Jakarta persistence 3.1 highlights

• autocloseable EntityManager and EntityManagerFactory
• Criteria CASE expression support Expressions as conditions
• JPQL (and criteria API)
  
• CEILING, EXP, FLOOR, LN, POWER, ROUND, SIGN
• LOCAL DATE/TIME/DATETIME

You can find the specification here.

Oracle SQLDeveloper connection fails / TNS listener not starting

I had a problem today connecting to my Oracle express database from SQL Developer on Windows 10 with the error: The network adapter could not establish the connection.
Connection did work from SQL*PLUS (Run SQL Command line).
The OracleXETNSListener service was stopped in my services and restarting it did not work.
Turns out the problem was that I changed my computer name yesterday and the service does not use localhost, but the computername.
To solve this I changed the hostname in these files:
%ORACLE_HOME%\app\oracle\product\11.2.0\server\network\ADMIN\listener.ora
%ORACLE_HOME%\app\oracle\product\11.2.0\server\network\ADMIN\tnsnames.ora
Stopped/started the database and everything's fine.

Saw these alternate solutions (did not test):
solution 1: Add the old hostname to C:\Windows\System32\drivers\etc\hosts
solution 2:

SQL> alter system set LOCAL_LISTENER='(ADDRESS=(PROTOCOL=TCP)(HOST=localhost)(PORT=1521))' scope=both;
SQL> alter system register;

JPA links (updated)

Reference implementation.

Official documentation:

• JSR 317 JPA 2 specification
• JSR 338 JPA 2.1 specification
• API Javadoc
• Hibernate API Javadoc

Others:

•  Wikibook (incomplete)

Providers often have good JPA documentation as well. Might include extensions (and JDO stuff) though:

• Open JPA
  
• EclipseLink JPA
• DataNucleus
• ObjectDB

Specific topics:

• JPA 2.x what's new
• Where to define JPQL queries
• Caching 
• Validation

Background:

•  ORM hate

Glassfish missing DataSource: Table/View XXX does not exist

I have a little old webapp connecting to a DB using a glassfish ConnectionPool.
This used to run fine but on a more recent glassfish (4.0) I do net get a good datasource from Glassfish, resulting in a Table/View <name> does not exist error message (the message is a general symptom for a failed DB connection, which can have many other reasons).
The problem exists if I configure the DataSource in web.xml and also if I inject it using @Resource.
The solution is to explicitly map the application reference to the JNDI name in WEB-INF/glassfish-web.xml:

<resource-ref>
    <res-ref-name>jdbc/theDB</res-ref-name>
    <jndi-name>jdbc/theDB</jndi-name>
</resource-ref>  

If you don't, Glassfish returns a ConnectionPoolDataSource. Some people corrected this by refering in their web.xml to the ConnectionPoolDataSource, but the solution above will work both for web.xml and Resource injection.

The Object Relational Gap (updated)

The Object	Relational Gap
transient	persistent
classes	tables
inheritance
attributes	columns
objects	rows
instance attribute implicity ID: reference	field explicit ID: primary key
relations	relations
references unidirectional  ordered (lists)	foreign keys bidirectional
behaviour centric	data centric
navigate to object behaviour based partitioning methods	operate on set relation based partitioning stored procedures
tight behaviour-data coupling	triggers, constraints
data hiding, encapsulation
	Permissions