启用dubbo validation后hessian反序列化异常解决方案

现象

启用dubbo参数验证,当在provider端开启验证validation=”true”。调用接口时,若接口参数为对象类型,对象属性验证失败,客户端会报org.hibernate.validator.internal.metadata.descriptor.ConstraintDescriptorImpl’ could not be instantiated异常的解决方案。

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2019-04-25T09:57:18.544+0800 [ERROR] business-service o.a.c.c.C.[.[.[.[dispatcherServlet] - - Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.reflect.UndeclaredThrowableException] with root cause
com.alibaba.dubbo.remoting.RemotingException: com.alibaba.com.caucho.hessian.io.HessianFieldException: org.hibernate.validator.internal.engine.ConstraintViolationImpl.constraintDescriptor: 'org.hibernate.validator.internal.metadata.descriptor.ConstraintDescriptorImpl' could not be instantiated
com.alibaba.com.caucho.hessian.io.HessianFieldException: org.hibernate.validator.internal.engine.ConstraintViolationImpl.constraintDescriptor: 'org.hibernate.validator.internal.metadata.descriptor.ConstraintDescriptorImpl' could not be instantiated
at com.alibaba.com.caucho.hessian.io.JavaDeserializer.logDeserializeError(JavaDeserializer.java:167)
at com.alibaba.com.caucho.hessian.io.JavaDeserializer$ObjectFieldDeserializer.deserialize(JavaDeserializer.java:410)
at com.alibaba.com.caucho.hessian.io.JavaDeserializer.readObject(JavaDeserializer.java:276)
at com.alibaba.com.caucho.hessian.io.JavaDeserializer.readObject(JavaDeserializer.java:203)
at com.alibaba.com.caucho.hessian.io.SerializerFactory.readObject(SerializerFactory.java:526)
... more
Caused by: com.alibaba.com.caucho.hessian.io.HessianProtocolException: 'org.hibernate.validator.internal.metadata.descriptor.ConstraintDescriptorImpl' could not be instantiated
at com.alibaba.com.caucho.hessian.io.JavaDeserializer.instantiate(JavaDeserializer.java:316)
at com.alibaba.com.caucho.hessian.io.JavaDeserializer.readObject(JavaDeserializer.java:201)
at com.alibaba.com.caucho.hessian.io.Hessian2Input.readObjectInstance(Hessian2Input.java:2818)
at com.alibaba.com.caucho.hessian.io.Hessian2Input.readObject(Hessian2Input.java:2145)
at com.alibaba.com.caucho.hessian.io.Hessian2Input.readObject(Hessian2Input.java:2074)
at com.alibaba.com.caucho.hessian.io.Hessian2Input.readObject(Hessian2Input.java:2118)
at com.alibaba.com.caucho.hessian.io.Hessian2Input.readObject(Hessian2Input.java:2074)
at com.alibaba.com.caucho.hessian.io.JavaDeserializer$ObjectFieldDeserializer.deserialize(JavaDeserializer.java:406)
... 41 more
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at com.alibaba.com.caucho.hessian.io.JavaDeserializer.instantiate(JavaDeserializer.java:312)
... 48 more
Caused by: java.lang.NullPointerException
at org.hibernate.validator.internal.metadata.descriptor.ConstraintDescriptorImpl.<init>(ConstraintDescriptorImpl.java:176)
at org.hibernate.validator.internal.metadata.descriptor.ConstraintDescriptorImpl.<init>(ConstraintDescriptorImpl.java:233)
... more

版本

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<dependency>
<groupId>org.apache.dubbo</groupId>
<artifactId>dubbo</artifactId>
<version>2.7.1</version>
</dependency>

同时测试了2.6.5也有同样的问题。

分析

异常表象为’org.hibernate.validator.internal.metadata.descriptor.ConstraintDescriptorImpl’ could not be instantiated,在继续跟踪栈信息是在下面的地方抛出了NullPointerException异常。

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Caused by: java.lang.NullPointerException
at org.hibernate.validator.internal.metadata.descriptor.ConstraintDescriptorImpl.<init>(ConstraintDescriptorImpl.java:176)
at org.hibernate.validator.internal.metadata.descriptor.ConstraintDescriptorImpl.<init>(ConstraintDescriptorImpl.java:233)

进入ConstraintDescriptorImpl.java:176行看下,代码如下:

