如何在Eclipse Oxygen中将Log4j与Maven和Java9结合使用? [英] How to use log4j with maven and java9 in Eclipse Oxygen?

问题描述

我尝试将Java8项目迁移到Java9.自动生成的module-info.java包含一个条目

I try to migrate a Java8 project to Java9. The auto generated module-info.java contains an entry

 requires log4j;

并显示错误:

log4j cannot be resolved to a module

=>如何正确地将log4j作为Java9的模块依赖项包括在内?

=> How do I correctly include log4j as a module dependency with Java9?

(对于以下依赖项，我也有同样的问题: 需要hibernate.core; 需要hibernate.jpa.2.1.api; 需要jcommander; 需要junit; 需要反思； )

(I have the same issue for following dependencies: requires hibernate.core; requires hibernate.jpa.2.1.api; requires jcommander; requires junit; requires reflections; )

我到目前为止所做的事情:

• 已安装Java 9.0.1
• 将Eclipse升级到Oxygen.1a版本(4.7.1a)
• 将我的Java项目的合规性级别更改为9

• 生成的module-info.java，右键单击project => Configure => Generate module-info.java

• Installed Java 9.0.1
• Upgraded Eclipse to Oxygen.1a Release (4.7.1a)
• Changed Compliance level of my Java project to 9

• Generated module-info.java with Right click on project=>Configure=>Generate module-info.java

更新了我pom.xml文件中的插件(另请参见

Updated the plugins in my pom.xml file (also see https://cwiki.apache.org/confluence/display/MAVEN/Java+9+-+Jigsaw) and set java version to 9:

    <!--  plugin for compile phase (and test-compile phase) -->
    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.7.0</version>
        <configuration>
            <!-- specify current java version here: -->
            <source>9</source>
            <target>9</target>
        </configuration>                
    </plugin>

由于log4j 1.2似乎不适用于Java9，因此pom.xml文件中的log4j版本已更新(请参见

推荐答案

module-info.java中的错误

即使项目的遵从级别已设置为Java9，Eclipse中的module-info.java也会显示误导性错误.

Even if the compliance level of the project has been set to Java9, there might be shown misleading errors for module-info.java in Eclipse.

我希望仅当我更改pom.xml文件时才需要更新maven项目.现在我了解到，更改module-info.java还需要手动更新maven项目.

I expected that an update of the maven project would only be required if I change the pom.xml file. Now I learned that changing the module-info.java also requires a manual update of the maven project.

=> 更新Maven项目(Alt + F5)

在更新之后，我的错误消失了.

After that update my errors vanished.

我还了解到，最好先更新pom.xml文件中的版本，然后生成module-info.java.否则，module-info.java将包含不存在的模块，例如"requires log4j"，而不是"requires log4j.api"

I also learned that it is better to first update the versions in the pom.xml file and then generate the module-info.java. Otherwise the module-info.java will include non-existing modules like "requires log4j" instead of "requires log4j.api"

module-info.java中的另一个误导性错误可能是由于pom打包引起的，请参见下文.

Another misleading error in module-info.java might occur due to pom packaging, see below.

未解决的进口

对于无法解决导入的问题，问题可能是该(旧)导入需要哪个对应的(新)模块?".可能有帮助的地方:

For the case that an import can not be resolved the question might be "Which corresponding (new) module do I need for that (old) import?". What might help here:

• 在下一页搜索所需的页面: http://cr.openjdk.java.net/~ mr/jigsaw/ea/module-summary.html (列出所有导出的JDK模块的软件包)

• Search at following page for the required page: http://cr.openjdk.java.net/~mr/jigsaw/ea/module-summary.html (lists all exported packages of the JDK-modules)

在旧的* .jar文件上使用JDeps获取所需的jar文件的列表，例如

Use JDeps on the (old) *.jar file to get a list of required jar files, e.g.

jdeps --class-path"lib"-递归MY-OLD.jar> output.txt

jdeps --class-path "lib" -recursive MY-OLD.jar >output.txt

使用jar查找jar文件的模块

Use jar to find the module for a jar file

jar --describe-module --file REQUIRED-JAR-FILE.jar

jar --describe-module --file REQUIRED-JAR-FILE.jar

另请参阅:

