我有一个从 oracle 数据库中获取 blob 的 java 方法(我使用的是 ojdbc8.jar)。此方法将 blob 写入 OutputStream(对于客户端):
// OutputStream os = response.getOutputStream(); // earlier
// Blob blob = resultSet.getBlob("data_binary"); // earlier
int length;
int bufSize = 4096;
byte buffer[] = new byte[bufSize];
try (InputStream is = blob.getBinaryStream()) {
while ((length = is.read(buffer, 0, bufSize)) != -1) {
out.write(buffer, 0, length);
out.flush();
}
out.flush();
}
并返回 InputStream(用于缓存):
return blob.getBinaryStream();
当我尝试(在另一个类上)将此 InputStream 写入磁盘时:
try (OutputStream os = new FileOutputStream(fileOnTheDisk)) {
IOUtils.copy(blobIS, os);
} catch (IOException e) {
e.printStackTrace();
}
我遇到异常:
java.io.IOException: Closed Connection
at oracle.jdbc.driver.OracleBlobInputStream.needBytes(OracleBlobInputStream.java:204)
at oracle.jdbc.driver.OracleBufferedStream.readInternal(OracleBufferedStream.java:169)
at oracle.jdbc.driver.OracleBufferedStream.read(OracleBufferedStream.java:143)
at oracle.jdbc.driver.OracleBufferedStream.read(OracleBufferedStream.java:132)
at org.apache.commons.io.IOUtils.copyLarge(IOUtils.java:1025)
at org.apache.commons.io.IOUtils.copy(IOUtils.java:999)
at ru.miit.databasereader.OracleDatabaseReader.getbo(OracleDatabaseReader.java:262)
at ru.miit.contentservlet.ContentGetter.getObject(ContentGetter.java:85)
at ru.miit.contentservlet.ContentServlet.doGet(ContentServlet.java:131)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:651)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:409)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:754)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1376)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Unknown Source)
Caused by: java.sql.SQLRecoverableException: Closed Connection
at oracle.sql.BLOB.getDBAccess(BLOB.java:1122)
at oracle.sql.BLOB.getBytes(BLOB.java:348)
at oracle.jdbc.driver.OracleBlobInputStream.needBytes(OracleBlobInputStream.java:181)
... 31 more
我需要一个解决方案,如何将此 blob.getBinaryStream()
写入另一个类的磁盘并了解问题所在。
我试图用这种(获取)方法将这个 blob 流写入磁盘,但没有得到异常。只有当我将这个流返回到另一个类(class)时,我才会有异常(exception)。
已更新
完整代码。磁盘缓存:
public class DiskCache {
public void put(final String location, final String name, final InputStream blobIS, OutpuStream servletOS) {
DatabaseReader databaseReader = new DatabaseReader ();
BinaryObject binaryobject = databaseReader.getBinaryDataByImageId(imageId, servletOS);
File fileOnTheDisk = new File(location + name);
try (OutputStream os = new FileOutputStream(fileOnTheDisk)) {
IOUtils.copy(binaryobject.getIS(), os);
} catch (IOException e) {
e.printStackTrace();
}
}
数据库读取器:
public class DatabaseReader{
public Connection getConnection() throws NamingException, SQLException {
Context initialContext = null;
try {
initialContext = new InitialContext();
DataSource dataSource = (DataSource) initialContext.lookup(DATASOURCE_NAME);
OracleConnection connection = (OracleConnection) dataSource.getConnection().unwrap(OracleConnection.class);
return connection;
} finally {
if (initialContext != null){
initialContext.close();
}
}
}
public BinaryObject getBinaryDataByImageId(final String imageId, OutputStream osServlet) throws SQLException, NamingException, IOException{
String sqlQuery = "***";
BinaryObject binaryObject = null;
try (Connection connection = getConnection();
OraclePreparedStatement preparedStatement = (OraclePreparedStatement) connection
.prepareStatement(sqlQuery)) {
try (ResultSet resultSet = preparedStatement.executeQuery()) {
resultSet.next();
Blob blob = resultSet.getBlob("blob_data");
writeToStream(blob, osServlet);
binaryObject = new BinaryObject(imageId, blob.getBinaryStream());
}
}
return binaryObject;
}
public void writeToStream(Blob blobData, OutputStream out) throws IOException, SQLException {
int length;
int bufSize = 4096;
byte buffer[] = new byte[bufSize];
try (InputStream is = blobData.getBinaryStream()) {
while ((length = is.read(buffer, 0, bufSize)) != -1) {
out.write(buffer, 0, length);
out.flush();
}
out.flush();
}
}
}
JNDI:
<Resource name="jdbc/database" auth="Container"
type="javax.sql.DataSource" maxActive="100"
maxIdle="30" maxWait="1000"
username="***"
password="***"
driverClassName="oracle.jdbc.OracleDriver"
url="jdbc:oracle:thin***"/>
最佳答案
在每个 ResultSet.next
步骤中,一个 blob 应该只被读取一次。在结果集关闭(它应该关闭)之后,以及在读取 blob 的输入流之后(也关闭流),你就不走运了。
如果您想快速为客户端提供服务,并在缓存中存储副本,您需要同时执行这两项操作:
// OutputStream os = response.getOutputStream(); // earlier
// Blob blob = resultSet.getBlob("data_binary"); // earlier
// OutputStream cacheOut
final int bufSize = 4096;
byte[] buffer = new byte[bufSize];
int length;
try (InputStream is = blob.getBinaryStream()) {
while ((length = is.read(buffer, 0, bufSize)) != -1) {
out.write(buffer, 0, length);
out.flush();
cacheOut.write(buffer, 0, length);
}
out.flush();
cacheOut.close();
}
任何其他任务都是内存密集型任务。
关于java - blob.getBinaryStream 独立关闭,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/48865822/