Loading Application Properties from a Database

Contents

• Overview
• Getting Started
  • Required Jars
  • Database Table Used in this Example
• How It Works
• Spring Configuration
• Code Example
• Application Context Initialization Output
• Related Links

Overview

This example will show you how to use a DatabaseConfiguration from the Jakarta Commons Configurations project and load the Database Properties into your application context.

If you want to take advantage of the features offered in commons configuration to load your application properties into your spring context, you can use spring modules to make the properties loaded from commons configurations available within your application context.

Getting Started

To follow this example for using commons configuration with spring, you will need the jars for spring, spring-modules and commons configuration. You will also need a database available.

Required Jars

To get started with this example, you will need three jar files.

• spring.jar (Spring Core) [PropertiesPlaceholderConfigurer]
• spring-modules.jar (Spring Modules) [CommonsConfigurationFactoryBean]
• commons-configuration.jar (Commons Configuration) [DatabaseConfiguration]

Database Table Used in this Example

For this example, the database has a schema in it called TEST_SCHEMA and a table called APPLICATION_PROPERTIES_TABLE with two columns KEY and VALUE*.

TEST_SCHEMA.APPLICATION_PROPERTIES_TABLE

KEY	VALUE
key.one	value one
file.location	somewhere/on/the/filesystem
pet.dogs.name	bart

* Note that this is only one example of a usable table structure.

How It Works

1. The DatabaseConfiguration is initialized from the injected datasource and is configured to load the properties from the table TEST_SCHEMA.APPLICATION_PROPERTIES using the column KEY as the key and VALUE as the value.
2. The CommonsConfigurationFactoryBean is initialized with the DatabaseConfiguration? bean as its configuration (It can have many but that is not used in this example).
3. The PropertyPlaceholderConfigurer is initialized with properties attribute being set to the CommonsConfigurationFactoryBean. The CommonsConfigurationFactoryBean? is a FactoryBean that creates a Properties object.
4. The PropertyPlaceholderConfigurer then makes the properties available to any bean within the current spring configuration file via the ${} notation.
5. The PropertiesPrinter is then initialized with the properties file.location, pet.dogs.name and file.location.
6. displayAllProperties() (initMethod) is then called on the PropertiesPrinter? and the following would be output:

File Location : somewhere/on/the/filesystem
Pet dogs name : bart
Key one       : value one

In Summary

• PropertiesPlaceholderConfigurer [Spring-Core] makes its properties available within the application context.
• CommonsConfigurationFactoryBean [Sprint Modules] creates a properties object using classes from commons configuration.
• DatabaseConfiguration [Commons Configuration] loads properties from a database table.

Spring Configuration

<!-- Required to connect to datasource -->
<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="DatabaseConfiguration"/>
</bean>
   
<bean name="DatabaseConfiguration"
         class="org.apache.commons.configuration.DatabaseConfiguration">
        <constructor-arg type="javax.sql.DataSource" ref="someDataSource"/>
        <constructor-arg index="1" value="TEST_SCHEMA.APPLICATION_PROPERTIES_TABLE"/>
        <constructor-arg index="2" value="KEY"/>
        <constructor-arg index="3" value="VALUE"/>
</bean>

<!-- Included to elaborate functionality -->

<bean name="PropertiesPrinter " class="example.PropertiesPrinter"
     initMethod="displayAllProperties">
    <property name="fileLocation" value="${file.location}"/>
    <property name="petDogsName" value="${pet.dogs.name}"/>
    <property name="keyOne" value="${key.one}"/>
</bean>

Code Example

package example;

public class PropertiesPrinter {
   public String fileLocation;
   public String petDogsName;
   public String keyOne;
   
   public void setFileLocation(String fileLocation) {
      this.fileLocation = fileLocation;
   }

   public void setPetDogsName(String petDogsName) {
      this.petDogsName = petDogsName;
   }
   
   public void setKeyOne(String keyOne) {
      this.keyOne = keyOne;
   }

   public void displayAllProperties() {
      System.out.println("File Location : " + this.fileLocation);
      System.out.println("Pet dogs name : " + this.petDogsName);
      System.out.println("Key one       : " + this.keyOne);
   }
}

Application Context Initialization Output

File Location : somewhere/on/the/filesystem
Pet dogs name : bart
Key one       : value one

Related Links

• Commons Configuration
• Spring Modules
• Spring
• Spring by example