sebthom.de

Bash: Capturing stderr in a variable while still printing to the console.

(1 votes)

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Posted on 31 January 2011 No comments

Storing the stdout output of a command in a variable and displaying it is simple:
```
OUTPUT=$(command)
echo $OUTPUT
```
If you have longer running commands where you want to display stdout in realtime and also store it in a variable you can tee the output to stderr:
```
OUTPUT=$(command | tee /dev/stderr)
```
```
OUTPUT=$(command | tee /proc/self/fd/2)
```
```
OUTPUT=$(command | tee >(cat - >&2))
```
If you have longer running commands where you want to display stdout/stderr in realtime and also store stderr in a variable it gets a bit complicated.
However, this can be achieved by switching stdout and stderr and then teeing the new stdout (which is stderr now) back to stderr for console output.
```
ERROR=$(command 3>&1 1>&2 2>&3 | tee /dev/stderr)
```
```
ERROR=$(command 3>&1 1>&2 2>&3 | tee /proc/self/fd/2)
```
```
ERROR=$(command 3>&1 1>&2 2>&3 | tee >(cat - >&2))
```
Good reading:
Bash FAQ: How can I store the return value/output of a command in a variable?

IT, Linux bash, stderr, stdout

Configuring EMF Teneo with Hibernate, Commons DBCP, Spring Hibernate Transaction Manager, and the OpenSessionInViewFilter

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Posted on 2 October 2010 No comments

While trying to get an application working with , Hibernate, Commons DBCP, Spring Hibernate Transaction Manager and the OpenSessionInViewFilter I encountered several unexpected issues. Here is an example of a working configuration for this software stack. Read the comments below the XML file for some explanations.

HbDataStoreWithDataSource.java:

package de.sebthom.util;

import java.sql.*;
import java.util.Properties;
import javax.sql.DataSource;
import org.eclipse.emf.teneo.PersistenceOptions;
import org.eclipse.emf.teneo.hibernate.HbSessionDataStore;
import org.hibernate.HibernateException;
import org.hibernate.cfg.*;
import org.hibernate.connection.ConnectionProvider;

/**
 * @author Sebastian Thomschke
 */
public class HbDataStoreWithDataSource extends HbSessionDataStore {
  public final static class CustomConnectionProvider implements ConnectionProvider {
    private DataSource ds;

    public void close() throws HibernateException { }

    public void closeConnection(final Connection conn) throws SQLException {
      conn.close();
    }

    public void configure(final Properties props) throws HibernateException {
      ds = _CONFIG_TIME_DS_HOLDER.get();
    }

    public Connection getConnection() throws SQLException {
      return ds.getConnection();
    }

   public boolean supportsAggressiveRelease() {
     return false;
   }
  }

  private static final long serialVersionUID = 1L;
  private static HbDataStoreWithDataSource INSTANCE;

  /**
   * the data source holder acts as a thread safe bridge between the DSConnectionProvider which is instantiated by Hibernate internally
   * and the data source injected into the session factory during spring configuration time.
   */
  private static final ThreadLocal _CONFIG_TIME_DS_HOLDER = new ThreadLocal();

  public static HbDataStoreWithDataSource getInstance() {
		return INSTANCE;
  }

  private final Properties props = new Properties();

  public HbDataStoreWithDataSource() {
    INSTANCE = this;

    props.setProperty(PersistenceOptions.ADD_INDEX_FOR_FOREIGN_KEY, "true");
    props.setProperty(PersistenceOptions.FETCH_CONTAINMENT_EAGERLY, "false");
    props.setProperty(PersistenceOptions.FETCH_ASSOCIATION_EXTRA_LAZY, "false");

    // tell Teneo to not change the table names, we do this using Hibernate's ImprovedNamingStrategy
    props.setProperty(PersistenceOptions.SQL_CASE_STRATEGY, "none");
    props.setProperty(PersistenceOptions.MAXIMUM_SQL_NAME_LENGTH, "-1");
  }

  protected Configuration createConfiguration() {
    Configuration cfg = super.createConfiguration();
    cfg.setNamingStrategy(ImprovedNamingStrategy.INSTANCE);

