【发布时间】：2012-06-28 04:37:58
【问题描述】：
获取二进制流时收到以下异常。
java.io.IOException: The stream is closed.
at com.microsoft.sqlserver.jdbc.BaseInputStream.checkClosed(SimpleInputStream.java:93)
at com.microsoft.sqlserver.jdbc.PLPInputStream.read(PLPInputStream.java:237)
at au.gov.vic.doi.tp.service.binary.dao.BinaryDAOImplTest.retrieveBinary(BinaryDAOImplTest.java:102)
我正在使用：Hibernate 4.1.1、MS SQL Server 2008 和最新的 MS SQL JDBC4 驱动程序。 我使用以下自定义映射类型“BlobToStreamUserType”从 SQL Blob (varchar(max)) 映射到 InputStream。 Hibernate 似乎没有提供将 SQL BLOB 映射到 Java InputStream 的类型，MaterializedBlobType 仅将 SQL BLOB 映射到 Java byte[]。
我正在使用“rs.getBinaryStream”返回一个真正的二进制流，而不是缓冲在内存中的流，原因是我们有大图像，如果多个用户同时访问会导致内存问题。
根据微软
Microsoft 驱动程序在 getBinaryStream 方面遵循 JDBC 规范 => 注意：在获取任何 >other 列的值之前，必须读取返回流中的所有数据。对 getter 方法的下一次调用会隐式关闭流。此外，当调用 InputStream.available 方法时，流可能会返回 0，无论是否有数据>可用。
所以 getBinaryStream 旨在返回真正的字节流。我们返回一个真正的>字节流，它没有在内存中缓冲，它是一个从服务器响应中直接读取的流。在为我们的实现获取所有字节之前，您无法关闭 contentDataResultSet。
我尝试将休眠属性 'hibernate.jdbc.use_streams_for_binary' 设置为 true 和 false，但这没有区别。
这是我的代码：
显示映射到自定义用户类型的图像实体类。
import java.io.InputStream;
import java.util.Date;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;
import org.hibernate.annotations.DynamicInsert;
import org.hibernate.annotations.DynamicUpdate;
import org.hibernate.annotations.GenericGenerator;
import org.hibernate.annotations.Type;
import com.google.common.base.Objects;
@Entity
@DynamicInsert(false)
@DynamicUpdate(false)
@Table(name = "Binary")
public class Binary
{
.........
@Lob
@Column(name = "image")
@Type(type = "my.package.BlobToStreamUserType")
public InputStream getImageStream()
{
return this.imageStream;
}
}
这是我的自定义映射类型：
public class BlobToStreamUserType implements UserType
{
public int[] sqlTypes()
{
return new int[]
{ Types.BLOB };
}
public Class returnedClass()
{
return InputStream.class;
}
public Object nullSafeGet(final ResultSet rs, final String[] names, final SessionImplementor session,
final Object owner) throws HibernateException, SQLException
{
return rs.getBinaryStream(names[0]);
}
public void nullSafeSet(final PreparedStatement st, final Object value, final int index,
final SessionImplementor session) throws HibernateException, SQLException
{
if (value != null)
{
if (!InputStream.class.isAssignableFrom(value.getClass()))
{
throw new HibernateException(value.getClass().toString() + " cannot be cast to a java.IO.InputStream");
}
InputStream inStream = (InputStream) value;
st.setBinaryStream(index, inStream);
}
else
{
st.setBytes(index, null);
}
}
public boolean equals(final Object x, final Object y) throws HibernateException
{
return ObjectUtils.equals(x, y);
}
public int hashCode(final Object x) throws HibernateException
{
assert (x != null);
return x.hashCode();
}
public Object deepCopy(final Object value) throws HibernateException
{
return value;
}
public boolean isMutable()
{
return false;
}
public Object replace(final Object original, final Object target, final Object owner) throws HibernateException
{
return original;
}
public Serializable disassemble(final Object value) throws HibernateException
{
//disassemble() is only called when caching the data in the second-level cache
// also safe for mutable objects
throw new UnsupportedOperationException("Not supported yet.");
}
public Object assemble(final Serializable cached, final Object owner) throws HibernateException
{
throw new UnsupportedOperationException("Not supported yet.");
}
}
这是我用来检索图像流的 DAO
public class BinaryDAOImpl extends AbstractSpringHibernateDAO implements BinaryDAO
{
public Binary getBinary(final String amsAssetId, final String assetMaintainer, final String variant,
final Integer sequence) throws GetException
{
try
{
Query query = super.getSession().createQuery(
"from Binary bin where bin.amsAssetId = :amsAssetId and bin.assetMaintainer = :assetMaintainer "
+ "and bin.variant = :variant and bin.sequence = :sequence");
query.setParameter("amsAssetId", amsAssetId);
query.setParameter("assetMaintainer", assetMaintainer);
query.setParameter("variant", variant);
query.setParameter("sequence", sequence);
return query.uniqueResult();
}
N.b 绕过休眠并直接从结果集中检索流的以下解决方法有效，并且允许我毫无例外地读取流。但是我宁愿使用休眠映射来检索真正的二进制流。
修改DAO方法
public Binary getBinary(final String amsAssetId, final String assetMaintainer, final String variant,
final Integer sequence) throws GetException
{
try
{
Query query = super.getSession().createQuery(
"from Binary bin where bin.amsAssetId = :amsAssetId and bin.assetMaintainer = :assetMaintainer "
+ "and bin.variant = :variant and bin.sequence = :sequence");
query.setParameter("amsAssetId", amsAssetId);
query.setParameter("assetMaintainer", assetMaintainer);
query.setParameter("variant", variant);
query.setParameter("sequence", sequence);
Binary binary = (Binary) query.uniqueResult();
final String id = binary.getId();
// Necessary until Hibernate supports InputStream mapping
binary.setImageStream(getSession().doReturningWork(new ReturningWork<InputStream>()
{
public InputStream execute(final Connection connection) throws SQLException
{
PreparedStatement statement = connection.prepareStatement("select image from Binary where id=?",
ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
statement.setString(1, id);
ResultSet resultSet = statement.executeQuery();
return (resultSet.first() ? resultSet.getBinaryStream(1) : null);
}
}));
return binary;
}
【问题讨论】：
标签： java sql-server-2008 jdbc stream hibernate-mapping