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public ConstraintDescriptorImpl(ConstraintHelper constraintHelper,
Member member,
ConstraintAnnotationDescriptor<T> annotationDescriptor,
ElementType type,
Class<?> implicitGroup,
ConstraintOrigin definedOn,
ConstraintType externalConstraintType) {
this.annotationDescriptor = annotationDescriptor;
this.elementType = type;
this.definedOn = definedOn;
this.isReportAsSingleInvalidConstraint = annotationDescriptor.getType().isAnnotationPresent(ReportAsSingleViolation.class);

... more

报空指针的位置就是

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this.isReportAsSingleInvalidConstraint = annotationDescriptor.getType().isAnnotationPresent(ReportAsSingleViolation.class);

结论

dubbo使用默认序列化协议hessian,在反序列化时根据构造函数参数个数优先级来取参数最少的构造器,由于ConstraintDescriptorImpl该类只一个构造器,debug进入发现在初始化时传入的参数全部为null,这就造成了NullPointerException异常,导致序列化失败。
从ConstraintViolationException继承结构可以看到其继承自ValidationException,并增加了一个参数private final Set<ConstraintViolation<?>> constraintViolations;用来将验证信息传递到consumer,反序列化的问题就是出在了Set<ConstraintViolation<?>>上。

upload successful

解决方案

知道了问题出在哪里,那解决起来还是很方便的。既然Set<ConstraintViolation<?>> constraintViolations是为了将校验信息传递到consumer,那我们自己自定义一个校验信息体就OK啦。
使用dubbo验证扩展自定义一个validation。

具体实现如下:
实现一个Validation接口,返回一个自定义的Validator

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package com.example.demo.dubbo.validation;

import org.apache.dubbo.common.URL;
import org.apache.dubbo.validation.Validation;
import org.apache.dubbo.validation.Validator;

/**
* @ClassName CustomValidation
* @Description
* @Author lixin
* @Date 2019-04-23 17:34
*/
public class CustomValidation implements Validation{

@Override
public Validator getValidator(URL url) {
return new CustomValidator(url);
}
}

CustomValidation实现,这里只需要简单的捕获一下ConstraintViolationException异常,将violations取出重新格式化即可,同时还保持了dubbo validation的原生逻辑支持

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package com.example.demo.dubbo.validation;

import org.apache.dubbo.common.URL;
import org.apache.dubbo.common.json.JSONArray;
import org.apache.dubbo.common.json.JSONObject;
import org.apache.dubbo.common.utils.ReflectUtils;
import org.apache.dubbo.validation.support.jvalidation.JValidator;
import org.apache.dubbo.validation.Validator;

import javax.validation.*;
import java.util.*;

/**
* 继承自{@link JValidator}保证了dubbo原生的vidation逻辑。
* 修改点:1、捕获ConstraintViolationException异常,将验证未通过异常改为ValidationException,解决dubbo hessian反序列化失败问题
* 2、格式化验证提示,使用json格式响应
*
* @Author lixin
* @Date 2019-04-23 17:35
*/
public class CustomValidator extends JValidator implements Validator {

private final Class<?> clazz;

@SuppressWarnings({"unchecked", "rawtypes"})
public CustomValidator(URL url) {
super(url);
this.clazz = ReflectUtils.forName(url.getServiceInterface());
}

@Override
public void validate(String methodName, Class<?>[] parameterTypes, Object[] arguments) throws Exception {

try{
super.validate(methodName,parameterTypes,arguments);
}catch (ConstraintViolationException e){
throw new ValidationException(constraintMessage(clazz.getName(),methodName,e.getConstraintViolations()));
}
}

private String constraintMessage(String className,String methodName,Set<ConstraintViolation<?>> violations){
JSONObject json = new JSONObject();
json.put("service",className);
json.put("method",methodName);

JSONArray details = new JSONArray();
for(ConstraintViolation violation : violations){
JSONObject detail = new JSONObject();
detail.put("bean",violation.getRootBean().getClass().getName());
detail.put("property",violation.getPropertyPath().toString());
detail.put("message",violation.getMessage());
details.add(detail);
}
json.put("details",details);
return json.toString();
}
}

使用方式

provider端启用(注解方式)

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@Service(validation = "xxx")

consumer端启用(注解方式)

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@Reference(validation = "xxx")

建议

1、在consumer端开启验证,以减少无用的请求打到provider端。
2、自定义的model类,增加默认构造器。