    // only if a DS is injected we register our connection provider
    if (_CONFIG_TIME_DS_HOLDER.get() != null)
      cfg.setProperty(Environment.CONNECTION_PROVIDER, CustomConnectionProvider.class.getName());
    return cfg;
  }

  public void setDataSource(final DataSource ds) {
    _CONFIG_TIME_DS_HOLDER.set(ds);
  }

  public final void setHibernateProperties(final Properties hibernateProperties) {
    throw new UnsupportedOperationException();
  }

  public final void setPersistenceProperties(final Properties persistenceOptions) {
    throw new UnsupportedOperationException();
  }

  public void setProperties(final Properties props) {
    this.props.putAll(props);
    super.setProperties(this.props);
  }
}

web.xml:


  openSessionInViewFilter
  org.springframework.orm.hibernate3.support.OpenSessionInViewFilter
    
singleSession
true
    
    
sessionFactoryBeanName
realSessionFactory
    


  openSessionInViewFilter
  /*
  REQUEST
  ERROR

applicationContext.xml:



  

  

      
${jdbc.driverClassName}
${jdbc.url}
${jdbc.username}
${jdbc.password}
false
${jdbc.maxConnections}
${jdbc.minConnections}
10000
${jdbc.minConnections}
${jdbc.validationQuery}
false
true
1200000
1800000
5
      
    
  

  

      hibernate.dialect=${hibernate.dialect}
      hibernate.hbm2ddl.auto=${hibernate.hbm2ddl.auto}
      hibernate.jdbc.batch_size=2000
      hibernate.show_sql=${hibernate.show_sql}
      hibernate.transaction.auto_close_session=false
      hibernate.current_session_context_class=org.springframework.orm.hibernate3.SpringSessionContext
      hibernate.transaction.factory_class=org.springframework.orm.hibernate3.SpringTransactionFactory
    

com.acme.ShopPackageImpl

Comments:

VERY IMPORTANT:The HibernateTransactionManager does NOT get the teneoSessionFactory(HbSessionDataStore) object passed in as sessionFactory, but the underlying Hibernate SessionFactory that can be retrieved from the HbSessionDataStore via the getSessionFactory() method. Not doing so will result in duplicate Hibernate Sessions completely breaking the transaction managment. This happens because in that case the TransactionSynchronizationManager will sometimes internally bind the hibernate session to the current thread based on different keys and thus does not find it again. Here are some stacktraces showing the problem:

TransactionSynchronizationManager.bindResource(Object, Object) line: 170
at OpenSessionInViewFilter.doFilterInternal(HttpServletRequest, HttpServletResponse, FilterChain) line: 183
=> results in TransactionSynchronizationManager.bindResource(HbSessionDataStore, SessionHolder) => as key the Teneo SessionFactory is used

TransactionSynchronizationManager.bindResource(Object, Object) line: 170
at SessionFactoryUtils.doGetSession(SessionFactory, Interceptor, SQLExceptionTranslator, boolean) line: 339
at SessionFactoryUtils.doGetSession(SessionFactory, boolean) line: 256
at SpringSessionContext.currentSession() line: 60
at SessionFactoryImpl.getCurrentSession() line: 700
at HbSessionDataStore(HbBaseSessionDataStore).getCurrentSession() line: 161
=> results in TransactionSynchronizationManager.bindResource(SessionFactoryImpl, SessionHolder) => as key the Hibernate SessionFactory is used

