Scott is born

2 weeks earlier than expected my second son is born: Scott. He and mums are doing very well!

PS: Is it just coincidence that he was born during SpringOne 2GX at the day official Grails support was announced for SpringSource Tool Suite/Eclipse?

Even more useful: ConfigObjectFactoryBean for Spring

Last week I blogged about a ConfigSlurperPlaceholderConfigurer for Spring. I've now come up with something more useful: a ConfigObjectFactoryBean for Spring!

It just creates a Groovy ConfigObject from the specified arguments (config file locations, environment and default environment).

It's more useful because you can use it to populate Spring's standard PropertyPlaceholderConfigurer and even expose the config properties map as a servlet context attribute using the ServletContextAttributeExporter. To populate the PropertyPlaceholderConfigurer and ServletContextAttributeExporter classes with appropriate beans derived from the ConfigObject (resp, java.util.Properties and java.util.Map), the factory-bean and factory-method attributes of the bean definition are used.

Source code of ConfigObjectFactoryBean can be found below. It includes extensive javadoc with example how to configure it in combination with the PropertyPlaceholderConfigurer and ServletContextAttributeExporter.

import groovy.util.ConfigObject;
import groovy.util.ConfigSlurper;

import javax.annotation.PostConstruct;

import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.core.io.Resource;

/**
 * {@link org.springframework.beans.factory.FactoryBean} that exposes a 
 * {@link groovy.util.ConfigObject} object loaded using a Groovy
 * {@link groovy.util.ConfigSlurper}.
 *
 * Supports the concept of per environment configuration via "environment" 
 * and "defaultEnvironment" properties. The "environment" property will be
 * typically set using a system property.
 *
 * Can be used in combination with a 
 * {@link org.springframework.beans.factory.config.PropertyPlaceholderConfigurer}
 * as demonstrated in the example below.
 *
 * Example XML context definition:
 *
 * <bean id="configObject" class="com.footdex.beans.factory.config.ConfigObjectFactoryBean">
 *     <property name="targetClass" value="javax.persistence.Persistence" />
 *     <property name="targetClass" value="javax.persistence.Persistence" />
 * <bean>
 *
 * <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
 *     <property name="properties">
 *         <bean factory-bean="configObject" factory-method="toProperties" />
 *     </property>
 * </bean>
 *
 * <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
 *     <property name="driverClassName"><value>${dataSource.driverClassName}</value></property>
 *     <property name="url"><value>${dataSource.url}</value></property>
 *     <property name="username"><value>${dataSource.username}</value></property>
 *     <property name="password"><value>${dataSource.password}</value></property>
 * </bean> 
 *
 * Example config.groovy:
 *
 * dataSource {
 *     driverClassName = "org.hsqldb.jdbcDriver"    
 *     username = "sa"
 *     password = ""                
 * }
 * environments {
 *     development {
 *         dataSource {
 *             url = "jdbc:hsqldb:mem:devDB"
 *         }
 *     }   
 *     test {
 *         dataSource {
 *             url = "jdbc:hsqldb:mem:testDb"
 *         }
 *     }   
 *     production {
 *         dataSource {
 *             url = "jdbc:hsqldb:file:prodDb;shutdown=true"
 *             password = "secret"
 *         }
 *     }
 * }
 *
 * {@link groovy.util.ConfigObject} properties can be exposed as servlet
 * context attribute easily: 
 *
 * <bean class="org.springframework.web.context.support.ServletContextAttributeExporter">
 *     <property name="attributes">
 *         <map>
 *             <entry key="configProperty">
 *                 <bean factory-bean="configObject" factory-method="flatten" />
 *             </entry>
 *         </map>
 *     </property>
 * </bean>
 *
 * And than can be accessed in jsp's like ${configProperty["sample.foo"]}.
 *
 * @author Marcel Overdijk
 * @see #setEnvironment
 * @see #setDefaultEnvironment
 * @see #setLocations
 * @see groovy.util.ConfigObject
 * @see groovy.util.ConfigSlurper
 */
public class ConfigObjectFactoryBean implements FactoryBean, InitializingBean {

    private String environment;
    private String defaultEnvironment;
    private Resource[] locations;
    private ConfigObject config;

    private String getEnvironment() {
        if (this.environment == null || this.environment.trim().length() == 0) {
            return this.defaultEnvironment;
        }
        else {
            return this.environment;
        }
    }

    public void setEnvironment(String environment) {
        this.environment = environment;
    }

    public void setDefaultEnvironment(String defaultEnvironment) {
        this.defaultEnvironment = defaultEnvironment;
    }

    public void setLocation(Resource location) {
        this.locations = new Resource[] { location };
    }

    public void setLocations(Resource[] locations) {
        this.locations = locations;
    }

    @PostConstruct
    public void yeah() {
        System.out.println("yeah!");
    }
    
    @Override
    public void afterPropertiesSet() throws Exception {
        config = new ConfigObject();
        ConfigSlurper configSlurper = new ConfigSlurper(getEnvironment());
        for (Resource location : locations) {
            config.merge(configSlurper.parse(location.getURL()));
        }
    }
    
    @Override
    public Object getObject() throws Exception {
        return this.config;
    }

    @Override
    public Class getObjectType() {
        return ConfigObject.class;
    }

    @Override
    public boolean isSingleton() {
        return true;
    }
}

Determining runtime environment on Google App Engine

Google recommends to determine the runtime environment of a Google App Engine application using ServletContext.getServerInfo(). In development this will be "Google App Engine Development/x.x.x" and in production it will be "Google App Engine/x.x.x".

