<form action="upload" method="post">
<input type="text" name="description" />
<input type="file" name="file" />
<input type="submit" />
</form>
要浏览和选择要上传的文件，您需要在表单中使用一个HTML <input type="file">字段。根据HTML规范中所述，您必须使用POST方法，并且表单的enctype属性必须设置为"multipart/form-data"。
<form action="upload" method="post" enctype="multipart/form-data">
<input type="text" name="description" />
<input type="file" name="file" />
<input type="submit" />
</form>
enctype时不同。multipart/form-data。它只支持默认的表单enctype application/x-www-form-urlencoded。当使用多部分表单数据时，request.getParameter()和相关方法都会返回null。这就是众所周知的Apache Commons FileUpload出现的地方。
ServletRequest#getInputStream() 自己解析请求体。然而，这是一项精确而繁琐的工作，需要对 RFC2388 有精确的了解。你不应该自己尝试或者复制粘贴从互联网上找到的一些自制的无库代码。许多在线资源在这方面都失败了，比如 roseindia.net。还有 上传 PDF 文件。你应该使用一个真正的库，这个库已经被数百万用户使用多年，并且经过了隐式测试，证明了其稳定性。
HttpServletRequest#getPart()来收集各个多部分表单数据项（大多数Servlet 3.0实现实际上在底层使用Apache Commons FileUpload来实现此功能！）。此外，普通表单字段可以通过getParameter()以常规方式获取。@MultipartConfig进行注解，以便让它识别和支持multipart/form-data请求，从而使getPart()正常工作。@WebServlet("/upload")
@MultipartConfig
public class UploadServlet extends HttpServlet {
// ...
}
doPost()方法：protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String description = request.getParameter("description"); // Retrieves <input type="text" name="description">
Part filePart = request.getPart("file"); // Retrieves <input type="file" name="file">
String fileName = Paths.get(filePart.getSubmittedFileName()).getFileName().toString(); // MSIE fix.
InputStream fileContent = filePart.getInputStream();
// ... (do your job here)
}
Path#getFileName()。这是一个针对MSIE的修复，用于获取文件名。该浏览器错误地将完整文件路径与文件名一起发送，而不仅仅是文件名。multiple="true"上传多个文件的话，<input type="file" name="files" multiple="true" />
<input type="file" name="files" />
<input type="file" name="files" />
<input type="file" name="files" />
...
request.getParts("files")这样的方法）：protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// ...
List<Part> fileParts = request.getParts().stream().filter(part -> "files".equals(part.getName()) && part.getSize() > 0).collect(Collectors.toList()); // Retrieves <input type="file" name="files" multiple="true">
for (Part filePart : fileParts) {
String fileName = Paths.get(filePart.getSubmittedFileName()).getFileName().toString(); // MSIE fix.
InputStream fileContent = filePart.getInputStream();
// ... (do your job here)
}
}
请注意，Part#getSubmittedFileName()是在Servlet 3.1中引入的（Tomcat 8，Jetty 9，WildFly 8，GlassFish 4等，它们自2013年以来就存在）。如果你还没有使用Servlet 3.1（真的吗？），那么你需要一个额外的实用方法来获取提交的文件名。
private static String getSubmittedFileName(Part part) {
for (String cd : part.getHeader("content-disposition").split(";")) {
if (cd.trim().startsWith("filename")) {
String fileName = cd.substring(cd.indexOf('=') + 1).trim().replace("\"", "");
return fileName.substring(fileName.lastIndexOf('/') + 1).substring(fileName.lastIndexOf('\\') + 1); // MSIE fix.
}
}
return null;
}
String fileName = getSubmittedFileName(filePart);
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
try {
List<FileItem> items = new ServletFileUpload(new DiskFileItemFactory()).parseRequest(request);
for (FileItem item : items) {
if (item.isFormField()) {
// Process regular form field (input type="text|radio|checkbox|etc", select, etc).
String fieldName = item.getFieldName();
String fieldValue = item.getString();
// ... (do your job here)
} else {
// Process form file field (input type="file").
String fieldName = item.getFieldName();
String fileName = FilenameUtils.getName(item.getName());
InputStream fileContent = item.getInputStream();
// ... (do your job here)
}
}
} catch (FileUploadException e) {
throw new ServletException("Cannot parse multipart request.", e);
}
// ...
