Jonathan Lalou's Blog

Question interessante d’un eleve il y a quelques semaines: quelle est la difference entre la Physique et la Chimie?

Reponse courte: la Chimie etudie les transformations de la matiere elle-meme au niveau de sa composition en especes chimiques, alors que la Physique etudie la matiere sans rapport avec les especes la composant: position, mouvement, temperature, charge, etc.

Plus precisement, en se basant sur un modele satellitaire de Bohr, la Chimie etudie les transformations de la matiere mettant en jeu des modifications sur les couches electroniques externes: reactions chimiques (oxydo-reduction, acido-basiques, etc.), ionisation, etc. On exclut le parametre temperature qui, bien que donnant une mesure du mouvement des electrons des couches externes, concerne en fait tous les electrons, quelle que soit leur couche.

La Physique etudie les autres modifications: deplacement, vitesse, temperature, forme, masse, electricite, fission, etc.:  ces dernieres notions ne se limitent pas aux couches electroniques externes mais concernent l’atome, la molecule, ou bien au contraire le noyau.

Neanmoins, plus on s’approche de l'”infiniment petit”, plus les distinctions s’estompent.

Context:

Client-server communication over JMS.

Stacktrace:

[java]Caused by: java.rmi.UnmarshalException: failed to unmarshal class weblogic.security.acl.internal.AuthenticatedUser; nested exception is:
java.io.StreamCorruptedException: invalid type code: 31
at weblogic.rjvm.ResponseImpl.unmarshalReturn(ResponseImpl.java:203)
at weblogic.rmi.internal.BasicRemoteRef.invoke(BasicRemoteRef.java:224)
at weblogic.common.internal.RMIBootServiceImpl_921_WLStub.authenticate(Unknown Source)
at weblogic.security.acl.internal.Security$1.run(Security.java:185)
at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:363)
at weblogic.security.service.SecurityManager.runAs(SecurityManager.java:147)
at weblogic.security.acl.internal.Security.authenticate(Security.java:181)
at weblogic.jndi.WLInitialContextFactoryDelegate.authenticateRemotely(WLInitialContextFactoryDelegate.java:726)
at weblogic.jndi.WLInitialContextFactoryDelegate.pushSubject(WLInitialContextFactoryDelegate.java:659)[/java]

Explanation – Fix

The client JVM was in version 1.6, the server was in 1.5.
To fix the issue, the client must be run with Java 1.5.
Possibly, the client may laucnh the JVM with the option -Dsun.lang.ClassLoader.allowArraySyntax=true.

Context

I have to send JMS messages on queues on clustered servers: t3://firstServer:1234 and t3://secondServer:5678.

The destination queues are retrieved in Spring, thanks to a property like:
[xml]<property name="providerURL" value="t3://firstServer:1234,t3://secondServer:5678"/>[/xml]

Error:

I receive the following error:

[java]javax.naming.ConfigurationException [Root exception is java.net.MalformedURLException: port expected: t3://firstServer:1234,t3://secondServer:5678][/java]

Explanation and fix:

When you send messages on many queues, you must not repeat the protocol (here: t3://)! Fixing the issue is very simple: you have to remove the second t3:// in Spring property:

[xml]<property name="providerURL" value="t3://firstServer:1234,secondServer:5678"/>[/xml]

Case

Spring application context file:

[xml]
<bean id="jmsQueueConnectionFactory"
class="org.springframework.jndi.JndiObjectFactoryBean">
<property name="jndiName" value="jonathan.jms-connection-factory.external"/>
<property name="jndiEnvironment">
<props>
<prop key="java.naming.factory.initial">weblogic.jndi.WLInitialContextFactory</prop>
<prop key="java.naming.provider.url">
t3://anOtherServer:8521
</prop>
<prop key="java.naming.security.principal">jonathan</prop>
<prop key="java.naming.security.credentials">jonathan</prop>
<prop key="weblogic.jndi.enableDefaultUser">true</prop>
</props>
</property>
</bean>
<bean id="mainJndiTemplate" class="org.springframework.jndi.JndiTemplate">
<property name="environment">
<props>
<prop key="java.naming.factory.initial">weblogic.jndi.WLInitialContextFactory</prop>
<prop key="java.naming.provider.url">t3://mainServer:1234</prop>
<prop key="java.naming.security.principal">myPrincipal</prop>
<prop key="java.naming.security.credentials">myPassword</prop>
<prop key="weblogic.jndi.enableDefaultUser">false</prop>
</props>
</property>
</bean>
[/xml]

Description

I use two instances of JndiTemplate to send JMS messages on two different queues, on two different Weblogic domains, using two different Ldap directories. When I try to send messages on the second server, it does not work: I get an error because the second server receives credentials that should be sent to the first server.

[Security:090398]Invalid Subject: principals=[...]

