Logback教程：创建maven工程，打印到控制台，输出到文件中-马育民老师

# 创建普通maven工程

略

# 修改pom.xml

添加下面依赖：

```
<dependencies>
    <dependency>
        <groupId>ch.qos.logback</groupId>
        <artifactId>logback-classic</artifactId>
        <version>1.2.3</version>
    </dependency>
</dependencies>
```

# logback.xml 配置文件

在 `resources` 文件夹下创建 `logback.xml` 文件，内容如下：

```
<?xml version="1.0" encoding="UTF-8"?>

<configuration scan="true">

<property name="log-dir" value="log" />
	<property name="log-name" value="logFile" />

<appender name="consoleAppender"
		class="ch.qos.logback.core.ConsoleAppender">
		<encoder>
			<pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36}:%L- %msg%n</pattern>
			
			<charset class="java.nio.charset.Charset">UTF-8</charset>
		</encoder>
	</appender>

<appender name="fileAppender"
		class="ch.qos.logback.core.rolling.RollingFileAppender">
		
		
		<file>${log-dir}/${log-name}.log</file>
		
		
		<rollingPolicy
			class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
			
			
			<fileNamePattern>${log-dir}/${log-name}.%d{yyyy-MM-dd}.%i.log</fileNamePattern>
			
			<MaxHistory>
				7
			</MaxHistory>
			
			<timeBasedFileNamingAndTriggeringPolicy
				class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
				<maxFileSize>5MB</maxFileSize>
			</timeBasedFileNamingAndTriggeringPolicy>
		</rollingPolicy>
		<encoder>
			
			<pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36}:%L- %msg%n</pattern>
			
			<charset class="java.nio.charset.Charset">UTF-8</charset>
		</encoder>
	</appender>

<root level="info">
		<appender-ref ref="consoleAppender"  />
		<appender-ref ref="fileAppender" />
	</root>
</configuration>
```

**重点：**

- `<root level="info">` 定义的日志级别是 `info`，大于等于该级别的打印日志，才会执行

- `<logger name="top.malaoshi.mapper" level="debug" />` 包下的日志级别是 `debug` ，不受`<root level="info">` 的控制

配置详见：
https://www.cnblogs.com/ryelqy/p/10314147.html

# 测试类

### Mapper

```
package top.malaoshi.mapper;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class Mapper {

static final Logger log= LoggerFactory.getLogger(Mapper.class);

public static void test(){
        String content="测试：abc 123 中文";
        log.trace("trace级别:: {}-{}",content);
        log.debug("debug级别:: {}-{}",content);
        log.info("info级别:: {}-{}",content);
        log.warn("warn级别:: {}-{}",content);
        log.error("error级别:: {}-{}",content);
    }
}
```

### 主启动类
```
package top.malaoshi;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import top.malaoshi.mapper.Mapper;

public class Main {
    static final Logger log= LoggerFactory.getLogger(Main.class);

public static void main(String[] args) {
        String content="hello world!--测试中文";
        log.trace("trace级别:: {}-{}",content);
        log.debug("debug级别:: {}-{}",content);
        log.info("info级别:: {}-{}",content);
        log.warn("warn级别:: {}-{}",content);
        log.error("error级别:: {}-{}",content);

Mapper.test();
    }
}
```

显示结果：

```
16:25:28.281 [main] INFO  top.malaoshi.Main:14- info级别:: hello world!
16:25:28.284 [main] WARN  top.malaoshi.Main:15- warn级别:: hello world!
16:25:28.284 [main] ERROR top.malaoshi.Main:16- error级别:: hello world!
16:25:05.565 [main] DEBUG top.malaoshi.mapper.Mapper:13- debug级别:: abc123
16:25:05.566 [main] INFO  top.malaoshi.mapper.Mapper:14- info级别:: abc123
16:25:05.566 [main] WARN  top.malaoshi.mapper.Mapper:15- warn级别:: abc123
16:25:05.566 [main] ERROR top.malaoshi.mapper.Mapper:16- error级别:: abc123
```

### 为什么显示下面3行？

原因：由于在配置文件中设置了：

```
<root level="info">
    <appender-ref ref="consoleAppender"  />
    <appender-ref ref="fileAppender" />
</root>
```

所以，只有 `日志打印级别 >= info`，才会显示到控制台，写入到文件中

### 为什么显示下面4行？

下面显示了 `debug` 级别的日志，不符合 `日志打印级别 >= info`

```
16:25:05.565 [main] DEBUG top.malaoshi.mapper.Mapper:13- debug级别:: abc123
16:25:05.566 [main] INFO  top.malaoshi.mapper.Mapper:14- info级别:: abc123
16:25:05.566 [main] WARN  top.malaoshi.mapper.Mapper:15- warn级别:: abc123
16:25:05.566 [main] ERROR top.malaoshi.mapper.Mapper:16- error级别:: abc123
```

原因：由于在配置文件中设置了：

```
<logger name="top.malaoshi.mapper" level="debug" />
```

所以，`top.malaoshi.mapper` 包及其子包的有效级别是`debug`，也就是说 `日志打印级别 >= debug`，就会显示到控制台，写入到文件中

**即：不受下面配置的控制：**

```
<root level="info">
    <appender-ref ref="consoleAppender"  />
    <appender-ref ref="fileAppender" />
</root>
```

原文出处：http://malaoshi.top/show_1IXStZM0rZW.html