TransactionSynchronizationManager.bindResource(Object, Object) line: 170
at HibernateTransactionManager.doBegin(Object, TransactionDefinition) line: 577
at HibernateTransactionManager(AbstractPlatformTransactionManager).getTransaction(TransactionDefinition) line: 371
at TransactionInterceptor(TransactionAspectSupport).createTransactionIfNecessary(PlatformTransactionManager, TransactionAttribute, String) line: 316
at TransactionInterceptor.invoke(MethodInvocation) line: 105
at ReflectiveMethodInvocation.proceed() line: 172
=> results in TransactionSynchronizationManager.bindResource(HbSessionDataStore, SessionHolder) => as key the Teneo SessionFactory is used

defaultAutoCommit is set to false to ensure that Spring has full control over the transaction and that the connection pool is not committing statements automatically based on it’s own strategies.
The example uses an extended version of the org.eclipse.emf.teneo.hibernate.HbSessionDataStore class that allows the usage of a DataSource object and that configures Teneo to not alter the table, column names but let’s Hibernate handle this via its ImprovedNamingStrategy.
hibernate.transaction.auto_close_session is set to false to avoid “SessionException: Session is closed!” in conjunction with the OpenSessionInViewListener.
hibernate.current_session_context_class and hibernate.transaction.factory_class are set to special Spring implementations to avoid “org.hibernate.HibernateException: No CurrentSessionContext configured!” when not using Spring Hibernate Template via HibernateDAOSupport. It is not recommended to use the Hibernate Template anymore, see http://blog.springsource.com/2007/06/26/so-should-you-still-use-springs-hibernatetemplate-andor-jpatemplate/

Java dbcp, emf, hibernate, Java, persistence, spring, teneo, transaction

Using EMF ECore model objects with Wicket components

(1 votes)

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Posted on 8 September 2010 1 comment

Apache Wicket uses so called model objects to bind data objects to Wicket components. The framework provides a number of model implementations to access data objects and their properties in various ways. The PropertyModel implementation for example is used to access and set the value of a Java object using reflection.

EPropertyModel

If you are working with EMF (Eclipse Modeling Framework) generated model classes you can also use PropertyModels to bind structural features (properties in EMF terminology) of an EObject to a Wicket component. E.g. if your EObject has an attribute called “comment” you could instantiate a model like this
```
IModel model = new PropertyModel(myEObject, "comment");
```
This approach has several disadvantages. First, the name of the attribute is declared as a String and not as a compile-time reference to the actual attribute. This means the application could break during runtime if you have renamed the attribute at one point and forgot to also change the String value. Second, this property model uses runtime reflection which is a slow alternative to compile time based access.
Java classes generated from EMF Models by default extend the EObject class which provides a compile-time reflection API. Using the generic eGet and eSet methods any public property of the EObject can be accessed. The EMF Generator also generates a Package class for each EMF package that holds a Literals interface listing all available attributes and references of all generated EClasses of the given package. If you lets say have an EClass “Ticket” with the attribute “comment” in the package “com.acme.service” you could utilize the compile time reflection API as follows:
```
EAttribute commentAttribute = com.acme.service.ServicePackage.Literals.TICKET__COMMENT;
Ticket newTicket = com.acme.service.ServiceFactory.eINSTANCE.create(Ticket.class);
newTicket.eSet(commentAttribute, "my comment");
```
Using the EMF compile-time reflection API I created a generic EMF ECore Feature Model implementation that leverages the compile-time references to structural features. Most of the code is actually related to working around the fact that EAttributes and EReferences are not serializable but which they should to be part safely referenced in a model that potentially is serialized by Wicket between requests.
```
import org.apache.wicket.model.IDetachable;
import org.apache.wicket.model.IObjectClassAwareModel;
import org.eclipse.emf.ecore.EClass;
import org.eclipse.emf.ecore.EClassifier;
import org.eclipse.emf.ecore.EObject;
import org.eclipse.emf.ecore.EPackage;
import org.eclipse.emf.ecore.EStructuralFeature;

/**
 * A property model to bind an attribute of an EMF ECore object
 *
 * @author Sebastian Thomschke
 */
@SuppressWarnings("unchecked")
public class EFeatureModel<T> implements IObjectClassAwareModel<T>
{
	private static final long serialVersionUID = 1L;

	private transient EStructuralFeature feat;
	private String featContainerClassName;
	private String featName;
	private String featPackageNsURI;

	private EObject target;

	public EFeatureModel(EObject target, EStructuralFeature efeature)
	{
		this.target = target;
		this.feat = efeature;
		this.featName = efeature.getName();
		this.featContainerClassName = efeature.getContainerClass().getName();
		this.featPackageNsURI = ((EPackage) efeature.eContainer().eContainer()).getNsURI();
	}

	public void detach()
	{
		if (target instanceof IDetachable) ((IDetachable) target).detach();
	}

	public EStructuralFeature getFeature()
	{
		if (feat == null)
		{
			EPackage ePackage = EPackage.Registry.INSTANCE.getEPackage(featPackageNsURI);
			for (Object eClassifierItem : ePackage.getEClassifiers())
			{
				EClassifier eClassifier = (EClassifier) eClassifierItem;
				if (eClassifier.getInstanceClass().getName().equals(featContainerClassName))
					feat = ((EClass) eClassifier).getEStructuralFeature(featName);
			}
		}
		return feat;
	}

	public T getObject()
	{
		return (T) target.eGet(getFeature());
	}

	public Class<T> getObjectClass()
	{
		return getFeature().getEType().getInstanceClass();
	}

	public void setObject(T object)
	{
		// do nothing if the object is the same instance that is returned by the getter
		// this is esp. important for collection properties
		if (target.eGet(getFeature()) == object) return;

		target.eSet(getFeature(), object);
	}

	@Override
	public String toString()
	{
		return new StringBuilder("Model:classname=[").append(getClass().getName()).append("]").append(":target=[")
				.append(target).append("]").toString();
	}
}
```
Using this new model implementation is as simple as using the PropertyModel provided by Wicket:
```
IModel model = new EFeatureModel(myTicket, com.acme.service.ServicePackage.Literals.TICKET__COMMENT);
```
You can now fully enjoy the compile-time safeness of your EMF model.

