logback-tyler

Logback-tyler translates logback-classic XML configuration files into Java.

The resulting java class named TylerConfigurator implements the Configurator interface. It can thus be declared as a custom configuration provider using Java's standard service-provider meachanism. Custom configurators are searched by looking up file resource located under the META-INF/services/ch.qos.logback.classic.spi.Configurator file in your project.

Running TylerConfigurator does not require XML parsers and usually executes noticeably faster than JoranConfigurator, logback's XML configurator. Moreover, TylerConfigurator does not use reflection. In addition, given that it ships with your project's binaries, it is harder to modify and offers an even smaller attack surface.

At runtime, TylerConfigurator does not have any additional dependencies other than logback-classic version 1.5.4.

Logback-tyler is located at the following Maven coordinates:

 <groupId>ch.qos.logback.tyler</groupId>
 <artifactId>tyler-base</artifactId>
 <version>0.7</version>

Here is a sample program to translate a logback.xml as string into Java.

import ch.qos.logback.core.joran.spi.JoranException;
import ch.qos.logback.core.model.Model;
import ch.qos.logback.core.util.StatusPrinter;

import java.io.IOException;

public class TylerExample {

    String xmlInput =
    """
            <configuration debug="true">
              <import class="ch.qos.logback.classic.encoder.PatternLayoutEncoder"/>
              
              <property name="APP_NAME" value="myApp"/>
             
              <contextName>${APP_NAME}</contextName>
             
              <appender class="ch.qos.logback.core.FileAppender" name="TOTO">
                <file>toto.log</file>
                <append>true</append>
                <immediateFlush>true</immediateFlush>
                <encoder>
                  <pattern>%-4relative [%thread] %-5level %logger{35} -%kvp- %msg%n</pattern>
                </encoder>   
              </appender>         
             
             
              <root level="DEBUG">
                <appender-ref ref="TOTO"/>
              </root>             
            </configuration>                 
    """;
    
    public static void main(String[] args)  throws JoranException, IOException {
        ContextBase context = new ContextBase();
        ModelToJava m2j = new ModelToJava(context);
        Model model = m2j.extractModel(xmlInput);
        String result = m2j.toJava(model);
        System.out.println(result);
        // print any error messages occuring during the translation
        StatusPrinter.print(context);
    }
}

running the above program will produce the following output

import ch.qos.logback.classic.Logger;
import ch.qos.logback.classic.LoggerContext;
import ch.qos.logback.classic.encoder.PatternLayoutEncoder;
import ch.qos.logback.classic.spi.Configurator;
import ch.qos.logback.classic.tyler.TylerConfiguratorBase;
import ch.qos.logback.core.Appender;
import ch.qos.logback.core.FileAppender;
import ch.qos.logback.core.joran.spi.NoAutoStartUtil;
import ch.qos.logback.core.spi.ContextAware;
import ch.qos.logback.core.spi.LifeCycle;
import java.lang.Override;

/**
 *
 * <p>This file was generated by logback-tyler version 0.7</p>
 *
 * <p>Eventual errors and warning are appended at the end.</p>
 *
 * <p>You can try, TylerConfigurator generation, that is the logback.xml
 * to Java translation at
 *
 *       https://logback.qos.ch/translator/services/xml2Java.html </p>
 *
 * <p>BEWARE: As of March 2024, TylerConfigurator generation from logback.xml
 * configuration files is still experimental and incomplete.
 * </p>
 *
 * <p>This class, i.e. TylerConfigurator, is intended to be copied and integrated
 * into the user's project as a custom configurator. It will configure logback
 * without XML.</p>
 *
 * <p>It requires logback-classic version 1.5.4 or later at runtime.</p>
 *
 * <p>Custom configurators are looked up via Java's service-provide facility. If a
 * custom provider is found, it takes precedence over logback's own configurators,
 * e.g. DefaultJoranConfigurator.</p>
 *
 * <p>See also item 1 of 'Configuration at initialization' section at
 *
 *     https://logback.qos.ch/manual/configuration.html#auto_configuration
 *
 * </p>
 */
class TylerConfigurator extends TylerConfiguratorBase implements Configurator {
  /**
   * <p>This method performs configuration per {@link Configurator} interface.</p>
   *
   * <p>If <code>TylerConfgiurator</code> is installed as a configurator service, this
   * method will be called by logback-classic during initialization.</p>
   */
  @Override
  public Configurator.ExecutionStatus configure(LoggerContext loggerCoontext) {
    setContext(loggerCoontext);
    addOnConsoleStatusListener();
    propertyModelHandlerHelper.handlePropertyModel(this, "APP_NAME", "myApp", "", "", "");
    setContextName(subst("${APP_NAME}"));
    Appender appenderRFILE = setupAppenderRFILE();
    logger_ROOT.addAppender(appenderRFILE);
    Logger logger_ROOT = setupLogger("ROOT", "DEBUG", null);
    return ExecutionStatus.DO_NOT_INVOKE_NEXT_IF_ANY;
  }

  Appender setupAppenderRFILE() {
    FileAppender appenderRFILE = new FileAppender();
    appenderRFILE.setContext(context);
    appenderRFILE.setName("RFILE");
    appenderRFILE.setFile("toto.log");
    appenderRFILE.setAppend(true);
    appenderRFILE.setImmediateFlush(true);

    // Configure component of type PatternLayoutEncoder
    PatternLayoutEncoder patternLayoutEncoder = new PatternLayoutEncoder();
    patternLayoutEncoder.setContext(context);
    
    patternLayoutEncoder.setPattern("%-4relative [%thread] %-5level %logger{35} -%kvp- %msg%n");
    patternLayoutEncoder.setParent(appenderRFILE);
    patternLayoutEncoder.start();
    
    // Inject component of type PatternLayoutEncoder into parent
    appenderRFILE.setEncoder(patternLayoutEncoder);

    appenderRFILE.start();
    return appenderRFILE;
  }
}

----------------
15:44:51,087 |-INFO in ch.qos.logback.tyler.base.handler.ImplicitModelHandler - Assuming default type [ch.qos.logback.classic.encoder.PatternLayoutEncoder] for [encoder] property
15:44:51,092 |-INFO in ch.qos.logback.core.model.processor.DefaultProcessor@1f760b47 - End of configuration.