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Spring config properties from database and properties

I asked a similar question, but based on the responses, I did a bad job describing what I am after. I have a spring 4 webapp that loads properties from a properties file. We consume those properties both via the "${proper.name"} expressions in spring, as well as by injecting a properties object into some of our classes.
We want to move most of the properties to a database table and make them reloadable. However, a few need to stay in local properties, potentially overriding the database setting. These should also be loaded dynamically after the app is running.
I know that once a particular bean is injected, it won't get reloaded, that doesn't concern me, it's up to that module to handle that. But I am having trouble getting the behavior I want. In particular, I have implemented an AbstractConfiguration from apache commons configuration to get the dual source and overriding I am after. But while it works for injecting the properties object, expressions loaded with "${prop.name}" don't work at all.
How can I get them to work? Did I override the wrong thing? Is it just some config detail?
<bean id="sysProperties" class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
<property name="targetObject" ref="databaseConfigurator" />
<property name="targetMethod" value="getProperties"/>
</bean>
<bean id="databaseConfigurator" class="my.util.config.MyDatabaseConfigurator">
<property name="datasource" ref="dataSource" />
<property name="propertyFile" value="/WEB-INF/my.properties" />
<property name="applicationName" value="ThisApp" />
</bean>
<bean id="dbConfigFactory" class="org.apache.commons.configuration.ConfigurationConverter" factory-method="getProperties">
<constructor-arg ref="databaseConfigurator" />
</bean>

I haven't tested this, but I think it might work.
<bean id="sysProperties" class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
<property name="targetObject" ref="databaseConfigurator" />
<property name="targetMethod" value="getProperties"/>
</bean>
<bean id="databaseConfigurator" class="my.util.config.MyDatabaseConfigurator">
<property name="datasource" ref="dataSource" />
<property name="propertyFile" value="/WEB-INF/my.properties" />
<property name="applicationName" value="ThisApp" />
</bean>
<bean name="PropertyPlaceholderConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="properties" ref="CommonsConfigurationFactoryBean"/>
</bean>
<bean name="CommonsConfigurationFactoryBean" class="org.springmodules.commons.configuration.CommonsConfigurationFactoryBean">
<constructor-arg ref="databaseConfigurator"/>
</bean>

Configuring JPA in Spring application

I am configuring Spring to use JPA by using Hibernate implementation. However I don't understand the process completly. I have gotten it to work by following different blogs etc. I have used EJB 3.1 and there I had a persistence.xml. However in spring I declared a LocalContainer...Bean and provided some properties to it, and I have no persistence.xml. Could someone explain how it works in Spring and what the declared bean is?
<bean id="emf" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="dataSource" ref="dataSource" />
<property name="jpaVendorAdapter">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter" />
</property>
<property name="packagesToScan" value="com.company.domain" />
<property name="jpaProperties">
<props>
<prop key="hibernate.dialect">
org.hibernate.dialect.PostgreSQL82Dialect
</prop>
</props>
</property>
</bean>

There are different flavors of Spring Configuration with JPA, one which requires persistence.xml and other which requires just bean declarations(no persistence.xml).
I am going to take up the Case-2 in your scenario:
The main reasons we want a persistence.xml is because of the following reasons:
Database connectivity details.
Java classes which are treated as Entities or packages in which to scan for Entities.
Other vendor specific settings like hibernate.show_sql or similar stuff.
Now if spring provides a way to mention all this together in bean configurations then there is no need to have the persistence.xml.
In case of your bean definitions, lets break it down.
<bean id="emf" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="dataSource" ref="dataSource" />
<property name="jpaVendorAdapter">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter" />
</property>
<property name="packagesToScan" value="com.company.domain" />
<property name="jpaProperties">
<props>
<prop key="hibernate.dialect">
org.hibernate.dialect.PostgreSQL82Dialect
</prop>
</props>
</property>
</bean>
First property, dataSource already contains the database settings.
Second property, jpaVendorAdapter is a property specific to Spring
Third property, packagesToScan this is a property of Spring to scan for entities, this we either do in persistence.xml by using "class" tags by mentioning each class FQN.
Fourth property, jpaProperties as the name suggests can either be in Spring or in persistence.xml
e.g.
<property name="hibernate.dialect" value="org.hibernate.dialect.PostgreSQL82Dialect" />
Since you have all the configurations already in Spring bean, there's no need to have a persistence.xml
Just to add a FootNote:
Spring 3.1 provides an alternative: LocalContainerEntityManagerFactoryBean that accepts a 'packagesToScan' property, specifying base packages to scan for #Entity classes.
Hope this answer your queries.