Making EObjects serializable

Wicket usually serializes components and their associated models between HTTP requests. If you are using the provided EPropertyModel your EObject classes must implement the Serializable interface. To achieve this, simply extend the EObject interface with the Serializables interface and set “Root Extends Interface” property in your genmodel configuration to this interface.
```
/**
 * @author Sebastian Thomschke
 */
public interface SerializableEObject extends EObject, Serializable {
}
```
When you now regenerate the model classes they will extend the SerializableEObject interface and Wicket will stop complaining about objects in the model being not serializable.

Java eclipse, ecore, emf, Java, reflection, wicket
Installing Tomcat 6 on Debian Squeeze

(5 votes)

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Posted on 13 March 2010 4 comments

This post describes how to setup Tomcat 6 on Debian Squeeze. The configured Tomcat serves requests on port 80 without the need of an additional web server. This is especially good for virtual servers (VPS) providing limit memory. It also has multiple virtual hosts configured, each with it’s own webapp with context root / and optional support for PHP via the Quercus PHP implementation.

Installing Sun Java 6

Ensure the non-free section is enabled for the APT repository configuration in /etc/apt/sources.list, e.g. “deb http://ftp.de.debian.org/debian testing main contrib non-free”
```
apt-get update
apt-get install sun-java6-jdk
echo 'JAVA_HOME="/usr/lib/jvm/java-6-sun"' >> /etc/environment
echo 'JRE_HOME="/usr/lib/jvm/java-6-sun/jre"' >> /etc/environment
```
Installing Tomcat 6
```
apt-get install tomcat6 tomcat6-admin
/etc/init.d/tomcat6 stop
```
Creating standard Tomcat directory layout
```
mkdir /opt/tomcat
cd /opt/tomcat
ln -s /etc/tomcat6/ conf
ln -s /usr/share/tomcat6/bin/ bin
ln -s /usr/share/tomcat6/lib/ lib
ln -s /var/lib/tomcat6/webapps webapps
ln -s /var/log/tomcat6/ logs
```
Creating a Tomcat admin user

