Configuration Framework

/**
 * Base XML configuration processor supporting multiple input sources.
 */
public abstract class GenericXMLConfigurator extends ContextAwareBase {
    /**
     * Configure from URL.
     * @param url configuration file URL
     * @throws JoranException if configuration fails
     */
    public void doConfigure(URL url) throws JoranException;
    
    /**
     * Configure from file.
     * @param file configuration file
     * @throws JoranException if configuration fails
     */
    public void doConfigure(File file) throws JoranException;
    
    /**
     * Configure from input stream.
     * @param inputStream configuration input stream
     * @throws JoranException if configuration fails
     */
    public void doConfigure(InputStream inputStream) throws JoranException;
    
    /**
     * Configure from input source.
     * @param inputSource SAX input source
     * @throws JoranException if configuration fails
     */
    public void doConfigure(InputSource inputSource) throws JoranException;
}

/**
 * Joran-based XML configurator with advanced processing capabilities.
 */
public class JoranConfigurator extends GenericXMLConfigurator {
    /**
     * Configure context from URL.
     * @param context target context
     * @param url configuration URL
     * @throws JoranException if configuration fails
     */
    public void configure(Context context, URL url) throws JoranException;
    
    /**
     * Record SAX events from input stream for later processing.
     * @param inputStream configuration input stream
     * @return list of recorded SAX events
     * @throws JoranException if recording fails
     */
    public List<SaxEvent> recordEvents(InputStream inputStream) throws JoranException;
}

/**
 * Central context providing shared services and configuration.
 */
public interface Context extends PropertyContainer {
    /**
     * Get the status manager for diagnostic messages.
     * @return status manager
     */
    StatusManager getStatusManager();
    
    /**
     * Store an object by key.
     * @param key object key
     * @param value object to store
     */
    void putObject(String key, Object value);
    
    /**
     * Retrieve stored object by key.
     * @param key object key
     * @return stored object or null
     */
    Object getObject(String key);
    
    /**
     * Get context name.
     * @return context name
     */
    String getName();
    
    /**
     * Set context name.
     * @param name context name
     */
    void setName(String name);
    
    /**
     * Get context birth time.
     * @return creation timestamp
     */
    long getBirthTime();
    
    /**
     * Get configuration lock for thread safety.
     * @return reentrant lock
     */
    ReentrantLock getConfigurationLock();
    
    /**
     * Get scheduled executor service.
     * @return scheduled executor
     */
    ScheduledExecutorService getScheduledExecutorService();
    
    /**
     * Get general executor service.
     * @return executor service
     */
    ExecutorService getExecutorService();
    
    /**
     * Get alternate executor service.
     * @return alternate executor
     */
    ExecutorService getAlternateExecutorService();
    
    /**
     * Register a lifecycle component for management.
     * @param component component to register
     */
    void register(LifeCycle component);
    
    /**
     * Add a scheduled future for tracking.
     * @param scheduledFuture future to track
     */
    void addScheduledFuture(ScheduledFuture<?> scheduledFuture);
    
    /**
     * Get sequence number generator.
     * @return sequence generator
     */
    SequenceNumberGenerator getSequenceNumberGenerator();
}

/**
 * Base context implementation with service management and lifecycle support.
 */
public class ContextBase implements Context {
    /**
     * Complete implementation of Context interface.
     * Provides property storage, object registry, executor services, and lifecycle management.
     */
    
    @Override
    public StatusManager getStatusManager();
    
    @Override
    public void putObject(String key, Object value);
    
    @Override
    public Object getObject(String key);
    
    @Override
    public String getProperty(String key);
    
    @Override
    public void putProperty(String key, String value);
    
    @Override
    public Map<String, String> getCopyOfPropertyMap();
    
    // ... additional Context methods
}

/**
 * Interface for property storage and retrieval.
 */
public interface PropertyContainer {
    /**
     * Get property value with variable substitution.
     * @param key property key
     * @return property value with variables substituted
     */
    String getProperty(String key);
    
    /**
     * Set property value.
     * @param key property key
     * @param value property value
     */
    void putProperty(String key, String value);
    
    /**
     * Get copy of all properties.
     * @return map of all properties
     */
    Map<String, String> getCopyOfPropertyMap();
}

/**
 * Interface for defining properties dynamically.
 */
public interface PropertyDefiner extends ContextAware {
    /**
     * Get the computed property value.
     * @return property value
     */
    String getPropertyValue();
}

