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报错详情

在使用GitHub的配套服务Travis-CI构建java项目，出现了问题；主要是含有lambda表达式的java8通不过，之前虽然jdk也是按照jdk8进行配置，但是这次在程序中使用了java8的新特性lambda表达式，所以导致构建失败了。网上找了好久，好像没有找到类似的文章，于是只能硬着头皮去看报错了。

以下是我的.travis.yml:

language: java
sudo: false
jdk:- openjdk8# codecov
script: "mvn cobertura:cobertura"after_success:- bash <(curl -s https://codecov.io/bash)

主要错误如下：（具体可见:https://travis-ci.org/yansheng836/GLPL/builds/596478583）

# 错误1
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project GLPL: Compilation failure
[ERROR] /home/travis/build/yansheng836/GLPL/src/main/java/xyz/yansheng/util/SpiderUtil.java:[118,51] lambda expressions are not supported in -source 1.5
[ERROR]   (use -source 8 or higher to enable lambda expressions)
[ERROR] -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException
The command "eval mvn install -DskipTests=true -Dmaven.javadoc.skip=true -B -V " failed. Retrying, 2 of 3# 错误2
Apache Maven 3.6.0 (97c98ec64a1fdfee7767ce5ffb20918da4f719f3; 2018-10-24T18:41:47Z)
Maven home: /usr/local/maven-3.6.0
Java version: 1.8.0_222, vendor: Private Build, runtime: /usr/lib/jvm/java-8-openjdk-amd64/jre
Default locale: en_US, platform encoding: UTF-8
OS name: "linux", version: "4.15.0-1037-gcp", arch: "amd64", family: "unix"
[INFO] Scanning for projects...
[INFO] 
[INFO] -------------------------< xyz.yansheng:GLPL >--------------------------
[INFO] Building GLPL 0.0.3-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] 
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ GLPL ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory /home/travis/build/yansheng836/GLPL/src/main/resources
[INFO] 
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ GLPL ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 5 source files to /home/travis/build/yansheng836/GLPL/target/classes
[INFO] -------------------------------------------------------------
[ERROR] COMPILATION ERROR : 
[INFO] -------------------------------------------------------------
[ERROR] /home/travis/build/yansheng836/GLPL/src/main/java/xyz/yansheng/util/SpiderUtil.java:[118,51] lambda expressions are not supported in -source 1.5(use -source 8 or higher to enable lambda expressions)
[INFO] 1 error
[INFO] -------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.646 s
[INFO] Finished at: 2019-10-11T07:05:21Z
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project GLPL: Compilation failure
[ERROR] /home/travis/build/yansheng836/GLPL/src/main/java/xyz/yansheng/util/SpiderUtil.java:[118,51] lambda expressions are not supported in -source 1.5
[ERROR]   (use -source 8 or higher to enable lambda expressions)
[ERROR] -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException
The command "eval mvn install -DskipTests=true -Dmaven.javadoc.skip=true -B -V " failed. Retrying, 3 of 3.# 最后面的错误汇总
The command "eval mvn install -DskipTests=true -Dmaven.javadoc.skip=true -B -V " failed 3 times.
The command "mvn install -DskipTests=true -Dmaven.javadoc.skip=true -B -V" failed and exited with 1 during .

分析

按照提示访问了 ：http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException，但是没有找到相关内容。

查看错误语句Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project GLPL: Compilation failure，感觉是这个插件的版本有问题，好像只能处理1.5版本，提示版本低了，不能处理lambda expressions。

于是与中央仓库查了下：https://mvnrepository.com/artifact/org.apache.maven.plugins/maven-compiler-plugin，发现3.1版本好像是2013年4月发布的，而jdk1.8是在2014年3月19日发布的，所以该版本不能处理java8的lambda expressions。

既然找到问题所在，那么离解决就跟进一步了。

解决方法

1.尝试

因为之前对 Travis-CI 了解得也不是很多，所以就算是我找到的问题的缘由，还是不太懂该怎么修改才能构建成功。

后面琢磨了一番，在pom.xml中添加了最新的依赖，而不是使用默认的设置：

<dependencies><!-- https://mvnrepository.com/artifact/org.apache.maven.plugins/maven-compiler-plugin --><dependency><groupId>org.apache.maven.plugins</groupId><artifactId>maven-compiler-plugin</artifactId><version>3.8.1</version></dependency>
</dependencies>

不过不知道是不是因为没有用或者是其他原因（Travis-CI是外网，可能有提交时没有实时构建），反正就是没有成功。

提示：GitHub开启Travis-CI服务后，它检测到有新的提交会自动构建。但是可能会有延迟，建议查看下提交的hash1是否是最新的，如果不是，先刷新，然后手动构建（如下图所示）：

2.解决

后来看到这篇文章：maven如何指定项目的jdk版本(使用maven-compiler-plugin)，感觉这是个方向，于是进行尝试：将该包作为构建插件，而不是依赖包：

<project>
……<build><plugins>……<!-- https://mvnrepository.com/artifact/org.apache.maven.plugins/maven-compiler-plugin --><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-compiler-plugin</artifactId><version>3.8.1</version><configuration><source>1.8</source><target>1.8</target></configuration></plugin></plugins></build>
</project>

提交、构建成功！