# Log4j2

參考資料:(<http://javabruce.blogspot.com/2016/03/log4j2.html>)

下載點:(<http://logging.apache.org/log4j/2.x/download.html>)

範例:

```
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
public class Log4j2Example {

    private static final Logger LOG = LogManager.getLogger(Log4j2Example.class.getName());
    public static void main(String[] args) {
        LOG.debug("This will be printed on debug");
        LOG.info("This will be printed on info");
        LOG.warn("This will be printed on warn");
        LOG.error("This will be printed on error");
        LOG.fatal("This will be printed on fatal");

        LOG.info("Appending string: {}.", "Hello, World");

    }

}
```

設定檔 log4j2.xml 放在classpath

```
<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">
    <Appenders>
        <Console name="Console" target="SYSTEM_OUT">
            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" />
        </Console>

    <File name="MyFile" fileName="D:/Brian/log.txt">
            <PatternLayout>
                <Pattern>%d %p %c{1.} [%t] %m%n</Pattern>
            </PatternLayout>
        </File>
    </Appenders>
    <Loggers>
        <Root level="error">
            <AppenderRef ref="Console" />
        <AppenderRef ref="MyFile" />
        </Root>
    </Loggers>
</Configuration>
```

File的屬性 fileName 設定路徑

Root 內要有配置 AppenderRef 的屬性 ref 要記錄log的名稱。


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://brianwu.gitbook.io/brian/java/log4j2.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.