1. 問題描述

使用maven可以非常方便的管理我們專案的各種依賴，但是也存在著一些問題。當我們在pom.xml檔案中引入新的jar包，那麼該jar包依賴的其它jar包也會自動被下載。如果這些自動下載的jar包和專案中已存在的jar包版本不一致，那麼就會造成jar包版本的衝突。

2. 解決方法

我們可以使用mvn命令來排查專案中存在版本衝突的jar包。

• 首先，在命令列跳轉到當前專案路徑（如果使用Idea等工具，可以直接在終端Terminal中執行mvn命令），為了便於查詢我們可以把依賴關係寫入一個臨時文字檔案tree.txt。

      mvn dependency:tree -Dverbose > tree.txt
 

• 然後，開啟生成的tree.txt檔案，全域性搜尋"conflict"關鍵字，即可找到版本衝突的jar包。

[INFO] +- io.springfox:springfox-swagger2:jar:2.6.1:compile
[INFO] |  +- io.swagger:swagger-annotations:jar:1.5.10:compile
[INFO] |  +- io.swagger:swagger-models:jar:1.5.10:compile
[INFO] |  |  +- com.fasterxml.jackson.core:jackson-annotations:jar:2.8.1:compile (version managed from 2.4.5)
[INFO] |  |  +- (org.slf4j:slf4j-api:jar:1.7.21:compile - version managed from 1.7.10; omitted for duplicate)
[INFO] |  |  \- (io.swagger:swagger-annotations:jar:1.5.10:compile - omitted for duplicate)
[INFO] |  +- io.springfox:springfox-spi:jar:2.6.1:compile
[INFO] |  |  \- io.springfox:springfox-core:jar:2.6.1:compile
[INFO] |  |     +- (com.google.guava:guava:jar:18.0:compile - omitted for duplicate)
[INFO] |  |     +- (com.fasterxml:classmate:jar:1.3.1:compile - omitted for duplicate)
[INFO] |  |     +- (org.slf4j:slf4j-api:jar:1.7.21:compile - version managed from 1.6.3; omitted for duplicate)
[INFO] |  |     +- (org.springframework.plugin:spring-plugin-core:jar:1.2.0.RELEASE:compile - omitted for duplicate)
[INFO] |  |     \- (org.springframework.plugin:spring-plugin-metadata:jar:1.2.0.RELEASE:compile - omitted for duplicate)
[INFO] |  +- io.springfox:springfox-schema:jar:2.6.1:compile
[INFO] |  |  +- (io.springfox:springfox-core:jar:2.6.1:compile - omitted for duplicate)
[INFO] |  |  \- (io.springfox:springfox-spi:jar:2.6.1:compile - omitted for duplicate)
[INFO] |  +- io.springfox:springfox-swagger-common:jar:2.6.1:compile
[INFO] |  |  +- (io.swagger:swagger-annotations:jar:1.5.10:compile - omitted for duplicate)
[INFO] |  |  +- (io.swagger:swagger-models:jar:1.5.10:compile - omitted for duplicate)
[INFO] |  |  +- (io.springfox:springfox-spi:jar:2.6.1:compile - omitted for duplicate)
[INFO] |  |  +- (io.springfox:springfox-schema:jar:2.6.1:compile - omitted for duplicate)
[INFO] |  |  +- (io.springfox:springfox-spring-web:jar:2.6.1:compile - omitted for duplicate)
[INFO] |  |  +- (com.google.guava:guava:jar:18.0:compile - omitted for duplicate)
[INFO] |  |  +- (com.fasterxml:classmate:jar:1.3.1:compile - omitted for duplicate)
[INFO] |  |  +- (org.slf4j:slf4j-api:jar:1.7.21:compile - version managed from 1.7.10; omitted for duplicate)
[INFO] |  |  +- (org.springframework.plugin:spring-plugin-core:jar:1.2.0.RELEASE:compile - omitted for duplicate)
[INFO] |  |  \- (org.springframework.plugin:spring-plugin-metadata:jar:1.2.0.RELEASE:compile - omitted for duplicate)
[INFO] |  +- io.springfox:springfox-spring-web:jar:2.6.1:compile
[INFO] |  |  +- (com.google.guava:guava:jar:18.0:compile - omitted for duplicate)
[INFO] |  |  +- (com.fasterxml:classmate:jar:1.3.1:compile - omitted for duplicate)
[INFO] |  |  +- (org.slf4j:slf4j-api:jar:1.7.21:compile - version managed from 1.7.10; omitted for duplicate)
[INFO] |  |  +- (org.springframework.plugin:spring-plugin-core:jar:1.2.0.RELEASE:compile - omitted for duplicate)
[INFO] |  |  +- (org.springframework.plugin:spring-plugin-metadata:jar:1.2.0.RELEASE:compile - omitted for duplicate)
[INFO] |  |  \- (io.springfox:springfox-spi:jar:2.6.1:compile - omitted for duplicate)
[INFO] |  +- (com.google.guava:guava:jar:18.0:compile - omitted for ---<conflict 關鍵字>--- with 15.0)
[INFO] |  +- com.fasterxml:classmate:jar:1.3.1:compile
[INFO] |  +- org.slf4j:slf4j-api:jar:1.7.21:compile