Apache Maven：-source 1.5中不支持Diamond运算符

Question

我使用以下命令构建并运行Java Apache Camel代码

mvn clean compile camel:run

该命令一直对我有用，但是当我有使用Diamond运算符的代码时，会出现错误。

我的钻石操作员：

private List<RestPropertyDefinition> restProperties = new ArrayList<>();

我的错误：

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project camel-rest-example: Compilation failure
[ERROR] /home/sindre/IdeaProjects/training/camelrestexample/src/main/java/com/test/EmployeeRoute.java:[21,73] diamond operator is not supported in -source 1.5
[ERROR]   (use -source 7 or higher to enable diamond operator)

我的POM文件：

<?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.test</groupId>
    <artifactId>camel-rest-example</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.apache.camel/camel-core -->
        <dependency>
            <groupId>org.apache.camel</groupId>
            <artifactId>camel-core</artifactId>
            <version>2.20.0</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.apache.camel/camel-spring -->
        <dependency>
            <groupId>org.apache.camel</groupId>
            <artifactId>camel-spring</artifactId>
            <version>2.20.0</version>
        </dependency>

        <dependency>
            <groupId>org.apache.camel</groupId>
            <artifactId>spi-annotations</artifactId>
            <version>2.20.0</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.apache.camel/camel-jms -->
        <dependency>
            <groupId>org.apache.camel</groupId>
            <artifactId>camel-jms</artifactId>
            <version>2.20.0</version>
        </dependency>

        <dependency>
            <groupId>org.apache.camel</groupId>
            <artifactId>camel-http4</artifactId>
            <version>2.20.0</version>
        </dependency>

        <dependency>
            <groupId>org.apache.camel</groupId>
            <artifactId>camel-quartz</artifactId>
            <version>2.20.0</version>
        </dependency>


        <!-- https://mvnrepository.com/artifact/org.apache.activemq/activemq-all -->
        <dependency>
            <groupId>org.apache.activemq</groupId>
            <artifactId>activemq-all</artifactId>
            <version>5.15.1</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-log4j12 -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>1.7.25</version>
            <scope>test</scope>
        </dependency>


    </dependencies>


    <build>
        <plugins>
            <!-- Allows the routes to be run via 'mvn camel:run' -->
            <plugin>
                <groupId>org.apache.camel</groupId>
                <artifactId>camel-maven-plugin</artifactId>
                <version>2.20.0</version>
            </plugin>
        </plugins>
    </build>
</project>

我在带有IntelliJ IDEA的Ubunut 18.04上使用Java 8。 看起来IntelliJ认为我正在使用Java 5？ 但是我的机器上只安装了Java 8

Answer 1

默认情况下，编译器似乎假定源代码级别为1.5。

使用pom告诉编译器这样的显式版本：

<build>
  <plugins>
    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-compiler-plugin</artifactId>
      <version>2.5.1</version>
      <configuration>
        <source>1.8</source>
        <target>1.8</target>
      </configuration>
    </plugin>

Answer 2

此问题是因为默认情况下，Java编译器配置为使用Java 1.5以获得最大兼容性，您可以通过添加以下条目来更改项目pom.xml的plugins标记中的编译器插件配置，从而显式覆盖maven的编译器插件。

<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>

您可以在此处找到有关Maven编译器插件用法的更多文档。