SimpleConfig

SimpleConfig - Java project configuration the easy way.

With SimpleConfig you can create XML configuration files that can then be easily accessed from code.

Some examples can be found here.

Basics

A very simple XML-Configuration could look like this:

<config>
    <text>Hello world!</text>
    <debug>true</debug>
</config>

We can then use this configuration in Java (see Config.java):

Config config = ConfigFactory.fromFile("my-config.xml");

String txt = config.getProperty("text"); // will be "Hello world!"
boolean debug = config.getBoolean("debug", false); // will be "true"

Nested Configurations

SimpleConfig also supports nested configurations:

<config>
    <user1>
        <name>Alex</name>
        <points>123</points>
    </user1>

    <user2>
        <name>Tom</name>
        <points>10</points>
    </user2>
</config>

We can then use this in Java:

Config config = ConfigFactory.fromFile("my-config.xml");

// get the configuration for user1
Config user1 = config.getSubconfig("user1");
String name1 = user1.getProperty("name"); // Alex
int points1 = user1.getInt("points", 0); // 123

// get the configuration for user2
Config user2 = config.getSubconfig("user2");
String name2 = user1.getProperty("name"); // Tom
int points2 = user1.getInt("points", 0); // 10

Components

You can also configure and create components (Java objects) defined in the config file.

For example, consider the following class:

package com.oprisnik.simpleconfig;

public class SimpleComponent implements Configurable {

  public static final String KEY_NAME = "name";

  private String mName = null;

  @Override
  public void init(Config config) throws BadConfigException {
    mName = config.getProperty(KEY_NAME, mName);
  }

  public String getName() {
    return mName;
  }
}

The SimpleComponent implements the Configurable interface. Hence it can be configured using our config file:

<config>
    <component1 class="com.oprisnik.simpleconfig.SimpleComponent">
        <name>Alex</name>
    </component1>

    <component2 class="com.oprisnik.simpleconfig.SimpleComponent">
      <name>Tom</name>
    </component2>
</config>

In Java, we can access it as follows:

SimpleComponent c1 = config.getComponentAndInit("component1", SimpleComponent.class);
String name1 = c1.getName(); // Alex

SimpleComponent c2 = config.getComponentAndInit("component2", SimpleComponent.class);
String name2 = c2.getName(); // Tom

The components do not necessarily need to implement the Configurable interface though. You can load any class from your configuration file if you want to. In this case the component will not be configured, only a new instance will be created using the default constructor.

In Java, you can get any component (without initializing it) by calling

MyClass something = config.getComponent("something", MyClass.class);

Default Class Values

As you can see, we have to define a class attribute in the XML file. If we want to omit this class attribute, we can add a default value to our Java code:

XML:

<config>
    <component>
        <name>Alex</name>
    </component>
</config>

Java:

SimpleComponent component = config.getComponentAndInit("component",
                            SimpleComponent.class, SimpleComponent.class);

String name = component.getName(); // "Alex"

Since we did not specify a class attribute for component1, the default implementation is used.

Suppose we have the following class:

public class ExtendedComponent extends SimpleComponent {

  @Override
  public String getName() {
    return "Extended: " + super.getName();
  }
}

Now we can modify the XML configuration file from above:

<config>
  <component class="com.oprisnik.simpleconfig.ExtendedComponent">
    <name>Alex</name>
  </component>
</config>

And use the same Java code as before:

SimpleComponent component = config.getComponentAndInit("component",
SimpleComponent.class, SimpleComponent.class);

String name = component.getName(); // "Extended: Alex"

The name will now be Extended: Alex since we have specified a class attribute in the configuration file and the default value is not used.

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