}
FilenameUtils#getName（）。这是一个用于获取文件名的MSIE修复程序。该浏览器错误地将完整的文件路径与名称一起发送，而不仅仅是文件名。Filter中，自动解析并将内容放回请求的参数映射中，以便您可以继续使用request.getParameter（）的常规方式，并通过request.getAttribute（）检索上传的文件。 {{link2：您可以在此博客文章中找到一个示例}}。
请注意，早于3.1.2版本的Glassfish存在一个bug，即getParameter()仍然返回null。如果您的目标容器是这样的版本且无法升级，那么您需要使用这个实用方法从getPart()中提取值：
private static String getValue(Part part) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(part.getInputStream(), "UTF-8"));
StringBuilder value = new StringBuilder();
char[] buffer = new char[1024];
for (int length = 0; (length = reader.read(buffer)) > 0;) {
value.append(buffer, 0, length);
}
return value.toString();
}
String description = getValue(request.getPart("description")); // Retrieves <input type="text" name="description">
getRealPath()或part.write()！）请参考以下答案，了解如何正确将获取到的InputStream（如上面代码片段中显示的fileContent变量）保存到磁盘或数据库：
请参考以下答案，了解如何正确地从磁盘或数据库中将保存的文件返回给客户端：
MultipartConfig条件（例如：maxFileSize），调用request.getParameter()将返回null。这是故意的吗？如果在调用getPart之前获取一些常规（文本）参数（并检查IllegalStateException），会发生什么情况？这会导致NullPointerException在我有机会检查IllegalStateException之前被抛出。 - theyuvReader和/或Writer将字节转换为字符时，可能会发生这种情况。不要这样做。在读写上传的文件时，在所有地方使用InputStream/OutputStream，而不是将字节转换为字符。PDF文件不是基于字符的文本文件。它是一个二进制文件。 - BalusC如果您恰好使用Spring MVC，请按照以下步骤操作（我将其保留在这里以便有人找到它时有用）：
使用具有 enctype 属性设置为 "multipart/form-data" 的表单（与BalusC的回答相同）：
<form action="upload" method="post" enctype="multipart/form-data">
<input type="file" name="file" />
<input type="submit" value="Upload"/>
</form>
在您的控制器中，将请求参数file映射到MultipartFile类型，方法如下：
@RequestMapping(value = "/upload", method = RequestMethod.POST)
public void handleUpload(@RequestParam("file") MultipartFile file) throws IOException {
if (!file.isEmpty()) {
byte[] bytes = file.getBytes(); // alternatively, file.getInputStream();
// application logic
}
}
使用MultipartFile的getOriginalFilename()和getSize()方法可以获取文件名和大小。
我已经在Spring版本4.1.1.RELEASE中进行了测试。
在Tomcat 6或Tomcat 7中没有组件或外部库
在web.xml文件中启用上传：
<servlet>
<servlet-name>jsp</servlet-name>
<servlet-class>org.apache.jasper.servlet.JspServlet</servlet-class>
<multipart-config>
<max-file-size>3145728</max-file-size>
<max-request-size>5242880</max-request-size>
</multipart-config>
<init-param>
<param-name>fork</param-name>
<param-value>false</param-value>
</init-param>
<init-param>
<param-name>xpoweredBy</param-name>
<param-value>false</param-value>
</init-param>
<load-on-startup>3</load-on-startup>
</servlet>
正如您所看到的：
<multipart-config>
<max-file-size>3145728</max-file-size>
<max-request-size>5242880</max-request-size>
</multipart-config>
使用JSP上传文件。文件：
在HTML文件中：
<form method="post" enctype="multipart/form-data" name="Form" >
<input type="file" name="fFoto" id="fFoto" value="" /></td>
<input type="file" name="fResumen" id="fResumen" value=""/>
在JSP文件或者Servlet中
InputStream isFoto = request.getPart("fFoto").getInputStream();
InputStream isResu = request.getPart("fResumen").getInputStream();
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte buf[] = new byte[8192];
int qt = 0;
while ((qt = isResu.read(buf)) != -1) {
baos.write(buf, 0, qt);
}
String sResumen = baos.toString();
将您的代码编辑为Servlet要求的格式，例如max-file-size、max-request-size和其他选项，您可以进行设置...
