深入Spring Boot: 怎样排查 java.lang.ArrayStoreException

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java.lang.ArrayStoreException 分析

这个demo来说明怎样排查一个spring boot 1应用升级到spring boot 2时可能出现的java.lang.ArrayStoreException

demo地址:https://github.com/hengyunabc/spring-boot-inside/tree/master/demo-ArrayStoreException

demo里有两个模块,springboot1-starterspringboot2-demo

springboot1-starter模块里,是一个简单的HealthIndicator实现

public class MyHealthIndicator extends AbstractHealthIndicator {
    @Override
    protected void doHealthCheck(Builder builder) throws Exception {
        builder.status(Status.UP);
        builder.withDetail("hello", "world");
    }
}
@Configuration
@AutoConfigureBefore(EndpointAutoConfiguration.class)
@AutoConfigureAfter(HealthIndicatorAutoConfiguration.class)
@ConditionalOnClass(value = { HealthIndicator.class })
public class MyHealthIndicatorAutoConfiguration {
    @Bean
    @ConditionalOnMissingBean(MyHealthIndicator.class)
    @ConditionalOnEnabledHealthIndicator("my")
    public MyHealthIndicator myHealthIndicator() {
        return new MyHealthIndicator();
    }
}

springboot2-demo则是一个简单的spring boot2应用,引用了springboot1-starter模块。

把工程导入IDE,执行springboot2-demo里的ArrayStoreExceptionDemoApplication,抛出的异常是

Caused by: java.lang.ArrayStoreException: sun.reflect.annotation.TypeNotPresentExceptionProxy
    at sun.reflect.annotation.AnnotationParser.parseClassArray(AnnotationParser.java:724) ~[na:1.8.0_112]
    at sun.reflect.annotation.AnnotationParser.parseArray(AnnotationParser.java:531) ~[na:1.8.0_112]
    at sun.reflect.annotation.AnnotationParser.parseMemberValue(AnnotationParser.java:355) ~[na:1.8.0_112]
    at sun.reflect.annotation.AnnotationParser.parseAnnotation2(AnnotationParser.java:286) ~[na:1.8.0_112]
    at sun.reflect.annotation.AnnotationParser.parseAnnotations2(AnnotationParser.java:120) ~[na:1.8.0_112]
    at sun.reflect.annotation.AnnotationParser.parseAnnotations(AnnotationParser.java:72) ~[na:1.8.0_112]
    at java.lang.Class.createAnnotationData(Class.java:3521) ~[na:1.8.0_112]
    at java.lang.Class.annotationData(Class.java:3510) ~[na:1.8.0_112]
    at java.lang.Class.createAnnotationData(Class.java:3526) ~[na:1.8.0_112]
    at java.lang.Class.annotationData(Class.java:3510) ~[na:1.8.0_112]
    at java.lang.Class.getAnnotation(Class.java:3415) ~[na:1.8.0_112]
    at java.lang.reflect.AnnotatedElement.isAnnotationPresent(AnnotatedElement.java:258) ~[na:1.8.0_112]
    at java.lang.Class.isAnnotationPresent(Class.java:3425) ~[na:1.8.0_112]
    at org.springframework.core.annotation.AnnotatedElementUtils.hasAnnotation(AnnotatedElementUtils.java:575) ~[spring-core-5.0.4.RELEASE.jar:5.0.4.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping.isHandler(RequestMappingHandlerMapping.java:177) ~[spring-webmvc-5.0.4.RELEASE.jar:5.0.4.RELEASE]
    at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.initHandlerMethods(AbstractHandlerMethodMapping.java:217) ~[spring-webmvc-5.0.4.RELEASE.jar:5.0.4.RELEASE]
    at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.afterPropertiesSet(AbstractHandlerMethodMapping.java:188) ~[spring-webmvc-5.0.4.RELEASE.jar:5.0.4.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping.afterPropertiesSet(RequestMappingHandlerMapping.java:129) ~[spring-webmvc-5.0.4.RELEASE.jar:5.0.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1769) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1706) ~[spring-beans-5.0.4.RELEASE.jar:5.0.4.RELEASE]
    ... 16 common frames omitted

使用 Java Exception Breakpoint

下面来排查这个问题。

在IDE里,新建一个断点,类型是Java Exception Breakpoint(如果不清楚怎么添加,可以搜索对应IDE的使用文档),异常类是上面抛出来的java.lang.ArrayStoreException

当断点起效时,查看AnnotationUtils.findAnnotation(Class<?>, Class<A>, Set<Annotation>) line: 686 函数的参数。

可以发现

  • clazz是 class com.example.springboot1starter.MyHealthIndicatorAutoConfiguration$$EnhancerBySpringCGLIB$$945c1f
  • annotationType是 interface org.springframework.boot.actuate.endpoint.annotation.Endpoint

说明是尝试从MyHealthIndicatorAutoConfiguration里查找@Endpoint信息时出错的。

MyHealthIndicatorAutoConfiguration上的确没有@Endpoint,但是为什么抛出java.lang.ArrayStoreException?

