Wrong data retrieval when using getString() instead of getClob() for clob columns

• Type: Bug
• Status: Closed
• Resolution: Won't Fix
• Affects Version/s: 7.0.X, Master
• Fix Version/s: None
• Component/s: Core Infrastructure > Database Access
• Labels: None
• Fix Priority: 3
• Bug Type: Database Upgrade

Preconditions:

1. Database upgrading from 6.2 to 7.0
2. Some content recorded using a clob structure with a size >= 4000 bytes
3. RDBMS Oracle using a ojdbc7.jar driver library.
   Important: There may be other RDBMS in a similar issue.

Steps to reproduce:

• Launch an upgrade process from 6.2 to 7.0 using Liferay upgrade client.

Expected behaviour:

• Upgrade process ends without any errors.

Observed behaviour:

• Some entities generate errors during upgrade because of data retrieval is truncated.
  Example:

  Caused by: com.liferay.portal.kernel.xml.DocumentException: Error on line 66 of document  : XML document structures must start and end within the same entity. Nested exception: XML document structures must start and end within the same entity.
          at com.liferay.portal.xml.SAXReaderImpl.read(SAXReaderImpl.java:408)
          at com.liferay.portal.xml.SAXReaderImpl.read(SAXReaderImpl.java:384)
          at com.liferay.portal.xml.SAXReaderImpl.read(SAXReaderImpl.java:419)
          at com.liferay.portal.kernel.xml.SAXReaderUtil.read(SAXReaderUtil.java:165)
          at com.liferay.journal.internal.upgrade.v0_0_5.UpgradeJournal.convertStaticContentToDynamic(UpgradeJournal.java:237)
          at com.liferay.journal.internal.upgrade.v0_0_5.UpgradeJournal.updateJournalArticles(UpgradeJournal.java
  

Root cause:
Our code uses

java.sql.ResultSet.getString(String)

method instead of

java.sql.ResultSet.getClob(String)

for data retrieval from clob columns.

Under some context, getString(String) method gets truncated data.

See also: https://docs.oracle.com/javase/8/docs/api/java/sql/Clob.html

Workaround:
Oracle Support admits some bugs using getString(String) method under ojdbc7.jar driver library.
Oracle Support recommends using ojdbc8.jar driver library with at least Oracle 12.2.0.1.0 JDBC 4.2 versioning.