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ď»żJava + J2EE

This page is a mix of czech and english, sorry for non-separated and loosely organized content, but hopefully you will find your subject by using Ctrl+F :-)

Hibernate and JPA 2.0 – Maven dependencies

JBoss startup failure Error installing to Create: name=ProfileKey@…[domain=default, server=default, name=farm]

Null-safe bean comparator for Apache commons-beans

Quartz intro and how to use Quartz in Wicket

My Wicket notes

SVNbot – an IRC bot announcing SVN commits, written in Java

My usual MySQL JDBC params:

jdbc:mysql://localhost/test?characterEncoding=UTF-8&characterSetResults=UTF-8&autoReconnect=true&zeroDateTimeBehavior=convertToNull

MySQL JDBC driver for Maven – mavenized Connector/J

PircBot Mavenized

PircBot IRC Bot framework library in a provisory Maven repository.

JAXB example – keywords: JAXB howto example tutorial intro.

Sardine – WebDAV client library for Java

JBoss AS Java system variables (-D for bin/run.sh)

JBoss Operation Network and Tomcat on Windows 2003: No-go

How to stop Jetty

JBoss WebServices (JBossWS) notes

Simple JBoss AS clustering example (2 nodes, JSP session replication).

Maven Tips

Maven and Log4j: Missing JMX dependencies – mavenized jmxri and jmxtools.

To start maven goals in debug mode:

mvnDebug test ...

This does not work for me:

mvn test -DargLine="-Xdebug -Xnoagent -Djava.compiler=NONE -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=4000"

Profile activation and properties

How to add existing Java project's .jars to Maven repository

How to create an application distribution package with Maven

How to create a JNPL file (for Java WebStart) with Maven

Quick and dirty mavenization – How to install an existing library with dependencies to Maven repository.

I've presented Maven 2 for the company I work for. Download here: Maven presentation for Red Hat / JBoss.

A short polemic against Ivy / Maven2 Comparison: Read my own opinion about How Maven 2 compares to Ivy.

Short code for Antrun Maven plugin

Java alternative of PHP's `preg_replace_callback`

Here.

XSLT transformation in Java

My XSLT + Java notes show:

How to call Xalan from a command line
A simple class for XSLT conversion using JDK's XSLT
Template which does some change and copies all other data

What I would change about Java

My Java feature requests

Enum with a lookup map

JAXB – a List with inherited classes

Groovy bootloader bug with DOMBuilder

Is this a bug?

JBoss

Unsign JBoss AS distribution: find . -type f -iname '*.jar' -exec zip -d '{}' META-INF/JBOSSCOD.{SF,RSA} \;

Filesystem Resource Adapter

Bootstrapping JBoss Embedded server A very brief how-to – just a maven deps and the bootstraping code.

Common JBoss AS mistakes and exceptions

JBoss vs. Spring An attempt to answer what to use as a base for an enterprise web application.

How to transform `web.xml` with XSTL and XPath

In short, the trick is that XPath doesn't work well with element names containing a minus. So you have to match e.g web-xml like this:

*[name()='web-xml']

How to incrementally update a JAXB-mapped object

Using a factory delegating the setters to the original object. To be eventually written later.

JSON with JAXB – Jackson

How to create JSON output from POJOs using JAXB annotations.

JBoss AOP in a standalone application – example / howto

Few articles about JBoss AOP:

JBoss Microcontainer in a standalone application

A brief introduction to usage of JBoss MC in a standalone app.

Java Concurency, Threads and Synchronization

Attempt for one modifier and many concurent readers – a variant of producers and consumers problem.

Maven: Order of execution of plugins in profiles

I was curious in which order Maven executes the plugins: Whether it uses POM profile appearance order, or uses the ordering from the command line's -P param value.

Here is the result of my try-out.

Spring AOP common mistake: CGLIB2 is not available

You've added a new bean to Spring. And want to do some AOP over its methods. But you run into this:

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'udalostiQueueController' defined in class path resource [properties/Actions.xml]: Initialization of bean failed; nested exception is org.springframework.aop.framework.AopConfigException: Cannot proxy target class because CGLIB2 is not available. Add CGLIB to the class path or specify proxy interfaces.

