Apache驼峰和spring-boot构造函数注入 - NPE

Question

我有以下简单的spring-boot应用程序,它使用apache camel:

DemoApplication.java:

@SpringBootApplication
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}

@Component
class MySampleRoute extends SpringRouteBuilder {

    @Override
    public void configure() throws Exception {
        from("file://data/input")
                .bean(SampleProcessor1.class)
                .to("file://data/output");
    }
}

我的豆子:

SampleProcessor1.java:

public class SampleProcessor1 {

    private SampleProcessor2 sampleProcessor2;

    @Autowired
    public SampleProcessor1(SampleProcessor2 sampleProcessor2) {
        this.sampleProcessor2 = sampleProcessor2;
    }

    @Handler
    public void handle(
            @Body GenericFile<String> file
    ) {

    }
}

SampleProcessor2.java:

@Component
public class SampleProcessor2 { }

当我运行这个应用程序并将一些文件放在data/input目录中时 - 我得到以下NPE:

java.lang.NullPointerException: null
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_111]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_111]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_111]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_111]
at org.apache.camel.component.bean.MethodInfo.invoke(MethodInfo.java:472) ~[camel-core-2.19.3.jar:2.19.3]
at org.apache.camel.component.bean.MethodInfo$1.doProceed(MethodInfo.java:291) ~[camel-core-2.19.3.jar:2.19.3]
at org.apache.camel.component.bean.MethodInfo$1.proceed(MethodInfo.java:264) ~[camel-core-2.19.3.jar:2.19.3]
at org.apache.camel.component.bean.BeanProcessor.process(BeanProcessor.java:178) ~[camel-core-2.19.3.jar:2.19.3]
at org.apache.camel.management.InstrumentationProcessor.process(InstrumentationProcessor.java:77) ~[camel-core-2.19.3.jar:2.19.3]
at org.apache.camel.processor.RedeliveryErrorHandler.process(RedeliveryErrorHandler.java:541) ~[camel-core-2.19.3.jar:2.19.3]
at org.apache.camel.processor.CamelInternalProcessor.process(CamelInternalProcessor.java:198) [camel-core-2.19.3.jar:2.19.3]
at org.apache.camel.processor.Pipeline.process(Pipeline.java:120) [camel-core-2.19.3.jar:2.19.3]
at org.apache.camel.processor.Pipeline.process(Pipeline.java:83) [camel-core-2.19.3.jar:2.19.3]
at org.apache.camel.processor.CamelInternalProcessor.process(CamelInternalProcessor.java:198) [camel-core-2.19.3.jar:2.19.3]
at org.apache.camel.component.file.GenericFileConsumer.processExchange(GenericFileConsumer.java:451) [camel-core-2.19.3.jar:2.19.3]
at org.apache.camel.component.file.GenericFileConsumer.processBatch(GenericFileConsumer.java:218) [camel-core-2.19.3.jar:2.19.3]
at org.apache.camel.component.file.GenericFileConsumer.poll(GenericFileConsumer.java:182) [camel-core-2.19.3.jar:2.19.3]
at org.apache.camel.impl.ScheduledPollConsumer.doRun(ScheduledPollConsumer.java:174) [camel-core-2.19.3.jar:2.19.3]
at org.apache.camel.impl.ScheduledPollConsumer.run(ScheduledPollConsumer.java:101) [camel-core-2.19.3.jar:2.19.3]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [na:1.8.0_111]
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308) [na:1.8.0_111]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180) [na:1.8.0_111]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294) [na:1.8.0_111]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_111]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_111]
at java.lang.Thread.run(Thread.java:745) [na:1.8.0_111]

但是,如果我尝试从中删除构造函数注入SampleProcessor1并使用,例如现场注入 - 那么就不会发生NPE并且一切正常.

SampleProcessor1.java - 工作版:

public class SampleProcessor1 {

    @Autowired
    private SampleProcessor2 sampleProcessor2;

    @Handler
    public void handle(
            @Body GenericFile<String> file
    ) {

    }
}

据我所知 - 问题出在构造函数注入 - 但我无法理解为什么.

所以我的问题是为什么我在使用构造函数注入时获得NPE？

我用spring-boot:1.5.7.RELEASE 和org.apache.camel:camel-spring-boot-starter:2.19.3

---

更新1:添加源代码到github:github上的存储库

---

更新2:

在NPE发生方法之前添加断点:

使用构造函数注入:

没有构造函数注入(使用字段注入):

Answer 1

在Camel 2.19.x或更早版本中不支持Spring构造函数注入.您需要升级到Camel 2.20.0或更高版本.

请参阅发行说明:http://camel.apache.org/camel-2200-release.html

• 使用Camel with Spring现在支持通过其FQN名称调用Bean,并让Spring使用自动布线构造函数实例化bean,而不是仅支持无参数构造函数.

另一种方法是使用bean id引用bean,让Spring更多地管理它

 .bean("mySampleProcessor")

然后在课堂上用这个名字声明它

@Component("mySampleProcessor")
public class SampleProcessor1 {
  ...
}