不支持的major.minor版本51.0，但一切都设置为JDK 1.6 [英] Unsupported major.minor version 51.0 but everything is set to JDK 1.6

问题描述

我有一个Maven Eclipse应用程序，我正在尝试使用以下命令在命令提示符下运行：

I have a Maven Eclipse application which I'm trying to run through the command prompt using the following command:

java -cp target/classes;"target/dependency/*" com.example.Main

不幸的是，它抛出错误：

Unfortunately, it throws an error:

UnsupportedClassVersionError : unsupported major.minor version 51.0

我做了一些挖掘，发现它与在较新版本的JDK上编译的应用程序有关，而不是它运行的JRE。显然51意味着它是为1.7而构建的，但我的计算机上没有JDK 7 ...

I did some digging and found out it has something to do with the application being compiled on a JDK of a newer version, than the JRE it runs on. Apparently the 51 means it was built for 1.7, but I don't have a JDK 7 on my computer...

所以我确保一切都设置为版本1.6：

So I made sure that everything is set to version 1.6 :

root中的system.properties文件包含

system.properties file in the root contains

java.runtime.version=1.6

添加了maven属性

<java.version>1.6</java.version>

在我的pom.xml中指定了maven编译器插件

Specified the maven compiler plugin in my pom.xml

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>2.1</version>
    <configuration>
        <source>1.6</source>
        <target>1.6</target>
    </configuration>
</plugin>

我使用返回的命令java -version检查了我的java版本

I checked the version of my java using the command java -version which returned

Java version "1.6.0_38"
Java(TM) SE Runtime Environment (build 1.6.0_38-b05)
Java HotSpot(TM) 64-bit Server VM (build 20.13-b02, mixed mode)

并更新设置maven-compiler-plugin后我的项目导致Eclipse自动将编译器级别设置为1.6，项目facet级别为1.6，并将JavaSE-1.6 jre系统库添加到我的项目中。

And an update of my project after setting the maven-compiler-plugin resulted in Eclipse automatically setting the compiler level to 1.6, the project facet level to 1.6 and adding the JavaSE-1.6 jre system library to my project.

所以我完全不知道这个JDK 1.7的来源。我从未在这台计算机上安装过JDK 1.7 ... ...

So I have absolutely no idea where this JDK 1.7 is coming from. I never installed JDK 1.7 on this computer to begin with...

另外，最初，maven-compiler-plugin不存在所以它是用1.5升构建的猜测。但我做了 mvn clean install ，然后是 mvn包，然后在所有设置完成后再次尝试命令调整后它仍会抛出同样的错误。

Also, originally, the maven-compiler-plugin wasn't present so it was build with 1.5 I guess. But I did a mvn clean install, then a mvn package, and then tried the command again after all the settings were adjusted and it still throws the same error.

推荐答案

可能你有一个需要Java 1.7的依赖项

Probably you have a dependency that needs Java 1.7

这篇关于不支持的major.minor版本51.0，但一切都设置为JDK 1.6的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！