java.io.IOException：Stream已关闭 [英] java.io.IOException: Stream closed

问题描述

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

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

PhotoHelperServlet 获取图像的名称

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：

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;
}

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：

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();
}

在ImageDAO中getPhotos（）方法

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;
}

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>

问题：

我正在关注例外：

java.io.IOException: Stream closed

此行：

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

完整异常：

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)

推荐答案

我认为基本代码流的布局如下：

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
}

并且关闭 ResultSet 已隐式关闭 InputStream 。看起来你的JDBC驱动程序没有将 ResultSet 的 InputStream 完全存储在内存或临时存储器中 ResultSet 已关闭。也许JDBC驱动程序有点简单，或者没有深思熟虑，或者图像太大而无法存储在内存中。谁知道。

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.

我首先要弄清楚你正在使用的JDBC驱动程序impl / version，然后查阅它的开发者文档以了解可能会改变的设置/修复此行为。如果你仍然无法解决问题，那么你必须按如下方式重新安排基本代码流：

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
}

或

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
}

第一种方法效率最高，只有代码笨拙。当您复制到 ByteArrayOutputStream 时，第二种方法是内存效率低，或者当您复制到 FileOutputStream 时性能效率低下。如果图像大多不小并且不超过兆字节或者其他东西，那么我只需将其复制到 ByteArrayOutputStream 。

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()));
// ...

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