Servlet实现文件上传的几种方法

1. 通过getInputStream()取得上传文件。

/**
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package net.individuals.web.servlet;

import java.io.DataInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
*
* @author Barudisshu
*/
@WebServlet(name = "UploadServlet", urlPatterns = {"/UploadServlet"})
public class UploadServlet extends HttpServlet {

/**
* Processes requests for both HTTP
* <code>GET</code> and
* <code>POST</code> methods.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
//读取请求Body
byte[] body = readBody(request);
//取得所有Body内容的字符串表示
String textBody = new String(body, "ISO-8859-1");
//取得上传的文件名称
String fileName = getFileName(textBody);
//取得文件开始与结束位置
Position p = getFilePosition(request, textBody);
//输出至文件
writeTo(fileName, body, p);
}

//构造类
class Position {

int begin;
int end;

public Position(int begin, int end) {
this.begin = begin;
this.end = end;
}
}

private byte[] readBody(HttpServletRequest request) throws IOException {
//获取请求文本字节长度
int formDataLength = request.getContentLength();
//取得ServletInputStream输入流对象
DataInputStream dataStream = new DataInputStream(request.getInputStream());
byte body[] = new byte[formDataLength];
int totalBytes = 0;
while (totalBytes < formDataLength) {
int bytes = dataStream.read(body, totalBytes, formDataLength);
totalBytes += bytes;
}
return body;
}

private Position getFilePosition(HttpServletRequest request, String textBody) throws IOException {
//取得文件区段边界信息
String contentType = request.getContentType();
String boundaryText = contentType.substring(contentType.lastIndexOf("=") + 1, contentType.length());
//取得实际上传文件的气势与结束位置
int pos = textBody.indexOf("filename=\"");
pos = textBody.indexOf("\n", pos) + 1;
pos = textBody.indexOf("\n", pos) + 1;
pos = textBody.indexOf("\n", pos) + 1;
int boundaryLoc = textBody.indexOf(boundaryText, pos) - 4;
int begin = ((textBody.substring(0, pos)).getBytes("ISO-8859-1")).length;
int end = ((textBody.substring(0, boundaryLoc)).getBytes("ISO-8859-1")).length;

return new Position(begin, end);
}

private String getFileName(String requestBody) {
String fileName = requestBody.substring(requestBody.indexOf("filename=\"") + 10);
fileName = fileName.substring(0, fileName.indexOf("\n"));
fileName = fileName.substring(fileName.indexOf("\n") + 1, fileName.indexOf("\""));

return fileName;
}

private void writeTo(String fileName, byte[] body, Position p) throws IOException {
FileOutputStream fileOutputStream = new FileOutputStream("e:/workspace/" + fileName);
fileOutputStream.write(body, p.begin, (p.end - p.begin));
fileOutputStream.flush();
fileOutputStream.close();
}

// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
/**
* Handles the HTTP
* <code>GET</code> method.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}

/**
* Handles the HTTP
* <code>POST</code> method.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}

/**
* Returns a short description of the servlet.
*
* @return a String containing servlet description
*/
@Override
public String getServletInfo() {
return "Short description";
}// </editor-fold>
}

2. 通过getPart()、getParts()取得上传文件。

body格式：

POST http://www.example.com HTTP/1.1
Content-Type:multipart/form-data; boundary=----WebKitFormBoundaryrGKCBY7qhFd3TrwA

------WebKitFormBoundaryrGKCBY7qhFd3TrwA
Content-Disposition: form-data; name="text"

title
------WebKitFormBoundaryrGKCBY7qhFd3TrwA
Content-Disposition: form-data; name="file"; filename="chrome.png"
Content-Type: image/png

PNG ... content of chrome.png ...
------WebKitFormBoundaryrGKCBY7qhFd3TrwA--

/**
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package net.individuals.web.servlet;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;

/**
*
* @author Barudisshu
*/
@MultipartConfig
@WebServlet(name = "UploadServlet", urlPatterns = {"/UploadServlet"})
public class UploadServlet extends HttpServlet {

/**
* Processes requests for both HTTP
* <code>GET</code> and
* <code>POST</code> methods.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
Part part = request.getPart("photo");
String fileName = getFileName(part);
writeTo(fileName, part);
}