common-io.1.4.jar文件包含在您的lib目录中，或者如果您正在使用像NetBeans这样的编辑器，则需要转到项目属性并添加JAR文件即可完成。common.io.jar文件，请搜索谷歌或只需访问Apache Tomcat网站，在那里您可以免费下载该文件。但请注意一件事：如果您是Windows用户，则下载二进制ZIP文件。.jar文件，但找到了.zip文件。你是不是要找.zip文件？ - Malwinder Singhpublic class ServletCommonfunctions extends HttpServlet implements
Connections {
private static final long serialVersionUID = 1L;
public ServletCommonfunctions() {}
protected void doPost(HttpServletRequest request,
HttpServletResponse response) throws ServletException,
IOException {}
public SortedMap<String, String> savefilesindirectory(
HttpServletRequest request, HttpServletResponse response)
throws IOException {
// Map<String, String> key_values = Collections.synchronizedMap(new
// TreeMap<String, String>());
SortedMap<String, String> key_values = new TreeMap<String, String>();
String dist = null, fact = null;
PrintWriter out = response.getWriter();
File file;
String filePath = "E:\\FSPATH1\\2KL06CS048\\";
System.out.println("Directory Created ????????????"
+ new File(filePath).mkdir());
int maxFileSize = 5000 * 1024;
int maxMemSize = 5000 * 1024;
// Verify the content type
String contentType = request.getContentType();
if ((contentType.indexOf("multipart/form-data") >= 0)) {
DiskFileItemFactory factory = new DiskFileItemFactory();
// Maximum size that will be stored in memory
factory.setSizeThreshold(maxMemSize);
// Location to save data that is larger than maxMemSize.
factory.setRepository(new File(filePath));
// Create a new file upload handler
ServletFileUpload upload = new ServletFileUpload(factory);
// maximum file size to be uploaded.
upload.setSizeMax(maxFileSize);
try {
// Parse the request to get file items.
@SuppressWarnings("unchecked")
List<FileItem> fileItems = upload.parseRequest(request);
// Process the uploaded file items
Iterator<FileItem> i = fileItems.iterator();
while (i.hasNext()) {
FileItem fi = (FileItem) i.next();
if (!fi.isFormField()) {
// Get the uploaded file parameters
String fileName = fi.getName();
// Write the file
if (fileName.lastIndexOf("\\") >= 0) {
file = new File(filePath
+ fileName.substring(fileName
.lastIndexOf("\\")));
} else {
file = new File(filePath
+ fileName.substring(fileName
.lastIndexOf("\\") + 1));
}
fi.write(file);
} else {
key_values.put(fi.getFieldName(), fi.getString());
}
}
} catch (Exception ex) {
System.out.println(ex);
}
}
return key_values;
}
}
对于Spring MVC
我成功地实现了一个更简单的版本，它能够处理表单输入，包括数据和图片。
<form action="/handleform" method="post" enctype="multipart/form-data">
<input type="text" name="name" />
<input type="text" name="age" />
<input type="file" name="file" />
<input type="submit" />
</form>
@Controller
public class FormController {
@RequestMapping(value="/handleform",method= RequestMethod.POST)
ModelAndView register(@RequestParam String name, @RequestParam int age, @RequestParam MultipartFile file)
throws ServletException, IOException {
System.out.println(name);
System.out.println(age);
if(!file.isEmpty()){
byte[] bytes = file.getBytes();
String filename = file.getOriginalFilename();
BufferedOutputStream stream =new BufferedOutputStream(new FileOutputStream(new File("D:/" + filename)));
stream.write(bytes);
stream.flush();
stream.close();
}
return new ModelAndView("index");
}
}
如果你正在使用内嵌Tomcat的Geronimo，这个问题的另一个来源是出现了。在这种情况下，在多次测试Commons IO和commons-fileupload之后，问题来自于处理commons-xxx JAR文件的父类加载器。这必须被防止。崩溃总是发生在:
fileItems = uploader.parseRequest(request);
List<FileItem>，而以前的版本中它是通用类型List。从http://osdir.com/ml/user-geronimo-apache/2011-03/msg00026.html粘贴：
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<web:web-app xmlns:app="http://geronimo.apache.org/xml/ns/j2ee/application-2.0" xmlns:client="http://geronimo.apache.org/xml/ns/j2ee/application-client-2.0" xmlns:conn="http://geronimo.apache.org/xml/ns/j2ee/connector-1.2" xmlns:dep="http://geronimo.apache.org/xml/ns/deployment-1.2" xmlns:ejb="http://openejb.apache.org/xml/ns/openejb-jar-2.2" xmlns:log="http://geronimo.apache.org/xml/ns/loginconfig-2.0" xmlns:name="http://geronimo.apache.org/xml/ns/naming-1.2" xmlns:pers="http://java.sun.com/xml/ns/persistence" xmlns:pkgen="http://openejb.apache.org/xml/ns/pkgen-2.1" xmlns:sec="http://geronimo.apache.org/xml/ns/security-2.0" xmlns:web="http://geronimo.apache.org/xml/ns/j2ee/web-2.0.1">
<dep:environment>
<dep:moduleId>
<dep:groupId>DataStar</dep:groupId>
<dep:artifactId>DataStar</dep:artifactId>
