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
PhotoHelperServlet获取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
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：
我得到以下异常：
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)
答案 0 :(得分：7)
我认为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
}
而ResultSet的结束隐含了InputStream。看起来，当InputStream关闭时，您的JDBC驱动程序不会将ResultSet ResultSet完全存储在内存中或临时存储中。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。谁知道呢。
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。如果您仍然无法弄明白，那么您必须重新安排基本代码流程，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
}
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
}
第一种方法是最有效的，只有代码是笨拙的。当您复制到ByteArrayOutputStream时，第二种方法是内存效率低下，或者当您复制到FileOutputStream时性能效率低下。如果图像大部分都很小并且不超过兆字节或者某些东西，那么我只需将其复制到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()));
// ...
答案 1 :(得分：2)
参考一下:
ImageLoad
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.StringWriter;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONException;
import org.json.JSONObject;
import android.content.Context;
import android.net.Uri;
import android.os.Environment;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.widget.ImageSwitcher;
import android.widget.ImageView;
/**
* 图片加载帮助类（自动异步加载、图片文件缓存、缓存文件管理）
*
* @author n.zhang
*
*/
public class ImageLoad {
private static final String TAG = "imageLoad";// 日志标签
private static final String TAG_REF = TAG + "Ref";
private Executor executor; // 线程池
private int defaultImageID;// 默认图片id
private Context context;// 你懂的
private HashMap<String, PathInfo> cache = new HashMap<String, PathInfo>();// URL
boolean sdCardExist = Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED); // 路径信息对应表
private LinkedList<PathInfo> use = new LinkedList<PathInfo>();// 已在使用的路径信息队列
private LinkedList<PathInfo> lost = new LinkedList<PathInfo>();// 还未使用的路径信息队列
private LinkedList<PathInfo> original = new LinkedList<PathInfo>();// 初始图片路径信息队列
private int index = 0;// id下标
/**
* 图片加载工具，默认10线程下载,缓存80张图片
*
* @param context
*/
public ImageLoad(Context context) {
this(context, 10, 80, 0);
}
/**
* 图片加载工具
*
* @param context
* 你懂的
* @param threadSize
* 最大线程数
* @param maxCacheSize
* 最大缓存图片数量
* @param defaultImageID
* 默认图片id
*/
public ImageLoad(Context context, int threadSize, int maxCacheSize, int defaultImageID) {
this.context = context;
this.defaultImageID = defaultImageID;
executor = Executors.newFixedThreadPool(threadSize);
loadImagePathInfo();
// 图片信息数量不足不满最大值，以空白图片信息补足。
newImagePathInfo(maxCacheSize);
for (PathInfo pi : original) {
if (null == pi.url) {
lost.offer(pi);
} else {
use.offer(pi);
cache.put(pi.url, pi);
}
}
File dir = null;
if (sdCardExist) {
dir = new File(Environment.getExternalStorageDirectory() + "/t_image/");
} else {
dir = new File(context.getCacheDir() + "/t_image/");
}
// 如果文件存在并且不是目录，则删除
if (dir.exists() && !dir.isDirectory()) {
dir.delete();
}
// 如果目录不存在，则创建
if (!dir.exists()) {
dir.mkdir();
}
}
/**
* 路径信息
*
* @author n.zhang
*
*/
public static class PathInfo {
private int id;// 图片id 此id用于生成存储图片的文件名。
private String url;// 图片url
}
/**
* 获得图片存储路径
*
* @param url
* @return
*/
public PathInfo getPath(String url) {
PathInfo pc = cache.get(url);
if (null == pc) {
pc = lost.poll();
}
if (null == pc) {
pc = use.poll();
refresh(pc);
}
return pc;
}
/**
* @info 微博使用加载数据路径
* @author FFMobile-cuihe
* @date 2012-3-1 下午2:13:10
* @Title: getsPath
* @Description: TODO
* @param@param url
* @param@return 设定文件
* @return PathInfo 返回类型
* @throws
*/
public PathInfo getsPath(String url) {
PathInfo pc = cache.get(url);
if (null == pc) {
pc = lost.peek();
}
// if (null == pc) {
// pc = use.peek();
// refresh(pc);
// }
return pc;
}
public PathInfo getLocalPath(String url) {
PathInfo pc = cache.get(url);
if (null == pc) {
pc = lost.peek();
}
return pc;
}
/**
* 刷新路径信息（从索引中删除对应关系、删除对应的图片文件、获取一个新id）
*
* @param pc
*/
private void refresh(PathInfo pc) {
long start = System.currentTimeMillis();
