.println("</div>");
out.println("</div>");
out.println("<div>");
out.println(" <div align='left'>description2:</div>");
out.println(" <div align='left'>");
out.println(description2);
out.println("</div>");
out.println("</div>");
out.println(" </body>");
out.println("</html>");
out.flush();
out.close();
}
/**
* initialization of the servlet. <br>
*
* @throws servletexception if an error occurs
*/
public void init() throws servletexception {
// put your code here
}
}
运行示例
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