尝试以简单例子复现异常

首先尝试直接 new MyHealthIndicatorAutoConfiguration :

    public static void main(String[] args) {
        MyHealthIndicatorAutoConfiguration cc = new MyHealthIndicatorAutoConfiguration();
    }

本以为会抛出异常来,但是发现执行正常。

再仔细看异常栈,可以发现是在at java.lang.Class.getDeclaredAnnotation(Class.java:3458)抛出的异常,则再尝试下面的代码:

推荐:深入Spring Boot :怎样排查 java.lang.ArrayStoreException

[这个demo来说明怎样排查一个spring boot 1应用升级到spring boot 2时可能出现的java.lang.ArrayStoreException。demo里有两个模块,springboot1-starter和springboot2-dem

    public static void main(String[] args) {
        MyHealthIndicatorAutoConfiguration.class.getDeclaredAnnotation(Endpoint.class);
    }

发现可以复现异常了:

Exception in thread "main" java.lang.ArrayStoreException: sun.reflect.annotation.TypeNotPresentExceptionProxy
    at sun.reflect.annotation.AnnotationParser.parseClassArray(AnnotationParser.java:724)
    at sun.reflect.annotation.AnnotationParser.parseArray(AnnotationParser.java:531)
    at sun.reflect.annotation.AnnotationParser.parseMemberValue(AnnotationParser.java:355)
    at sun.reflect.annotation.AnnotationParser.parseAnnotation2(AnnotationParser.java:286)
    at sun.reflect.annotation.AnnotationParser.parseAnnotations2(AnnotationParser.java:120)
    at sun.reflect.annotation.AnnotationParser.parseAnnotations(AnnotationParser.java:72)
    at java.lang.Class.createAnnotationData(Class.java:3521)
    at java.lang.Class.annotationData(Class.java:3510)
    at java.lang.Class.getDeclaredAnnotation(Class.java:3458)

 

为什么会是java.lang.ArrayStoreException

再仔细看异常信息:java.lang.ArrayStoreException: sun.reflect.annotation.TypeNotPresentExceptionProxy

ArrayStoreException是一个数组越界的异常,它只有一个String信息,并没有cause

那么我们尝试在 sun.reflect.annotation.TypeNotPresentExceptionProxy 的构造函数里打断点。

public class TypeNotPresentExceptionProxy extends ExceptionProxy {
    private static final long serialVersionUID = 5565925172427947573L;
    String typeName;
    Throwable cause;

    public TypeNotPresentExceptionProxy(String typeName, Throwable cause) {
        this.typeName = typeName;
        this.cause = cause;
    }

在断点里,我们可以发现:

  • typeName是 org.springframework.boot.actuate.autoconfigure.EndpointAutoConfiguration
  • cause是 java.lang.ClassNotFoundException: org.springframework.boot.actuate.autoconfigure.EndpointAutoConfiguration

终于真相大白了,是找不到org.springframework.boot.actuate.autoconfigure.EndpointAutoConfiguration这个类。

那么它是怎么变成ArrayStoreException的呢?

仔细看下代码,可以发现AnnotationParser.parseClassValue把异常包装成为Object

//sun.reflect.annotation.AnnotationParser.parseClassValue(ByteBuffer, ConstantPool, Class<?>)
    private static Object parseClassValue(ByteBuffer buf,
                                          ConstantPool constPool,
                                          Class<?> container) {
        int classIndex = buf.getShort() & 0xFFFF;
        try {
            try {
                String sig = constPool.getUTF8At(classIndex);
                return parseSig(sig, container);
            } catch (IllegalArgumentException ex) {
                // support obsolete early jsr175 format class files
                return constPool.getClassAt(classIndex);
            }
        } catch (NoClassDefFoundError e) {
            return new TypeNotPresentExceptionProxy("[unknown]", e);
        }
        catch (TypeNotPresentException e) {
            return new TypeNotPresentExceptionProxy(e.typeName(), e.getCause());
        }
    }

然后在sun.reflect.annotation.AnnotationParser.parseClassArray(int, ByteBuffer, ConstantPool, Class<?>)里尝试直接设置到数组里

// sun.reflect.annotation.AnnotationParser.parseClassArray(int, ByteBuffer, ConstantPool, Class<?>)
result[i] = parseClassValue(buf, constPool, container);

而这里数组越界了,ArrayStoreException只有越界的Object的类型信息,也就是上面的

java.lang.ArrayStoreException: sun.reflect.annotation.TypeNotPresentExceptionProxy

解决问题

发现是java.lang.ClassNotFoundException: org.springframework.boot.actuate.autoconfigure.EndpointAutoConfiguration,则加上@ConditionalOnClass的检查就可以了:

@Configuration
@AutoConfigureBefore(EndpointAutoConfiguration.class)
@AutoConfigureAfter(HealthIndicatorAutoConfiguration.class)
@ConditionalOnClass(value = {HealthIndicator.class, EndpointAutoConfiguration.class})
public class MyHealthIndicatorAutoConfiguration {

准确来说是spring boot2把一些类的package改了:

spring boot 1里类名是:

  • org.springframework.boot.actuate.autoconfigure.EndpointAutoConfiguration

spring boot 2里类名是:

  • org.springframework.boot.actuate.autoconfigure.endpoint.EndpointAutoConfiguration

总结

  • 当类加载时,并不会加载它的annotation的field所引用的Class<?>,当调用Class.getDeclaredAnnotation(Class<A>)里才会加载

    以上面的例子来说,就是@AutoConfigureBefore(EndpointAutoConfiguration.class)里的EndpointAutoConfiguration并不会和MyHealthIndicatorAutoConfiguration一起被加载。

  • jdk内部的解析字节码的代码不合理,把ClassNotFoundException异常吃掉了
  • 排查问题需要一步步深入调试

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