File logFile = null;
try {
cache.remove(pc.url);
File file = toFile(pc);
file.delete();
logFile = file;
pc.id = index++;
pc.url = null;
} finally {
Log.d(TAG_REF, "ref time {" + (System.currentTimeMillis() - start) + "}; ref {" + logFile + "}");
}
}
/**
* 获得file对象
*
* @param pi
* 路径缓存
* @return
*/
public File toFile(PathInfo pi) {
if (sdCardExist) {
return new File(Environment.getExternalStorageDirectory() + "/t_image/" + pi.id + ".jpg");
} else {
return new File(context.getCacheDir() + "/t_image/" + pi.id + ".jpg");
}
}
/**
* 请求加载图片
*
* @param url
* @param ilCallback
*/
public void request(String url, final ILCallback ilCallback) {
final long start = System.currentTimeMillis();
final PathInfo pc = getPath(url);
File file = toFile(pc);
if (null != pc.url) {
ilCallback.seed(Uri.fromFile(file));
Log.d(TAG, "load time {" + (System.currentTimeMillis() - start) + "}; cache {" + pc.url + "} ");
} else {
pc.url = url;
Handler mHandler = new Handler() {
public void handleMessage(Message msg) {
if (null == msg.obj) {
ilCallback.seed(Uri.EMPTY);
Log.d(TAG, "load lost time {" + (System.currentTimeMillis() - start) + "}; network lost {"
+ pc.url + "}");
} else {
ilCallback.seed((Uri) msg.obj);
Log.d(TAG, "load time {" + (System.currentTimeMillis() - start) + "}; network {" + pc.url + "}");
}
};
};
executor.execute(new DownloadImageTask(pc, file, mHandler));
}
}
private void localRequest(String url, final ILCallback ilCallback) {
final long start = System.currentTimeMillis();
final PathInfo pc = getLocalPath(url);
File file = toFile(pc);
if (null != pc.url) {
ilCallback.seed(Uri.fromFile(file));
Log.d(TAG, "load time {" + (System.currentTimeMillis() - start) + "}; cache {" + pc.url + "} ");
}
}
public void localRequest(String url, ImageView iv) {
localRequest(url, new ImageViewCallback(iv));
}
/**
* 请求加载图片
*
* @param url
* @param iv
*/
public void request(String url, ImageView iv) {
request(url, new ImageViewCallback(iv));
}
/**
* 请求加载图片
*
* @param url
* @param iv
*/
// public void request(String url, ImageButton iv) {
// request(url, new ImageButtonCallbacks(iv));
// }
/**
* 请求加载图片
*
* @param url
* @param iv
*/
// public void request(String url, Button iv) {
// request(url, new ButtonCallbacks(iv));
// }
/**
* 请求加载图片
*
* @param url
* @param iv
*/
public void request(String url, ImageSwitcher iv) {
request(url, new ImageSwitcherCallbacks(iv));
}
/**
* 下载图片任务
*
* @author Administrator
*
*/
private class DownloadImageTask implements Runnable {
private Handler hc;
private PathInfo pi;
private File file;
public DownloadImageTask(PathInfo pi, File file, Handler hc) {
this.pi = pi;
this.file = file;
this.hc = hc;
}
public void run() {
try {
byte[] b = requestHttp(pi.url);
if (null == b) {
throw new IOException("数据为空");
}
writeFile(file, b);
use.offer(pi);
cache.put(pi.url, pi);
Message message = new Message();
message.obj = Uri.fromFile(file);
hc.sendMessage(message);
} catch (IOException e) {
Message message = hc.obtainMessage(0, Uri.EMPTY);
hc.sendMessage(message);
Log.i(TAG, "image download lost.", e);
} catch (RuntimeException e) {
Message message = hc.obtainMessage(0, Uri.EMPTY);
hc.sendMessage(message);
Log.i(TAG, "image download lost.", e);
}
}
}
private void writeFile(File file, byte[] data) throws IOException {
FileOutputStream out = new FileOutputStream(file);
try {
out.write(data);
} finally {
out.close();
}
}
private static byte[] requestHttp(String url) throws IOException {
DefaultHttpClient client = new DefaultHttpClient();
System.gc();
try {
HttpGet get = new HttpGet(url);
HttpResponse res = client.execute(get);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
if (200 == res.getStatusLine().getStatusCode()) {
res.getEntity().writeTo(baos);
return baos.toByteArray();
} else {
throw new IOException("httpStatusCode:" + res.getStatusLine().getStatusCode());
}
} finally {
client.getConnectionManager().shutdown();
}
}
/**
* 读取图片路径信息
*
