文件上传：即通过网页方式，打开文件对话框，选择文件并上传到服务器
如：
发送email时选择附件，修改用户头像等
当点击上传后，文件存储到对应的目录
上传成功后，后端返回数据
前端
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style>
.main{
}
.main input{
margin: 20px;
}
.main input[type='submit']{
background-color: cornflowerblue;
color: #fff;
border: 1px solid #ccc;
border-radius: 1px;
padding: 8px 18px;
}
</style>
</head>
<body>
<div class="main">
<form method="post" action="FileUploadService" enctype="multipart/form-data">
<input type="file" name="fileUpload"/><br />
<input type="submit" value="上传"/><br />
</form>
</div>
</body>
</html>后端
package my;
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.text.SimpleDateFormat;
import java.util.Date;
import java.util.UUID;
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.FileItemIterator;
import org.apache.commons.fileupload.FileItemStream;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.fileupload.util.Streams;
import org.json.JSONObject;
/**
* Servlet implementation class FileUploadService
*/
@WebServlet("/FileUploadService")
public class FileUploadService extends HttpServlet
{
//文件上传的临时目录
File tmpDir;
@Override
public void init() throws ServletException
{
File webRoot = new File(getServletContext().getRealPath("/"));
tmpDir = new File(webRoot, "upload");
tmpDir.mkdirs(); //上传进来的文件存放在 WebRoot/upload/ 下
}
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
JSONObject jresp = new JSONObject();
try
{
Object data = doUpload(request, response);
jresp.put("error", 0);
jresp.put("reason", "OK");
if(data != null)
jresp.put("data", data);
} catch (Exception e)
{
jresp.put("error", -1);
jresp.put("reason", e.getMessage());
}
response.setCharacterEncoding("UTF-8");
response.setContentType("text/plain");
PrintWriter out = response.getWriter();
out.write(jresp.toString(2));
out.close();
}
private Object doUpload(HttpServletRequest request,
HttpServletResponse response) throws Exception
{
boolean isMultipart = ServletFileUpload.isMultipartContent(request);
if(!isMultipart)
throw new Exception("请求编码必须为：multipart/form-data!");
request.setCharacterEncoding("utf-8");
// ServletFileUpload ： commons包里提供的工具类
ServletFileUpload upload = new ServletFileUpload();
AfFileUploadInfo info = new AfFileUploadInfo();
FileItemIterator iter = upload.getItemIterator(request);
while(iter.hasNext())
{
//表单域
FileItemStream item = iter.next();
String fieldName = item.getFieldName();
InputStream fieldStream = item.openStream();
if(item.isFormField())
{
// 普通表单域: 直接读取值
// 指的是<input>,<select>,<textarea>输入控件的值, 字符串类型
String fieldValue = Streams.asString(fieldStream, "utf-8");
printLog("表单域:" + fieldName + "=" + fieldValue);
}
else
{
// 文件域, 指<file>控件的值，指文件的数据
// 生成唯一的文件名
info.realName = item.getName(); // 原始文件名
info.suffix = fileSuffix(info.realName); // 后缀
info.tmpFileName = createTmpFileName(info.suffix); // 服务器临时文件名
info.tmpFile = new File(tmpDir, info.tmpFileName);
info.fileSize = 0; // 文件大小
printLog("文件上传开始:" + info.realName + " >> " + info.tmpFile);
// 从FieldStream读取数据, 保存到目标文件
info.tmpFile.getParentFile().mkdirs();
FileOutputStream fileStream = new FileOutputStream(info.tmpFile);
try{
// 从请求里读取文件数据，保存到本地文件
info.fileSize = copy(fieldStream, fileStream);
}finally{
try{ fileStream.close();}catch(Exception e){}
try{ fieldStream.close();}catch(Exception e){}
}
printLog("文件上传完成:" + info.realName + ", 大小: " + info.fileSize);
}
}
return info.tmpFileName;
}
private long copy(InputStream in, OutputStream out) throws Exception
{
long count = 0;
byte[] buf = new byte[8192];
while(true)
{
int n = in.read(buf);
if(n < 0)
break;
if(n == 0)
continue;
out.write(buf, 0, n);
count +=n;
}
return count;
}
//////////////////////////////////////////////////
private void printLog(String message)
{
System.out.println(message);
}
//生成唯一的ID
private String createUUID()
{
String s = UUID.randomUUID().toString();
String s2 = s.substring(0,8)+s.substring(9,13)+s.substring(14,18)+s.substring(19,23)+s.substring(24);
return s2.toUpperCase();
}
// 得到一个保证不重复的临时文件名
private String createTmpFileName(String suffix)
{
SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd-HHmmss");
String datestr = sdf.format(new Date());
String name = datestr + "-" + createUUID() + "." + suffix;
return name;
}
// 得到文件的后缀名
public String fileSuffix(String fileName)
{
int p = fileName.lastIndexOf('.');
if(p >= 0)
{
return fileName.substring(p+1).toLowerCase(); //转换成小写
}
return "";
}
}package my;
import java.io.File;
public class AfFileUploadInfo
{
public String realName; //原始文件名
public String suffix; //后缀
public String tmpFileName; //服务器临时文件名
public File tmpFile;
public long fileSize; //文件大小
}