In /opt/tomcat/conf/tomcat-users.xml add an entry like:
```
<user name="ADMIN_USERNAME" password="ADMIN_PASSWORD" roles="admin,manager" />
```
Setting up virtual hosts

For each virtual host execute the following command. Replace “mydomain.com” with the desired virtual host name, but omit the “www.” part.
```
mkdir -p /opt/tomcat/webapps.mydomain.com/ROOT
```
In the <Engine> tag of “/opt/tomcat/conf/server.xml” add one host entry for each virtual host.
```
<Host name="mydomain.com" appBase="/opt/tomcat/webapps.mydomain.com">
    <Alias>www.mydomain.com>/Alias>
    <Valve className="org.apache.catalina.valves.AccessLogValve" prefix="mydomain_access_log." suffix=".txt" pattern="common"/>
</Host>
```
The <Alias> tag tells Tomcat to redirect from www.mydomain.com to mydomain.com.
The <Valve> tag enables access logging in the standard logging format.

Using xinetd to configure port 80 for Tomcat

Binding a service on port 80 requires root permissions. Thus we use port forwarding to “bind” Tomcat to port 80. My VPS does not support the use of “iptables -j REDIRECT” therefore I am using xinetd as a web proxy.
Ensure that no other service is listening on port 80/443:
```
netstat -pan | grep ":80\|:443"
```
Register the required xinetd services:
```
echo echo "
service www
{
        socket_type     = stream
        protocol        = tcp
        user            = root
        wait            = no
        bind            = 88.80.198.181
        port            = 80
        redirect        = localhost 8080
        disable         = no
        flags           = REUSE
        log_type        = FILE /var/log/wwwaccess.log
        log_on_success  -= PID HOST DURATION EXIT

        per_source      = UNLIMITED
        instances       = UNLIMITED
}

service https
{
        socket_type     = stream
        protocol        = tcp
        user            = root
        wait            = no
        bind            = 88.80.198.181
        port            = 443
        redirect        = localhost 8443
        disable         = no
        flags           = REUSE
        log_type        = FILE /var/log/httpsaccess.log
        log_on_success  -= PID HOST DURATION EXIT

        per_source      = UNLIMITED
        instances       = UNLIMITED
}
" > /etc/init.d/tomcat
/etc/init.d/xinetd restart
```
If you want to use a different service name, e.g. “tomcat” instead of “www” you must add this service to /var/services, e.g. “tomcat 80/tcp”
In /opt/tomcat/conf/server.xml modify the <Connector> as follows:
```
<Connector port="8080" protocol="HTTP/1.1"
               connectionTimeout="20000"
               redirectPort="8443" proxyPort="80" address="127.0.0.1" />
```
This binds Tomcat to localhost. It also tells Tomcat that port 80 is the proxy port which is necessary for correct URL generation.
From now on the Tomcat admin applications are only accessible via localhost. You can use SSH port forwarding to still access the applications from your workstation’s web browser. E.g. if you are using PuTTY you can use this command line option “-L 8080:localhost:8080″ to forward the server’s local 8080 port to your workstation’s local 8080 port. On your workstation’s browser you then simply enter http://localhost:8080/manager/html and are connected to the server’s Tomcat admin application.

Enabling PHP support (optional)

Download Quercus.
```
mkdir -p /opt/downloads
wget -o /opt/downloads/quercus-4.0.3.war http://caucho.com/download/quercus-4.0.3.war
```
Install Quercus as a shared library.
```
unzip -j /opt/downloads/quercus-4.0.3.war \*.jar -d /opt/tomcat/lib
```
Enable PHP support for the virtual hosts by installing the quercus web.xml. For each virtual host execute:
```
unzip /opt/downloads/quercus-4.0.3.war *web.xml -d /opt/tomcat/webapps.mydomain.com/ROOT
```
Starting Tomcat
```
/etc/init.d/tomcat start
```
References
Java, Linux Java, PHP, port 80, port forwarding, quercus, tomcat, vhost, virtual servers, VPS, xinetd
Leveraging PyDev’s auto completion for indirectly created objects

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Posted on 20 February 2010 1 comment

This is just a quick tip how to enable auto completion in PyDev for indirectly created objects.