//取得上传文件名
private String getFileName(Part part) {
String header = part.getHeader("Content-Disposition");
String fileName = header.substring(header.indexOf("filename=\"") + 10, header.lastIndexOf("\""));

return fileName;
}

//存储文件
private void writeTo(String fileName, Part part) throws IOException, FileNotFoundException {
InputStream in = part.getInputStream();
OutputStream out = new FileOutputStream("e:/workspace/" + fileName);
byte[] buffer = new byte[1024];
int length = -1;
while ((length = in.read(buffer)) != -1) {
out.write(buffer, 0, length);
}

in.close();
out.close();
}

// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
/**
* Handles the HTTP
* <code>GET</code> method.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}

/**
* Handles the HTTP
* <code>POST</code> method.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}

/**
* Returns a short description of the servlet.
*
* @return a String containing servlet description
*/
@Override
public String getServletInfo() {
return "Short description";
}// </editor-fold>
}

另一种较为简单的方法：

/**
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package net.individuals.web.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;

/**
*采用part的wirte(String fileName)上传，浏览器将产生临时TMP文件。
* @author Barudisshu
*/
@MultipartConfig(location = "e:/workspace")
@WebServlet(name = "UploadServlet", urlPatterns = {"/UploadServlet"})
public class UploadServlet extends HttpServlet {

/**
* Processes requests for both HTTP
* <code>GET</code> and
* <code>POST</code> methods.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//处理中文文件名
request.setCharacterEncoding("UTF-8");
Part part = request.getPart("photo");
String fileName = getFileName(part);
//将文件写入location指定的目录
part.write(fileName);
}

private String getFileName(Part part) {
String header = part.getHeader("Content-Disposition");
String fileName = header.substring(header.indexOf("filename=\"") + 10, header.lastIndexOf("\""));
return fileName;
}

// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
/**
* Handles the HTTP
* <code>GET</code> method.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}

/**
* Handles the HTTP
* <code>POST</code> method.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}

/**
* Returns a short description of the servlet.
*
* @return a String containing servlet description
*/
@Override
public String getServletInfo() {
return "Short description";
}// </editor-fold>
}

使用getParts()上传多个文件：

<!--
To change this template, choose Tools | Templates
and open the template in the editor.
-->
<!DOCTYPE html>
<html>
<head>
<title></title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
<div>
<form action="UploadServlet3" method="POST" enctype="multipart/form-data">
<table>
<tr>
<td><label for="file1">文件1：</label></td>
<td><input type="file" id="file1" name="file"></td>
</tr>
<tr>
<td><label for="file2">文件2：</label></td>
<td><input type="file" id="file2" name="file"></td>
</tr>
<tr>
<td><label for="file3">文件3：</label></td>
<td><input type="file" id="file3" name="file"></td>
</tr>
<tr>
<td colspan="2"><input type="submit" value="上传" name="upload"></td>
</tr>
</table>
</form>
</div>
</body>
</html>

对应Servlet代码：

/**
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package net.individuals.web.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;

/**
*
* @author Barudisshu
*/
@MultipartConfig(location = "e:/workspace")
@WebServlet(name = "UploadServlet", urlPatterns = {"/UploadServlet"})
public class UploadServlet extends HttpServlet {

/**
* Processes requests for both HTTP
* <code>GET</code> and
* <code>POST</code> methods.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
//迭代Collection中所有Part对象
for (Part part : request.getParts()) {
//只处理上传文件区段
if (part.getName().startsWith("file")) {
String fileName = getFileName(part);
part.write(fileName);
}
}
}

private String getFileName(Part part) {
String header = part.getHeader("Content-Disposition");
String fileName = header.substring(header.indexOf("filename=\"") + 10, header.lastIndexOf("\""));
header.lastIndexOf("\"");
return fileName;
}

// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
/**
* Handles the HTTP
* <code>GET</code> method.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}

/**
* Handles the HTTP
* <code>POST</code> method.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}

/**
* Returns a short description of the servlet.
*
* @return a String containing servlet description
*/
@Override
public String getServletInfo() {
return "Short description";
}// </editor-fold>
}