为什么我得到 Unsupported major.minor 版本 51.0

Question

我正在尝试使用 Gradle 2.14.1 编译 Spring Boot 1.3.6.RELEASE 应用程序的基本框架。 我需要使用 Java 6。我无法升级到 Java 7 或 8。

为什么我的 gradle 构建失败了

Unsupported major.minor version 51.0

异常似乎指向了行

apply plugin: 'spring-boot'

我的 gradle.properties 文件包含：

org.gradle.java.home=C:/Program Files/Java/jdk1.6.0_45

我尝试包含以下内容以使用 Tomcat 7 而不是 Tomcat 8，但这没有帮助。

configurations.all {
    resolutionStrategy {
        eachDependency {
            if (it.requested.group == 'org.apache.tomcat.embed') {
                it.useVersion '7.0.56'
            }
        }
    }
} 

我遵循了与 Java 6 相关的 Spring Boot 参考指南中的建议。使用 tomcat 7 而不是 8。 我没有使用 JTA。

* Exception is:
org.gradle.api.GradleScriptException: A problem occurred evaluating root project 'myProject'.
        at org.gradle.groovy.scripts.internal.DefaultScriptRunnerFactory$ScriptRunnerImpl.run(DefaultScriptRunnerFactory
.java:93)
        at org.gradle.configuration.DefaultScriptPluginFactory$ScriptPluginImpl$2.run(DefaultScriptPluginFactory.java:17
7)
        at org.gradle.configuration.ProjectScriptTarget.addConfiguration(ProjectScriptTarget.java:77)
        at org.gradle.configuration.DefaultScriptPluginFactory$ScriptPluginImpl.apply(DefaultScriptPluginFactory.java:18
2)
        at org.gradle.configuration.project.BuildScriptProcessor.execute(BuildScriptProcessor.java:38)
        at org.gradle.configuration.project.BuildScriptProcessor.execute(BuildScriptProcessor.java:25)
        at org.gradle.configuration.project.ConfigureActionsProjectEvaluator.evaluate(ConfigureActionsProjectEvaluator.j
ava:34)
        at org.gradle.configuration.project.LifecycleProjectEvaluator.evaluate(LifecycleProjectEvaluator.java:55)
        at org.gradle.api.internal.project.AbstractProject.evaluate(AbstractProject.java:540)
        at org.gradle.api.internal.project.AbstractProject.evaluate(AbstractProject.java:93)
        at org.gradle.execution.TaskPathProjectEvaluator.configureHierarchy(TaskPathProjectEvaluator.java:42)
        at org.gradle.configuration.DefaultBuildConfigurer.configure(DefaultBuildConfigurer.java:35)
        at org.gradle.initialization.DefaultGradleLauncher$2.run(DefaultGradleLauncher.java:124)
        at org.gradle.internal.Factories$1.create(Factories.java:22)
        at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:91)
        at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:53)
        at org.gradle.initialization.DefaultGradleLauncher.doBuildStages(DefaultGradleLauncher.java:121)
        at org.gradle.initialization.DefaultGradleLauncher.access$200(DefaultGradleLauncher.java:32)
        at org.gradle.initialization.DefaultGradleLauncher$1.create(DefaultGradleLauncher.java:98)
        at org.gradle.initialization.DefaultGradleLauncher$1.create(DefaultGradleLauncher.java:92)
        at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:91)
        at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:63)
        at org.gradle.initialization.DefaultGradleLauncher.doBuild(DefaultGradleLauncher.java:92)
        at org.gradle.initialization.DefaultGradleLauncher.run(DefaultGradleLauncher.java:83)
        at org.gradle.launcher.exec.InProcessBuildActionExecuter$DefaultBuildController.run(InProcessBuildActionExecuter
.java:99)
        at org.gradle.tooling.internal.provider.ExecuteBuildActionRunner.run(ExecuteBuildActionRunner.java:28)
        at org.gradle.launcher.exec.ChainingBuildActionRunner.run(ChainingBuildActionRunner.java:35)
        at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:48)
        at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:30)
        at org.gradle.launcher.exec.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:81)
        at org.gradle.launcher.exec.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:46)
        at org.gradle.launcher.daemon.server.exec.ExecuteBuild.doBuild(ExecuteBuild.java:52)
        at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
        at org.gradle.launcher.daemon.server.exec.WatchForDisconnection.execute(WatchForDisconnection.java:37)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
        at org.gradle.launcher.daemon.server.exec.ResetDeprecationLogger.execute(ResetDeprecationLogger.java:26)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
        at org.gradle.launcher.daemon.server.exec.RequestStopIfSingleUsedDaemon.execute(RequestStopIfSingleUsedDaemon.ja
va:34)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
        at org.gradle.launcher.daemon.server.exec.ForwardClientInput$2.call(ForwardClientInput.java:74)
        at org.gradle.launcher.daemon.server.exec.ForwardClientInput$2.call(ForwardClientInput.java:72)
        at org.gradle.util.Swapper.swap(Swapper.java:38)
        at org.gradle.launcher.daemon.server.exec.ForwardClientInput.execute(ForwardClientInput.java:72)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
        at org.gradle.launcher.daemon.server.health.DaemonHealthTracker.execute(DaemonHealthTracker.java:40)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
        at org.gradle.launcher.daemon.server.exec.LogToClient.doBuild(LogToClient.java:60)
        at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
        at org.gradle.launcher.daemon.server.exec.EstablishBuildEnvironment.doBuild(EstablishBuildEnvironment.java:72)
        at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
        at org.gradle.launcher.daemon.server.health.HintGCAfterBuild.execute(HintGCAfterBuild.java:41)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
        at org.gradle.launcher.daemon.server.exec.StartBuildOrRespondWithBusy$1.run(StartBuildOrRespondWithBusy.java:50)