Caused by: org.springframework.aop.framework.AopConfigException: Cannot proxy target class because CGLIB2 is not available. Add CGLIB to the class path or specify proxy interfaces.
        at org.springframework.aop.framework.DefaultAopProxyFactory.createAopProxy(DefaultAopProxyFactory.java:67)
        at org.springframework.aop.framework.ProxyCreatorSupport.createAopProxy(ProxyCreatorSupport.java:106)
        at org.springframework.aop.framework.ProxyFactory.getProxy(ProxyFactory.java:110)
        etc.

The reason is simple: To do AOP, Spring needs either CGLIB to do class instrumentation (bytecode magic) at runtime, or you have to use your bean through an interface.

So, put all your public methods into an interface and put all it's methods into an implementation. Use the implementation in Spring as the bean class, and when obtaining the bean in the code, store it into interface-typed reference.

public interface MyBean {
  public void doSomethingInAOP();
}

public class MyBeanImpl implements MyBean {
  public void doSomethingInAOP(){ ... }
}

<bean id="myBean" class="info.insolvencnirejstrik.controllers.MyBeanImpl" />

<aop:config>

  <aop:pointcut id="controllerMethods" expression="execution(* info.insolvencnirejstrik.controllers.*.*(..))"/>

  <aop:advisor advice-ref="txAdvice" pointcut-ref="controllerMethods"/>

</aop:config>

MyBean bean = appContext.getBean("myBean");

Ibatis instantiation error

Ibatis instantiation exception can arise from the lack of default constructor.

StackOverflowError with Xerces 2.0.2

Beware of DBCP in combination with Spring and iBatis using Maven. DBCP uses Xerces 2.0.2, which is old buggy version and causes stack overflow exception when parsing Spring's applicationContext.xml, which uses namespaces (e.g. for AOP).

Caused by: java.lang.StackOverflowError at org.apache.xerces.util.URI.isConformantSchemeName

Because Maven uses the „nearest node in dependency graph“ rule for resolving version conflicts, it choses DBCP's Xerces 2.0.2, because other dependencies have Xerces deeper.

Maven Unzip Plugin

I'm going to write unzip plugin for Maven2. Stay tuned.

Update: So here it is: Maven Unzip Plugin

Enjoy :-)

Jabber (XMPP) Maven plugin

I've created a simple plugin for Maven2, which can send a message from the Maven build process.

See Jabber (XMPP) Maven plugin

Used in the Insolvenďż˝nďż˝ rejstďż˝ďż˝k project.

JPA and Hibernate mapping with MySQL – common errors and exceptions

Some tips for those tampering with Java Persistence API and Hibernate – how to tame the exceptions comming from Hibernate EntityManager, Hibernate Annotations and JDBC.

ImmutableProperties class

I've created an immutable adapter of the java.util.Properties class. Not that there aren't bunches of similar over the net…

How to read properties file in Spring Framework

A new short tutorial on how to provide properties read from a file to a bean.

Parametrized Spring Configuration

Here's a short sketch of my idea about parametrizing Spring configuration, using placeholders (PropertyPlaceholderConfigurer) and overrides (PropertyOverrideConfigurer).

Web service client from WSDL using Axis2

Here's how to create web service client from WSDL using Axis2.

Logov?n? v Jav? ? `log4j` a `java.util.logging`

Sepsal jsem si stru?n? ?vod do logov?n? v Jav?
s uk?zkou konfigurace.

JPA with Hibernate common mistakes

ERROR [org.hibernate.LazyInitializationException] (main:) could not initialize proxy - no Session
Exception in thread "main" org.hibernate.LazyInitializationException: could not initialize proxy - no Session
        at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:57)
org.hibernate.LazyInitializationException: could not initialize proxy - no Session
        at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:111)
        at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:57)
        at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:111)
        at org.hibernate.proxy.pojo.cglib.CGLIBLazyInitializer.invoke(CGLIBLazyInitializer.java:150)
        at cz.dynawest.isir.entities.User$$EnhancerByCGLIB$$f6910a6b.setMail(<generated>)
        at cz.dynawest.isir.test.Manipulace.main(Manipulace.java:49)
        at org.hibernate.proxy.pojo.cglib.CGLIBLazyInitializer.invoke(CGLIBLazyInitializer.java:150)
        at cz.dynawest.isir.entities.User$$EnhancerByCGLIB$$f6910a6b.setMail(<generated>)
        at cz.dynawest.isir.test.Manipulace.main(Manipulace.java:49)\--

**Two common reasons:**

1) You have loaded an entity containing a collection (List, Set, ...), but by default,
Hibernate does not load their members; instead, it puts a proxy, which waits for the case
you access the collection and then loads it.