• https://blog.codefx.org/tools/jdeps-tutorial-analyze-java-project-dependencies/#Getting-To-Know-JDeps

  重新导出依赖项

  为了对祖父母项目自动显示log4j

  In order to automatically make log4j visible for a grandparent project

  grandparent => parent => log4j
  

  您可能想使用

  requires transitive log4j.api 
  

  在父级而不是

  requires log4j.api
  

  在祖父母中.另请参阅:

  in grandparent. Also see:

  > Required和require之间有什么区别Java 9模块声明中的传递语句

  POM包装

  我的主要问题似乎是我的Java8 pom.xml文件使用了pom封装:

  My main issue seems to be that my Java8 pom.xml file used pom packaging:

  <packaging>pom</packaging>
  

  如果我删除该行，则module-info.java中不会显示任何错误

  If I remove that line, no errors are shown in module-info.java

  也请参见以下额外问题:如何在Java9.0.1和Eclipse Oxygen 1a发行版(4.7.1a)中的pom打包?

  Also see this extra question: How to use maven with Java9.0.1 and pom packaging in Eclipse Oxygen 1a Release (4.7.1a)?

  新的log4j版本

  A.除了更改"requires log4j" =>"requires log4j.api"外，我还必须针对与Java9兼容的新log4j版本修改调用代码:

  A. In addition to the change "requires log4j" => "requires log4j.api" I had to adapt the calling code for the new log4j version that is compatible to Java9:

  私有静态Logger sysLog = Logger.getLogger(Main.class);

  private static Logger sysLog = Logger.getLogger(Main.class);

  到

  私有静态Logger sysLog = LogManager.getLogger(Main.class);

  private static Logger sysLog = LogManager.getLogger(Main.class);

  B. log4j 2没有PropertyConfigurator.另请参阅以下相关问题:

  B. log4j 2 does not have PropertyConfigurator. Also see this related question:

  log4j2中的PropertyConfigurator

  C. log4j 2不支持log4j.properties文件.以前我用

  C. log4j 2 does not support log4j.properties files. Previously I used

  src/main/resources/META-INF/log4j.properties

  src/main/resources/META-INF/log4j.properties

  进行配置.现在我用

  src/main/resources/log4j2.xml

  src/main/resources/log4j2.xml

  另请参见

  • Log4j 2不支持log4j.properties文件不再吗?

  将log4j.properties转换为log4j.xml

  工作示例作为参考

  pom.xml:

  <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>Log4JWithJava9</groupId>
    <artifactId>Log4JWithJava9</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <build>
      <sourceDirectory>src</sourceDirectory>
      <plugins>
        <plugin>
          <artifactId>maven-compiler-plugin</artifactId>
          <version>3.7.0</version>
          <configuration>
            <release>9</release>
          </configuration>
        </plugin>
      </plugins>
    </build>
  
    <dependencies>
    <dependency>
              <groupId>org.apache.logging.log4j</groupId>
              <artifactId>log4j-api</artifactId>
              <version>2.9.1</version>
            </dependency>
            <dependency>
              <groupId>org.apache.logging.log4j</groupId>
              <artifactId>log4j-core</artifactId>
              <version>2.9.1</version>
            </dependency>
    </dependencies>
  
  </project>
  

  module-info.java:

  module-info.java:

  module Log4JWithJava9 {
      requires javafx.base;
      requires log4j.api; 
  }
  

  Main.java:

  Main.java:

  import org.apache.logging.log4j.LogManager;
  import org.apache.logging.log4j.Logger;
  
  
  public class Main {
  
      private static Logger sysLog = LogManager.getLogger(Main.class);
  
      public static void main(String[] args) {
  
      }
  
  }
  

  Eclipse插件

  为了将log4j添加到eclipse插件中，我将文件log4j-api-2.10.0.jar复制到文件夹"lib"中，并将jar文件添加到Java Build Path => Libraries => ModulePath

  In order to add log4j to an eclipse plugin, I copied the file log4j-api-2.10.0.jar in a folder "lib" and added the jar file to Java Build Path=>Libraries=>ModulePath

  我不得不使用requires org.apache.logging.log4j

  这篇关于如何在Eclipse Oxygen中将Log4j与Maven和Java9结合使用?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！