But in some places, like Service classes, you might not have a access to the ServletContext object. Easiest way to work around this is to create a ServletContextListener which determines the environment and then stores it in a System property. The System property can be accesses from any place. You can of course also write a (static) Environment.get() utility class which return the System property.

Below you can find an example implementation of such a ServletContextListener to determine the runtime environment. As you can read the javadocs you can also use other environments then development and production. To start the application in test mode, just add a VM argument when you start your application using "-Druntime.environment=test".

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

/**
 * Simple listener to set the App Engine runtime environment via a system property.
 *
 * Example web.xnl definition:
 *
 * <listener>
 *     <listener-class>com.footdex.web.listener.RuntimeEnvironmentConfigurerListener</listener-class>
 * </listener>
 *
 * The runtime environment can then be accessed from any place (without reference to
 * ServletContext) via System.getProperty(RuntimeEnvironmentConfigurerListener.KEY).
 *
 * In case a system property is already set for the RuntimeEnvironmentConfigurerListener.KEY,
 * the system property will not be overridden. This allows to startup the application
 * in a custom environment other than development or production. This can be done typically
 * using a VM argument like "-Druntime.environment=test". 
 *
 * @author Marcel Overdijk
 */
public class RuntimeEnvironmentConfigurerListener implements ServletContextListener {

    public static final String KEY = "runtime.environment";
    public static final String DEVELOPMENT = "development";
    public static final String PRODUCTION = "production";

    @Override
    public void contextInitialized(ServletContextEvent event) {
        if (System.getProperty(KEY) == null) {
            String serverInfo = event.getServletContext().getServerInfo();
            // ServletContext.getServerInfo() will return "Google App Engine Development/x.x.x" 
            // when run locally, and "Google App Engine/x.x.x" otherwise.
            if (serverInfo.contains("Development")) {
                System.setProperty(KEY, DEVELOPMENT);
            }
            else {
                System.setProperty(KEY, PRODUCTION);
            }
        }
    }

    @Override
    public void contextDestroyed(ServletContextEvent event) {
    }
}

ConfigSlurperPlaceholderConfigurer for Spring

Lately I'm working on Spring 3.0 hobby project in my spare time. Frequent readers of my blog or followers me on Twitter might think: Why plain Spring and not just Grails? So let me explain that first:

1. I love Grails (and Groovy), and if I could make the decision I would use it on every project! But...


2. I want to host my hobby project cheap, and even Amazon EC2/AWS is to expensive currently. So I decided to host my application on Google App Engine. And to be honest, Grails support for GAE is just alpha/beta state in my opinion (I hope it will change one day). So Grails was not an option.


3. I've been coding Groovy and Grails for a while now and also doing commercial projects. But I have the feeling my basic Java and Spring knowledge might become a little bit rusty. And to face the facts, there is a change that one of my next clients will not use Groovy/Grails, but just Java and one of the 1,000,000 Java frameworks outhere. So with my hobby project I will be up to date with the latest Java and Spring 3.0 expertise!

But let's get back to the title of this post: ConfigSlurperPlaceholderConfigurer for Spring. In my hobby project I needed the concept of per environment configuration. Yes, in Grails you have it out-of-the-box but in Spring not.

I searched the web and found some interesting thoughts:

• RuntimeEnvironmentPropertiesConfigurer - A subclass of PropertyPlaceholderConfigurer which uses a specific config file based on a system property


• Configleon - Also an interesting mini framework for per environment configs


• GroovyPlaceholderConfigurer - A subclass of PropertyPlaceholderConfigurer which uses a Groovy ConfigSlurper

What I like about Grails' concept of per environment configuration is that you can define global config properties and just override them in a specific environment if needed. So if 90% of my properties are the same for each environment I don't need to specify them for all environment but just once.

This concept was not supported by the RuntimeEnvironmentPropertiesConfigurer, and also not by the GroovyPlaceholderConfigurer. I know the GroovyPlaceholderConfigurer uses a Groovy ConfigSlurper and this does support per environment configuration (Grails uses it!). So I decided to create a proper ConfigSlurperPlaceholderConfigurer which also supports different environments using a system property. At the end this is how my Spring config now looks:

Example XML context definition:

<bean class="org.springframework.beans.factory.config.ConfigSlurperPlaceholderConfigurer">
    <property name="environment" value="#{systemProperties['runtime.environment']}" />
    <property name="defaultEnvironment" value="production" />
    <property name="location" value="/WEB-INF/config.groovy" />
</bean>

<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
    <property name="driverClassName"><value>${dataSource.driverClassName}</value></property>
    <property name="url"><value>${dataSource.url}</value></property>
    <property name="username"><value>${dataSource.username}</value></property>
    <property name="password"><value>${dataSource.password}</value></property>
</bean>

Example config.groovy:

dataSource {
    driverClassName = "org.hsqldb.jdbcDriver"    
    username = "sa"
    password = ""                
}
environments {
    development {
        dataSource {
            url = "jdbc:hsqldb:mem:devDB"
        }
    }   
    test {
        dataSource {
            url = "jdbc:hsqldb:mem:testDb"
        }
    }   
    production {
        dataSource {
            url = "jdbc:hsqldb:file:prodDb;shutdown=true"
            password = "secret"
        }
    }
}

I created a new issue in Spring JIRA to add this to core. If you are interested you can vote for the issue. It also contains the source code if you want to use it in your own project.