Quick fix

Remove the properties weblogic.jndi.enableDefaultUser from within the XML.

Case

• let’s consider an EJB Bean AnimalBean, linked to a table JL_Animal
• let’s have a human understandable name for the Pojo, let’s say: Animal
• let an EJB entity have following finders:

[java]
* @ejb.finder
* signature = "Collection findByBirthDate(java.lang.Integer birthDate)"
* query = "SELECT OBJECT(o) FROM AnimalBean AS o WHERE o.birthDate = ?1"
*
* @ejb.finder
* signature = "Collection findByCountryAndBirthDate(java.lang.String from,java.lang.Integer birthDate)"
* query = "SELECT OBJECT(o) FROM AnimalBean AS o WHERE o.country = ?1 AND o.birthDate = ?2"[/java]

Read the rest of this entry »

Abstract

You need a fake SMTP server, for any reason: either your application does not deploy without an SMTP, or you need see what mails are sent and their attached files, etc.
Read the rest of this entry »

Abstract:

Developpers happen to forget to implement concrete classes on creating new implementations. Indeed, IDEs fill methods content with canonical return values, (null for object, 0 for numerics, etc.). Consequently, errors appear only on deployment stage, when it is not on running.

To avoid this, here is the tip I use: raising a default exception. If unit tests are generated, then the exception is raised on development stage, which is better than after one hour compiling / deployment / execution ;-).

Process:

On IntelliJ IDEA, open:

• Project Settings
  • File Templates
    • Code
      • Implemented Method Body
      • write: throw new UnsupportedOperationException("Class Name : ${CLASS_NAME} - Method Name : ${METHOD_NAME}");

Case:

I need copy the content of all tables from one Oracle schema to another one, specifically: I must copy raw data from a production DB to a developper one.

Context:

• The DBA do not allow DBLinks
• Oracle source and destination schemas share the same structure (name of the tables, names and types of columns, etc.

Fix:

Here is a small script I wrote, of course it can be improved:
[bash]
#!/usr/bin/bash
SRC_LOGIN=XYZ
SRC_PASSWORD=XYZ
SRC_DB=production
DBDEST_LOGIN=XYZ
DEST_PASSWORD=XYZ
DEST_DB=developmentDB

echo "select object_name from user_objects where object_type = ‘TABLE’ order by object_name;" | \
sqlplus $SRC_LOGIN/$SRC_PASSWORD@$SRC_DB | \
grep -v OBJECT_NAME | grep -v "-" | grep -v "^$" | \
sed "1,9d" | tac | sed "1,3d" | tac | \
sort | uniq > allTables.txt

for table in `more allTables.txt`
do
rm -rf $table.sql
echo "exporting $table"
exp $SRC_LOGIN/$SRC_PASSWORD@$SRC_DB file=$table.sql buffer=10485867 tables="$table" direct=y
echo "importing $table"
echo "truncate table $table;" | \
sqlplus $DEST_LOGIN/$DEST_PASSWORD@$DEST_DB
imp $DEST_LOGIN/$DEST_PASSWORD@$DEST_DB file=$table.sql \
buffer=10485867 tables="$table" \
fromuser=$SRC_LOGIN touser=$DEST_LOGIN ignore=y
rm -rf $table.sql
done

rm -rf allTables.txt[/bash]

A little more explanations:

• echo "select object_name from user_objects where object_type = 'TABLE';" | sqlplus $SRC_LOGIN/$SRC_PASSWORD@$SRC_DB: this allow to retrieve the names of all the tables from the DB
• grep -v OBJECT_NAME | grep -v "-" | grep -v "^$" : this removes empty lines and useless trace from Oracle SQLPlus
• sed "1,9d" | tac | sed "1,3d" | tac: removes the 9 first lines and the 3 last ones. tac in Unix allow to reverse the content of a file
• sort | uniq : sort lines and remove duplicates
• exp $SRC_LOGIN/$SRC_PASSWORD@$SRC_DB file=$table.sql buffer=10485867 tables="$table" direct=y: exports the content of the table $table
• echo "truncate table $table;" | sqlplus $DEST_LOGIN/$DEST_PASSWORD@$DEST_DB: truncates destination table. This is useful in case the script must be played more than once, for instance.
• imp $DEST_LOGIN/$DEST_PASSWORD@$DEST_DB file=$table.sql buffer=10485867 tables="$table" fromuser=$SRC_LOGIN touser=$DEST_LOGIN ignore=y: import the content of the table

Some improvement ideas:

• handle sequences, triggers, stored procedures, etc.
• create the complete destination DB owing to source DB, ie do not assume anymore that the DBs share the same structure

Here is an interesting case I have encountered this morning.

