Question

For multiple image retrieval I am calling a PhotoHelperServlet with an anchor tag to get imageNames(multiple images) as follows

PhotoHelperServlet to get names of Images

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

// Getting userid from session

Image image = new Image();
image.setUserid(userid);

ImageDAO imageDAO = new ImageDAO();

try {

    List<Image> imageId = imageDAO.listNames(image);

    if (imageId == null) { 
        // check if imageId is retreived
    }

    request.setAttribute("imageId", imageId);

    //Redirect it to home page
    RequestDispatcher rd = request.getRequestDispatcher("/webplugin/jsp/profile/photos.jsp");
    rd.forward(request, response);

catch (Exception e) {
    e.printStackTrace();
}

In ImageDAO listNames() method :

public List<Image> listNames(Image image) throws IllegalArgumentException, SQLException, ClassNotFoundException {

    Connection connection = null;
    PreparedStatement preparedStatement = null;
    ResultSet resultset = null;
    Database database = new Database();
    List<Image> imageId = new ArrayList<Image>();

    try {

        connection = database.openConnection();
        preparedStatement = connection.prepareStatement(SQL_GET_PHOTOID);                  
        preparedStatement.setLong(1, image.getUserid());
        resultset = preparedStatement.executeQuery();

        while(resultset.next()) {
            image.setPhotoid(resultset.getLong(1));
            imageId.add(image);
        }

    } catch (SQLException e) {
        throw new SQLException(e);
    } finally {
        close(connection, preparedStatement, resultset);
    }
    return imageId;
}

In JSP code:

<c:forEach items="${imageId}" var="imageid">
    <img src="Photos/${imageid}">
</c:forEach>

In PhotoServlet doGet() method to get a photo:

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

String imageid = request.getPathInfo().substring(1);

if(imageid == null) {
    // check for null and response.senderror
}

ImageDAO imageDAO = new ImageDAO();

try {

    Image image = imageDAO.getPhotos(imageid);

    if(image == null) {}

    BufferedInputStream input = null;
    BufferedOutputStream output = null;

    try {

        input = new BufferedInputStream(image.getPhoto(), DEFAULT_BUFFER_SIZE);
        output = new BufferedOutputStream(response.getOutputStream(), DEFAULT_BUFFER_SIZE);

        // Write file contents to response.
        byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
        int length;
        while ((length = input.read(buffer)) > 0) {
            output.write(buffer, 0, length);
        }
    } finally {
        if (output != null) try { output.close(); } catch (IOException logOrIgnore) {}
        if (input != null) try { input.close(); } catch (IOException logOrIgnore) {}
    }

} catch(Exception e) {
    e.printStackTrace();
}

In ImageDAO getPhotos() method

public Image getPhotos(String imageid) throws IllegalArgumentException, SQLException, ClassNotFoundException {

    Connection connection = null;
    PreparedStatement preparedStatement = null;
    ResultSet resultset = null;
    Database database = new Database();
    Image image = new Image();

    try {

        connection = database.openConnection();
        preparedStatement = connection.prepareStatement(SQL_GET_PHOTO);                  
        preparedStatement.setString(1, imageid);
        resultset = preparedStatement.executeQuery();

        while(resultset.next()) {
            image.setPhoto(resultset.getBinaryStream(1));
        }

    } catch (SQLException e) {
        throw new SQLException(e);
    } finally {
        close(connection, preparedStatement, resultset);
    }
    return image;
}

In web.xml

<!-- Getting each photo -->
<servlet>
    <servlet-name>Photos Module</servlet-name>
    <servlet-class>app.controllers.PhotoServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>Photos Module</servlet-name>
    <url-pattern>/Photos/*</url-pattern>
</servlet-mapping>

<!-- Getting photo names -->
<servlet>
    <servlet-name>Photo Module</servlet-name>
    <servlet-class>app.controllers.PhotoHelperServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>Photo Module</servlet-name>
    <url-pattern>/Photo</url-pattern>
</servlet-mapping>

Question:

I am getting following Exception:

java.io.IOException: Stream closed

on this Line:

at app.controllers.PhotoServlet.doGet(PhotoServlet.java:94)
while ((length = input.read(buffer)) > 0) {

The full Exception:

java.io.IOException: Stream closed
at java.io.BufferedInputStream.getInIfOpen(BufferedInputStream.java:134)
at java.io.BufferedInputStream.read1(BufferedInputStream.java:256)
at java.io.BufferedInputStream.read(BufferedInputStream.java:317)
at java.io.FilterInputStream.read(FilterInputStream.java:90)
at app.controllers.PhotoServlet.doGet(PhotoServlet.java:94)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:498)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:562)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:394)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:243)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:188)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:166)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)

Answer 1

I’d imagine that the basic code flow is laid out like follows:

try {
    Get connection, statement, resultset
    Use connection, statement, resultset
    Get inputstream of resultset
} finally {
    Close resultset, statement, connection
}

try {
    Get outputstream
    Use inputstream of resultset, outputstream
} finally {
    Close outputstream, inputstream of resultset
}

And that the close of the ResultSet has implicitly closed the InputStream. It look like that your JDBC driver does not store the InputStream of the ResultSet fully in memory or on temp storage when the ResultSet is closed. Perhaps the JDBC driver is a bit simplistic, or not well thought designed, or the image is too large to be stored in memory. Who knows.

I’d first figure out what JDBC driver impl/version you’re using and then consult its developer documentation to learn about settings which may be able to change/fix this behaviour. If you still can’t figure it out, then you’d have to rearrange the basic code flow as follows:

try {
    Get connection, statement, resultset
    Use connection, statement, resultset
    try {
        Get inputstream of resultset, outputstream
        Use inputstream of resultset, outputstream
    } finally {
        Close outputstream, inputstream of resultset
    }
} finally {
    Close resultset, statement, connection
}

Or

try {
    Get connection, statement, resultset
    Use connection, statement, resultset
    Get inputstream of resultset
    Copy inputstream of resultset
} finally {
    Close resultset, statement, connection
}

try {
    Get outputstream
    Use copy of inputstream, outputstream
} finally {
    Close outputstream, copy of inputstream
}

The first approach is the most efficient, only the code is clumsy. The second approach is memory inefficient when you’re copying to ByteArrayOutputStream, or performance inefficient when you’re copying to FileOutputStream. If the images are mostly small and do not exceed a megabyte or something, then I’d just copy it to ByteArrayOutputStream.

InputStream input = null;
OutputStream output = null;

try {
    input = new BufferedInputStream(resultSet.getBinaryStream("columnName"), DEFAULT_BUFFER_SIZE);
    output = new ByteArrayOutputStream();
    byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];

    for (int length; ((length = input.read(buffer)) > 0;) {
        output.write(buffer, 0, length);
    }
} finally {
    if (output != null) try { output.close(); } catch (IOException ignore) {}
    if (input != null) try { input.close(); } catch (IOException ignore) {}
}

Image image = new Image();
image.setPhoto(new ByteArrayInputStream(output.toByteArray()));
// ...