主要出错信息：
> Could not resolve all artifacts for configuration ‘:classpath‘.
> Could not resolve com.cinnober.gradle:semver-git:2.2.3.
Required by:
project :
> Could not resolve com.cinnober.gradle:semver-git:2.2.3.
> Could not get resource ‘https://plugins.gradle.org/m2/com/cinnober/gradle/semver-git/2.2.3/semver-git-2.2.3.pom‘.
> Could not GET ‘https://plugins.gradle.org/m2/com/cinnober/gradle/semver-git/2.2.3/semver-git-2.2.3.pom‘.
> sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
> Could not resolve com.cinnober.gradle:semver-git:2.2.3.
> Could not get resource ‘https://repo.maven.apache.org/maven2/com/cinnober/gradle/semver-git/2.2.3/semver-git-2.2.3.pom‘.
> Could not GET ‘https://repo.maven.apache.org/maven2/com/cinnober/gradle/semver-git/2.2.3/semver-git-2.2.3.pom‘.
> sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
> Could not resolve com.cinnober.gradle:semver-git:2.2.3.
> Could not get resource ‘https://plugins.gradle.org/m2/com/cinnober/gradle/semver-git/2.2.3/semver-git-2.2.3.pom‘.
> Could not GET ‘https://plugins.gradle.org/m2/com/cinnober/gradle/semver-git/2.2.3/semver-git-2.2.3.pom‘.
> sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
> Could not resolve org.apache.httpcomponents:httpmime:4.3.
Required by:
project : > com.github.kt3k.coveralls:com.github.kt3k.coveralls.gradle.plugin:2.6.3 > org.kt3k.gradle.plugin:coveralls-gradle-plugin:2.6.3
> Could not resolve org.apache.httpcomponents:httpmime:4.3.
> Could not get resource ‘https://plugins.gradle.org/m2/org/apache/httpcomponents/httpmime/4.3/httpmime-4.3.pom‘.
> Could not GET ‘https://plugins.gradle.org/m2/org/apache/httpcomponents/httpmime/4.3/httpmime-4.3.pom‘.
> sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
> Could not resolve org.apache.httpcomponents:httpmime:4.3.
> Could not get resource ‘https://repo.maven.apache.org/maven2/org/apache/httpcomponents/httpmime/4.3/httpmime-4.3.pom‘.
> Could not GET ‘https://repo.maven.apache.org/maven2/org/apache/httpcomponents/httpmime/4.3/httpmime-4.3.pom‘.
> sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
> Could not resolve org.apache.httpcomponents:httpmime:4.3.
> Could not get resource ‘https://plugins.gradle.org/m2/org/apache/httpcomponents/httpmime/4.3/httpmime-4.3.pom‘.
> Could not GET ‘https://plugins.gradle.org/m2/org/apache/httpcomponents/httpmime/4.3/httpmime-4.3.pom‘.
> sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
> Could not resolve org.eclipse.jgit:org.eclipse.jgit:3.6.0.201412230720-r.
Required by:
project : > com.github.kt3k.coveralls:com.github.kt3k.coveralls.gradle.plugin:2.6.3 > org.kt3k.gradle.plugin:coveralls-gradle-plugin:2.6.3
> Could not resolve org.eclipse.jgit:org.eclipse.jgit:3.6.0.201412230720-r.
> Could not get resource ‘https://plugins.gradle.org/m2/org/eclipse/jgit/org.eclipse.jgit/3.6.0.201412230720-r/org.eclipse.jgit-3.6.0.201412230720-r.pom‘.
> Could not GET ‘https://plugins.gradle.org/m2/org/eclipse/jgit/org.eclipse.jgit/3.6.0.201412230720-r/org.eclipse.jgit-3.6.0.201412230720-r.pom‘.
> sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
> Could not resolve org.eclipse.jgit:org.eclipse.jgit:3.6.0.201412230720-r.