Is there a shorthand for creating a String constant in Spring context XML file?

I need to define a string value in Spring context XML file that is shared by multiple beans.
This is how I do it:
<bean id="aSharedProperty" class="java.lang.String">
<constructor-arg type="java.lang.String" value="All beans need me :)"/>
</bean>
Creating a java.lang.String bean by passing a constructor argument of java.lang.String seems kludgy.
Is there a shortcut?
I know this property can be passed using PropertyOverrideConfigurer, but I want to keep this property within the XML file.

You can use PropertyPlaceholderConfigurer and keep values in xml:
<context:property-placeholder properties-ref="myProperties"/>
<bean id="myProperties"
class="org.springframework.beans.factory.config.PropertiesFactoryBean">
<property name="properties">
<props>
<prop key="aSharedProperty">All beans need me :)</prop>
</props>
</property>
</bean>
Then you reference it with:
<bean id="myBean" class="my.package.MyClass">
<property name="someField" value="${aSharedProperty}"/>
</bean>

A shorthand to the solution proposed by mrembisz goes like this:
<context:property-placeholder properties-ref="myProperties"/>
<util:properties id="myProperties">
<prop key="aSharedProperty">All beans need me :)</prop>
</util:properties>

You may be able to use the following:
<bean id="abstractParent" abstract="true">
<property name="sharedProperty" value="All child beans need me" />
</bean>
<bean id="bean1" class="MyClass1" parent="abstractParent">
...non-shared properties...
</bean>
<bean id="bean2" class="MyClass2" parent="abstractParent">
...non-shared properties...
</bean>
However, that relies on the property having the same name, so may not be applicable for you.

Something I've used in the past is SpEL to make sure that a bean has the same value as another:
<bean id="myBean" class="xxx.yyy.Foo" >
<property name="myProperty" value="1729" />
</bean>
<bean id="copyCat" class="xxx.yyy.Bar" >
<property name="anotherProperty" value="#{myBean.myProperty}" />
</bean>
I have found this to be particularly useful when setting the value did something other than a simple assignment.

How to set dynamically a bean reference in Spring?

<bean id="Mybean" class="Bean">
<property name="config" ref="dev"/>
</bean>
<bean id="dev" class="Dev">
<property name="x" ref="Dev1">
<property name="y" ref="Dev2">
<property name="z" ref="Dev3">
</bean>
<bean id="stag" class="Dev">
<property name="x" ref="Stag1">
<property name="y" ref="Stag2">
<property name="z" ref="Stag3">
</bean>
In the above scenario, the config property in the bean MyBean change from environment to environment. At the time of dev, reference of config change to dev. And in staging, the reference change to stag. The problem comes at the time of checked in the spring file. We have to analyze everytime the reference of config before checked in. If the reference of config with the value of dev checked in, we might have to explain a lot of questions.
Is there any solution to solve to make it automate?
Note: Spring version is 2.0.1

Use the PropertyPlaceholderConfigurer from Spring, and remove an unused bean :
<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="location">
<value>env.properties</value>
</property>
</bean>
<bean id="Mybean" class="Bean">
<property name="config" ref="config"/>
</bean>
<bean id="config" class="Config">
<property name="x" ref="${x}">
<property name="y" ref="${y}">
<property name="z" ref="${z}">
</bean>
and the env.properties file contains the following properties :
x=Dev1
y=Dev2
z=Dev3
or
x=Stag1
y=Stag2
z=Stag3

setup up the placeholder bean by specfiy， let spring know you want the placeholder
set up the config for the "my bean" by using the "${env}"
for example:
<beans>
<bean id="configBean" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="location"><value>env.properties</value></property>
</bean>
<bean id="Mybean" class="Bean">
<property name="config" ref="${env}"/>
</bean>
</beans>
and you need the add the env = dev key-value to the env.properties file

Assuming you meant Spring 3.1, rather than Spring 2.1 (which doesn't exist), then you can use the new "Environment Profiles" feature that was introduced in 3.1. This allows you to define a set of beans for each of your environments, and then select the "active" one at runtime.
See this SpringSource Blog Entry for examples.

