通过appassembler-maven-plugin生成的脚本无法在Spring Boot应用程序中找到主类 [英] Script generated via appassembler-maven-plugin is not able to find main class in Spring Boot application

问题描述

我使用appassembler-maven-plugin生成的启动脚本有问题。
我有一个只有一个类的基本spring-boot应用程序：

I have a problem with the start script that I generate with appassembler-maven-plugin. I have a basic spring-boot application with only one class:

@SpringBootApplication
public class ScriptDemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(ScriptDemoApplication.class, args);
    }
}

和我的pom.xml

and my pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<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>org.home.sziolkow</groupId>
    <artifactId>script-demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>script-demo</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.4.1.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.7</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>

            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <mainClass>${start-class}</mainClass>
                </configuration>
                <executions>
                    <execution>
                        <goals>
                            <goal>
                                repackage
                            </goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>appassembler-maven-plugin</artifactId>
                <version>1.10</version>
                <configuration>
                    <goal>
                        package
                    </goal>
                    <showConsoleWindow>
                        true
                    </showConsoleWindow>
                    <platforms>
                        <platform>unix</platform>
                    </platforms>
                    <programs>
                        <program>
                            <mainClass>org.home.sziolkow.ScriptDemoApplication</mainClass>
                            <id>app</id>
                        </program>
                    </programs>
                </configuration>
            </plugin>

        </plugins>
    </build>

</project>

我运行maven： mvn package appassembler：assemble

生成包和脚本但是当我尝试运行 ./ target / appassembler / bin / app ，我得到

Package and scripts are generated but when I try to run ./target/appassembler/bin/app, I get

错误：无法找到或加载主类org.home.sziolkow.ScriptDemoApplication

Error: Could not find or load main class org.home.sziolkow.ScriptDemoApplication

我测试了生成的包，我可以毫无问题地启动应用程序：

I tested generated packages and I can start the application without problems with:

java -jar ./target/appassembler/repo/org/home/sziolkow/script-demo/0.0.1-SNAPSHOT/script-demo-0.0.1-SNAPSHOT.jar 

推荐答案

由于Spring Boot重新打包JAR的方式，你遇到了麻烦它是一个可执行的JAR。来自文档：

You're having this trouble because of the way Spring Boot is repackaging your JAR, in order to make it an executable JAR. From the documentation:

可执行存档不能用作依赖项，因为可执行的jar格式包 BOOT-INF / classes 中的应用程序类。这意味着当可执行jar用作依赖项时无法找到它们。

The executable archive cannot be used as a dependency as the exectuable jar format packages application classes in BOOT-INF/classes. This means that they cannot be found when the executable jar is used as a dependency.

基本上，Spring Boot Maven插件重新打包你的JAR并将您的类放入 BOOT-INF / classes ， BOOT-INF / lib 中的所有JAR依赖项，并启动其 JarLauncher 类作为主类，它将在这些位置搜索类和JAR。

Essentially, the Spring Boot Maven Plugin repackages your JAR and puts your classes inside BOOT-INF/classes, all the JAR dependencies inside BOOT-INF/lib, and launches its JarLauncher class as main class, which will search for classes and JARs at those locations.

所以你有2解决方案：不要使用Spring Boot将JAR重新打包成可执行的JAR，或者根本不使用Appassembler插件。

So you have 2 solutions: do not use Spring Boot to repackage your JAR into an executable JAR, or do not use the Appassembler plugin at all.

由于Spring Boot为您创建了一个可执行的JAR，因此不需要使用Appassembler插件生成脚本。删除 appassembler-maven-plugin 的插件声明，并拥有：

Since Spring Boot creates an executable JAR for you, generating scripts with the Appassembler plugin is not necessary. Remove the plugin declaration for appassembler-maven-plugin and have:

<plugin>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-maven-plugin</artifactId>
  <configuration>
    <mainClass>org.home.sziolkow.ScriptDemoApplication</mainClass>
  </configuration>
  <executions>
    <execution>
      <goals>
        <goal>repackage</goal>
      </goals>
    </execution>
  </executions>
</plugin>

POM的唯一变化是添加< mainClass> 指向主类的参数，以及 appassembler-maven-plugin 的删除。启动 mvn clean package 时，您将能够直接启动生成的可执行JAR：

The only change with your POM is the addition of the <mainClass> parameter pointing to your main class, and the removal of the appassembler-maven-plugin. When launching mvn clean package, you'll be able to launch the generated executable JAR directly with:

java -jar target/script-demo-0.0.1-SNAPSHOT.jar

如果可执行文件名称中的版本0.0.1-SNAPSHOT存在问题，您只需设置< finalName> 即可你的POM：

If the version 0.0.1-SNAPSHOT in the name of the executable is an issue, you can simply set a <finalName> in your POM:

<build>
  <finalName>${project.artifactId}</finalName>
  <!-- ... -->
</build>

然后使用 java -jar target / script启动可执行JAR -demo.jar 。

如前所述，自从Spring Boot repackage 目标将类和JAR放在 BOOT-INF 文件夹中，我们需要摆脱它。所以删除 spring-boot-maven-plugin 插件声明，并进入你的POM：

As said before, since Spring Boot repackage goal put the classes and JARs inside a BOOT-INF folder, we need to get rid of that. So remove the spring-boot-maven-plugin plugin declaration, and have in your POM:

<plugin>
  <groupId>org.codehaus.mojo</groupId>
  <artifactId>appassembler-maven-plugin</artifactId>
  <version>1.10</version>
  <executions>
    <execution>
      <id>assemble</id>
      <goals>
        <goal>assemble</goal>
      </goals>
      <phase>package</phase>
      <configuration>
        <showConsoleWindow>true</showConsoleWindow>
        <platforms>
          <platform>unix</platform>
        </platforms>
        <programs>
          <program>
            <mainClass>org.home.sziolkow.ScriptDemoApplication</mainClass>
            <id>app</id>
          </program>
        </programs>
      </configuration>
    </execution>
  </executions>
</plugin>

与当前POM的区别在于Appassembler绑定到包阶段，以便在不调用 appassembler：assemble 的情况下启动执行。然后，当运行 mvn clean package 时，您将能够使用Appassembler生成的脚本启动您的应用程序：

The difference with your current POM is that the Appassembler is bound to the package phase, so that the execution is launched without invoking appassembler:assemble. Then, when running mvn clean package, you'll be able to start your application using the scripts generated by the Appassembler:

./target/appassembler/bin/app

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