> Could not get resource ‘https://repo.maven.apache.org/maven2/org/eclipse/jgit/org.eclipse.jgit/3.6.0.201412230720-r/org.eclipse.jgit-3.6.0.201412230720-r.pom‘.
> Could not GET ‘https://repo.maven.apache.org/maven2/org/eclipse/jgit/org.eclipse.jgit/3.6.0.201412230720-r/org.eclipse.jgit-3.6.0.201412230720-r.pom‘.
> sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
> Could not resolve org.eclipse.jgit:org.eclipse.jgit:3.6.0.201412230720-r.
> Could not get resource ‘https://plugins.gradle.org/m2/org/eclipse/jgit/org.eclipse.jgit/3.6.0.201412230720-r/org.eclipse.jgit-3.6.0.201412230720-r.pom‘.
> Could not GET ‘https://plugins.gradle.org/m2/org/eclipse/jgit/org.eclipse.jgit/3.6.0.201412230720-r/org.eclipse.jgit-3.6.0.201412230720-r.pom‘.
> sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
> Could not resolve org.codehaus.groovy.modules.http-builder:http-builder:0.7.1.
Required by:
project : > com.github.kt3k.coveralls:com.github.kt3k.coveralls.gradle.plugin:2.6.3 > org.kt3k.gradle.plugin:coveralls-gradle-plugin:2.6.3
> Could not resolve org.codehaus.groovy.modules.http-builder:http-builder:0.7.1.
> Could not get resource ‘https://plugins.gradle.org/m2/org/codehaus/groovy/modules/http-builder/http-builder/0.7.1/http-builder-0.7.1.pom‘.
> Could not GET ‘https://plugins.gradle.org/m2/org/codehaus/groovy/modules/http-builder/http-builder/0.7.1/http-builder-0.7.1.pom‘.
> sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
> Could not resolve org.codehaus.groovy.modules.http-builder:http-builder:0.7.1.
> Could not get resource ‘https://repo.maven.apache.org/maven2/org/codehaus/groovy/modules/http-builder/http-builder/0.7.1/http-builder-0.7.1.pom‘.
> Could not GET ‘https://repo.maven.apache.org/maven2/org/codehaus/groovy/modules/http-builder/http-builder/0.7.1/http-builder-0.7.1.pom‘.
> sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
> Could not resolve org.codehaus.groovy.modules.http-builder:http-builder:0.7.1.
> Could not get resource ‘https://plugins.gradle.org/m2/org/codehaus/groovy/modules/http-builder/http-builder/0.7.1/http-builder-0.7.1.pom‘.
> Could not GET ‘https://plugins.gradle.org/m2/org/codehaus/groovy/modules/http-builder/http-builder/0.7.1/http-builder-0.7.1.pom‘.
> sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.
* Get more help at https://help.gradle.org
BUILD FAILED in 15s
解决方法
尝试了添加网站证书到 JAVA_HOME 依然没用。
修改 gradlew 文件，在
# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script
这一行下加一行：
GRADLE_OPTS=-Dgradle.user.home=/mnt/e/temp
即指定 gradle 临时目录，这不是重点，重点是：
把前面出错信息中下载失败的各种资源 （pom文件或jar文件）直接通过浏览器下载到这个指定的临时目录中，然后再执行
./gradlew clean build
如果最终发现还是有几个 jar 包提示下载出错，则在上面设置的临时目录下找到以下路径：caches/modules-2/files-2.1，这里就是下载的 jar 包的临时目录，按照出错的 jar 包路径创建对应的文件夹。如org.eclipse.jgit，具体再参照已经下载成功的一些 jar 包的目录路径（因为各个包生成的目录路径还不一样）。把手动下载的 jar 包放进去（不一定产生作用），再执行 上述的build命令，再去看看，有可能就下载成功了。
也有可能此时目录已经生成，但在最末端的文件夹内只有一个 pom 文件，此时在跟 pom 文件目录同级的目录下创建一个文件夹，名称随便起，然再执行 build 命令
原文：https://www.cnblogs.com/wuzhiblog/p/13620906.html