有个 maven 项目日志打印的问题请教下 v 友们

[fangcan]

项目里面使用了 mybatis

1. 当项目里面没有设置依赖 logback 和 slf4j 时, mybatis 相关的日志（比如 sql 等）没有打印出来，也没有报错。
2. 在 pom 里面设置依赖 logback 和 slf4j 后就能打印出 mybatis 的日志了

疑问点：

1. 为什么我自己的 pom 里面不配置日志相关依赖就不打印 mybatis 的日志但是也不报错？
2. 依赖包之间日志工具是怎么样的一个关系？不同的依赖包使用不同的日志工具会有怎样的影响？

》表达的不太好，有疑问可以评论下 感谢

附上 dependencies

<dependencies>
        <dependency>
            <groupId>cn.hutool</groupId>
            <artifactId>hutool-all</artifactId>
            <version>4.4.5</version>
        </dependency>
        <!-- jsoup Java HTML Parser Java 版的 Html 解析工具 https://jsoup.org/-->
        <dependency>
            <groupId>org.jsoup</groupId>
            <artifactId>jsoup</artifactId>
            <version>1.11.3</version>
        </dependency>
        <!-- Servlet -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.1.0</version>
            <scope>provided</scope>
        </dependency>

        <!--spring 相关-->
        <!-- https://mvnrepository.com/artifact/org.springframework/spring-context -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>4.3.18.RELEASE</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.springframework/spring-core -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>4.3.18.RELEASE</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.springframework/spring-beans -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-beans</artifactId>
            <version>4.3.18.RELEASE</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.springframework/spring-webmvc -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>4.3.18.RELEASE</version>
        </dependency>
        <!--数据库事务管理-->
        <!-- https://mvnrepository.com/artifact/org.springframework/spring-jdbc -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>4.3.18.RELEASE</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.springframework/spring-tx -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-tx</artifactId>
            <version>4.3.18.RELEASE</version>
        </dependency>


        <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis-spring -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis-spring</artifactId>
            <version>1.3.2</version>
        </dependency>

        <!--mybatis-->
        <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.6</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.38</version>
        </dependency>
        <dependency>
            <groupId>commons-dbcp</groupId>
            <artifactId>commons-dbcp</artifactId>
            <version>1.4</version>
        </dependency>

        <!-- springmvc rest api responseBody 需要使用 转换器使用-->
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-core</artifactId>
            <version>${jackson.version}</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>${jackson.version}</version>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.16.10</version>
            <scope>provided</scope>
        </dependency>

        <!-- log start -->
        <!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-api -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>1.7.26</version>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-core</artifactId>
            <version>${logback.version}</version>
        </dependency>
      <!--  <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-access</artifactId>
            <version>${logback.version}</version>
        </dependency>-->
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>${logback.version}</version>
        </dependency>

    </dependencies>

[arrow8899]

https://github.com/mybatis/mybatis-3/blob/master/src/main/java/org/apache/ibatis/logging/LogFactory.java
你看下代码就知道了，mybatis 写日志时会依次尝试 slf4j, commonslogging,log4j 等日志库，如果没有找到对应实现，就走 noLogging 的逻辑，不写日志。

[arrow8899]

一个项目内可以有多种写日志的实现，不会互相影响。

[fangcan]

@arrow8899 感谢 确实是有这个方法，不过没看明白，求指教下

[fangcan]

@arrow8899

[fangcan]

@arrow8899 下面是具体的方法，我看尝试的每个方法都是传入了 mybatis 的对于不同的 log 的实现，那不是第一个方法就能成立了么？
private static void setImplementation(Class<? extends Log> implClass) {
try {
Constructor<? extends Log> candidate = implClass.getConstructor(String.class);
Log log = candidate.newInstance(LogFactory.class.getName());
if (log.isDebugEnabled()) {
log.debug("Logging initialized using '" + implClass + "' adapter.");
}
logConstructor = candidate;
} catch (Throwable t) {
throw new LogException("Error setting Log implementation. Cause: " + t, t);
}
}