Servlet处理POST上传的文件
WEB文件上传也是采用POST的方式。不过需要将FORM的enctype属性设置为：multipart/form-data。由于上传的文件会比较大，因此需要设置该参数指定浏览器使用二进制上传。如果不设置，enctype属性默认是application/x-www-form-urlencoded，浏览器将使用ASCII向服务器发送数据，导致发送文件失败。
上传文件使用文件域(<input type="file">)，并把FORM的Enctype设置为multipart/form/data。
工程结构如下：
以下是上传文件的客户端代码：upload.html。
<!DOCTYPE html>
<html>
<head>
<title>upload.html</title>
<meta http-equiv="content-type" content="text/html";charset="UTF-8" >
</head>
<body>
<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 class='line'>
<div align='left' class="leftDiv">上传文件一</div>
<div align='left' class="rightDiv">
<input type="file" name="file1" class="text">
</div>
</div>
<div class='line'>
<div align='left' class="leftDiv">上传文件二</div>
<div align='left' class="rightDiv">
<input type="file" name="file2" class="text">
</div>
</div>
<div class='line'>
<div align='left' class="leftDiv">上传文件说明一</div>
<div align='left' class="rightDiv">
<input type="text" name="description1" class="text">
</div>
</div>
<div class='line'>
<div align='left' class="leftDiv">上传文件说明二</div>
<div align='left' class="rightDiv">
<input type="text" name="description2" class="text">
</div>
</div>
<div class='line'>
<div align='left' class="leftDiv">上传文件说明二</div>
<div align='left' class="rightDiv">
<input type="submit" value=" 上传文件" class="button">
</div>
</div>
</fieldset>
</div>
</form>
</body>
</html>
运行结果如下：
上传文件服务器端：
由于上传文件时浏览器是以二进制的方式发送数据，因此Servlet里不能简单的通过HttpServletRequest的getParameter()方法。要想获取内容，就必须更具HTTP协议所规定的的格式解析浏览器提交的Request。
这里，使用Apache开源的jar包。Commons Fileupload是Apache commons众多开源组件中的一员。可以从Apache网站中进行下载：
注意：虽然编码过程只用到：commons-fileupload-1.3.2.jar包，但是运行过程必须用到commons-io-2.5.jar包，两者缺一不可!
将这两个包放到/WEB-INF/lib下。
UploadServlet的源码如下：
package com.hello.firstweb;
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 org.apache.commons.io.IOUtils;
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")
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();
//输出到客户端浏览器
out.println("<HTML>");
out.println("<meta http-equiv=\"content-type\" content=\"text/html\";charset=\"UTF-8\">");
DiskFileUpload diskFileUpload = new DiskFileUpload(); //解析request
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/>");
//服务器端文件，放在upload文件夹下面
file1 = new File(this.getServletContext().getRealPath("attachment"),remoteFile.getName());
file1.getParentFile().mkdirs(); //创建文件夹路径
file1.createNewFile(); //创建新文件
InputStream ins = fileItem.getInputStream(); //FileItem的内容
OutputStream ous = new FileOutputStream(file1); //输出到file1中
try{
byte[] buffer = new byte[1024]; //缓冲字节
int len = 0;
while((len = ins.read(buffer))>-1)
ous.write(buffer, 0, len);
out.println("已保存文件"+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/>");
//服务器端文件，放在upload文件夹下面
file2 = new File(this.getServletContext().getRealPath("attachment"),remoteFile.getName());
file2.getParentFile().mkdirs(); //创建文件夹路径
file2.createNewFile(); //创建新文件
InputStream ins = fileItem.getInputStream(); //FileItem的内容
OutputStream ous = new FileOutputStream(file2); //输出到file1中
try{
byte[] buffer = new byte[1024]; //缓冲字节
int len = 0;
while((len = ins.read(buffer))>-1)
ous.write(buffer, 0, len);
out.println("已保存文件"+file2.getAbsolutePath()+"<br/>");
}finally{
ous.close();
ins.close();
}
}
}
}out.println("Request 解析完毕");
}catch (FileUploadException e){}
if(file1!=null){ //输出file1链接
out.println("<div class = 'line'>");
out.println(" <div align='left' class='leftDiv'>file1:</div>");
out.println(" <div align='left' class='rightDiv'>");
out.println(" <a href='"+request.getContextPath()+"/attachment/"+file1.getName()+"' target=_blank>"+file1.getName()+"</a>");
out.println(" </div>");
out.println(" </div>");
}
if(file2!=null){ //输出file1链接
out.println("<div class = 'line'>");
out.println(" <div align='left' class='leftDiv'>file1:</div>");
out.println(" <div align='left' class='rightDiv'>");
out.println(" <a href='"+request.getContextPath()+"/attachment/"+file2.getName()+"'target=_blank>"+file2.getName()+"</a>");
out.println(" </div>");
out.println(" </div>");
}
out.println("<div class = 'line'>");
out.println(" <div align='left' class='leftDiv'>description1:</div>");
out.println(description1);
out.println("</div>");
out.println("</div>");
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
}
}
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