客户端运行的代码很简单，服务器要复杂一点。要想获取其中的内容，必须根据HTTP协议所规定的格式来解析浏览器提交的Request.
解析二进制流比较麻烦。已经有许多类库已经完成了这项工作，例如SmartUpload与Apache Commons Fileupload.SmartUpload是一个商业类库，解析Request过程中数据存放在内存里，因此速度较快，但上传较大文件时会发生内存溢出。Apache Commons Fileupload是一个免费的开源的类库。一些框架比如Struts里集成了Apache Common Fileupload类库来实现文件上传。
如图所示：
代码如下：
package com.helloweenvsfei.servlet;
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.net.URLEncoder;
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 {
private static final long serialVersionUID = 7523024737218332088L;
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");
}
@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");
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("");
out.println("");
out.println(" A Servlet");
out.println(" ");
out.println(" ");
out.println("
");
out.println("
");
out.println(" ");
out.println(" 上传日志：");
out.println(" ");
// 使用 DiskFileUpload 对象解析 request
DiskFileUpload diskFileUpload = new DiskFileUpload();
try {
// 将 解析的结果 放置在 List 中
List list = diskFileUpload.parseRequest(request);
out.println("遍历所有的 FileItem ...
");
// 遍历 list 中所有的 FileItem
for(FileItem fileItem : list){
if(fileItem.isFormField()){
// 如果是 文本域
if("description1".equals(fileItem.getFieldName())){
// 如果该 FileItem 名称为 description1
out.println("遍历到 description1 ...
");
description1 = new String(fileItem.getString().getBytes(), "UTF-8");
}
if("description2".equals(fileItem.getFieldName())){
// 如果该 FileItem 名称为 description2
out.println("遍历到 description2 ...
");
description2 = new String(fileItem.getString().getBytes(), "UTF-8");
}
}
else{
// 否则，为文件域
if("file1".equals(fileItem.getFieldName())){
// 客户端文件路径构建的 File 对象
File remoteFile = new File(new String(fileItem.getName().getBytes(), "UTF-8"));
out.println("遍历到 file1 ...
");
out.println("客户端文件位置: " + remoteFile.getAbsolutePath() + "
");
// 服务器端文件，放在 upload 文件夹下
file1 = new File(this.getServletContext().getRealPath("attachment"), remoteFile.getName());
file1.getParentFile().mkdirs();
file1.createNewFile();
// 写文件，将 FileItem 的文件内容写到文件中
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("已保存文件" + file1.getAbsolutePath() + "
");
}finally{
ous.close();
ins.close();
}
}
if("file2".equals(fileItem.getFieldName())){
// 客户端文件路径构建的 File 对象
File remoteFile = new File(new String(fileItem.getName().getBytes(), "UTF-8"));
out.println("遍历到 file2 ...
");
out.println("客户端文件位置: " + remoteFile.getAbsolutePath() + "
");
// 服务器端文件，放在 upload 文件夹下
file2 = new File(this.getServletContext().getRealPath("attachment"), remoteFile.getName());
file2.getParentFile().mkdirs();
file2.createNewFile();
// 写文件，将 FileItem 的文件内容写到文件中
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("已保存文件" + file2.getAbsolutePath() + "
");
}finally{
ous.close();
ins.close();
}
}
}
}
out.println("Request 解析完毕");
} catch (FileUploadException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
out.println(" ");
out.println(" ");
if(file1 != null){
out.println(" ");
out.println(" file1：");
out.println(" ");
out.println(" " + file1.getName() + "" );
out.println(" ");
out.println(" ");
}
if(file2 != null){
out.println(" ");
out.println(" file2：");
out.println(" ");
out.println(" " + file2.getName() + "" );
out.println(" ");
out.println(" ");
}
out.println(" ");
out.println(" description1：");
out.println(" ");
out.println(description1);
out.println(" ");
out.println(" ");
out.println(" ");
out.println(" description2：");
out.println(" ");
out.println(description2);
out.println(" ");
out.println(" ");
out.println("");
out.println(" ");
out.println("");
out.flush();
out.close();
}
}程序运行效果如图所示：
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