flink cep中缺少“map”的泛型类型参数

8dtrkrch 于 2021-06-25 发布在 Flink

关注(0)|答案(2)|浏览(318)

flink-cep中检测模式的代码如下所示

// Generate temperature warnings for each matched warning pattern

DataStream<TemperatureEvent> warnings = tempPatternStream.select(
    (Map<String, MonitoringEvent> pattern) -> {
        TemperatureEvent first = (TemperatureEvent) pattern.get("first");

        return new TemperatureEvent(first.getRackID(), first.getTemperature()) ;
    }
);

如果在mac中使用command+f9构建，则显示以下错误

Exception in thread "main" org.apache.flink.api.common.functions.InvalidTypesException: The generic type parameters of 'Map' are missing. 
It seems that your compiler has not stored them into the .class file. 
Currently, only the Eclipse JDT compiler preserves the type information necessary to use the lambdas feature type-safely. 
See the documentation for more information about how to compile jobs containing lambda expressions.
    at org.apache.flink.api.java.typeutils.TypeExtractor.validateLambdaGenericParameter(TypeExtractor.java:1316)
    at org.apache.flink.api.java.typeutils.TypeExtractor.validateLambdaGenericParameters(TypeExtractor.java:1302)
    at org.apache.flink.api.java.typeutils.TypeExtractor.getUnaryOperatorReturnType(TypeExtractor.java:346)
    at org.apache.flink.cep.PatternStream.select(PatternStream.java:64)
    at org.stsffap.cep.monitoring.CEPMonitoring.main(CEPMonitoring.java:85

然而，建筑设计 mvn clean install 然后通过control+r运行显示输出，
我想知道为什么总是这样？
有办法吗？
ps：但是我使用的是EclipseJDT插件，即使它在日志中显示错误。pom.xml的内容如下

<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>
                    <compilerId>jdt</compilerId>
                </configuration>
                <dependencies>
                    <dependency>
                        <groupId>org.eclipse.tycho</groupId>
                        <artifactId>tycho-compiler-jdt</artifactId>
                        <version>0.21.0</version>
                    </dependency>
                </dependencies>
            </plugin>

欢迎您提出建议，谢谢

Maven apache-flink flink-streaming flink-cep eclipse-jdt

来源：https://stackoverflow.com/questions/45663700/the-generic-type-parameters-of-map-are-missing-in-flink-cep

2条答案

按热度按时间

ej83mcc01#

首先，检查你的身体 jdk 版本，是 1.8 ? 同时升级 tycho-compiler-jdt 至 1.0.0 您的san插件如下：

<plugin>
    <!-- Use compiler plugin with tycho as the adapter to the JDT compiler. -->
    <artifactId>maven-compiler-plugin</artifactId>
    <configuration>
        <source>1.8</source>
        <target>1.8</target>
        <compilerId>jdt</compilerId>
    </configuration>
    <dependencies>
        <!-- This dependency provides the implementation of compiler "jdt": -->
        <dependency>
            <groupId>org.eclipse.tycho</groupId>
            <artifactId>tycho-compiler-jdt</artifactId>
            <version>1.0.0</version>
        </dependency>
    </dependencies>
</plugin>

您可以参考来源：https://ci.apache.org/projects/flink/flink-docs-release-1.4/dev/java8.html
在此之后，您必须使用maven在cli上构建项目。一旦通过maven构建了程序，您也可以从intellij中运行它。

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tgabmvqs2#

我知道Java8lambda非常方便。但是，它们几乎不通过反射提供类型信息，这就是为什么flink在生成底层序列化程序时遇到问题的原因。为了在ide中运行flink程序，我建议在涉及泛型类型时使用java匿名类而不是lambdas。

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