错误的类文件: *** 类文件具有错误的版本 61.0, 应为 52.0 请删除该文件或确保该文件位于正确的类路径子目录中

一、问题

用maven对一个开源项目打包时，遇到了“错误的类文件: *** 类文件具有错误的版本 61.0, 应为 52.0 请删除该文件或确保该文件位于正确的类路径子目录中。”：

在这里插入图片描述

二、原因

原因是当前java环境是Java 8（版本52.0），但项目中依赖的某个类文件（比如上面的的org.eclipse.core.runtime.Plugin）是由Java 17（版本61.0）编译生成的，Java运行时环境只能运行与其自身版本相同或者更低版本编译的类文件。

下面来验证下，把有问题的jar解压一下：

jar -xvf org.eclipse.core.runtime-3.31.100.jar

把有报错这个类反编译一下：

javap -verbose org/eclipse/core/runtime/Plugin.class

可以看到这个类确实是由Java 17（版本61.0）编译生成的，反编译后的字节码指令中，major version的值是61：

  Last modified 2024-5-24; size 9363 bytesMD5 checksum b41961b4155bfdabeeb67952fdec406fCompiled from "Plugin.java"
public abstract class org.eclipse.core.runtime.Plugin implements org.osgi.framework.BundleActivatorminor version: 0major version: 61flags: ACC_PUBLIC, ACC_SUPER, ACC_ABSTRACT
Constant pool:#1 = Class              #2            // org/eclipse/core/runtime/Plugin#2 = Utf8               org/eclipse/core/runtime/Plugin#3 = Class              #4            // java/lang/Object#4 = Utf8               java/lang/Object#5 = Class              #6            // org/osgi/framework/BundleActivator#6 = Utf8               org/osgi/framework/BundleActivator#7 = Utf8               PLUGIN_PREFERENCE_SCOPE省略……

记录一下每个版本的 Java 对应的类文件格式版本号major version（截止2024-07-18）：

Java SE 1.1 = 45
Java SE 1.2 = 46
Java SE 1.3 = 47
Java SE 1.4 = 48
Java SE 5.0 = 49
Java SE 6.0 = 50
Java SE 7.0 = 51
Java SE 8.0 = 52
Java SE 9.0 = 53
Java SE 10 = 54
Java SE 11 = 55
Java SE 12 = 56
Java SE 13 = 57
Java SE 14 = 58
Java SE 15 = 59
Java SE 16 = 60
Java SE 17 = 61
Java SE 18 = 62
Java SE 19 = 63
Java SE 20 = 64

三、解决

那这个问题怎么解决呢？

1 . 升级当前环境的jdk版本，操作简单，但一般不太现实

2 . 降低对应依赖的版本

比如在我这个项目中，有问题（编译时Java版本太高）的包是org.eclipse.core.runtime，版本是3.31.100，那么就需要降低这个包的版本。大概有以下几种做法：

（1）如果项目中直接引用了这个包（比如在pom文件中定义了），那直接修改版本号就行（试着一点一点降版本 -> 编译试试 -> 不行再降降版本 -> 再编译试试……）