        at org.gradle.launcher.daemon.server.DaemonStateCoordinator$1.run(DaemonStateCoordinator.java:237)
        at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:54)
        at org.gradle.internal.concurrent.StoppableExecutorImpl$1.run(StoppableExecutorImpl.java:40)
Caused by: java.lang.UnsupportedClassVersionError: io/spring/gradle/dependencymanagement/exclusions/Exclusions : Unsuppo
rted major.minor version 51.0
        at io.spring.gradle.dependencymanagement.DependencyManagementPlugin.apply(DependencyManagementPlugin.groovy:58)
        at io.spring.gradle.dependencymanagement.DependencyManagementPlugin.apply(DependencyManagementPlugin.groovy)
        at org.gradle.api.internal.plugins.ImperativeOnlyPluginApplicator.applyImperative(ImperativeOnlyPluginApplicator
.java:35)
        at org.gradle.api.internal.plugins.RuleBasedPluginApplicator.applyImperative(RuleBasedPluginApplicator.java:43)
        at org.gradle.api.internal.plugins.DefaultPluginManager.doApply(DefaultPluginManager.java:137)
        at org.gradle.api.internal.plugins.DefaultPluginManager.addImperativePlugin(DefaultPluginManager.java:67)
        at org.gradle.api.internal.plugins.DefaultPluginManager.addImperativePlugin(DefaultPluginManager.java:73)
        at org.gradle.api.internal.plugins.DefaultPluginContainer.apply(DefaultPluginContainer.java:60)
        at org.springframework.boot.gradle.dependencymanagement.DependencyManagementPluginFeatures.apply(DependencyManag
ementPluginFeatures.java:44)
        at org.springframework.boot.gradle.SpringBootPlugin.apply(SpringBootPlugin.java:47)
        at org.springframework.boot.gradle.SpringBootPlugin.apply(SpringBootPlugin.java:38)
        at org.gradle.api.internal.plugins.ImperativeOnlyPluginApplicator.applyImperative(ImperativeOnlyPluginApplicator
.java:35)
        at org.gradle.api.internal.plugins.RuleBasedPluginApplicator.applyImperative(RuleBasedPluginApplicator.java:43)
        at org.gradle.api.internal.plugins.DefaultPluginManager.doApply(DefaultPluginManager.java:137)
        at org.gradle.api.internal.plugins.DefaultPluginManager.apply(DefaultPluginManager.java:112)
        at org.gradle.api.internal.plugins.DefaultObjectConfigurationAction.applyType(DefaultObjectConfigurationAction.j
ava:113)
        at org.gradle.api.internal.plugins.DefaultObjectConfigurationAction.access$200(DefaultObjectConfigurationAction.
java:36)
        at org.gradle.api.internal.plugins.DefaultObjectConfigurationAction$3.run(DefaultObjectConfigurationAction.java:
80)
        at org.gradle.api.internal.plugins.DefaultObjectConfigurationAction.execute(DefaultObjectConfigurationAction.jav
a:136)
        at org.gradle.api.internal.project.AbstractPluginAware.apply(AbstractPluginAware.java:46)
        at org.gradle.api.internal.project.ProjectScript.apply(ProjectScript.java:34)
        at org.gradle.api.Script$apply$0.callCurrent(Unknown Source)
        at build_eb0vk878b797zgtn3oumoubtl.run(C:\Users\...\myProject\build.gradle:25)
        at org.gradle.groovy.scripts.internal.DefaultScriptRunnerFactory$ScriptRunnerImpl.run(DefaultScriptRunnerFactory
.java:91)
        ... 58 more

Answer 1

Java 6 的使用正是导致问题的原因。似乎所需的库之一至少支持 Java 7/8 - 没有解决方法，您可能必须迁移到更新的 Java 版本。

Answer 2

该错误是由使用 Java 7 编译的依赖项引起的，因此无法使用 Java 6。

话虽如此，从Spring Boot's documentation 阅读有关系统要求的信息，如果您执行一些额外的配置，似乎支持 Java 6。

关于嵌入式 servlet 容器的兼容性，在 79.9 How to use Java 6 部分你应该使用 Tomcat 7 或 Jetty 8，这是 gradle 配置：

您可以通过设置tomcat.version来更改Tomcat版本 属性：

ext['tomcat.version'] = '7.0.59'
dependencies {
    compile 'org.springframework.boot:spring-boot-starter-web'
}

显然，如果可以的话，您最好升级到更新的 JVM 版本。

Answer 3

Spring Boot 的 Gradle 插件使用的依赖管理插件需要 Java 7。这意味着您必须使用 Java 7（或更高版本）构建应用程序，但您仍然可以使用 Java 6 运行它。