java.io.IOException:Stream已关闭

Question

对于多个图像检索,我PhotoHelperServlet使用锚标记调用a 来获取imageNames(多个图像),如下所示

PhotoHelperServlet 得到的名字 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();
}

在ImageDAO listNames()方法中:

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;
}

在JSP代码中:

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

在PhotoServlet doGet()方法中获取照片:

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();
}

在ImageDAO getPhotos()方法中

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;
}

在web.xml中

<!-- 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>

题:

我得到以下例外:

java.io.IOException: Stream closed

在这条线上:

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

完整例外:

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

我想,基本代码流的布局如下:

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
}

并且关闭了ResultSet已经暗中关闭了InputStream.它看起来像你的JDBC驱动程序不存储InputStream的ResultSet的时候完全在内存或临时存储ResultSet关闭.也许JDBC驱动程序有点简单,或者设计不合理,或者图像太大而无法存储在内存中.谁知道.

我首先要弄清楚您正在使用的JDBC驱动程序impl/version,然后查阅其开发人员文档以了解可能能够更改/修复此行为的设置.如果您仍然无法解决问题,那么您必须重新安排基本代码流,如下所示:

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
}

要么

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
}

第一种方法是最有效的,只有代码是笨拙的.第二种方法是在复制时内存效率低ByteArrayOutputStream,或者在复制时效率低下FileOutputStream.如果图像大多数小而且不超过兆字节或其他东西,那么我只是将其复制到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()));
// ...