<dep:version>1.0</dep:version>
<dep:type>car</dep:type>
</dep:moduleId>
<!-- Don't load commons-io or fileupload from parent classloaders -->
<dep:hidden-classes>
<dep:filter>org.apache.commons.io</dep:filter>
<dep:filter>org.apache.commons.fileupload</dep:filter>
</dep:hidden-classes>
<dep:inverse-classloading/>
</dep:environment>
<web:context-root>/DataStar</web:context-root>
</web:web-app>
https://osdir.com/）- HTTPS 版本也是如此。 - Peter Mortensen这里是一个使用Apache Commons-FileUpload的示例：
// apache commons-fileupload to handle file upload
DiskFileItemFactory factory = new DiskFileItemFactory();
factory.setRepository(new File(DataSources.TORRENTS_DIR()));
ServletFileUpload fileUpload = new ServletFileUpload(factory);
List<FileItem> items = fileUpload.parseRequest(req.raw());
FileItem item = items.stream()
.filter(e ->
"the_upload_name".equals(e.getFieldName()))
.findFirst().get();
String fileName = item.getName();
item.write(new File(dir, fileName));
log.info(fileName);
首先，您必须将表单的enctype属性设置为"multipart/form-data"
如下所示。
<form action="Controller" method="post" enctype="multipart/form-data">
<label class="file-upload"> Click here to upload an Image </label>
<input type="file" name="file" id="file" required>
</form>
@MultipartConfig
public class Controller extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
insertImage(request, response);
}
private void addProduct(HttpServletRequest request, HttpServletResponse response) {
Part filePart = request.getPart("file");
String imageName = Paths.get(filePart.getSubmittedFileName()).getFileName().toString();
String imageSavePath = "specify image path to save image"; //path to save image
FileOutputStream outputStream = null;
InputStream fileContent = null;
try {
outputStream = new FileOutputStream(new File(imageSavePath + File.separator + imageName));
// Creating a new file with file path and the file name
fileContent = filePart.getInputStream();
// Getting the input stream
int readBytes = 0;
byte[] readArray = new byte[1024];
// Initializing a byte array with size 1024
while ((readBytes = fileContent.read(readArray)) != -1) {
outputStream.write(readArray, 0, readBytes);
} // This loop will write the contents of the byte array unitl the end to the output stream
} catch (Exception ex) {
System.out.println("Error Writing File: " + ex);
} finally {
if (outputStream != null) {
outputStream.close();
// Closing the output stream
}
if (fileContent != null) {
fileContent.close();
// Closing the input stream
}
}
}
}
您可以使用JSP / Servlet上传文件。
<form action="UploadFileServlet" method="post">
<input type="text" name="description" />
<input type="file" name="file" />
<input type="submit" />
</form>
另一方面，在服务器端，请使用以下代码。
package com.abc..servlet;
import java.io.File;
---------
--------
/**
* Servlet implementation class UploadFileServlet
*/
public class UploadFileServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public UploadFileServlet() {
super();
// TODO Auto-generated constructor stub
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
response.sendRedirect("../jsp/ErrorPage.jsp");
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
PrintWriter out = response.getWriter();
HttpSession httpSession = request.getSession();
String filePathUpload = (String) httpSession.getAttribute("path") != null ? httpSession.getAttribute("path").toString() : "" ;
String path1 = filePathUpload;
String filename = null;
File path = null;
FileItem item = null;
boolean isMultipart = ServletFileUpload.isMultipartContent(request);
if (isMultipart) {
FileItemFactory factory = new DiskFileItemFactory();
ServletFileUpload upload = new ServletFileUpload(factory);
String FieldName = "";
try {
List items = upload.parseRequest(request);
Iterator iterator = items.iterator();
while (iterator.hasNext()) {
item = (FileItem) iterator.next();
if (fieldname.equals("description")) {
description = item.getString();
}
}
if (!item.isFormField()) {
filename = item.getName();
path = new File(path1 + File.separator);
if (!path.exists()) {
boolean status = path.mkdirs();
}
/* Start of code fro privilege */
File uploadedFile = new File(path + Filename); // for copy file
item.write(uploadedFile);
}
} else {
f1 = item.getName();
}
} // END OF WHILE
response.sendRedirect("welcome.jsp");
} catch (FileUploadException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}
}
}