/**
 * Property definer that returns "true" if a resource exists.
 */
public class ResourceExistsPropertyDefiner extends PropertyDefinerBase {
    /**
     * Set the resource path to check.
     * @param resource resource path (classpath or file)
     */
    public void setResource(String resource);
    
    /**
     * Get the resource path.
     * @return resource path
     */
    public String getResource();
    
    /**
     * Returns "true" if resource exists, "false" otherwise.
     * @return "true" or "false"
     */
    @Override
    public String getPropertyValue();
}

/**
 * Property definer that returns "true" if a file exists.
 */
public class FileExistsPropertyDefiner extends PropertyDefinerBase {
    /**
     * Set the file path to check.
     * @param path file path
     */
    public void setPath(String path);
    
    /**
     * Get the file path.
     * @return file path
     */
    public String getPath();
    
    /**
     * Returns "true" if file exists, "false" otherwise.
     * @return "true" or "false"
     */
    @Override
    public String getPropertyValue();
}

/**
 * Property definer that returns the canonical hostname.
 */
public class CanonicalHostNamePropertyDefiner extends PropertyDefinerBase {
    /**
     * Returns the canonical hostname of the local machine.
     * @return canonical hostname
     */
    @Override
    public String getPropertyValue();
}

/**
 * Base class for configuration actions that process XML elements.
 */
public abstract class Action implements ContextAware {
    /**
     * Called when element starts.
     * @param interpreter SAX event interpreter
     * @param name element name
     * @param attributes element attributes
     * @throws ActionException if action fails
     */
    public abstract void begin(SaxEventInterpreter interpreter, 
                             String name, Attributes attributes) throws ActionException;
    
    /**
     * Called when element ends.
     * @param interpreter SAX event interpreter
     * @param name element name
     * @throws ActionException if action fails
     */
    public abstract void end(SaxEventInterpreter interpreter, 
                           String name) throws ActionException;
    
    /**
     * Called with element body text.
     * @param interpreter SAX event interpreter
     * @param body element body text
     * @throws ActionException if action fails
     */
    public void body(SaxEventInterpreter interpreter, String body) throws ActionException;
}

/**
 * Action for processing <property> elements in configuration.
 */
public class PropertyAction extends Action {
    @Override
    public void begin(SaxEventInterpreter interpreter, String name, Attributes attributes);
    
    @Override
    public void end(SaxEventInterpreter interpreter, String name);
}

/**
 * Action for processing <define> elements that create PropertyDefiners.
 */
public class DefinePropertyAction extends Action {
    @Override
    public void begin(SaxEventInterpreter interpreter, String name, Attributes attributes);
    
    @Override
    public void end(SaxEventInterpreter interpreter, String name);
}

/**
 * Base class for boolean conditions in configuration.
 */
public abstract class Condition implements ContextAware {
    /**
     * Evaluate the condition.
     * @return true if condition is met
     */
    public abstract boolean evaluate();
}

/**
 * Property wrapper for script evaluation in conditional configuration.
 */
public class PropertyWrapperForScripts {
    /**
     * Get property value.
     * @param key property key
     * @return property value
     */
    public String property(String key);
    
    /**
     * Short form for property access.
     * @param key property key  
     * @return property value
     */
    public String p(String key);
    
    /**
     * Check if property is null.
     * @param key property key
     * @return true if null or undefined
     */
    public boolean isNull(String key);
    
    /**
     * Check if property is defined.
     * @param key property key
     * @return true if defined
     */
    public boolean isDefined(String key);
}

/**
 * Base class for configuration model elements.
 */
public class Model {
    /**
     * Add a sub-model as a child.
     * @param model child model
     */
    public void addSubModel(Model model);
    
    /**
     * Get all sub-models.
     * @return list of child models
     */
    public List<Model> getSubModels();
    
    /**
     * Set the XML tag name.
     * @param tag tag name
     */
    public void setTag(String tag);
    
    /**
     * Get the XML tag name.
     * @return tag name
     */
    public String getTag();
    
    /**
     * Set the body text content.
     * @param bodyText body text
     */
    public void setBodyText(String bodyText);
    
    /**
     * Get the body text content.
     * @return body text
     */
    public String getBodyText();
}

/**
 * Model for component elements with class names.
 */
public class ComponentModel extends Model {
    /**
     * Set the component class name.
     * @param className fully qualified class name
     */
    public void setClassName(String className);
    
    /**
     * Get the component class name.
     * @return class name
     */
    public String getClassName();
}

