Java的.郎.空指针异常 [英] java . lang. NullPointerException
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问题描述
如果您能找到我的问题在哪里以及如何解决它，我将不胜感激. (java.lang.NullPointerException)
这是我从中获取文本字段的html文件，我上传了2个文件
index.html
I would be very gratefull if you could find where is my problem and how can I fix it. (java.lang.NullPointerException)
here is my html from where I get a textfield and I upload 2 files
index.html
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h3>File Upload:</h3>
<form action="UploadServlet" method="post"
enctype="multipart/form-data">
<br><br><br><br><br>
Insert your ID (marca) - ex: 101358
<br>
<input type="text" name="rid" size="40" />
<br><br>
Browse your files:
<br>
<input type="file" name="file" size="30" />
<br />
<br/>
<input type="file" name="file" size="30" />
<br />
<br>
<input type="submit" value="Upload File" />
</form>
</body>
</html>
在此servlet中，我将上传的文件保存到特定的文件夹中，然后连接到数据库，该数据库要存储从html获取的字符串和来自上传的文件的文件路径.
UploadServlet.java
in this servlet I save the uploaded files into a specific folder and after that I am connecting to a database where I want to store the string got from html and the file paths from the uploaded files
UploadServlet.java
public class UploadServlet extends HttpServlet {
/**
*
*/
private static final long serialVersionUID = 1L;
private boolean isMultipart;
private String filePath;
private int maxFileSize = 50 * 1024;
private int maxMemSize = 4 * 1024;
private File file ;
public void init( ){
// Get the file location where it would be stored.
filePath = getServletContext().getInitParameter("file-upload");
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, java.io.IOException {
// Check that we have a file upload request
isMultipart = ServletFileUpload.isMultipartContent(request);
response.setContentType("text/html");
java.io.PrintWriter out = response.getWriter( );
if( !isMultipart ){
out.println("<html>");
out.println("<head>");
out.println("<title>Servlet upload</title>");
out.println("</head>");
out.println("<body>");
out.println("<p>No file uploaded</p>");
out.println("</body>");
out.println("</html>");
return;
}
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("c:\\temp"));
// 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.
List fileItems = upload.parseRequest(request);
// Process the uploaded file items
Iterator i = fileItems.iterator();
out.println("<html>");
out.println("<head>");
out.println("<title>Servlet upload</title>");
out.println("</head>");
out.println("<body>");
//while ( i.hasNext () )
//{
FileItem fi = (FileItem)i.next();
if ( !fi.isFormField () )
{
// Get the uploaded file parameters
//String fieldName = fi.getFieldName();
String fileName = fi.getName();
//String contentType = fi.getContentType();
//boolean isInMemory = fi.isInMemory();
//long sizeInBytes = fi.getSize();
// Write the file
if( fileName.lastIndexOf("\\") >= 0 ){
file = new File( "C:/UploadedFiles/" + fileName.substring( fileName.lastIndexOf("\\"))) ;
}else{
file = new File( "C:/UploadedFiles/" + fileName.substring(fileName.lastIndexOf("\\")+1)) ;
}
fi.write( file ) ;
out.println("Uploaded Filename: " + fileName + " --- saved in C:/UploadedFiles/ " + "<br>");
}
FileItem fi2 = (FileItem)i.next();
if ( !fi2.isFormField () )
{
// Get the uploaded file parameters
//String fieldName2 = fi2.getFieldName();
String fileName2 = fi2.getName();
//String contentType2 = fi2.getContentType();
//boolean isInMemory = fi2.isInMemory();
//long sizeInBytes = fi2.getSize();
// Write the file
if( fileName2.lastIndexOf("\\") >= 0 ){
file = new File( "C:/UploadedFiles/" + fileName2.substring( fileName2.lastIndexOf("\\"))) ;
}else{
file = new File( "C:/UploadedFiles/" + fileName2.substring(fileName2.lastIndexOf("\\")+1)) ;
}
fi2.write( file ) ;
out.println("Uploaded Filename: " + fileName2 + " --- saved in C:/UploadedFiles/ " + "<br>");
}
//}
out.println("</body>");
out.println("</html>");
String idmarca = request.getParameter("rid");
String itemName1 = fi.getName();
String path1 = new String("C:\\UploadedFiles\\" + itemName1.substring(itemName1.lastIndexOf("\\")));
String itemName2 = fi2.getName();
String path2 = new String("C:\\UploadedFiles\\" + itemName2.substring(itemName2.lastIndexOf("\\")));
Connection con = null;
PreparedStatement ps;
try{
String driver = "sun.jdbc.odbc.JdbcOdbcDriver";
Class.forName(driver);
String db = "jdbc:odbc:upload";
con = DriverManager.getConnection(db, "", "");
String sql = "INSERT INTO file1(marca,file1,file2) VALUES(?, ?, ?)";
ps = con.prepareStatement(sql);
ps.setString(1, idmarca);
ps.setString(2, path1);
ps.setString(3, path2);
int s = ps.executeUpdate();
if(s>0){
System.out.println("Uploaded successfully !");
}
else{
System.out.println("Error!");
}
}
catch(Exception e){
e.printStackTrace();
}
finally {
// close all the connections.
//ps.close();
//con.close();
}
}catch(Exception ex) {
ex.printStackTrace();
}
}
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, java.io.IOException {
throw new ServletException("GET method used with " + getClass( ).getName( )+": POST method required.");
}
}
我认为NPE在数据库连接中的某个位置.
I think that the NPE is somewhere in the database connection.
java.lang.NullPointerException
at UploadServlet.doPost(UploadServlet.java:126)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:987)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:579)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:307)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)
推荐答案
AbstractConnectionHandler.process(AbstractProtocol.java:579) 在org.apache.tomcat.util.net.JIoEndpoint
AbstractConnectionHandler.process(AbstractProtocol.java:579) at org.apache.tomcat.util.net.JIoEndpoint
SocketProcessor.run(JIoEndpoint.java:307) 在java.util.concurrent.ThreadPoolExecutor
SocketProcessor.run(JIoEndpoint.java:307) at java.util.concurrent.ThreadPoolExecutor
Worker.runTask(ThreadPoolExecutor.java:886) 在java.util.concurrent.ThreadPoolExecutor
Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor
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