java - 日志记录不显示

Question

我在我的应用程序中使用 JUL。通常，Netbeans 会打开一个输出选项卡，其中显示“Tomcat”并显示我生成的日志。一切正常。但突然，我意识到我的日志根本没有显示，只有 System.out 被打印。甚至连最高级的 LOG.log(Level.SEVERE, ".....

} catch(Exception e) {
      System.out.println("This gets printed in Netbeans tab");
      LOG.log(Level.SEVERE, "This doesnt");
}

我怀疑它可能是我包含的一个库，它扰乱了我的日志。这可能吗？库可以改变我的日志的显示方式吗？由于我有点迷失，我该如何调查这个问题？

Answer 1

I suspect it can be a library I included, which is messing with my logs. Is that possible at all?

是的。 JUL to SLF4J Bridge可以从 JUL 根记录器中删除控制台处理程序。某些库调用 LogManager.reset 可以删除并关闭所有处理程序。

Can a library change the way my logs are shown?

是的。一旦安装了日志桥，JUL 记录就不再由 JUL 格式化程序格式化。

How can I investigate this, since I am a bit lost?

修改记录器树需要权限，以便您可以安装 SecurityManager具有所有权限，但然后使用 -Djava.security.debug="access,stack" 打开调试跟踪确定正在修改记录器树的调用者。

如果这不起作用，您可以使用良好的 ole' System.out 在加载库之前和之后打印记录器树和附加的处理程序。然后开始添加删除库，直到看到记录器发生变化。

import java.io.File;
import java.io.IOException;
import java.io.PrintStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Enumeration;
import java.util.logging.Handler;
import java.util.logging.Level;
import java.util.logging.LogManager;
import java.util.logging.Logger;

public class DebugLogging {

    private static final Logger log = Logger.getLogger("test");

    public static void main(String[] a) {
        log.log(Level.FINEST, "Finest");
        log.log(Level.FINER, "FINER");
        log.log(Level.FINE, "FINE");
        log.log(Level.CONFIG, "CONFIG");
        log.log(Level.INFO, "INFO");
        log.log(Level.WARNING, "WARNING");
        log.log(Level.SEVERE, "SEVERE");
        log.finest("Finest Log");
        log.finer("Finer Log");
        log.fine("Fine Log");
        log.config("Config Log");
        log.info("Info Log");
        log.warning("Warning Log");
        log.severe("Severe Log");
        printConfig(System.err);
    }

    private static void printConfig(PrintStream ps) {
        String cname = System.getProperty("java.util.logging.config.class");
        if (cname != null) {
            try {
                ClassLoader sys = ClassLoader.getSystemClassLoader();
                Class<?> c = Class.forName(cname, false, sys);
                ps.println(sys.getClass().getName() +" found log configuration class " + c.getName());
            } catch (LinkageError | ClassNotFoundException | RuntimeException cnfe) {
                ps.println("Unable to load " + cname);
                cnfe.printStackTrace(ps);
            }
        } else {
            ps.println("java.util.logging.config.class was null");
        }
        
        String file = System.getProperty("java.util.logging.config.file");
        if (file != null) {
           ps.println("java.util.logging.config.file=" + file);
           try {
               ps.println("CanonicalPath=" + new File(file).getCanonicalPath());
           } catch (RuntimeException | IOException ioe) {
               ps.println("Unable to resolve path for " + file);
               ioe.printStackTrace(ps);
           }

           try {
               Path p = Paths.get(file);
               if (Files.isReadable(p)) {
                   ps.println(file + " is readable and has size " + Files.size(p));
               } else {
                   if (Files.exists(p)) {
                       ps.println(file + " exists for " + System.getProperty("user.name") + " but is not readable.");
                   } else {
                       ps.println(file + " doesn't exist for " + System.getProperty("user.name"));
                   }
               }
           } catch (RuntimeException | IOException ioe) {
               ps.println("Unable to read " + file);
               ioe.printStackTrace(ps);
           }
        } else {
            ps.println("java.util.logging.config.file was null");
        }

        LogManager lm = LogManager.getLogManager();
        ps.append("LogManager=").println(lm.getClass().getName());
        synchronized (lm) {
            Enumeration<String> e = lm.getLoggerNames();
            while (e.hasMoreElements()) {
                Logger l = lm.getLogger(e.nextElement());
                if (l != null) {
                    print(l, ps);
                }
            }
        }
    }

    private static void print(Logger l, PrintStream ps) {
        String scn = l.getClass().getSimpleName();
        ps.append("scn=").append(scn).append(", n=").append(l.getName())
                .append(", uph=").append(String.valueOf(l.getUseParentHandlers()))
                .append(", l=").append(String.valueOf(l.getLevel()))
                .append(", fl=").println(l.getFilter());
        for (Handler h : l.getHandlers()) {
            ps.append("\t").append(l.getName()).append("->")
                    .append(h.getClass().getName()).append(", h=")
                    .append(String.valueOf(h.getLevel())).append(", fl=")
                    .append(String.valueOf(h.getFilter())).println();
        }
    }
}