如何解决java9中的模块读取包错误

Posted 2023-02-26

【中文标题】如何解决java9中的模块读取包错误

【英文标题】：How to resolve module reads package error in java9

【发布时间】：2017-11-25 15:14:32

【问题描述】：

我正在尝试使用 spring-boot 了解 java 9 中的新模块化，因此我想运行一些简单的应用程序，例如：https://github.com/tmatyashovsky/java9-springboot

我正在使用带有 java 9 的 maven 3.5.0：

Apache Maven 3.5.0 (ff8f5e7444045639af65f6095c62210b5713f426; 2017-04-03T21:39:06+02:00)
Maven home: ~/soft/apache-maven-3.5.0
Java version: 9-ea, vendor: Oracle Corporation
Java home: /usr/lib/jvm/java-9-oracle
Default locale: en_US, platform encoding: UTF-8
OS name: "linux", version: "4.4.0-79-generic", arch: "amd64", family: "unix"

问题是我仍然有一些例外。这是什么意思，我应该如何解决？

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.6.1:compile (default-compile) on project api: Compilation failure: Compilation failure: 
[ERROR] module  reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module spring.core reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module spring.jcl reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module spring.aop reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module spring.expression reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module spring.boot.starter.web reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module spring.boot.starter reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module spring.boot reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module spring.boot.autoconfigure reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module spring.boot.starter.logging reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module logback.classic reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module logback.core reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module slf4j.api reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module jul.to.slf4j reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module log4j.over.slf4j reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module spring.boot.starter.json reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module jackson.databind reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module jackson.annotations reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module jackson.core reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module jackson.datatype.jdk8 reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module jackson.datatype.jsr310 reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module jackson.module.parameter.names reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module spring.boot.starter.tomcat reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module tomcat.embed.core reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module tomcat.embed.el reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module tomcat.embed.websocket reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module hibernate.validator reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module validation.api reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module jboss.logging reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module classmate reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module spring.web reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module spring.webmvc reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module spring.context reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module spring.beans reads package javax.annotation from both tomcat.embed.core and java.xml.ws.annotation
[ERROR] module com.lohika.morning.java9modules.service reads package javax.annotation from both java.xml.ws.annotation and tomcat.embed.core

【问题讨论】：

您使用的是哪个版本的 JDK9？

最新抢先体验

@hudi 最新版本：jdk-9+175，你能确认一下吗？

是构建：jdk-9+175

【参考方案1】：

问题是你的模块路径在不同的模块（java.xml.ws.annotation和tomcat.embed.core中包含相同的包（javax.annotation） )，为了使配置更可靠，模块系统禁止。这称为split package。当列出两次读取（即“看到”）该软件包的所有模块时，模块系统会告诉您同样多的信息。那么现在该怎么办呢？

首要任务是检查两个包是否包含相同的类。如果是的话，你很幸运。现在您需要做的就是确保模块系统只看到其中之一，有两种可能性：

如果从其中一个模块中，您只需要一个包而无需其他任何东西，请将其从您的配置中取出并改用另一个。也许您可以停止明确要求​​ java.xml.ws.annotation？ 如果你把 tomcat.embed.core 放在类路径上，它的包版本将被完全忽略，整个系统，包括类路径上的代码只会在 java.xml.ws.annotation 中看到包。

如果包的两个变体都包含 (a) 另一个不包含的类型以及 (b) 您的应用程序需要的类型，那么您的处境将更加艰难。首先，这让人怀疑 tomcat.embed.core 做了一些可疑的事情（尽管我不确定）。我知道的唯一可以帮助的可能是non-standard javac option --patch-module。

【讨论】：

尝试对现有的大型多模块项目和大量遗留依赖项进行此操作。祝你好运。如果我必须从头开始编写一个新程序，我只会使用 java 模块。

【参考方案2】：

我收到以下错误：

[ERROR] 模块 hibernate.core 从 ParentProject 和 hibernate.core 读取包 org.hibernate.dialect

尝试为我的项目ParentProject 执行 mvn clean install 时。 为ParentProject 自动生成的module-info.java 包含条目

...
exports hibernate.core;
...
requires ChildProject;
...

ChildProject 的 module-info.java 包含

requires hibernate.core;

从ParentProject 中删除exports hibernate.core; 行为我解决了这个问题。

=> 小心在 Eclipse 中自动生成的 module-info.java。

【参考方案3】：

在 Spring Boot 和嵌入式 Tomcat 的情况下，我遇到了类似的问题。有一个拆分包，包含在javax.annotation:javax.annotation-api 和org.apache.tomcat:tomcat-annotations-api 中。

javax.annotation:javax.annotation-api 是org.springframework.boot:spring-boot-starter-web 的传递依赖。

为了解决 Spring Boot 和嵌入式 Tomcat 的特殊情况，添加如下所示的依赖项是解决方案。我明确删除了javax.annotation-api 的依赖关系。这是因为tomcat-annotations-api 也提供了所有必需的包和类。

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
        <exclusions>
            <exclusion>
                <!-- served by tomcat-annotations-api instead -->
                <groupId>javax.annotation</groupId>
                <artifactId>javax.annotation-api</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>
        <groupId>org.apache.tomcat</groupId>
        <artifactId>tomcat-annotations-api</artifactId>
    </dependency>