Jonathan Lalou's Blog

Archive for the ‘en-US’ Category

One month ago, I trained an Indian team, located in Mumbai, on Scrum methology.
Here are the slides of the presentation. It is mainly in English, but with a bit of Hindi in order to please the Indian attendees 😉

The presentation is hosted by Google Docs, under Creative Commons CC-by-cc licence.

DTDs are useful when your XML editor take them in account: detecting errors, suggestions, complete statements… For instance, I save much time with IntelliJ IDEA automatic completion ; unlike, Eclipse amazingly does not implement this feature.

Here is a list of some widely used DTDs:

Tangosol and Log4J DTDs are included within their distribution JARs: you have to extract them or to give their path to IntelliJ IDEA.

This post describes how to install and play with a emulator of GingerBread (Android 2.3)  device on your desktop (or laptop) computer:

• go to this page, download Android SDK related to your system.
• unzip / install it, let’s say in $android-sdk-home
• launch Android SDK Manager (with $android-sdk-home\SDK Manager.exe under Windows, $android-sdk-home/android on other systems)
• on the left panel, select Available Packages, and select Android Repository packages you would like to install, and possibly other third party add-ons.
• go to Virtual Devices >
  • New >
  • give a name, for instance “GingerBread” >
  • Target “Android 2.3.3…” >
  • SD Car Size: 2MiB >
  • leave other options >
  • Create AVD
• wait a little…
• still in Virtual Devices panel, select the AVD you have just created (called hereGingerBread) > Start
• wait… a lot
• enjoy!

EDIT: I could not resist and I have installed HoneyComb, too 😉

Case

You have to enable JMX in an application deployed within WebLogic, so that to access MBeans from Java Visual VM for instance

Solution

On launching WebLogic server instance, add the following properties:

[java]-Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=8888 -Dcom.sun.management.jmxremote.ssl=false -Dcom.sun.management.jmxremote.authenticate=false[/java]

Case

You need include tools.jar as a dependency in a pom.xml, for instance in order to use Java 5’s annotations and APT. From a “Maven’s view point”, tools.jar is not a regular JAR defined by a groupId and artefactId.

Solution

Add this block in your pom.xml:

[xml]<dependency>
<groupId>com.sun</groupId>
<artifactId>tools</artifactId>
<version>1.6.0_24</version>
<scope>system</scope>
<systemPath>${java.home}/../lib/tools.jar</systemPath>
</dependency>[/xml]

(You can also add it in your settings.xml)

You can do the same for any other “non-regular” JAR, available in your file system.

Case

In a JDBC DAO, I execute a query to retrieve an object. I get this error:

[java]java.sql.SQLException: Wrong data type: NUMBER in statement [CREATE TABLE Jonathan_Table (TableColumn NUMBER][/java]

Stacktrace

[java]java.sql.SQLException: Wrong data type: NUMBER in statement [CREATE TABLE Jonathan_Table (TableColumn NUMBER]
at org.hsqldb.jdbc.Util.throwError(Unknown Source)
at org.hsqldb.jdbc.jdbcPreparedStatement.executeUpdate(Unknown Source)
at com.bnpp.pb.risklayer.services.dao.jdbc.JdbcPrimeRiskServerDaoUnitTest.getDataSet(JdbcPrimeRiskServerDaoUnitTest.java:57)
at org.dbunit.DatabaseTestCase.setUp(DatabaseTestCase.java:154)[/java]

Explanation and fix

My original DB is under Oracle, but my DBUnit tests works on HSQL. Yet, types NUMBER and VARCHAR2 are not available under HSQL, this is why the exception is raised.
To fixe the issue, rewrite your scripts, replacing NUMBER and VARCHAR2 with NUMERIC and VARCHAR.

Case

On a unit test with JDBC / DBUnit, extending org.dbunit.DBTestCase, I get this error:

[java]Table ‘Jonathan_Lalou_Table’ not found in tableMap=org.dbunit.dataset.OrderedTableNameMap[_tableNames=[], _tableMap={}, _caseSensitiveTableNames=false][/java]

Explanation and fix

Indeed, even when you provide a dataset through a flat XML file, DBUnit does not create the tables, but only fills them in. I know, this is paradoxal and most developpers would like to create implicitly the tables prior to filling them…

To fix the issue, add a block like this one, for instance when overriding the method getDataSet():

[java]final PreparedStatement preparedStatement;
preparedStatement = getDatabaseTester().getConnection().getConnection().prepareStatement("CREATE TABLE Jonathan_Lalou_Table … ");
preparedStatement.executeUpdate();[/java]

