使用 java 9 和 maven 的 spring 引导应用程序编译失败

Question

我正在尝试构建使用 java-9 并将部署到 heroku 的 spring-boot 应用程序。作为构建工具，我使用 maven.

我使用 initializr 生成了 spring boot 1.5 应用程序。我添加了 heroku 个特定文件，并将 toolchains.xml 添加到 maven-compiler-plugin 的 .m2 存储库。

我的pom.xml看起来像这样

<?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>com.lapots.breed.platform.cloud</groupId>
    <artifactId>java-cloud-sample</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>java-cloud-sample</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.6.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>1.9</java.version>
        <maven.compiler.source>1.9</maven.compiler.source>
        <maven.compiler.target>1.9</maven.compiler.target>
        <maven.compiler.release>9</maven.compiler.release>
    </properties>

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

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.postgresql</groupId>
            <artifactId>postgresql</artifactId>
            <scope>runtime</scope>
        </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>
                <executions>
                    <execution>
                        <goals>
                            <goal>build-info</goal>
                        </goals>
                        <configuration>
                            <additionalProperties>
                                <encoding.source>${project.build.sourceEncoding}</encoding.source>
                                <encoding.reporting>${project.reporting.outputEncoding}</encoding.reporting>
                                <java.source>${maven.compiler.source}</java.source>
                                <java.target>${maven.compiler.target}</java.target>
                            </additionalProperties>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <version>3.6.0</version>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-toolchains-plugin</artifactId>
                <version>1.1</version>
                <configuration>
                    <toolchains>
                        <jdk>
                            <version>1.9</version>
                            <vendor>oracle</vendor>
                        </jdk>
                    </toolchains>
                </configuration>
                <executions>
                    <execution>
                        <goals>
                            <goal>toolchain</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>


</project>

当我尝试使用 mvn clean package 编译项目时出现错误

[ERROR] COMPILATION ERROR :
[INFO] -------------------------------------------------------------
[ERROR] javac: invalid flag: -Xmodule:null
Usage: javac <options> <source files>
use --help for a list of possible options

[INFO] 1 error
[INFO] -------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 3.031 s
[INFO] Finished at: 2017-08-30T21:08:25+03:00
[INFO] Final Memory: 20M/309M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.6.0:testCompile (default-testCompile) on
 project java-cloud-sample: Compilation failure
[ERROR] javac: invalid flag: -Xmodule:null
[ERROR] Usage: javac <options> <source files>
[ERROR] use --help for a list of possible options
[ERROR]
[ERROR]
[ERROR] -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException

module-info 看起来像这样

module com.lapots.breed.platform.cloud.javacloudsample {
    requires spring.boot;
}

问题是什么？此处提供项目 github repository

Answer 1

看起来您的 toolchains.xml 不包含 Java 9 的条目。试试这个：

<toolchain>
    <type>jdk</type>
    <provides>
        <version>1.9</version>
        <vendor>oracle</vendor>
    </provides>
    <configuration>
        <jdkHome>/path/to/jdk/9</jdkHome>
    </configuration>
</toolchain>

Answer 2

maven-compiler-plugin 3.6.0 基于 module-info.class 的第一个签名，它已经改变了几次。它与当前的 Java 9 签名不兼容。在使用最新版本的 JDK 9.

时，您应该使用 3.6.2

Answer 3

@Robert 正确指出您需要更新 maven-compiler-plugin。添加到它，也如 Maven/Jigsaw+9 over the maven plugins. The minimum compatible version of maven-compiler-plugin with current jdk-9+181 中所述，3.6.2 可以用作 :

<!--Minimum compatible version required-->
<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.6.2</version>
    <configuration>
        <jdkToolchain>
            <version>9</version>
        </jdkToolchain>
    </configuration>
</plugin>

这里引用 examples of maven-compiler-plugin with module-info.java 之一：

For projects that want to be compatible with older versions of Java (i.e 1.8 or below), but also want to provide a module-info.java for Java 9 projects must be aware that they need to call javac twice: the module-info.java must be compiled with release=9, while the rest of the sources must be compiled with a lower version of source/target.

可以使用(JAVA_HOME设置为1.8.x):

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.6.2</version>
    <executions>
      <execution>
        <id>default-compile</id>
        <configuration>
          <!-- compile everything to ensure module-info contains right entries -->
          <!-- required when JAVA_HOME is JDK 8 or below -->
          <jdkToolchain>
            <version>9</version>
          </jdkToolchain>
          <release>9</release>
        </configuration>
      </execution>
      <execution>
        <id>base-compile</id>
        <goals>
          <goal>compile</goal>
        </goals>
        <!-- recompile everything for target VM except the module-info.java -->
        <configuration>
          <excludes>
            <exclude>module-info.java</exclude>
          </excludes>
        </configuration>
      </execution>
    </executions>
    <!-- defaults for compile and testCompile -->
    <configuration>
      <!-- jdkToolchain required when JAVA_HOME is JDK 9 or above -->
      <jdkToolchain>
        <version>[1.5,9)</version>
      </jdkToolchain>
      <source>1.5</source>
      <target>1.5</target>
    </configuration>
</plugin>

但有几点需要注意：

... you will need at least Maven 3.3.1 to specify a custom jdkToolchain in your plugin configuration

或者您也可以将 JAVA_HOME 配置为 /jdk9/Contents/Home/bin 并使用以下配置：

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.6.2</version>
    <executions>
      <execution>
        <id>default-compile</id>
        <configuration>
          <!-- compile everything to ensure module-info contains right entries -->
          <release>9</release>
        </configuration>
      </execution>
      <execution>
        <id>base-compile</id>
        <goals>
          <goal>compile</goal>
        </goals>
        <!-- recompile everything for target VM except the module-info.java -->
        <configuration>
          <excludes>
            <exclude>module-info.java</exclude>
          </excludes>
        </configuration>
      </execution>
    </executions>
    <!-- defaults for compile and testCompile -->
    <configuration>
      <!-- Only required when JAVA_HOME isn't at least Java 9 and when haven't configured the maven-toolchains-plugin -->
      <jdkToolchain>
        <version>9</version>
      </jdkToolchain>
      <release>6</release>
    </configuration>
</plugin>

使用 java 9 和 maven 的 spring 引导应用程序编译失败

compilation failure for spring boot application with java 9 and maven

java

maven

heroku

spring-boot

java-9