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Spring : Initialization of properties before any bean creation

I have the project structure as following -
Facade -> Service-> DAO
In the DAO layer, when the beans are initialized then many dependencies are injected from a property file. Therefore, the properties file must be read first and then the remaining dao beans must be created. When the application is started then it gives an error that Spring cannot resolve a placeholder.
The DAO-application-context.xml is like-
<bean
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="prop">
<value>app.properties</value>
</property>
</bean>
<import resource = "a-dao.xml" />
<import resource = "b-dao.xml" />
<import resource = "c-dao.xml" />
Now in all the child application contexts i.e. a-dao, etc, we have-
<bean ....>
<property name = "xyz">
<value>${appValue}<value/>
</property>
<bean>
The error received is that appValue cannot be resolved. I think that it may be due to incorrect sequence of bean creation. However, the same config is working in another larger project.
I have checked Order of Spring Bean Initialization but implementing that solution would not be feasible. Is there any other way ?

Reg this Block of Configuration, property prop seems to be wrong
<bean
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="prop">
<value>app.properties</value>
</property>
</bean>
According to the Spring documentation
You could use the property location or locations to set the one or multiple values of the properties file.
So the code should be refactored to
<bean
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="location">
<value>app.properties</value>
</property>
</bean>

How to handle Spring application configuration?

I have standalone Spring application that has its setting in DMBS. I have an idea to use only one code (that specifies particular instance) when application is starting and application reads own setting from database. Setting values are then used for creating beans in applicationContext XML file and later in beans itself.
So far (developing phase) I used one properties file and read it in such way:
<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="locations">
<list>
<value>classpath:/taskproducer.properties</value>
</list>
</property>
</bean>
What is the best way how to handle setting from database in Spring application?

You are heading the right way. Property files should indeed contain the database configuration properties.
If you want to go one-step further, you can have profile-specific property files, e.g. development-specific configuration and production-specific.
Take a look at this video for some nice instructions on this subject.
EDIT: in case I misunderstood, and you wanted some guidance on how to setup your database using these properties, here is an example of a Spring XML configuration, based on properties from a configuration file.
Short mention: for example, you would setup your DataSource like this:
<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
<property name="driverClassName" value="${database.driverClassName}" />
<property name="url" value="${database.url}" />
<property name="username" value="${database.username}" />
<property name="password" value="${database.password}" />
</bean>
Then in your property file you would have defined the following properties:
database.url=http://localhost:3306/mydb
database.username=sa
database.password=
Hope this is helpful

You can create a configurer bean which reads props from DB
class DbProperties extends java.util.Properties {
DbProperties() {
String v1 = ... // read prop from db
setProperty("p1", "v1");
}
}
add it to Spring context
...
<context:annotation-config />
<bean id="c1" class="DbProperties" />
<bean id="b1" class="B1"/>
<!--
<context:property-placeholder location="taskproducer.properties" />
-->
<context:property-placeholder properties-ref="c1"/>
and use it
class B1 {
#Value("${p1}")
int x;
}

How to use environment variables with properties file in Spring context file

I am trying to read in a configuration file based on a system environment variable. My environment variable is FOO_ENV with value dev and dev.properties contains the properties bar.host and bar.port.
<context:property-placeholder />
<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="location" value="classpath:${FOO_ENV}.properties"></property>
<property name="ignoreUnresolvablePlaceholders" value="true" />
</bean>
<bean id="myServer" class="org.apache.solr.client.solrj.impl.HttpSolrServer">
<property name="ignoreUnresolvablePlaceholders" value="true" />
<constructor-arg type="String" value="http://${my.host}:${my.port}/" />
</bean>
When I deploy this in tomcat, I get the following error:
11:48:39.324 [localhost-startStop-14] ERROR o.s.web.context.ContextLoader - Context initialization failed
org.springframework.beans.factory.BeanDefinitionStoreException: Invalid bean definition with name 'myServer' defined in ServletContext resource [/WEB-INF/my-context.xml]:
Could not resolve placeholder 'my.host' in string value [http://${my.host}:${my.port}]
at org.springframework.beans.factory.config.PlaceholderConfigurerSupport.doProcessProperties(PlaceholderConfigurerSupport.java:209) ~[spring-beans-3.1.2.RELEASE.jar:3.1.2.RELEASE]
By replacing $FOO_ENV with dev in the context file, I have determined that the properties file can be read correctly. By changing FOO_ENV to other names, I can show that Spring is reading the environment variable.
It seems that the element
<property name="ignoreUnresolvablePlaceholders" value="true" />
should allow Spring to ignore that ${my.host} is not an environment variable, but though I've tried it in various places, I still get the same error, which indicates that my.host is not found.

You actually have two PropertyPlaceHolderConfigurers defined here. One via the context namespace and one explicitly. Spring is probably picking the one created via the context namespace. You could either set 'ignore-unresolvable' on the context tag and remove your propertyConfigurer bean like so:
<context:property-placeholder ignore-unresolvable="true"/>
Or if you need more control over PropertyPlaceHolderConfigurer go the other way and remove the context:property-placeholder tag.

