要么是通过系统属性

-Dorg.slf4j.simpleLogger.defaultLogLevel=debug

或simplelogger。属性文件

详情见https://www.slf4j.org/api/org/slf4j/simple/SimpleLogger.html

你可以通过设置system属性来改变它:

public class App {
  public static void main(String[] args) {
    // for the code below to work, it must be executed before the
    ​// logger is created. see note below
    System.setProperty(org.slf4j.impl.SimpleLogger.DEFAULT_LOG_LEVEL_KEY, "TRACE");
       
    ​org.slf4j.Logger log = LoggerFactory.getLogger(App.class);
       ​
    ​log.trace("trace");
    ​log.debug("debug");
    ​log.info("info");
    ​log.warn("warning");
    ​log.error("error");
  ​}
​}

日志级别为ERROR > WARN > INFO > DEBUG > TRACE。

请注意，一旦创建了日志记录器，日志级别就不能更改。如果您需要动态地更改日志级别，那么您可能希望将log4j与SLF4J结合使用。

这是一个简单日志记录器的示例。你可以放在类路径上的属性(取消注释你想使用的属性):

# SLF4J's SimpleLogger configuration file
# Simple implementation of Logger that sends all enabled log messages, for all defined loggers, to System.err.

# Default logging detail level for all instances of SimpleLogger.
# Must be one of ("trace", "debug", "info", "warn", or "error").
# If not specified, defaults to "info".
#org.slf4j.simpleLogger.defaultLogLevel=info

# Logging detail level for a SimpleLogger instance named "xxxxx".
# Must be one of ("trace", "debug", "info", "warn", or "error").
# If not specified, the default logging detail level is used.
#org.slf4j.simpleLogger.log.xxxxx=

# Set to true if you want the current date and time to be included in output messages.
# Default is false, and will output the number of milliseconds elapsed since startup.
#org.slf4j.simpleLogger.showDateTime=false

# The date and time format to be used in the output messages.
# The pattern describing the date and time format is the same that is used in java.text.SimpleDateFormat.
# If the format is not specified or is invalid, the default format is used.
# The default format is yyyy-MM-dd HH:mm:ss:SSS Z.
#org.slf4j.simpleLogger.dateTimeFormat=yyyy-MM-dd HH:mm:ss:SSS Z

# Set to true if you want to output the current thread name.
# Defaults to true.
#org.slf4j.simpleLogger.showThreadName=true

# Set to true if you want the Logger instance name to be included in output messages.
# Defaults to true.
#org.slf4j.simpleLogger.showLogName=true

# Set to true if you want the last component of the name to be included in output messages.
# Defaults to false.
#org.slf4j.simpleLogger.showShortLogName=false

在Maven或Gradle项目中，“类路径”上的一个方便位置是src/main/resources/simplelogger.properties。

我注意到Eemuli说在创建日志级别后不能更改它们——虽然这可能是设计，但并不完全正确。

我遇到了这样一种情况:我正在使用一个登录到slf4j的库——而且我在写maven mojo插件时正在使用这个库。

Maven使用slf4j SimpleLogger的(黑客)版本，我无法让我的插件代码将其日志重新路由到像log4j这样的东西，这是我可以控制的。

而且我不能更改maven日志记录配置。

因此，为了使一些嘈杂的信息消息安静下来，我发现我可以使用这样的反射，在运行时使用SimpleLogger。

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.slf4j.spi.LocationAwareLogger;
    try
    {
        Logger l = LoggerFactory.getLogger("full.classname.of.noisy.logger");  //This is actually a MavenSimpleLogger, but due to various classloader issues, can't work with the directly.
        Field f = l.getClass().getSuperclass().getDeclaredField("currentLogLevel");
        f.setAccessible(true);
        f.set(l, LocationAwareLogger.WARN_INT);
    }
    catch (Exception e)
    {
        getLog().warn("Failed to reset the log level of " + loggerName + ", it will continue being noisy.", e);
    }

当然，请注意，这不是一个非常稳定/可靠的解决方案……因为它将在下一次maven人员更改记录器时崩溃。

我不知道为什么。我使用simplelogger。属性和org.slf4j.simpleLogger。showDatetime，它不起作用。

我查找了SimpleLogger类源代码，得到了这部分代码

static {
      // Add props from the resource simplelogger.properties
      InputStream in = (InputStream)AccessController.doPrivileged(
              new PrivilegedAction() {
                  public Object run() {
                      ClassLoader threadCL = Thread.currentThread().getContextClassLoader();
                      if (threadCL != null) {
                          return threadCL.getResourceAsStream(CONFIGURATION_FILE);
                      } else {
                          return ClassLoader.getSystemResourceAsStream(CONFIGURATION_FILE);
                      }
                  }
              });
      if(null != in) {
          try {
              simpleLoggerProps.load(in);
              in.close();
          } catch(java.io.IOException e) {
              // ignored
          }
      }

      showLogName    = getBooleanProperty(systemPrefix + "showlogname",      showLogName);
      showShortName  = getBooleanProperty(systemPrefix + "showShortLogname", showShortName);
      showDateTime   = getBooleanProperty(systemPrefix + "showdatetime",     showDateTime);
      showThreadName = getBooleanProperty(systemPrefix + "showthreadname",   showThreadName);
      dateTimeFormat = getStringProperty(systemPrefix + "dateTimeFormat",    dateTimeFormat);

      if(showDateTime) {
          try {
              dateFormatter = new SimpleDateFormat(dateTimeFormat);
          } catch(IllegalArgumentException e) {
              Util.report("Bad date format in " + CONFIGURATION_FILE + "; reverting to default", e);
              // If the format pattern is invalid - use the default format
              dateTimeFormat = DEFAULT_DATE_TIME_FORMAT;
              dateFormatter = new SimpleDateFormat(dateTimeFormat);
          }
      }
  }

systemPrefix +“showdatetime”是org.slf4j.simplelogger.showdatetime 当我尝试编写org.slf4j.simplelogger时。Showdatetime =true对于simplelogger。属性，工作正常。我希望它能帮助一些人。