2) You've loaded the entity using JPA's `getReference()` or Hibernate's `load()`.
That creates a proxy object, which holds only an ID.
Try calling JPA's `find()`, resp. Hibernate's `get()` //(sure, JPA quite messed the nomenclature...)//


So you're trying to manipulate the entity without having any open transaction (session).
Hibernate generally needs every database operation to happen in a transaction,
opened either explicitly (using e.g. `EntityManager.getTransaction()`)
or implicitly (using e.g. Spring AOP).



------------------------------------------------

org.hibernate.PersistentObjectException: detached entity passed to persist

You load or create an entity in one transaction, which then ends, and then you try to call persist(). Instead, you must call merge(), because that's the method which is meant to re-attach detached entities. Use persist() to store the entity when you change it inside the same transaction as it was loaded in.

Generally speaking:

If you load an entity using a DAO, usualy you have a transaction in that DAO's methods. Thus when changing the entity inside DAO, use persist(); When you change it outside DAO and then call some DAO method to save it, call merge().

Za??tky se Spring AOP (Aspect Oriented Programming)

Rozchodil jsem Spring AOP a zde d?v?m stru?n? n?vod, jak si Spring AOP rozchod?te taky.

FreeMarker templates via Spring in non-web application

Note on how to use FreeMarker configured by Spring Dependency Injection in a standalone (non-web) application.

iBatis inline map format: empty String in nullValue

If i want to set a nullValue replacement for an empty String I use this in an explicit parameterMap:
<parameter property="street" jdbcType="VARCHAR" nullValue=""/>
I want to do the same thing using inline parameters. I've tried the following:
#street:VARCHAR:""#
#street:VARCHAR:#
#street,jdbcType=VARCHAR,nullValue=""#
#street,jdbcType=VARCHAR,nullValue=#
but none works.

How should i write the statement?

Thanks, Ondra

I recommend not using nullValue replacement. It's confusing and doesn't work the way most people would expect it to, quite the opposite actually. It's used to map nullable columns to non-nullable class members, like int, long, double, boolean etc…

It will not be available in iBATIS 3.

Clinton Begin

Quite bad news for me :(

I use nullValue as a convenient brief instrument to unify both null values OR empty String to NULL in the database (e.g. when importing from Excel and some cells are empty (that yields null) and some have empty strings). Handling it in Java or SQL code would clutter it quite much.

Can we expect some substitute for this in iBatis 3?

Ondra

While waiting for response, I realized this:

In case of MySQL, one can use NULLIF(expr1,expr2) function in INSERT, which returns NULL if expr1 = expr2 is true, otherwise returns expr1.

INSERT INTO table SET name = NULLIF(#name#,'');

`java.lang.InstantiationException` in iBatis when using java.util.Map

Exception:

JavaBeansDataExchange could not instantiate result class.  Cause: java.lang.InstantiationException: java.util.Map

SQL mapping code:

<select id="getMatchingDluzniciForUser" parameterClass="long" resultClass="map">
SELECT * FROM table
</select>

Cause: iBatis is trying to instantiate java.util.Map, which is an interface, thus can't be instantiated.

Fix: Instead, use java.util.HashMap or other Map implementation as the result class.

Compiling Connector/J

If you try to compile MySQL Connector/J from the source, after resolving dependencies, you will probably end up with many compiler errors.

That is because of the special way how Connector/J is compiled. Let Mark Matthews say it

The issue is that you can't compile Connector/J with just JDK6, as the driver supports JDBC4 and pre-JDBC4 APIs from the same codebase, and there are new classes and methods in JDBC4 that aren't available pre-JDK6.Therefore, the way it works is that you have to set JAVA_HOME to point to JDK-1.4 or 1.5, and then set the Ant properties „com.mysql.jdbc.java6.javac“ with the full path to your JDK6 java compiler, and „com.mysql.jdbc.java6.rtjar“ with the full path to your JDK6 runtime class libraries, when invoking Ant.