You can do it using PropertyPlaceholderConfigurer or using #Profile
Also See
is-there-any-way-to-enable-or-disable-the-spring-bean-definition-in-applicationc
PropertyPlaceholderConfigurer example

PropertyPlaceholderConfigurer is the answer, yet I would imagine that you would like this to happen without the need to stay updating your properties file for each environment.
My suggestion would therefore be as follows
Use PropertyPlaceholderConfigurer, but do not create a properties file
By default, PropertyPlaceholderConfigurer first tries to find a value in a properties file, but if that fails, it will look for one in system properties
So all you need to do is to define both beans the same way that you are doing it, i.e. dev and stag.. which is a fine approach since you're clearly showing the different configurations... it would help if you also added some alias to show clearly the setting you want to use.
Next, pass in a system property defining what mode you are in... and ideally explicitly set PropertyPlaceholderConfigurer to use System properties.
So.. your config would look something like this
<bean
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"
systemPropertiesMode="2"/>
<bean id="Mybean" class="Bean">
<property name="config" ref="${launch.mode}"/>
</bean>
<bean id="dev" name="dev_mode" class="Dev">
<property name="x" ref="Dev1">
<property name="y" ref="Dev2">
<property name="z" ref="Dev3">
</bean>
<bean id="stag" name="staging_mode" class="Dev">
<property name="x" ref="Stag1">
<property name="y" ref="Stag2">
<property name="z" ref="Stag3">
</bean>
You can then pass in the property upon startup in the following fashion
-D<property-name>=<value>
So in this case you'd use
-Dlaunch.mode=dev_mode
Or
-Dlaunch.mode=staging_mode
And you won't need to touch any of the configuration files.
Just a further note on systemPropertiesMode, accepted values are the following:
0 - never look in system properties
1 - use system properties as a fallback (i.e. if not found in properties files)
2 - system properties always override (the mode i'm suggesting)
Hope it helps :)
Note: This recommendation is only applicable to Spring < 3.1, since from 3.1 onward, the recommended approach is to use #Profile

Spring provides a mechanism called property placeholders. This way you can set certain properties in a database/properties file and spring will fill them in on startup.
The class to use for this is located here.

No Hibernate Session bound to thread, and configuration does not allow creation of non-transactional one here

What is this error about? "No Hibernate Session bound to thread, and configuration does not allow creation of non-transactional one here".
My spring config file looks something like this.
<bean id="jndiDataSource"
class="org.springframework.jndi.JndiObjectFactoryBean">
<property name="jndiName">
<value>java:/devDS</value>
</property>
</bean>
<bean id="stsaDBFactory"
class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
<property name="dataSource" ref="jndiDataSource" />
<property name="annotatedClasses">
<list>
<value>xx.yy.zz.User</value>
<value>xx.yy.UserResponse</value>
</list>
</property>
<property name="hibernateProperties">
<props>
<prop key="hibernate.show_sql">true</prop>
<prop key="hibernate.hbmddl.auto">create</prop>
</props>
</property>
</bean>
<!-- ################################### Aspects ################################################## -->
<bean id="txManager"
class="org.springframework.orm.hibernate3.HibernateTransactionManager">
<property name="sessionFactory">
<ref local="stsaDBFactory" />
</property>
</bean>
All the DAO test passes when i test them outside of the container using junit. When I deploy it in jBoss as a portal app,I get this exception. Also it works fine if i remove the portal specific configuration and make it a simple web app and deploy it on jboss.Any idea?

You have defined a TransactionManager in your spring config but you are trying to execute a hibernate query in a method that is not transactional. Try adding #Transactional to your method or class.

I got around this problem by specifying the current_session_context_class in hibernate config to be "thread", as per the simple configuration shown in the hibernate configuration documentation.
But it recommends that its not safe for production usage.
Trying to add the following in your hibernate config should also help:
<property name="current_session_context_class">org.hibernate.context.ThreadLocalSessionContext</property>
Check out http://docs.jboss.org/hibernate/core/3.6/reference/en-US/html/architecture.html#architecture-current-session for more details.