2
我想上传一个文件，但我得到一个NullPointerException异常。零件空指针异常
我得到的错误是
SEVERE: java.lang.NullPointerException at servlet.UploadServlet.doPost(UploadServlet.java:36)
在这条线：
InputStream is = part.getInputStream();
这里是Servlet和JSP页面的代码。
UploadServlet
@MultipartConfig(fileSizeThreshold = 1024 * 1024 * 10, maxFileSize = 1024 * 1024 * 50, maxRequestSize = 1024 * 1024 * 50)
public class UploadServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
try {
Part part = request.getPart("file");
InputStream is = part.getInputStream();
String filename = getFileName(part);
String relativeWebPath = "/WEB-INF/uploads";
String absoluteFilePath = getServletContext().getRealPath(relativeWebPath);
File uploadedFile = new File(absoluteFilePath, filename);
FileOutputStream os = new FileOutputStream(uploadedFile);
int i = is.read();
while (i != -1) {
os.write(i);
i = is.read();
}
os.close();
} catch (Exception ex) {
ex.printStackTrace();
} finally {
out.close();
}
}
private String getFileName(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);
}
}
return null;
}
}
upload.jsp
<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<link rel="stylesheet" type="text/css" href="css/style.css">
<title>MobMel::Upload</title>
</head>
<body>
<form action="UploadServlet" method="post" enctype="multipart/form-data">
<table class="upload">
<tr>
<td>File</td>
<td><input type="file" name="file"></td>
</tr>
<tr>
<td></td>
<td><input type="submit" value="Upload"></td>
</tr>
</table>
</form>
</body>
</html>
的web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.1" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd">
<servlet>
<servlet-name>RegisterServlet</servlet-name>
<servlet-class>servlet.RegisterServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>LoginServlet</servlet-name>
<servlet-class>servlet.LoginServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>ProfileServlet</servlet-name>
<servlet-class>servlet.ProfileServlet</servlet-class>
</servlet>
<servlet>
<servlet-name>UploadServlet</servlet-name>
<servlet-class>servlet.UploadServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>RegisterServlet</servlet-name>
<url-pattern>/RegisterServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/LoginServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>ProfileServlet</servlet-name>
<url-pattern>/ProfileServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>UploadServlet</servlet-name>
<url-pattern>/UploadServlet</url-pattern>
</servlet-mapping>
<session-config>
<session-timeout>
30
</session-timeout>
</session-config>
</web-app>
我希望你们能HEL我解决这个问题。
感谢
你确定'request.getPart（“file”）;'返回的是null以外的内容吗？你可以在你的代码中添加一行来检查它吗？ – csmckelvey 2014-09-05 16:16:34
当我使用part.getName（）它返回“文件”，当我使用toString（）它返回一些长字符串。 – 2014-09-05 16:30:58
如果您在未选择文件的情况下提交表单，getPart将返回null，因此无论如何您都需要处理此用户错误。 – 2014-09-05 16:31:04