`SQLException` for zero `DATETIME` or `TIMESTAMP` column? Use `zeroDateTimeBehavior`

When working with MySQL over JDBC and the driver encounters a zero DATE, TIME, or DATETIME value (that is, e.g, ‚0000–00–00‘ for DATE), an exception is thrown:

java.sql.SQLException: Cannot convert value '0000-00-00 00:00:00' from column 4 to TIMESTAMP.

In this case, using SQL commands like

SET GLOBAL sql_mode = 'NO_ZERO_DATE';

does not help much, because that works only in „strict SQL mode“, and needs to be set for every connection, or globally for the whole server.

What helps is setting JDBC driver's zeroDateTimeBehavior property to convertToNull:

What should happen when the driver encounters DATETIME values that are composed entirely of zeroes (used by MySQL to represent invalid dates)? Valid values are "exception", "round" and "convertToNull".

The way to set it depends on the way you configure JDBC driver. The most common case is to use connection URL parameters. In my case it reads:

jdbc:mysql://localhost/test?zeroDateTimeBehavior=convertToNull&autoReconnect=true&characterEncoding=UTF-8&characterSetResults=UTF-8

`java` and `javaw` difference

What's the difference between java and javaw?

N?vod: Import projektu ze SVN do NetBeans projektu

Cht?l jsem se trochu povrtat v projektu Apache POI, ale jak pr?vodci v NetBeans, tak instrukce na str?nce projektu p?edpokl?daj?, ?e se SVN um?te, jak kdy? bi?em mrsk?, co? v m?m p??pad? bylo dote? p?esn? naopak :-)

Proto jsem sepsal velmi stru?n? n?vod, jak do NetBeans dostat projekt ze Subversion repository.

Levn? Java/JSP/J2EE hosting

Pokud hled?te levn? hosting pro svoji J2EE webovou aplikaci, mo?n? v?s zaujme tato nab?dka.

Converting a number to Excel column character name

When working with Excel sheets, you might need to convert the column number to it's letter name – like 1 to A, 2 to B, 43 to AQ, etc. It's not as trivial as converting a number between two radixes. Here is my solution.

Uz?v?ry v jazyce Java – p?es m?stn? vnit?n? t??du

P?i tvorb? GUI k jednomu syst?mu se mi zastesklo po snadnosti uz?v?r? v JavaScriptu. Prozkoumal jsem mo?nosti uz?v?r? v Jav?.

Spring Framework – ?vod

P?ipravil jsem velmi stru?n? tutori?l na rozb?h?n? jedn? ??sti Spring Frameworku, a sice Beans Factory. V ?e?tin?.

Hibernate super-quick start in NetBeans

Here's my how-to for starting a Hibernate project using Java Persistence API (JPA).

Later, I'll write something about object-relational mapping.

Hibernate Compatibility Matrix Error

Beware of the Hibernate Compatibility Matrix at http://www.hibernate.org/6.html.

Hibernate EntityManager 3.3.2 GA is said to be compatible with Hibernate Annotations 3.3.x. But, it is not compatible with Hibernate Annotations 3.3.0 – only with Hibernate Annotations 3.3.1. This information could spare you few minutes, as it would do to me if I knew it :)

java.lang.NoSuchMethodError: org.hibernate.cfg.AnnotationConfiguration.addProperties(Ljava/util/Properties;)Lorg/hibernate/cfg/AnnotationConfiguration;

Simplest One-line Formatter for `java.util.logging`

I didn't like the two-line output of java.util.logging.SimpleFormatter. On current widescreen LCDs, whole log record can fit at a single line. So I've written cz.dynawest.logging.SimplestFormatter. Compare:

13.7.2008 0:47:10 cz.dynawest.isir.Conversion3Controller ZpracujArchiv - INFO:   Test
13.7.2008 0:47:10 cz.dynawest.isir.Conversion3Controller ZpracujArchiv - INFO:   Test2

vs.

13.7.2008 0:47:10 cz.dynawest.isir.Conversion3Controller ZpracujArchiv
INFO:   Test
13.7.2008 0:47:10 cz.dynawest.isir.Conversion3Controller ZpracujArchiv
INFO:   Test2

If you like it, the source code is available for download here.