（2）如果项目中没有直接引用这个包，那可以通过maven依赖树看下是哪个包引用的它，还是以我这个项目为例：

mvn dependency:tree -Dverbose 
[INFO] Scanning for projects...
[INFO] 
[INFO] ---------------------< org.jacoco:org.jacoco.core >---------------------
[INFO] Building JaCoCo :: Core 0.8.4
[INFO]   from pom.xml
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] 
[INFO] --- dependency:2.2:tree (default-cli) @ org.jacoco.core ---
[INFO] org.jacoco:org.jacoco.core:jar:0.8.4
[INFO] +- org.ow2.asm:asm:jar:7.1:compile
[INFO] +- org.ow2.asm:asm-commons:jar:7.1:compile
[INFO] |  +- (org.ow2.asm:asm:jar:7.1:compile - omitted for duplicate)
[INFO] |  +- (org.ow2.asm:asm-tree:jar:7.1:compile - omitted for duplicate)
[INFO] |  \- org.ow2.asm:asm-analysis:jar:7.1:compile
[INFO] |     \- (org.ow2.asm:asm-tree:jar:7.1:compile - omitted for duplicate)
[INFO] +- org.ow2.asm:asm-tree:jar:7.1:compile
[INFO] |  \- (org.ow2.asm:asm:jar:7.1:compile - omitted for duplicate)
[INFO] +- org.eclipse.jdt:org.eclipse.jdt.core:jar:3.19.0:compile
[INFO] |  +- org.eclipse.platform:org.eclipse.core.resources:jar:3.20.200:compile
[INFO] |  |  +- org.eclipse.platform:org.eclipse.core.expressions:jar:3.9.400:compile
[INFO] |  |  |  \- (org.eclipse.platform:org.eclipse.core.runtime:jar:3.31.100:compile - omitted for duplicate)
[INFO] |  |  +- (org.eclipse.platform:org.eclipse.core.filesystem:jar:1.10.400:compile - omitted for duplicate)
[INFO] |  |  +- (org.eclipse.platform:org.eclipse.core.runtime:jar:3.31.100:compile - omitted for duplicate)
[INFO] |  |  \- org.eclipse.platform:org.eclipse.osgi:jar:3.20.0:compile
[INFO] |  +- org.eclipse.platform:org.eclipse.core.runtime:jar:3.31.100:compile
[INFO] |  |  +- (org.eclipse.platform:org.eclipse.osgi:jar:3.20.0:compile - omitted for duplicate)
[INFO] |  |  +- org.eclipse.platform:org.eclipse.equinox.common:jar:3.19.100:compile
[INFO] |  |  |  \- (org.eclipse.platform:org.eclipse.osgi:jar:3.20.0:compile - omitted for duplicate)
[INFO] |  |  +- org.eclipse.platform:org.eclipse.core.jobs:jar:3.15.300:compile
[INFO] |  |  |  +- (org.eclipse.platform:org.eclipse.equinox.common:jar:3.19.100:compile - omitted for duplicate)
[INFO] |  |  |  \- (org.eclipse.platform:org.eclipse.osgi:jar:3.20.0:compile - omitted for duplicate)
[INFO] |  |  +- org.eclipse.platform:org.eclipse.equinox.registry:jar:3.12.100:compile
[INFO] |  |  |  \- (org.eclipse.platform:org.eclipse.equinox.common:jar:3.19.100:compile - omitted for duplicate)
[INFO] |  |  +- org.eclipse.platform:org.eclipse.equinox.preferences:jar:3.11.100:compile
[INFO] |  |  |  +- (org.eclipse.platform:org.eclipse.equinox.common:jar:3.19.100:compile - omitted for duplicate)
[INFO] |  |  |  +- org.osgi:org.osgi.service.prefs:jar:1.1.2:compile
[INFO] |  |  |  |  \- org.osgi:osgi.annotation:jar:8.0.1:compile
[INFO] |  |  |  \- (org.eclipse.platform:org.eclipse.osgi:jar:3.20.0:compile - omitted for duplicate)
[INFO] |  |  +- org.eclipse.platform:org.eclipse.core.contenttype:jar:3.9.400:compile
[INFO] |  |  |  +- (org.eclipse.platform:org.eclipse.equinox.preferences:jar:3.11.100:compile - omitted for duplicate)
[INFO] |  |  |  +- (org.eclipse.platform:org.eclipse.equinox.registry:jar:3.12.100:compile - omitted for duplicate)
[INFO] |  |  |  +- (org.eclipse.platform:org.eclipse.equinox.common:jar:3.19.100:compile - omitted for duplicate)
[INFO] |  |  |  \- (org.eclipse.platform:org.eclipse.osgi:jar:3.20.0:compile - omitted for duplicate)
[INFO] |  |  \- org.eclipse.platform:org.eclipse.equinox.app:jar:1.7.100:compile
[INFO] |  |     +- (org.eclipse.platform:org.eclipse.equinox.registry:jar:3.12.100:compile - omitted for duplicate)
[INFO] |  |     \- (org.eclipse.platform:org.eclipse.equinox.common:jar:3.19.100:compile - omitted for duplicate)
[INFO] |  +- org.eclipse.platform:org.eclipse.core.filesystem:jar:1.10.400:compile
[INFO] |  |  +- (org.eclipse.platform:org.eclipse.equinox.common:jar:3.19.100:compile - omitted for duplicate)
[INFO] |  |  +- (org.eclipse.platform:org.eclipse.equinox.registry:jar:3.12.100:compile - omitted for duplicate)
[INFO] |  |  +- (org.eclipse.platform:org.eclipse.osgi:jar:3.20.0:compile - omitted for duplicate)
[INFO] |  |  \- (org.eclipse.platform:org.eclipse.core.runtime:jar:3.31.100:compile - omitted for duplicate)
[INFO] |  \- org.eclipse.platform:org.eclipse.text:jar:3.14.100:compile
[INFO] |     +- org.eclipse.platform:org.eclipse.core.commands:jar:3.12.100:compile
[INFO] |     |  \- (org.eclipse.platform:org.eclipse.equinox.common:jar:3.19.100:compile - omitted for duplicate)
[INFO] |     +- (org.eclipse.platform:org.eclipse.equinox.common:jar:3.19.100:compile - omitted for duplicate)
[INFO] |     +- (org.eclipse.platform:org.eclipse.equinox.preferences:jar:3.11.100:compile - omitted for duplicate)
[INFO] |     \- (org.eclipse.platform:org.eclipse.core.runtime:jar:3.31.100:compile - omitted for duplicate)
[INFO] \- org.eclipse.jgit:org.eclipse.jgit:jar:5.5.0.201909110433-r:compile
[INFO]    +- com.jcraft:jsch:jar:0.1.55:compile
[INFO]    +- com.jcraft:jzlib:jar:1.1.1:compile
[INFO]    +- com.googlecode.javaewah:JavaEWAH:jar:1.1.6:compile
[INFO]    +- org.slf4j:slf4j-api:jar:1.7.2:compile
[INFO]    +- org.bouncycastle:bcpg-jdk15on:jar:1.61:compile
[INFO]    |  \- (org.bouncycastle:bcprov-jdk15on:jar:1.61:compile - omitted for duplicate)
[INFO]    +- org.bouncycastle:bcprov-jdk15on:jar:1.61:compile
[INFO]    \- org.bouncycastle:bcpkix-jdk15on:jar:1.61:compile
[INFO]       \- (org.bouncycastle:bcprov-jdk15on:jar:1.61:compile - omitted for duplicate)
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.700 s
[INFO] Finished at: 2024-07-18T22:08:14+08:00
[INFO] ------------------------------------------------------------------------

