Log4j2：以编程方式在文件名中创建带有时间戳的文件追加器

Question

There is a possibility to create to add a timestamp to log4j2 logging files using [property] configuration:

appender.FILE.type = FILE
appender.FILE.name = FILE
appender.FILE.fileName = file-with-date-${date:yyyy-MM-dd}.log
appender.FILE.layout.type = PatternLayout
appender.FILE.layout.pattern =[%p] %m%n

This will produce log files in the file-with-date-2017-11-30.log . How can I achieve the same behavior using programmatic configuration? This is what I have tried so far:

PatternLayout layout = PatternLayout.newBuilder()
            .withConfiguration(ctx.getConfiguration())
            .withPattern("%m%n").build();

FileAppender fileAppender = FileAppender.newBuilder()
        .withLayout(layout)
        .withFileName( "file-with-date-${date:yyyy-MM-dd}.log")
        .withName("pattern")
        .build();

But this produces the following file: file-with-date-${date:yyyy-MM-dd}.log . So using properties configuration: a log file with current date is crated, using programmatically created appender ${date:yyyy-MM-dd}.log gets ignored.

Answer 1

Apparently StrSubstitutor can help in this situation.

final LoggerContext ctx = (LoggerContext) LogManager.getContext(false);
final Configuration config = ctx.getConfiguration();
String fileName = config.
              getStrSubstitutor().replace("file-with-date-${date:yyyy-MM-dd}.log");

FileAppender fileAppender = FileAppender.newBuilder()
        .withLayout(layout)
        .withFileName(filename)
        .withName("pattern")
        .build();