Reload4J Interoperability

Apache has announced Log4J 1 has reached end-of-life, the Reload4J project has taken over maintaining the API:

<reload4j.version>1.2.19</reload4j.version>

<dependency>
  <groupId>ch.qos.reload4j</groupId>
  <artifactId>reload4j</artifactId>
  <version>${reload4j.version}</version>
</dependency>

If your application uses Log4J directly during compile time, you can safely set up with:

GeoTools.setLoggerFactory(Log4JLoggerFactory.getInstance());

If your application only depends reload4j being provided at runtime:

Logging.ALL.setLoggerFactory("org.geotools.util.logging.Log4JLoggerFactory");

Note

If reload4j is not found on the CLASSPATH Log4JLoggerFactory results in unpredictable behavior!

It will typically throws a NoClassDefFoundError (the unchecked error, not the checked exception) at some future point. The error may not be thrown at the moment setLoggerFactory is invoked, but rather be delayed until a message is first logged, which may surprise the user.

Reference:

Reload4J Guidance

In a more complicated setup using multiple libraries you may also end up including:

  • slf4j-reload4j: used to bridge any components using slf4j api

    <dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>slf4j-reload4j</artifactId>
    <version>${slf4j.version}</version>
</dependency>

  • jcl-over-sl4j: used to bridge any components using commons-logging to sl4j (which can be bridged to reload4j above).

    <dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>jcl-over-slf4j</artifactId>
    <version>${slf4j.version}</version>
</dependency>

  • commons-logging: Assume Log4J 1 API

    Use commons-logging.properties:

    org.apache.commons.logging.Log=org.apache.commons.logging.impl.Log4JLogger

  • Use of multiple logging frameworks prevents GeoTools.init() ability to determine which API to use requiring the use of:

    Logging.ALL.setLoggerFactory("org.geotools.util.logging.Log4JLoggerFactory");

Reload4J Integration

The following example is taken from our integration testing, this test only has the reload4j in play so GeoTools.init()` is able to unambiguously determine ``Log4JLoggerFactory can be used.

  1. Setup pom.xml with dependencies on geotools and reload4j:

    <project
  xmlns="http://maven.apache.org/POM/4.0.0"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>org.geotools.tutorial</groupId>
  <artifactId>reload4j</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>
  <name>GeoTools Reload4J Integration Example</name>
  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.deploy.skip>true</maven.deploy.skip>
    <geotools.version>30-SNAPSHOT</geotools.version>
    <reload4j.version>1.2.19</reload4j.version>
  </properties>
  <dependencies>
    <dependency>
      <groupId>org.geotools</groupId>
      <artifactId>gt-metadata</artifactId>
      <version>${geotools.version}</version>
    </dependency>
    <dependency>
      <groupId>org.geotools.ogc</groupId>
      <artifactId>net.opengis.ows</artifactId>
      <version>${geotools.version}</version>
    </dependency>
    <dependency>
      <groupId>ch.qos.reload4j</groupId>
      <artifactId>reload4j</artifactId>
      <version>${reload4j.version}</version>
    </dependency>
  </dependencies>
  <repositories>
    <repository>
    <id>osgeo</id>
    <name>OSGeo Release Repository</name>
    <url>https://repo.osgeo.org/repository/release/</url>
    <snapshots><enabled>false</enabled></snapshots>
    <releases><enabled>true</enabled></releases>
    </repository>
    <repository>
    <id>osgeo-snapshot</id>
    <name>OSGeo Snapshot Repository</name>
    <url>https://repo.osgeo.org/repository/snapshot/</url>
    <snapshots><enabled>true</enabled></snapshots>
    <releases><enabled>false</enabled></releases>
    </repository>
  </repositories>

  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-jar-plugin</artifactId>
        <version>3.3.0</version>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.11.0</version>
        <configuration>
          <source>11</source>
          <target>11</target>
        </configuration>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-resources-plugin</artifactId>
        <version>3.1.0</version>
      </plugin>
      <plugin>
        <groupId>org.codehaus.mojo</groupId>
        <artifactId>exec-maven-plugin</artifactId>
        <version>3.1.0</version>
        <configuration>
          <executable>java</executable>
          <arguments>
            <argument>-classpath</argument>
            <classpath/>
            <argument>-Djava.awt.headless=true</argument>
            <argument>org.geotools.tutorial.reload.Reload4JIntegration</argument>
          </arguments>
        </configuration>
      </plugin>
    </plugins>
  </build>
</project>

  2. Configure reload4j wtih log4j.properties added to src/main/resources:

    log4j.rootLogger=ERROR, stdout

log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout

# Pattern to output the caller's file name and line number.
log4j.appender.stdout.layout.ConversionPattern=%d{dd MMM HH:mm:ss} %p [%c{2}] - %m%n

log4j.category.org.geotools=ALL

  3. During startup log4j will search for log4j.properties on the CLASSPATH, or to search for a different file use the system property:

    -Dlog4j.configuration=log4-debug.properties

  4. Application Reload4Integration.java startup example for src/min/java.

    Example is taking care to call GeoTools.init() prior to logger use:

    /*
 *    GeoTools - The Open Source Java GIS Toolkit
 *    http://geotools.org
 *
 *    (C) 2022, Open Source Geospatial Foundation (OSGeo)
 *
 *    This file is hereby placed into the Public Domain. This means anyone is
 *    free to do whatever they wish with this file. Use it well and enjoy!
 */
package org.geotools.tutorial.reload;

import java.util.logging.Logger;
import org.geotools.util.factory.GeoTools;
import org.geotools.util.logging.Logging;
import org.geotools.util.logging.Log4JLoggerFactory;

/** Example illustrating use of Reload4J (providing Log4J 1 API) and startup environment. */
public class Reload4JIntegration {

    public static final Logger LOGGER = initLogger();

    public static void main(String args[]) {
        LOGGER.info("Welcome to Reload4J Integration Example");
        if (!LOGGER.getClass().getName().equals("org.geotools.util.logging.Log4JLogger")) {
            LOGGER.severe("Log4JLogger expected, but was:" + LOGGER.getClass().getName());
        }
        // Log4J Properties
        checkProperty("log4j.defaultInitOverride");
        checkProperty("log4j.configuratorClass");
        checkProperty("log4j.configuratorClass");

        if (System.getProperties().containsKey("log4j.configuration")) {
            LOGGER.config("log4j.configurationFile=" + System.getProperty("log4j.configuration"));
        }

        LOGGER.config("Configuration " + Log4JLoggerFactory.getInstance().lookupConfiguration());

        LOGGER.finest("Everything is finest...");
        LOGGER.finer("Everything is finer...");
        LOGGER.fine("Everything is fine...");
        LOGGER.config("Everything is configured...");
        LOGGER.log(Logging.OPERATION, "Everything is operating...");
        LOGGER.info("Everything is okay.");
        LOGGER.warning("Everything is alarming!");
        LOGGER.severe("Everything is terrible!");
        LOGGER.log(Logging.FATAL, "Everything has died!");
    }

    private static Logger initLogger() {
        GeoTools.init();
        return Logging.getLogger(Reload4JIntegration.class);
    }

    private static void checkProperty(String property) {
        if (System.getProperties().containsKey(property)) {
            LOGGER.config(property + "=" + System.getProperty(property));
        }
    }
}

  1. An exec:exec target is provided to make this easier to test:

    mvn exec:exec

    Note

    Avoid testing with exec:java which uses maven java runtime environment (already pre-configured for logging).