使用maven创builddocker图像

我正在使用maven插件com.spotify构build一个docker镜像。 当我执行下面的命令时给出错误：

mvn clean package docker:build 

[错误]无法执行目标io.fabric8：docker-maven-plugin：0.16.4：构build项目（默认 – cli）xbs-docker：执行目标io.fabric8的默认cli：docker-maven-plugin：0.16 .4：编译失败：没有给定，没有DOCKER_HOST环境variables，没有读/写'/var/run/docker.sock'或'//./pipe/docker_engine'，没有configurationDocker机器的外部提供程序 – > [Help 1]

当我设置DOCKER_HOST = tcp：// localhost：2375时，它给出下面的错误：

  Failed to execute goal io.fabric8:docker-maven-plugin:0.16.4:build (default-cli) on project <project_name>: Execution default-cli of goal io.fabric8:docker-maven-plugin:0.16.4:build failed. NullPointerException -> [Help 1] org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal io.fabric8:docker-maven-plugin:0.16.4:build (default-cli) on project <project_name>: Execution default-cli of goal io.fabric8:docker-maven-plugin:0.16.4:build failed. at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:212) at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153) at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145) at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116) at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80) at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51) at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128) at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307) at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193) at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106) at org.apache.maven.cli.MavenCli.execute(MavenCli.java:863) at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:288) at org.apache.maven.cli.MavenCli.main(MavenCli.java:199) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289) at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229) at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415) at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356) Caused by: org.apache.maven.plugin.PluginExecutionException: Execution default-cli of goal io.fabric8:docker-maven-plugin:0.16.4:build failed. at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:145) at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:207) ... 20 more Caused by: java.lang.NullPointerException at io.fabric8.maven.docker.access.DockerConnectionDetector.getCertPath(DockerConnectionDetector.java:108) at io.fabric8.maven.docker.AbstractDockerMojo.createDockerAccess(AbstractDockerMojo.java:277) at io.fabric8.maven.docker.AbstractDockerMojo.execute(AbstractDockerMojo.java:191) at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134) ... 21 more 

请帮我解决这个问题。