How to fetch value of the Datasource in spring frarmework using JAVA code?

I have spring application and using property file want to read the values from the PropertyPlaceholderConfigurer. Here datasource is given as Id.
I want to read the values of the datasource property jdbc.driverClassName value using java code.
Scenario should be: 1st bean will be executed. It will load the data from the jdbc.property file. All the values in the datasource should be read from the java code.
How to read the values from the Java code for PropertyPlaceholderConfigurer(datasource)?
Given the executed scenario below :
Create a properties file (database.properties), include your database details, put it into your project class path.
jdbc.driverClassName=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mkyongjava
jdbc.username=root
jdbc.password=password
<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="location">
<value>database.properties</value>
</property>
</bean>
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="${jdbc.driverClassName}" />
<property name="url" value="{jdbc.url}" />
<property name="username" value="{jdbc.username}" />
<property name="password" value="{jdbc.password}" />
</bean>
Please help me out using java code to read the data from the given datasource?
Or any useful link from where i can find out the resolution.

There are two simple options:
Get a reference to the application context (if you instantiated it yourself, that should be easy- if you initialized it using say web.xml, you might be able to retrieve it using org.springframework.web.context.support.WebApplicationContextUtils). Then obtain the bean using BeanContext<T>.T getBean(String name, Class<T> requiredType), retrieve the properties using DriverManagerDataSource's getters.
Inject the same values into one of your own beans; Spring will put the same values for you

How do I read JVM arguments in the Spring applicationContext.xml

I have a JSF web application with Spring and I am trying to figure out a way to reference the JVM arguments from the applicationContext.xml. I am starting the JVM with an environment argument (-Denv=development, for example). I have found and tried a few different approaches including:
<bean id="myBean" class="com.foo.bar.myClass">
<property name="environment">
<value>${environment}</value>
</property>
</bean>
But, when the setter method is invoked in MyClass, the string "${environment}" is passed, instead of "development". I have a work around in place to use System.getProperty(), but it would be nicer, and cleaner, to be able to set these values via Spring. Is there any way to do this?
Edit:
What I should have mentioned before is that I am loading properties from my database using a JDBC connection. This seems to add complexity, because when I add a property placeholder to my configuration, the properties loaded from the database are overridden by the property placeholder. I'm not sure if it's order-dependent or something. It's like I can do one or the other, but not both.
Edit:
I'm currently loading the properties using the following configuration:
<bean id="myDataSource" class="org.springframework.jndi.JndiObjectFactoryBean">
<property name="jndiName" value="jdbc.mydb.myschema"/>
</bean>
<bean id="props" class="com.foo.bar.JdbcPropertiesFactoryBean">
<property name="jdbcTemplate">
<bean class="org.springframework.jdbc.core.JdbcTemplate">
<constructor-arg ref="myDataSource" />
</bean>
</property>
</bean>
<context:property-placeholder properties-ref="props" />

You can use Spring EL expressions, then it is #{systemProperties.test} for -Dtest="hallo welt"
In your case it should be:
<bean id="myBean" class="com.foo.bar.myClass">
<property name="environment">
<value>#{systemProperties.environment}</value>
</property>
</bean>
The # instead of $ is no mistake!
$ would refer to place holders, while # refers to beans, and systemProperties is a bean.
May it is only a spelling error, but may it is the cause for your problem: In the example for your command line statement you name the variable env
(-Denv=development, for example...
But in the spring configuration you name it environment. But both must be equals of course!

If you register a PropertyPlaceholderConfigurer it will use system properties as a fallback.
For example, add
<context:property-placeholder/>
to your configuration. Then you can use ${environment} in either your XML configuration or in #Value annotations.

You can load a property file based on system property env like this:
<bean id="applicationProperties"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="ignoreResourceNotFound" value="false" />
<property name="ignoreUnresolvablePlaceholders" value="true" />
<property name="searchSystemEnvironment" value="false" />
<property name="locations">
<list>
<value>classpath:myapp-${env:prod}.properties</value>
</list>
</property>
</bean>
If env is not set default it to production otherwise development and testing teams can have their flavor of app by setting -Denv=development or -Denv=testing accordingly.

Use #{systemProperties['env']}. Basically pass the propertyName used in the Java command line as -DpropertyName=value. In this case it was -Denv=development so used env.

Interestingly, Spring has evolved to handled this need more gracefully with PropertySources:
http://spring.io/blog/2011/02/15/spring-3-1-m1-unified-property-management/
With a few configurations and perhaps a custom ApplicationInitializer if you are working on a Web app, you can have the property placeholder handle System, Environment, and custom properties. Spring provides PropertySourcesPlaceholderConfigurer which is used when you have in your Spring config. That one will look for properties in your properties files, then System, and then finally Environment.

Spring 3.0.7
<context:property-placeholder location="classpath:${env:config-prd.properties}" />
And at runtime set:
-Denv=config-dev.properties
If not set "env" will use default "config-prd.properties".