Question

我正在尝试构建一个使用lambda表达式的Kafka Streams应用程序。

我的maven构建配置是 mvn clean install

当我做RunAs＆gt; Maven构建，我收到以下错误：

[ERROR] COMPILATION ERROR : 
[INFO] -------------------------------------------------------------
[ERROR] /home/junaid/eMumba/StreamsExample/streams.examples/src/main/java/myapps/Pipe.java:[53,38] lambda expressions are not supported in -source 1.5
  (use -source 8 or higher to enable lambda expressions)
[INFO] 1 error
[INFO] -------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2.265 s
[INFO] Finished at: 2018-02-24T14:50:04+05:00
[INFO] Final Memory: 11M/150M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project streams.examples: Compilation failure
[ERROR] /home/junaid/eMumba/StreamsExample/streams.examples/src/main/java/myapps/Pipe.java:[53,38] lambda expressions are not supported in -source 1.5
[ERROR] (use -source 8 or higher to enable lambda expressions)

在Java Build Path我JRE System Library [JavaSE 1.8]。

在Preferences > Java > Installed JREs我有java-8-openjdk

这是我的 pom.xml ：

我最后添加了org.apache.maven.plugins：maven-compiler-plugin依赖项。

<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>streamsexamples</groupId>
    <artifactId>streams.examples</artifactId>
    <version>0.1</version>
    <packaging>jar</packaging>

    <name>Kafka Streams Quickstart :: Java</name>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <kafka.version>1.0.0</kafka.version>
        <slf4j.version>1.7.7</slf4j.version>
        <log4j.version>1.2.17</log4j.version>
    </properties>

    <!-- Execute "mvn clean package -Pbuild-jar" to build a jar file out of 
        this project! -->

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-dependency-plugin</artifactId>
                <executions>
                    <execution>
                        <id>copy-dependencies</id>
                        <phase>prepare-package</phase>
                        <goals>
                            <goal>copy-dependencies</goal>
                        </goals>
                        <configuration>
                            <outputDirectory>
                                ${project.build.directory}/libs
                            </outputDirectory>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jar-plugin</artifactId>
                <version>3.0.2</version>
                <configuration>
                    <archive>
                        <manifest>
                            <addClasspath>true</addClasspath>
                            <classpathPrefix>libs/</classpathPrefix>
                            <mainClass>
                                myapps.Pipe
                            </mainClass>
                        </manifest>
                    </archive>
                </configuration>
            </plugin>
        </plugins>
    </build>

    <dependencies>
        <!-- Apache Kafka dependencies -->
        <dependency>
            <groupId>org.apache.kafka</groupId>
            <artifactId>kafka-streams</artifactId>
            <version>${kafka.version}</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.json/json -->
        <dependency>
            <groupId>org.json</groupId>
            <artifactId>json</artifactId>
            <version>20180130</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.apache.maven.plugins/maven-compiler-plugin -->
        <dependency>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.1</version>
        </dependency>

    </dependencies>
</project>

我该怎么做才能解决这个问题？

Answer 1

尝试将源版本和目标版本添加到您的pom：

<plugins>
  <plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.7.0</version>
    <configuration>
      <source>1.8</source>
      <target>1.8</target>
    </configuration>
  </plugin>
</plugins>

请参阅https://maven.apache.org/plugins/maven-compiler-plugin/examples/set-compiler-source-and-target.html

Answer 2

使用此pom.xml。指定maven-compiler-plugin的源版本和目标版本。

<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>streamsexamples</groupId>
<artifactId>streams.examples</artifactId>
<version>0.1</version>
<packaging>jar</packaging>

<name>Kafka Streams Quickstart :: Java</name>

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <kafka.version>1.0.0</kafka.version>
    <slf4j.version>1.7.7</slf4j.version>
    <log4j.version>1.2.17</log4j.version>
</properties>

<!-- Execute "mvn clean package -Pbuild-jar" to build a jar file out of 
    this project! -->

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-dependency-plugin</artifactId>
            <executions>
                <execution>
                    <id>copy-dependencies</id>
                    <phase>prepare-package</phase>
                    <goals>
                        <goal>copy-dependencies</goal>
                    </goals>
                    <configuration>
                        <outputDirectory>
                            ${project.build.directory}/libs
                        </outputDirectory>
                    </configuration>
                </execution>
            </executions>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-jar-plugin</artifactId>
            <version>3.0.2</version>
            <configuration>
                <archive>
                    <manifest>
                        <addClasspath>true</addClasspath>
                        <classpathPrefix>libs/</classpathPrefix>
                        <mainClass>
                            myapps.Pipe
                        </mainClass>
                    </manifest>
                </archive>
            </configuration>
        </plugin>

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.1</version>
            <configuration>
                <source>1.8</source>
                <target>1.8</target>
            </configuration>
        </plugin>
    </plugins>
</build>

<dependencies>
    <!-- Apache Kafka dependencies -->
    <dependency>
        <groupId>org.apache.kafka</groupId>
        <artifactId>kafka-streams</artifactId>
        <version>${kafka.version}</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.json/json -->
    <dependency>
        <groupId>org.json</groupId>
        <artifactId>json</artifactId>
        <version>20180130</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.apache.maven.plugins/maven-compiler-plugin -->


</dependencies>

Java错误 - -source 1.5不支持lambda表达式（使用-source 8或更高版本来启用lambda表达式）

2 个答案: