2018-12-14

多绑定

Multiple bindings were found on the class path

SLF4J API is designed to bind with one and only one underlying logging framework at a time. If more than one binding is present on the class path, SLF4J will emit a warning, listing the location of those bindings.

When multiple bindings are available on the class path, select one and only one binding you wish to use, and remove the other bindings. For example, if you have both slf4j-simple-1.8.0-beta2.jar and slf4j-nop-1.8.0-beta2.jar on the class path and you wish to use the nop (no-operation) binding, then remove slf4j-simple-1.8.0-beta2.jar from the class path. 

The list of locations that SLF4J provides in this warning usually provides sufficient information to identify the dependency transitively pulling in an unwanted SLF4J binding into your project. In your project's pom.xml file, exclude this SLF4J binding when declaring the unscrupulous dependency. For example, cassandra-all version 0.8.1 declares both log4j and slf4j-log4j12 as compile-time dependencies. Thus, when you include cassandra-all as a dependency in your project, the cassandra-all declaration will cause both slf4j-log4j12.jar and log4j.jar to be pulled in as dependencies. In case you do not wish to use log4j as the the SLF4J backend, you can instruct Maven to exclude these two artifacts as shown next:

<dependencies><dependency><groupId> org.apache.cassandra</groupId><artifactId>cassandra-all</artifactId><version>0.8.1</version>

<exclusions><exclusion><groupId>org.slf4j</groupId><artifactId>slf4j-log4j12</artifactId></exclusion><exclusion><groupId>log4j</groupId><artifactId>log4j</artifactId></exclusion></exclusions>

</dependency></dependencies>