在将kotlin与spring-boot结合使用时，启用Hystrix会导致NullPointerException

Question

When I add Hystrix support to a kotlin spring boot project, some fields of an abstract class are suddenly null. It seems the Hystrix proxy does not handle fields properly:

I have an abstract kotlin class ClientHandler having two fields logger and test directly initialized. I have a kotlin subclass SomeHandler of ClientHandler which I use via autowiring in a class. As expected when using the subclass the two fields are initialized.

But when I add Hystrix support (uncomment @EnableHystrix and @HystrixCommand ) the two fields logger and test in the abstract class are suddenly null.

Do you have any ideas why this happens? Spring adds a proxy class to the SomeHandler class, Hystrix does the same. So I assume something goes wrong in the double proxying in combination with Kotlin!? I did the same with a java class and everything went fine.

package com.test

import mu.KotlinLogging
import org.springframework.stereotype.Component
import java.lang.RuntimeException

abstract class ClientHandler {

    protected val logger = KotlinLogging.logger {}
    private val test = "test"

    //@HystrixCommand(commandKey = "Some Service")
    fun send(communication: Communication): ResponseObject {
        try {
            return callApi(communication)
        } catch (e: Exception) {
            logger.warn("Could not send information", e)
            return ResponseObject()
        }
    }

    protected abstract fun callApi(communication: Communication): ResponseObject
}

@Component
class SomeHandler : ClientHandler() {

    override fun callApi(communication: Communication): ResponseObject {

        throw RuntimeException()
    }
}

class Communication {

}

class ResponseObject {

}

The application

package com.test

import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication

//@EnableHystrix
@SpringBootApplication
class SomeApplication {

    fun main(args: Array<String>) {
        runApplication<SomeApplication>(*args)
    }
}

The test

package com.test

import org.hibernate.validator.internal.util.Contracts.assertNotNull
import org.junit.Test
import org.junit.runner.RunWith
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.boot.test.context.SpringBootTest
import org.springframework.test.context.junit4.SpringRunner

@RunWith(SpringRunner::class)
@SpringBootTest
class CustomerApiImplTest {

    @Autowired
    private lateinit var someHandler: SomeHandler

    @Test
    fun testIt() {
        val communication = Communication()
        val responseEntity = someHandler.send(communication)

        assertNotNull(responseEntity)
    }
}

The 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>test</groupId>
    <artifactId>test</artifactId>
    <version>1.0-SNAPSHOT</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.3.RELEASE</version>
    </parent>

    <properties>
        <kotlin.version>1.3.21</kotlin.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-reflect</artifactId>
            <version>${kotlin.version}</version>
        </dependency>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-stdlib-jdk8</artifactId>
            <version>${kotlin.version}</version>
        </dependency>
        <dependency>
            <groupId>org.jetbrains.kotlinx</groupId>
            <artifactId>kotlinx-coroutines-core</artifactId>
            <version>1.1.1</version>
        </dependency>
        <dependency>
            <groupId>io.github.microutils</groupId>
            <artifactId>kotlin-logging</artifactId>
            <version>1.6.25</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
            <version>2.1.1.RELEASE</version>
        </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>repackage</goal>
                            <goal>build-info</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.jetbrains.kotlin</groupId>
                <artifactId>kotlin-maven-plugin</artifactId>
                <version>${kotlin.version}</version>
                <executions>
                    <execution>
                        <id>compile</id>
                        <phase>compile</phase>
                        <goals>
                            <goal>compile</goal>
                        </goals>
                        <configuration>
                            <sourceDirs>
                                <source>src/main/java</source>
                                <source>target/generated-sources/swagger/src/gen/java/main</source>
                            </sourceDirs>
                        </configuration>
                    </execution>
                    <execution>
                        <id>test-compile</id>
                        <phase>test-compile</phase>
                        <goals>
                            <goal>test-compile</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <jvmTarget>1.8</jvmTarget>
                    <args>
                        <arg>-Xjsr305=strict</arg> <!-- Enable strict mode for JSR-305 annotations -->
                    </args>
                    <compilerPlugins>
                        <plugin>spring</plugin>
                    </compilerPlugins>
                </configuration>
                <dependencies>
                    <dependency>
                        <groupId>org.jetbrains.kotlin</groupId>
                        <artifactId>kotlin-maven-allopen</artifactId>
                        <version>${kotlin.version}</version>
                    </dependency>
                </dependencies>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <executions>
                    <execution>
                        <id>compile</id>
                        <phase>compile</phase>
                        <goals>
                            <goal>compile</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>testCompile</id>
                        <phase>test-compile</phase>
                        <goals>
                            <goal>testCompile</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

</project>

Answer 1

我能够自己弄清楚： send函数必须是开放的，因此Hystrix和Spring将围绕包含两个字段的抽象类创建一个适当的Proxy。