Java tipy a triky

Patďż˝ďż˝te mezi programďż˝tory, kteďż˝ďż˝ prvnďż˝ hledajďż˝ ďż˝eďż˝enďż˝ na Google jako slovnďż˝ ďż˝lohu a aďż˝ pak studujďż˝ jakďż˝koliv API? Pak vďż˝m moďż˝nďż˝ pomďż˝ďż˝e moje strďż˝nka tipďż˝ pro Javu. Zatďż˝m nenďż˝ nijak moc rozsďż˝hlďż˝, budu postupnďż˝ doplďż˝ovat.
Podobnďż˝ch tipďż˝ a trikďż˝ jsou po webu kvanta, ale ne tolik v ďż˝eďż˝tinďż˝.

Update: Tak nakonec stejnďż˝ vďż˝e zveďż˝ejďż˝uju v angliďż˝tinďż˝…

Bug in MySQL JDBC implementation – Connector/J

I've found a bug in Connector/J ver. 5.1.6. It appears upon subsequently called Connection.isValid(), which uses unsynchronized threads.

Reported at http://bugs.mysql.com/bug.php?….

Java Runtime Environment or Java Developement Kit not found on 64-bit system

I have 64-bit version of Windows XP and 64-bit version of JDK and JRE.
During instalation of jEdit, I got this message from the installer:

Setup was unable to find an installed Java Runtime Environment or Java Developement Kit of version 1.4, or higher. You must have installed at least JDK or JRE 1.4 to continue setup.

jEdit installer looks for 32-bit version of JRE. Install it alongside the 64-bit version to fix the problem.

The same problem was with NetBeans installer.

Texy! Java Implementation

Anyone knows about any? Please, let me know via e-mail.

Texy! syntax use cases here.

Java implementace pďż˝ekladaďż˝e Texy!

Zdravďż˝m,
nechtďż˝l by nďż˝kdo ďż˝irou nďż˝hodou implementovat pďż˝ekladaďż˝ Texy v Javďż˝?

www.texy.info

Mohlo by to bďż˝t dobrďż˝ tďż˝ma projektu / bakalďż˝ďż˝ky… Formďż˝lnďż˝ specifikace nenďż˝, jen podle popisu syntaxe a ukďż˝zek pouďż˝itďż˝…

Java komunita by vďż˝s jistďż˝ oslavovala :-)
Ondra

Autor Texy David Grudl sestavil sadu testovacďż˝ch souborďż˝, na kterďż˝ch lze ovďż˝ďż˝it implementaci pďż˝ekladaďż˝e. K dispozici na http://download.texy.info/refs.zip

Algou a omegou pďż˝vodnďż˝ PHP imiplementace jsou PCRE. Knihovna pro Javu, kterďż˝ zvlďż˝dďż˝ PCRE podle Perl 5, je na http://jakarta.apache.org/oro/ .

Ondra ?i?ka

?pln? za??tky v Jav?

Java ďż˝asto zaďż˝ďż˝teďż˝nďż˝ka odradďż˝ relativnďż˝ sloďż˝itost pďż˝ďż˝pravy kďż˝du a jeho pďż˝ekladu do ďż˝ehokoliv spustitelnďż˝ho (v roce 1998 to byl i mďż˝j pďż˝ďż˝pad a Javou jsem se prokousal aďż˝ o dalďż˝ďż˝ dva roky pozdďż˝ji :-) .

Pro ten pďż˝ďż˝pad jsem pďż˝ipravil velmi polopatickďż˝ nďż˝vod, jak vytvoďż˝it zdrojďż˝k v Javďż˝, jak ho pďż˝eloďż˝it do souboru .class a jak jej spustit.

J2EE – Java pro web

V poslednďż˝ dobďż˝ se prokousďż˝vďż˝m svďż˝tem J2EE. Je to svďż˝t rozsďż˝hlďż˝ a nepďż˝ehlednďż˝. V tďż˝to souvislosti uvedu jeden trefnďż˝ citďż˝t:

Entrance to this world is a cultural conversion, not a choice of one simple programming language over another.

-- GBdirect, „Active Web Sites and Comparison of Scripting Languages“

Pro kamarďż˝da jsem zaďż˝al psďż˝t velmi struďż˝nďż˝ ďż˝vod, aby se hned zkraje neutopil v zďż˝plavďż˝ tďż˝ďż˝ aďż˝ pďż˝tipďż˝smennďż˝ch zkratek.

Ondra.Žižka.cz