java - JUL 日志记录 - 消息上的实例前缀

Question

我希望我的记录器在每条消息上添加一个文本字符串前缀，因为我需要确定类的哪个实例记录了该消息。我怎样才能做到这一点？

我不想记住在每个日志记录方法调用上添加前缀，所以我正在寻找一个更像是直接插入的解决方案。当然，记录器本身不能再像正常情况那样是静态的。

我研究了 Fomatter 和 Handler 的使用，但无法解决这个特定用例的问题。 JUL 几乎是为类级记录器设计的，而不是实例级记录器。也许我的处理方式是错误的？

想留在 JUL。

Answer 1

I've investigated use of Fomatters and Handlers but haven't been able to crack the nut for this particular use case. JUL is pretty much designed for class-level loggers, not instance-level loggers. Perhaps I'm going about this the wrong way?

JUL 中仅包含两个格式化程序。 XMLFormatter包括记录器名称。 SimpleFormatter包括可设置为包含记录器名称的格式属性。这是一个测试程序，可确保您已正确设置所有内容。

import java.util.logging.Level;
import java.util.logging.LogManager;
import java.util.logging.LogRecord;


public class SimpleFormatTest {

    public static void main(String[] args) throws Exception {
        //final String format = "%1$ta %1$tb %1$td, %1$tY %1$tl:%1$tM:%1$tS.%1$tL %1$Tp %2$s%n%4$s: %5$s%n";
        final String format = "%1$tc %2$s%n%3$s %4$s: %5$s%6$s%n";
        final String key = "java.util.logging.SimpleFormatter.format";
        test(format);
        test(System.getProperty(key, format));
        test(LogManager.getLogManager().getProperty(key));
    }

    private static void test(String format) {
        if (format != null) {
            System.out.println("============");
            LogRecord record = new LogRecord(Level.INFO, "msg");
            record.setLoggerName("logger.name");
            record.setSourceClassName(SimpleFormatTest.class.getName());
            record.setSourceMethodName("test");
            System.out.println(String.format(format,
                    new java.util.Date(record.getMillis()),
                    record.getSourceClassName(),
                    record.getLoggerName(),
                    record.getLevel().getLocalizedName(),
                    record.getMessage(),
                    record.getThrown() == null ? "" : record.getThrown()));
            System.out.println("============");
        }
    }
}

But I was looking for a solution that would include the prefix in message text. I cannot know what Formatter the user would want to use and he may choose to not log the logger name (in contrast nobody will ever create a Formatter which omits the message text).

在您的应用程序中包含一个logging.properties。您可以添加一个前提条件检查，使您的代码根本无法工作。这将强制用户设置配置。

 public class NoStart {
    public static void main(String[] args) throws IOException {
        String id = "logger.name";
        LogRecord record = new LogRecord(Level.INFO, "msg");
        record.setLoggerName(id);
        File f = File.createTempFile("test", ".tmp");
        try {
            FileHandler fh = new FileHandler(f.getCanonicalPath(), false);
            try {
                Formatter fmt = fh.getFormatter();
                String r = fmt.format(record);
                if (!r.contains(id)) {
                    throw new IllegalStateException("Formatter must contain logger name.");
                }
            } finally {
                fh.close();
            }
        } finally {
            f.delete();
        }
    }
}

否则，您可以创建自定义过滤器来修改 LogRecord 消息。

public class PrefixMessageFilter implements Filter {

    private final String instanceId;
    private final Filter target;

    public PrefixMessageFilter(final String instanceId, final Filter target) {
        this.instanceId = instanceId;
        this.target = target;
    }

    @Override
    public boolean isLoggable(LogRecord record) {
        record.setMessage(instanceId + ' ' + record.getMessage());
        return target == null || target.isLoggable(record);
    }

    //Example code to setup filter.
    private Logger logger = Logger.getLogger(toString());
    {
        logger.setFilter(new PrefixMessageFilter(toString(), logger.getFilter()));
    }
}

您只需在首次使用时修改记录器即可。