We Keep Coding

How to Change Property Value at Runtime without restart application server in Spring MVC

We have Spring scheduled job with cron expression which is configured in database. I need to change schedule time without restart the application server. But i could not achieve this and i have tried many ways using SO solutions in other link, but none worked for me. Below is my code snippet.
Scheduler time will get from database during dispatcher servlet initializing and assign in the property variable test.scheduler
Scheduler.java
#Scheduled(cron = "${test.scheduler}")
public void testScheduler() {
System.out.println("Dynamic Scheduler Run Test"+new java.util.Date().getTime());
}
dispatcher-servlet.xml
<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="systemPropertiesModeName" value="SYSTEM_PROPERTIES_MODE_OVERRIDE" />
<property name="properties">
<bean class="org.apache.commons.configuration.ConfigurationConverter" factory-method="getProperties">
<constructor-arg>
<bean class="org.apache.commons.configuration.DatabaseConfiguration">
<constructor-arg>
<ref bean="dataSource" />
</constructor-arg>
<constructor-arg value="TABLE_NAME" />
<constructor-arg value="TABLE_KEY" />
<constructor-arg value="TABLE_VALUE" />
</bean>
</constructor-arg>
</bean>
</property>
</bean>
From the table (TABLE_NAME), there is column's key is test.scheduler & value is 0 0/5 * * * ?

As far as I am aware, SpEL won't let you change the value of your scheduler once it has been initialised.
If you are using Spring Boot, you will be able to use Actuator to trigger a refreshed event:-
http://localhost:8080/actuator/refresh
In which case, you can make the bean implement RefreshedScope and update your scheduler by triggering the RefreshScopeRefreshedEvent:
#EventListener(RefreshScopeRefreshedEvent.class)
public void onRefresh(RefreshScopeRefreshedEvent event) {
// Read the database, update the scheduler.
}
An example implementation of this can be seen here.
This might not be the perfect solution to your problems but I am posting it for visibility and to help others.
An alternative solution may involve using a Trigger to determine the next execution time. An example StackOverflow answer can be seen here.

Determine for which aggregation a bean is created

I have the following definition:
<bean id="logger" factory-method="createLog" scope="prototype" class="com.test.beans.LogBean" ></bean>
<bean id="aone" class="com.test.beans.AggregationOne">
<property name="log" ref="logger"></property>
</bean>
<bean id="atwo" class="com.test.beans.AggregationTwo">
<property name="log" ref="logger"></property>
</bean>
Is it possible to recognize for which object (aone or atwo) bean 'logger' is being created?
Why I'm asking: in a legacy application I have one log instance for all classes. I want to change level for some packages, but can't do that (except using filters, what I don't want). For that purpose I want to utilize some spring magic, if it exists for that case )

I don't think it can be done this way. What you could try is a BeanPostProcessor implementation which detects common logger object in beans and replaces it with a specific one.

Spring syntax for setting a Class object?

Is there a way to set a property in spring to, not an instance of a class, but the class object itself? i.e.
Rather than
<bean>
<property name="prototype" class="a.b.c.Foo">...
giving you an instance of "Foo", something like:
<bean>
<property name="prototype" class="java.lang.Class" value="a.b.c.Foo.class"...
edit:
best (working) solution so far - use the normal instantiation and derive the class in the setter. In terms of solutions I think this we'd describe this as "cheating":
<bean class="Bar">
<property name="prototype" class="a.b.c.Foo">...
public class Bar{
public void setPrototype(Object o){
this.prototypeClass=o.getClass();
edit:
dtsazza's method works as well.
edit:
pedromarce's method works as well.

<bean>
<property name="x">
<value type="java.lang.Class">a.b.c.Foo</value>
</property>
</bean>
That should work.

You could certainly use the static factory method Class.forName(), if there's no more elegant syntax (and I don't believe there is):
<property name="x">
<bean class="java.lang.Class" factory-method="forName">
<constructor-arg value="a.b.c.Foo"/>
</bean>
</property>

No. With a bean tag you instruct Spring on how to instantiate a class.

Would <property name="x" class="a.b.c.Foo.class"> work? That should be an instance of a Class object...

"Recycling" names within a spring application context

lets say, I have a lot of stuff within my spring application context which looks like that
<bean name="foo.0001" class="com.example.MyClass">
<property name="name" value="foo.name.0001"/>
<property name="zap">
<bean class="com.example.Other">
<property name="name" value="foo.name.0001"/>
</bean>
</property>
<property name="bar">
<bean class="com.example.NextOther">
<property name="name" value="foo.name.0001"/>
</bean>
</property>
</bean>
so the string foo.name.0001 appears within the bean definition several times. Because it is a larger system with several blocks of this configuration, it is quite annoying to modify each of those ids. Ideally I would want to set it only once within a block. Is there a possibility to set some kind of property which exists only in a local scope of a bean definition?