Context

I must test a Hibernate implementation of a DAO, using DBUnit and its XML dataset files as a minimal database. A CRUD unit test fails, I get this trace:

Explanation

In my dataset, I had set some primary keys at 0, 1, …, 10. Owing to my Hibernate mapping, the primary keys are generated thanks to a sequence.
On another hand, with the CRUD test, the primary keys 0, 1, …, 10 are also assigned to newly created objects.

Here is the issue: there are collisions between the XML dataset file objects and the objects created with Hibernate, because obviously two objects never share the same primary key!

Very interesting case. At firt, I spotted these errors:

SQL Error: -22, SQLState: S0002

and:

java.sql.SQLException: Table not found in statement

But here is the complete stacktrace:

"2009-10-13 12:29:17,934 ERROR hbm2ddl.SchemaExport - Unsuccessful: create table MY_ORACLE_TABLE (myOracleTableId integer not null, optimisticTimestamp timestamp not null, position double, primary key (myOracleTableId))
2009-10-13 12:29:17,934 ERROR hbm2ddl.SchemaExport - Unexpected token: POSITION in statement [create table MY_ORACLE_TABLE (myOracleTableId integer not null, optimisticTimestamp timestamp not null, position]
(...)
2009-10-13 12:29:17,949 ERROR hbm2ddl.SchemaExport - Table not found: MY_ORACLE_TABLE in statement [alter table MY_ORACLE_TABLE]
2009-10-13 12:29:17,980 DEBUG util.HibernatePersistenceTestCase - ++++++++++++++ Using Pattern HibernateMyOracleTableDAOUnitTest-testFindmyOracleTableByPK_OK.xml
2009-10-13 12:29:17,996 DEBUG util.HibernatePersistenceTestCase - ++++++++++++++ Using Pattern HibernateMyOracleTableDAOUnitTest.xml
2009-10-13 12:29:17,996 DEBUG util.HibernatePersistenceTestCase - --------------- Using dataset : HibernateMyOracleTableDAOUnitTest.xml
2009-10-13 12:29:18,355 WARN util.JDBCExceptionReporter - SQL Error: -22, SQLState: S0002
2009-10-13 12:29:18,355 ERROR util.JDBCExceptionReporter - Table not found in statement [select (...) where myOracleTable0_.myOracleTableId=?]
2009-10-13 12:29:18,371 DEBUG util.HibernatePersistenceTestCase - ++++++++++++++ Using Pattern HibernateMyOracleTableDAOUnitTest-testFindmyOracleTableByPK_OK.xml
2009-10-13 12:29:18,371 DEBUG util.HibernatePersistenceTestCase - ++++++++++++++ Using Pattern HibernateMyOracleTableDAOUnitTest.xml
2009-10-13 12:29:18,387 DEBUG util.HibernatePersistenceTestCase - --------------- Using dataset : HibernateMyOracleTableDAOUnitTest.xml

org.hibernate.exception.SQLGrammarException: could not load an entity: [com.(...)myOracleTable#147]
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:67)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
at org.hibernate.loader.Loader.loadEntity(Loader.java:1799)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:47)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:41)
at org.hibernate.persister.entity.AbstractEntityPersister.load(AbstractEntityPersister.java:2730)
at org.hibernate.event.def.DefaultLoadEventListener.loadFromDatasource(DefaultLoadEventListener.java:365)
at org.hibernate.event.def.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:346)
at org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:123)
at org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:161)
at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:87)
at org.hibernate.impl.SessionImpl.fireLoad(SessionImpl.java:862)
at org.hibernate.impl.SessionImpl.load(SessionImpl.java:781)
at org.hibernate.impl.SessionImpl.load(SessionImpl.java:774)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:301)
at $Proxy0.load(Unknown Source)
(...)HibernateMyOracleTableDAOUnitTest.java:37)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:40)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:90)
Caused by: java.sql.SQLException: Table not found in statement [select (...) where myOracleTable0.myOracleTableId=?]
at org.hsqldb.jdbc.Util.throwError(Unknown Source)
at org.hsqldb.jdbc.jdbcPreparedStatement.(Unknown Source)
at org.hsqldb.jdbc.jdbcConnection.prepareStatement(Unknown Source)
at org.hibernate.jdbc.AbstractBatcher.getPreparedStatement(AbstractBatcher.java:442)
at org.hibernate.jdbc.AbstractBatcher.getPreparedStatement(AbstractBatcher.java:368)
at org.hibernate.jdbc.AbstractBatcher.prepareQueryStatement(AbstractBatcher.java:105)
at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1561)
at org.hibernate.loader.Loader.doQuery(Loader.java:661)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:224)
at org.hibernate.loader.Loader.loadEntity(Loader.java:1785)
... 42 more"

I have helped you with red bold words… Can you see the issue?

Yes, indeed position is a reserved keyword in SQL! To fix this issue, you have no choice but to rename your column.