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Problem with displaying image using jsp

Greenhorn

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posted 20 years ago

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Hello everyone,

I have searched all the information about how to display images from database using jsp in this forum, but none of the problems is samilar to mine.

I used a servlet class to retrieve the image blob data and wrote it to the response outputstream.

-------------------------------------------------------------------
String getResourceSql = "select content from tblContent where contentID = 9";
ResultSet docRs = stat.executeQuery(getResourceSql);

if (docRs.next()){
byte[] doc = (byte[])(docRs.getObject("content"));
System.out.println("data length " + doc.length);
ServletOutputStream ostr = response.getOutputStream();
ostr.write(doc);
ostr.flush();
ostr.close();
System.out.println("test");
}

---------------------------------------------------------------------

And after, I wrote a jsp file to call the servelt to display the image as below:

<html>
<body>

<img src="/meg/ImageServlet?contentId=8"/>

</body>
</html>

I could get the servlet test message (data length and "test" string ) printed out in Tomcat dos window, which means that the servlet was called successfully. However, the image could not be displayed in the jsp page (only a red cross). I wonder what is wrong with my code?

Thanks a lot in advance!

Honour Cooker

Greenhorn

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posted 20 years ago

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Sorry, a little typing mistake from my provious message. The contentID in my jsp page shouldn't be important as I already hardcoded it in the servlet class.

JulianInactive KennedyInactive

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posted 20 years ago

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Do you set the content type or any other header information?

Jules

JulianInactive KennedyInactive

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posted 20 years ago

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Honour,

The following simple example works perfectly for me:

Perhaps you could adapt it to your needs.

Jules

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Greenhorn

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posted 20 years ago

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Hi Julian,

Thank you very much for help. I have replaced your sample code with my database code. It worked good as gold.

My problem is to extract image blob from database not a local file. Inspired by you, I tried to extract blob and saved it as a gif file same as your way to see if the jsp page show image or not. Strangly, the saved gif file even could not be opened by photoshop(jsp too). So I suspect the reason why jsp can not show blob image from database is that the data format has been changed somehow during inserting and retriving to/from database. I don't know why it could happen. By the way, I only set one response header:response.setContentType = "image/gif".

Do you have any ideas? Thanks a lot!

Honour

JulianInactive KennedyInactive

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posted 20 years ago

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OK, firstly are you sure the data you're writing to the database in the first place are correct?

Secondly, if you post your database writing and reading code snippets in a new thread on the JDBC forum here you're likely to get more help. Let us know which database and JDBC driver you're using too.

Jules

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Greenhorn

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This is upload.jsp I use to save image to mysql database. I am using com.mysql.jdbc.Driver

----------------------------------------------------

<%@ page import="java.io.*" %>
<%@ page import="java.sql.*" %>

<%
String contentType = request.getContentType();
if ((contentType != null) && (contentType.indexOf("multipart/form-data") >= 0)) {

DataInputStream in = new DataInputStream(request.getInputStream());
int formDataLength = request.getContentLength();

byte dataBytes[] = new byte[formDataLength];
int byteRead = 0;
int totalBytesRead = 0;
while (totalBytesRead < formDataLength) {
byteRead = in.read(dataBytes, totalBytesRead, formDataLength);
totalBytesRead += byteRead;
}

try {
Class.forName("com.mysql.jdbc.Driver").newInstance();
out.println("Driver Loaded!");
} catch (Exception E) {
out.println("Unable to load driver.");
}

try {
String connectionURL = "jdbc:mysql://localhost:3306/meg?user=;password=";
Connection C = DriverManager.getConnection(connectionURL,"","");
C.setAutoCommit(false);

String insert = "insert into tblContent (content) values (?)";

PreparedStatement pstmt = C.prepareStatement(insert);
pstmt.setObject(1, dataBytes);
pstmt.executeUpdate();

pstmt.close();
C.close();
out.println("Inserted row " );

} catch (SQLException E) {
out.print( "SQLException: " + E.getMessage());
} catch (Exception E) {
out.print("Error " + E.toString());
}

}
%>

-------------------------------------------------------
Thanks!

JulianInactive KennedyInactive

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posted 20 years ago

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pstmt.setObject(1, dataBytes); probably won't help matters. Try using setBytes() instead. That may do the trick.

Jules

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Greenhorn

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posted 20 years ago

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Thanks. The problem is still not fixed. I could see the binary data saved in table via phpAdmin. The saved in and retrieved out binary length are the same. I am going to take another way to save the file path to database instead.

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