通过依赖树可以发现，在项目（pom文件）中是org.eclipse.jdt.core引用了它，并且org.eclipse.jdt.core的版本是3.19.0，那可以试着降低org.eclipse.jdt.core的版本号，比如3.18.0、3.17.0……

但是，也有可能org.eclipse.jdt.core很多个版本依赖的都是同一个有问题的版本，比如3.19.0和3.18.0这两个版本的org.eclipse.jdt.core 依赖的org.eclipse.core.runtime的版本是号都是3.31.100的，这时也可以直接用依赖管理dependencyManagement和依赖排除来强制指定org.eclipse.core.runtime的版本，比如在pom文件中强制指定org.eclipse.core.runtime的版本（我在https://mvnrepository.com/中把org.eclipse.core.runtime所有的版本号都试了一下，最终找到3.22.0版本是Java 8编译的）：

直接用依赖管理强制指定版本：

<dependencies><dependency><groupId>org.eclipse.jdt</groupId><artifactId>org.eclipse.jdt.core</artifactId><version>3.19.0</version></dependency>
</dependencies>
<dependencyManagement><dependencies><dependency><groupId>org.eclipse.platform</groupId><artifactId>org.eclipse.core.runtime</artifactId><version>3.22.0</version></dependency></dependencies>
</dependencyManagement>

或者先排除，再引入:

<dependencies><dependency><groupId>org.eclipse.jdt</groupId><artifactId>org.eclipse.jdt.core</artifactId><version>3.19.0</version><exclusions><exclusion><groupId>org.eclipse.platform</groupId><artifactId>org.eclipse.core.runtime</artifactId></exclusion></exclusions></dependency><dependency><groupId>org.eclipse.platform</groupId><artifactId>org.eclipse.core.runtime</artifactId><version>3.22.0</version></dependency>
</dependencies>