[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-5704) New getSubString() handling in ClobProxy is incompatible with MySQL JDBC PS.setClob(int, Clob) for empty CLOB

[Christopher G. Stach II (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-5704?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=38962#action_38962 ] 

Christopher G. Stach II commented on HHH-5704:
----------------------------------------------

Since it always starts at 1, start > getLength() should fail for any database driver with an emtpy lob. The check should probably be start - 1 > getLength() and possibly even an additional check for start + length - 1 > getLength() to avoid overruns.

> New getSubString() handling in ClobProxy is incompatible with MySQL JDBC PS.setClob(int, Clob) for empty CLOB
> -------------------------------------------------------------------------------------------------------------
>
>                 Key: HHH-5704
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-5704
>             Project: Hibernate Core
>          Issue Type: Bug
>    Affects Versions: 3.6.0
>         Environment: MySQL JDBC 5.1.12 / 5.1.13
>            Reporter: Sergey Vladimirov
>
> For all empty but not-null CLOBs MySQL drivers do the following (com.mysql.jdbc.PreparedStatement):
> 			String forcedEncoding = this.connection.getClobCharacterEncoding();
> 			
> 			if (forcedEncoding == null) {
> 				setString(i, x.getSubString(1L, (int) x.length()));
> 			} else {
> 				try {
> 					setBytes(i, x.getSubString(1L, 
> 							(int)x.length()).getBytes(forcedEncoding));
> 				} catch (UnsupportedEncodingException uee) {
> 					throw SQLError.createSQLException("Unsupported character encoding " + 
> 							forcedEncoding, SQLError.SQL_STATE_ILLEGAL_ARGUMENT, getExceptionInterceptor());
> 				}
> 			}
> As you can see, getSubString is called with first argument (start) equal to 1, even if length of CLOB is 0. Of course, it's not very good, but it worked for previous versions of Hibernate. But in 3.6.0 getSubString() handling in ClobProxy introduces additional checks that prevents the code above from working:
> if ( start > getLength() ) {
>     throw new SQLException( "Start position [" + start + "] cannot exceed overall CLOB length [" + getLength() + "]" );
> }
> Thus this code will now thrown an exception if content is empty (but not null!) CLOB. Here the part of stack trace:
> 31.10 16:46:03 .AbstractFlushingEventListener ERROR Could not synchronize database state with session
> org.hibernate.exception.GenericJDBCException: could not insert: [ru.arptek.classes.dummy.Article$Content]
>         at org.hibernate.exception.SQLStateConverter.handledNonSpecificException(SQLStateConverter.java:140)
>         at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:128)
>         at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
>         at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2436)
>         at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2856)
>         at org.hibernate.action.EntityInsertAction.execute(EntityInsertAction.java:79)
>         at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:273)
>         at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:265)
>         at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:184)
>         at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:321)
>         at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:51)
>         at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1216)
>         at org.hibernate.ejb.AbstractEntityManagerImpl.flush(AbstractEntityManagerImpl.java:795)
>         at ru.arptek.arpsite.content.WebObjectHome.create(WebObjectHome.java:122)
> (...)
> Caused by: java.sql.SQLException: Start position [1] cannot exceed overall CLOB length [0]
>         at org.hibernate.engine.jdbc.ClobProxy.invoke(ClobProxy.java:146)
>         at $Proxy52.getSubString(Unknown Source)
>         at com.mysql.jdbc.PreparedStatement.setClob(PreparedStatement.java:3542)
>         at com.mysql.jdbc.jdbc2.optional.PreparedStatementWrapper.setClob(PreparedStatementWrapper.java:299)
>         at org.apache.commons.dbcp.DelegatingPreparedStatement.setClob(DelegatingPreparedStatement.java:187)
>         at org.apache.commons.dbcp.DelegatingPreparedStatement.setClob(DelegatingPreparedStatement.java:187)
>         at org.hibernate.type.descriptor.sql.ClobTypeDescriptor$1.doBind(ClobTypeDescriptor.java:60)
>         at org.hibernate.type.descriptor.sql.BasicBinder.bind(BasicBinder.java:89)
>         at org.hibernate.type.AbstractStandardBasicType.nullSafeSet(AbstractStandardBasicType.java:282)
>         at org.hibernate.type.AbstractStandardBasicType.nullSafeSet(AbstractStandardBasicType.java:277)
>         at org.hibernate.type.AbstractSingleColumnStandardBasicType.nullSafeSet(AbstractSingleColumnStandardBasicType.java:85)
>         at org.hibernate.persister.entity.AbstractEntityPersister.dehydrate(AbstractEntityPersister.java:2166)
>         at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2412)
>         ... 70 more
> I believe there should be additional check like:
> long start = (Long) args[0];
> if ( start < 1 ) {
>         throw new SQLException( "Start position 1-based; must be 1 or more." );
> }
> int length = (Integer) args[1];
> if ( length < 0 ) {
>         throw new SQLException( "Length must be great-than-or-equal to zero." );
> }
> // workaround for MySQL incompatibility
> if ( start == 1 && length == 0) {
>     return "";
> } else if ( start > getLength() ) {
>     throw new SQLException( "Start position [" + start + "] cannot exceed overall CLOB length [" + getLength() + "]" );
> }
> return getSubString( start-1, length );

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