Java 记录器 - 标记的撇号问题

Question

我对 java.util.logging 有一些无法解释的行为。让我们看一下这两个示例:

首先:

boolean var = false;
log.log( Level.WARNING, "Cant {0}", new Object[] { var } );

输出:

Cant false

---

第二个:

boolean var = false;
log.log( Level.WARNING, "Can't {0}", new Object[] { var } );

输出:

Can't {0}

为什么包含撇号 (') 会导致记录器不扩展 token ？

Answer 1

看来无论您使用何种日志记录机制，都在内部使用 MessageFormat 类。如果是这样，那么您需要转义撇号字符，因为它是一个单引号字符。单引号字符用于引用不需要解释的文本。

MessageFormat javadocs :

Within a String, a pair of single quotes can be used to quote any arbitrary characters except single quotes. For example, pattern string "'{0}'" represents string "{0}", not a FormatElement. A single quote itself must be represented by doubled single quotes '' throughout a String.

(强调我的)

尝试

log.log( Level.WARNING, "Can''t {0}", new Object[] { var } );

这段代码:

MessageFormat mf = new MessageFormat("Can''t {0}");
System.out.println(mf.format(new Object[] {false}));

产生这个输出:

Can't false