I'm not sure how that would logically work, as you would still have to reference that value somehow to pass it to the nested beans. If you are worried about defining it multiple times, you can have a look at Springs PropertyPlaceholderConfigurer. It will allow you to the following:
<property name="bar">
<bean class="com.example.NextOther">
<property name="name" value="${foo.name.001}"/>
</bean>
</property>
This would allow you to define it once, and reference it from multiple locations.

It depends how much effort you want to put into to this but your requirements could be fufilled by a spring custom namespace. These are ideal when you have lots of identical blocks of beans each configured differently.
Basically you'd define the xml schema then write a bean definition parser that sets up the beans as required.
See here for more details:
http://www.javaworld.com/javaworld/jw-02-2008/jw-02-springcomponents.html
This is how Spring security simplified its xml configuration.

Is it possible to have multiple PropertyPlaceHolderConfigurer in my applicationContext?

I need to load a specific applicationContext.xml file according to a given system property. This itself loads a file with the actual configuration. Therefore I need two PropertyPlaceHolderConfigurer, one which resolves the system param, and the other one within the actual configuration.
Any ideas how to do this?

Yes you can do more than one. Be sure to set ignoreUnresolvablePlaceholders so that the first will ignore any placeholders that it can't resolve.
<bean id="ppConfig1" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="ignoreUnresolvablePlaceholders" value="true"/>
<property name="locations">
<list>
<value>classpath*:/my.properties</value>
</list>
</property>
</bean>
<bean id="ppConfig2" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="ignoreUnresolvablePlaceholders" value="false"/>
<property name="locations">
<list>
<value>classpath*:/myOther.properties</value>
</list>
</property>
</bean>
Depending on your application, you should investigate systemPropertiesMode, it allows you to load properties from a file, but allow the system properties to override values in the property file if set.

Another solution is to use placeholderPrefix property of PropertyPlaceholderConfigurer. You specify it for the second (third, fourth...) configurer, and then prefix all your corresponding placeholders, thus there will be no conflict.
<bean id="mySecondConfigurer"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"
p:location="classpath:/myprops.properties"
p:placeholderPrefix="myprefix-"/>
<bean class="com.mycompany.MyClass" p:myprop="${myprefix-value.from.myprops}"/>

Beware -- there might be a bug related to multiple configurers. See http://jira.spring.io/browse/SPR-5719 for more details.
I'm unable to get multiple to work locally... but I'm not yet blaming anyone but myself.

On my own side, playing with PropertyPlaceholderConfigurer both properties :
order (should be lower for first accessed/parsed PPC)
ignoreUnresolvablePlaceholders ("false" for first accessed/parsed PPC, "true" for next one)
and also give 2 distinct id(s) to both PPC (to avoid one to be overwritten by the other)
works perfectly
Hope it helps

You can't do this directly, and this JIRA issue from Spring explains why (check the comment from Chris Beams for a detailed explanation):
https://jira.springsource.org/browse/SPR-6428
However, he does provide a workaround using Spring 3.1 or later, which is to use the PropertySourcesPlaceholderConfigurer class instead of PropertyPlaceholderConfigurer class.
You can download a Maven-based project that demonstrates the problem and the solution from the Spring framework issues github:
https://github.com/SpringSource/spring-framework-issues
Look for the issue number, SPR-6428, in the downloaded projects.

We have the following approach working:
<util:properties id="defaultProperties">
<prop key="stand.name">DEV</prop>
<prop key="host">localhost</prop>
</util:properties>
<context:property-placeholder
location="file:${app.properties.path:app.properties}"
properties-ref="defaultProperties"/>
System property app.properties.path can be used to override path to config file.
And application bundles some default values for placeholders that cannot be defined with defaults in common modules.

Just giving 2 distinct ids worked for me. I am using spring 3.0.4.
Hope that helps.

In case, you need to define two PPC's (like in my situation) and use them independently. By setting property placeholderPrefix, you can retrieve values from desired PPC. This will be handy when both set of PPC's properties has same keys, and if you don't use this the property of ppc2 will override ppc1.
Defining your xml:
<bean name="ppc1"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="properties" ref="ref to your props1" />
<property name="placeholderPrefix" value="$prefix1-{" />
</bean>
<bean name="ppc2"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="properties" ref="ref to your props2" />
<property name="placeholderPrefix" value="$prefix2-{" />
</bean>
Retrieving during Run time:
#Value(value = "$prefix1-{name}")
private String myPropValue1;
#Value(value = "$prefix2-{name}")
private String myPropValue2;