* @return
*/
@SuppressWarnings("unchecked")
private void loadImagePathInfo() {
long start = System.currentTimeMillis();
File file = new File(context.getCacheDir() + "/imagePathCache.json");
try {
if (!file.isFile()) {
// 文件不存在。
Log.d(TAG, "path info file does not exist");
imageGc();
return;
}
StringWriter sw = new StringWriter();
char[] buf = new char[1024];
int len;
FileReader fr = new FileReader(file);
while (-1 != (len = fr.read(buf))) {
sw.write(buf, 0, len);
}
fr.close();
JSONObject json = new JSONObject(sw.toString());
Iterator<String> it = json.keys();
while (it.hasNext()) {
String key = it.next();
int id = json.getInt(key);
PathInfo pi = new PathInfo();
pi.url = key;
pi.id = id;
if (index < id) {
index = id;
}
original.add(pi);
}
// 打开文件文件缓存成功
Log.i(TAG, "load path info ok.");
} catch (IOException e) {
Log.i(TAG, "load path info lost - IOException.", e);
imageGc();
} catch (JSONException e) {
Log.i(TAG, "load path info lost - JSONException.", e);
imageGc();
} finally {
if (file.exists()) {
file.delete();
Log.d(TAG, "delete path info file");
}
Log.d(TAG, "load path info time {" + (System.currentTimeMillis() - start) + "}");
}
}
/**
* 如果路径信息加载失败，清理图片目录。
*/
private void imageGc() {
long start = System.currentTimeMillis();
try {
File dir;
if (sdCardExist) {
dir = new File(Environment.getExternalStorageDirectory() + "/t_image/");
} else {
dir = new File(context.getCacheDir() + "/t_image/");
}
if (dir.isDirectory()) {
for (File file : dir.listFiles()) {
file.delete();
// gc
Log.d(TAG_REF, "gc {" + file + "}");
}
}
} finally {
// gc 计时
Log.d(TAG_REF, "gc time {" + (System.currentTimeMillis() - start) + "}");
}
}
private void newImagePathInfo(int max_size) {
for (int i = original.size(); i < max_size; i++) {
PathInfo pc = new PathInfo();
pc.id = index++;
original.add(pc);
}
}
/**
* 保存图片路径信息（如记录，下次程序打开，可读取该记录已存图片继续可用）
*/
public void saveImagePathInfo() {
long start = System.currentTimeMillis();
try {
JSONObject json = new JSONObject();
for (PathInfo pi : use) {
try {
json.put(pi.url, pi.id);
} catch (JSONException e) {
e.printStackTrace();
}
}
File file = new File(context.getCacheDir() + "/imagePathCache.json");
try {
FileWriter fw = new FileWriter(file);
fw.write(json.toString());
fw.close();
Log.i(TAG, "image file info save ok.");
} catch (IOException e) {
e.printStackTrace();
Log.i(TAG, "image file info save lost.");
file.delete();
}
} finally {
Log.d(TAG, "save time {" + (System.currentTimeMillis() - start) + "}");
}
}
/**
* 图片加载回调
*
* @author n.zhang
*
*/
public static interface ILCallback {
public void seed(Uri uri);
}
private class ImageViewCallback implements ILCallback {
public ImageViewCallback(ImageView iv) {
if (defaultImageID > 0) {
iv.setImageResource(defaultImageID);
}
this.iv = iv;
}
private ImageView iv;
public void seed(Uri uri) {
File f = new File(uri.getPath());
iv.setImageURI(Uri.parse(f.toString()));
f = null;
}
}
// private class ImageButtonCallbacks implements ILCallback {
// public ImageButtonCallbacks(ImageButton iv) {
// if (defaultImageID > 0) {
// iv.setBackgroundResource(defaultImageID);
////iv.setImageResource(defaultImageID);
// }
// this.iv = iv;
// }
//
// private ImageButton iv;
//
// public void seed(Uri uri) {
// iv.setImageURI(uri);
// }
// }
// private class ButtonCallbacks implements ILCallback {
// public ButtonCallbacks(Button iv) {
// if (defaultImageID > 0) {
// iv.setBackgroundResource(defaultImageID);
////iv.setImageResource(defaultImageID);
// }
// this.iv = iv;
// }
//
// private Button iv;
//
// public void seed(Uri uri) {
// iv.setImageURI(uri);
// }
// }
private class ImageSwitcherCallbacks implements ILCallback {
public ImageSwitcherCallbacks(ImageSwitcher iv) {
if (defaultImageID > 0) {
iv.setImageResource(defaultImageID);
}
this.iv = iv;
}
private ImageSwitcher iv;
public void seed(Uri uri) {
iv.setImageURI(uri);
}
}
}
答案 2 :(得分：0)
看起来问题实际上并不在您发布的代码中。出于某种原因，流input已关闭。所以你可能正在关闭image.getPhoto()