By default, PyDev has no problems in presenting you the possible object attributes and methods on a variable if that variable gets a new object instance assigned directly in the code.

For example, when you first type …
```
mybook = Book()
```
… and in the next line you enter …
```
mybook.
```
… PyDev will dutifully present you the statically declared features for the Book class in a popup.

If you however get that Book instance as the result of another method, e.g. …
```
mybook = bookstore.findBook("foobar")
```
… PyDev currently seems to be helpless.

Because of Python’s dynamic nature it is of course a bit harder for an IDE to figure out what kind of objects may a method. But PyDev could for example honor the @return / @rtype PyDoc annotations (which you can add to the findBook’s method declaration) but currently it just does not.

To still have autocompletion you have two options:
1. Temporarily instantiate a Book object in the code.
```
mybook = Book()
mybook = bookstore.findBook("foobar")
mybook. #--> now you have auto completion
```
  This has the drawback, that if you forget to remove the first line before you finish coding an unneccessary Book instance will be created on every execution during runtime.
2. Use an assertion to ensure that the mybook variable contains an object of type Book
```
mybook = bookstore.findBook("foobar")
assert isinstance(mybook, Book)
mybook. #--> now you have auto completion
```
Jython Jython, pydev, pydoc, python, rtype
OVal 1.40 released

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Posted on 28 September 2009 No comments

I am happy to announce the immediate availability of Version 1.40 OVal the Object Validation Framework for Java. This release fixes some minor issues and provides the following two new features:

1. Enabling/disabling constraints based on the object state:
Using the newly introduced when attribute for constraints it is possible to specify under which circumstances the constraint will be considered during object validation. The when attribute holds a formula in one of the supported scripting languages. If the formula returns true, the constraint will be activated for the current validation cycle otherwise it is ignored. In the following example the alias attribute must have a value only when the name attribute is not set.
```
public class User {
   private String name;

   @NotNull(when = "groovy:_this.name == null")
   private String alias;

   // . . .
}
```
2. Fine grain control over how constraints are applied on arrays, maps, collections and their elements
The newly introduced attribute appliesTo allows you to specify if and how a constraint declared for a map, a collection or an array is applied to their elements as well or exclusively. See the following example how this works:
```
public class BusinessObject {

   // the ids field may be null, but if it is not null
   // none of it's items must be null
   @NotNull(appliesTo = { ConstraintTarget.VALUES })
   private String[] ids;

   // only the field itself must not be null,
   // the list can contain null values
   @NotNull(appliesTo = { ConstraintTarget.CONTAINER })
   private List items;

   // the field must not be null as well as all keys
   // and values of the map
   @NotNull(appliesTo = { ConstraintTarget.CONTAINER, ConstraintTarget.KEYS, ConstraintTarget.VALUES })
   private Map itemsByGroup;

   // . . .
}
```
Download
You can get the lates binaries and source files of OVal from here: http://sourceforge.net/projects/oval/files/

Java
« Older Entries

Sebastian Thomschke

Bash: Capturing stderr in a variable while still printing to the console.

Configuring EMF Teneo with Hibernate, Commons DBCP, Spring Hibernate Transaction Manager, and the OpenSessionInViewFilter

Using EMF ECore model objects with Wicket components

EPropertyModel

Making EObjects serializable

Installing Tomcat 6 on Debian Squeeze

Installing Sun Java 6

Installing Tomcat 6

Creating standard Tomcat directory layout

Creating a Tomcat admin user

Setting up virtual hosts

Using xinetd to configure port 80 for Tomcat

Enabling PHP support (optional)

Starting Tomcat

References

Leveraging PyDev’s auto completion for indirectly created objects

OVal 1.40 released

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