避免字符串連接以獲取大型日誌消息

Question

使用類似slf4j的優點之一是避免使用參數化日誌記錄進行字符串連接。但是，如果您有很長的日誌消息 ，您如何避免性能下降？

logger.debug("This is a very long message that prints two values." + 
    " However since the message is long, we still incur the performance hit" + 
    " of String concatenation when logging {} and {} ", value1, value2); 

是否有任何方法可以避免這種性能成本，而不使用難看的if塊來檢查日誌級別？

if (logger.isDebugEnabled()) { 
    logger.debug("This is a very long message that prints two values." + 
     " However since the message is long, we still incur the performance hit" + 
     " of String concatenation when logging {} and {}", value1, value2); 
} 

Answer 1

沒有字符串連接。

編譯器將爲您創建一個長的字符串文字。