I have to fix all critical “Violations” owing to Sonar.
Let’s consider a basic block:
[java] public void setSushis(float[] sushis) {
this.sushis = sushis;
}[/java]
This piece of code raises this error in Sonar:
[java] Security – Array is stored directly : The user-supplied array ‘sushis’ is stored directly.[/java]
In a naive step, I modified the code as this:
[java] public void setSushis(float[] sushis) {
this.sushis = sushis.clone();
}[/java]
This may have been OK… but, now, I get the following error within GWT compilation:
[java]Cannot invoke clone() on the array type float[][/java]

To fix the issue, I amended the code as follows:
[java] public void setSushis(float[] theSushis) {
this.sushis= new float[theSushis.length];
System.arraycopy(theSushis, 0, this.sushis, 0, theSushis.length);
}[/java]

Disclaimer: even though I followed Sonar’s advice and requirements, I am a little skeptic about this kind of “violation”. 😐

Case

Starting a WebLogic 9.2 instance, I got this message:

[java]Server subsystem failed. Reason: weblogic.security.SecurityInitializationException: Authentication for user weblogic denied[/java]

Anyway, I checked the admin login and passwords were OK, since I had never changed them.

Stacktrace

[java]<Mar 18, 2011 11:14:03 AM CET> <Critical> <WebLogicServer> <BEA-000386> <Server subsystem failed. Reason: weblogic.security.SecurityInitializationException: Authentication for user weblogic denied
weblogic.security.SecurityInitializationException: Authentication for user weblogic denied
at weblogic.security.service.CommonSecurityServiceManagerDelegateImpl.doBootAuthorization(CommonSecurityServiceManagerDelegateImpl.java:947)
at weblogic.security.service.CommonSecurityServiceManagerDelegateImpl.initialize(CommonSecurityServiceManagerDelegateImpl.java:1029)
at weblogic.security.service.SecurityServiceManager.initialize(SecurityServiceManager.java:854)
at weblogic.security.SecurityService.start(SecurityService.java:141)
at weblogic.t3.srvr.SubsystemRequest.run(SubsystemRequest.java:64)
[/java]

Fix

• Go to $DOMAIN_HOME/servers/admin/data/
• Rename ldap as ldap.OLD
• Restart WebLogic admin
• Then, a file $DOMAIN_HOME/servers/admin/security/boot.properties should appear and contain the encrypted login and passwords.The issue should be fixed.

Case

I introduced an Oracle Coherence cache withing my application, which is deployed as a WAR within WebLogic  Server. In a first step, I used an instance of Oracle Coherence / Coherence Web already built in WebLogic. Then, for a couple a reasons, I detroyed the Coherence cluster. Deploying the application, the following error appeared:

[java]java.lang.RuntimeException: Failed to start Service "Cluster" (ServiceState=SERVICE_STOPPED, STATE_ANNOUNCE)[/java]

Complete Stacktrace

[java]java.lang.RuntimeException: Failed to start Service "Cluster" (ServiceState=SERVICE_STOPPED, STATE_ANNOUNCE)
at com.tangosol.coherence.component.util.daemon.queueProcessor.Service.start(Service.CDB:38)
at com.tangosol.coherence.component.util.daemon.queueProcessor.service.Grid.start(Grid.CDB:38)
at com.tangosol.coherence.component.net.Cluster.onStart(Cluster.CDB:366)
at com.tangosol.coherence.component.net.Cluster.start(Cluster.CDB:11)
at com.tangosol.coherence.component.util.SafeCluster.startCluster(SafeCluster.CDB:3)[/java]

Explanation and Fix

The Coherence cluster view available in WebLogic server is a view of the Tangosol configuration, available in the files tangosol-coherence*.xml of Coherence’s JAR. To fix the issue, create a file tangosol-coherence-override.xml, in your classpath. Fill the file with a minimum content, such as:

[xml]<?xml version=’1.0′?>
<!DOCTYPE coherence SYSTEM "coherence.dtd">
<coherence>
<cluster-config>
<multicast-listener>
<time-to-live system-property="tangosol.coherence.ttl">0</time-to-live>
<join-timeout-milliseconds>3000</join-timeout-milliseconds>
</multicast-listener>
<unicast-listener>
<address>127.0.0.1</address>
<port>8088</port>
<port-auto-adjust>true</port-auto-adjust>
<priority>8</priority>
</unicast-listener>
<packet-publisher>
<packet-delivery>
<timeout-milliseconds>30000</timeout-milliseconds>
</packet-delivery>
</packet-publisher>
<service-guardian>
<timeout-milliseconds system-property="tangosol.coherence.guard.timeout">35000</timeout-milliseconds>
</service-guardian>
</cluster-config>
<logging-config>
<severity-level system-property="tangosol.coherence.log.level">5</severity-level>
<character-limit system-property="tangosol.coherence.log.limit">0</character-limit>
</logging-config>
</coherence>
[/xml]

Of course, you can amend and improve the file to match your requirements.
NB: in case your file is ignored by Coherence, override the property tangosol.coherence.override with value tangosol-coherence-override.xml.