Logging

Logging support

Struts logs through Log4j2. The struts2-core artifact declares log4j-api and log4j-core, and configuration is plain Log4j2 configuration — a log4j2.xml on the classpath, typically under src/main/resources. See Debugging Struts for an example configuration and the framework packages worth raising to DEBUG.

The pluggable logging layer that XWork used to provide — com.opensymphony.xwork2.util.logging.LoggerFactory, the xwork.loggerFactory system property and the Commons Logging / SLF4J / JDK Logger delegates — was deprecated in Struts 2.5 and removed in Struts 6.0.0. There is no framework-level logging abstraction to configure any more, and setting -Dxwork.loggerFactory has no effect.

The Log4j2 bridges for third-party libraries (log4j-jcl for Commons Logging, log4j-slf4j-impl for SLF4J) are a separate concern and remain available. They route logging emitted by transitive dependencies into Log4j2.

Struts 7.3.0 finished the job: the last java.util.logging and SLF4J call sites inside the framework — in the dependency-injection container, its finalizable reference queue and the Tiles plugin’s Velocity renderable — now log through Log4j2, and the slf4j-api dependency was dropped from struts2-core, see WW-5620. That dependency was declared optional, so it was never propagated to applications and nothing changes on your classpath. Struts 6.11.0 still declares it.

Removed in Struts 7.3.0: the internal DI container no longer provides a Logger binding. @Inject-ing a java.util.logging.Logger into a container-managed bean used to yield a JUL logger named after the declaring class; that binding was removed along with the JUL usage, so such an injection no longer resolves. Declare a Log4j2 logger directly instead, as shown below.

Usage

Declare a Log4j2 logger in your own classes as usual:

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

public class MyAction {

    private static final Logger LOG = LogManager.getLogger(MyAction.class);

    private String userName;

    public String execute() {
        LOG.debug("MyAction executed with UserName [{}]", userName);
        return "success";
    }

    // getter / setter

}

Note the {} placeholder — Log4j2 parameterised messages, not the #0 syntax used by the removed XWork logger.

Routing Struts logging elsewhere

Because Struts logs against the Log4j2 API rather than its own abstraction, redirecting its output is a Log4j2 concern: either configure Log4j2 appenders as you need them, or put a bridge to your logging backend of choice on the classpath in place of log4j-core. Nothing needs to be declared in struts.xml.