/**
 * Utility for variable substitution in configuration values.
 */
public class OptionHelper {
    /**
     * Substitute variables in a string using property container.
     * Variables are in ${variable} format.
     * @param val string with variables
     * @param pc property container for variable lookup
     * @return string with variables substituted
     */
    public static String substVars(String val, PropertyContainer pc);
    
    /**
     * Instantiate class by name with context.
     * @param className class name to instantiate
     * @param superClass expected superclass
     * @param context context for dependency injection
     * @return instantiated object
     */
    public static Object instantiateByClassName(String className, 
                                              Class<?> superClass, 
                                              Context context);
}

<configuration>
    <!-- Set properties -->
    <property name="LOG_DIR" value="/var/log/myapp" />
    <property name="LOG_LEVEL" value="INFO" />
    
    <!-- Define dynamic properties -->
    <define name="HOSTNAME" class="ch.qos.logback.core.property.CanonicalHostNamePropertyDefiner" />
    
    <!-- Configure appender -->
    <appender name="FILE" class="ch.qos.logback.core.FileAppender">
        <file>${LOG_DIR}/application-${HOSTNAME}.log</file>
        <append>true</append>
        <encoder>
            <pattern>%d{yyyy-MM-dd HH:mm:ss} [%thread] %-5level %logger{36} - %msg%n</pattern>
        </encoder>
    </appender>
    
    <!-- Configure rolling appender -->
    <appender name="ROLLING" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <file>${LOG_DIR}/app.log</file>
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <fileNamePattern>${LOG_DIR}/app.%d{yyyy-MM-dd}.%i.log.gz</fileNamePattern>
            <maxFileSize>100MB</maxFileSize>
            <maxHistory>30</maxHistory>
            <totalSizeCap>10GB</totalSizeCap>
        </rollingPolicy>
        <encoder>
            <pattern>%d{yyyy-MM-dd HH:mm:ss} %-5level %logger - %msg%n</pattern>
        </encoder>
    </appender>
</configuration>

<configuration>
    <property name="ENV" value="${ENV:-development}" />
    
    <!-- Development configuration -->
    <if condition='property("ENV").equals("development")'>
        <then>
            <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
                <encoder>
                    <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
                </encoder>
            </appender>
        </then>
    </if>
    
    <!-- Production configuration -->  
    <if condition='property("ENV").equals("production")'>
        <then>
            <appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
                <file>/var/log/app/application.log</file>
                <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
                    <fileNamePattern>/var/log/app/application.%d{yyyy-MM-dd}.log.gz</fileNamePattern>
                    <maxHistory>90</maxHistory>
                </rollingPolicy>
                <encoder>
                    <pattern>%d{yyyy-MM-dd HH:mm:ss} [%thread] %-5level %logger - %msg%n</pattern>
                </encoder>
            </appender>
        </then>
    </if>
</configuration>

import ch.qos.logback.core.joran.JoranConfigurator;
import ch.qos.logback.core.Context;
import ch.qos.logback.core.ContextBase;

// Create context
Context context = new ContextBase();

// Set properties programmatically
context.putProperty("LOG_DIR", "/tmp/logs");
context.putProperty("APP_NAME", "MyApplication");

// Configure from file
JoranConfigurator configurator = new JoranConfigurator();
configurator.setContext(context);

try {
    // Load configuration from classpath
    URL configUrl = getClass().getResource("/logback-config.xml");
    configurator.doConfigure(configUrl);
} catch (JoranException e) {
    // Handle configuration error
    StatusPrinter.printInCaseOfErrorsOrWarnings(context);
}

import ch.qos.logback.core.spi.PropertyDefiner;
import ch.qos.logback.core.spi.ContextAwareBase;

public class EnvironmentPropertyDefiner extends ContextAwareBase implements PropertyDefiner {
    private String variableName;
    private String defaultValue;
    
    @Override
    public String getPropertyValue() {
        String value = System.getenv(variableName);
        if (value == null) {
            value = System.getProperty(variableName, defaultValue);
        }
        return value != null ? value : defaultValue;
    }
    
    public void setVariableName(String variableName) {
        this.variableName = variableName;
    }
    
    public void setDefaultValue(String defaultValue) {
        this.defaultValue = defaultValue;
    }
}

<configuration>
    <define name="PORT" class="com.example.EnvironmentPropertyDefiner">
        <variableName>SERVER_PORT</variableName>
        <defaultValue>8080</defaultValue>
    </define>
    
    <property name="LOG_FILE" value="/var/log/app-${PORT}.log" />
</configuration>