先說說坑
JSON.toString在序列化對象時，默認(rèn)通過的是get*()方法來查找屬性，而不是具體某個屬性，同時回忽略transient注解的屬性丰捷。
測試案例如下
public class FastJsonTest {
public static void main(String[] args) {
Person person = new Person();
person.setBirth(new Date());
System.out.println(JSON.toJSONString(person));
}
public static class Person{
private Integer age =123;
private transient Date birth;
public Date getBirth() {
return birth;
}
public void setBirth(Date birth) {
this.birth = birth;
}
public String getName(){
return "scj";
}
}
}
輸出
{"name":"scj"}
問題發(fā)生
最近在迭代一個老項目坯墨，升級中間件框架版本(不升級不給打包部署)后寂汇，在項目啟動的時候居然拋出以下異常
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.masaike.yama.platform.domain.model.product.ProductServiceEntity.properties, could not initialize proxy - no Session
at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:582)
at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:201)
at org.hibernate.collection.internal.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:145)
at org.hibernate.collection.internal.PersistentBag.size(PersistentBag.java:261)
at com.masaike.yama.platform.infrastructure.converter.ProductServiceConverterImpl.productServicePropertyVOListToProductServicePropertyDTOList(ProductServiceConverterImpl.java:139)
at com.masaike.yama.platform.infrastructure.converter.ProductServiceConverterImpl.map(ProductServiceConverterImpl.java:50)
at com.masaike.yama.platform.infrastructure.converter.ProductServiceConverterImpl.entityListToDTOList(ProductServiceConverterImpl.java:32)
at com.masaike.yama.platform.query.ProductServiceQueryServiceImpl.getAllProductService(ProductServiceQueryServiceImpl.java:43)
at com.alibaba.fastjson.serializer.ASMSerializer_12_ProductServiceQueryServiceImpl.write(Unknown Source)
at com.alibaba.fastjson.serializer.JSONSerializer.writeWithFieldName(JSONSerializer.java:333)
at com.alibaba.fastjson.serializer.ASMSerializer_1_InterfaceInfo.write(Unknown Source)
at com.alibaba.fastjson.serializer.JSONSerializer.write(JSONSerializer.java:285)
at com.alibaba.fastjson.JSON.toJSONString(JSON.java:745)
at com.alibaba.fastjson.JSON.toJSONString(JSON.java:683)
at com.alibaba.fastjson.JSON.toJSONString(JSON.java:648)
at com.alibaba.dubbo.config.masaikehttp.ExportedInterfaceManager.addInterface(ExportedInterfaceManager.java:104)//關(guān)鍵點
at com.alibaba.dubbo.config.ServiceConfig.doExport(ServiceConfig.java:321)
at com.alibaba.dubbo.config.ServiceConfig.export(ServiceConfig.java:218)
at com.alibaba.dubbo.config.spring.ServiceBean.onApplicationEvent(ServiceBean.java:123)
at com.alibaba.dubbo.config.spring.ServiceBean.onApplicationEvent(ServiceBean.java:49)
at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172)
at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165)
at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139)
at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:400)
at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:354)
at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:886)
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.finishRefresh(ServletWebServerApplicationContext.java:161)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:551)
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140)
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:754)
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:386)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:307)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1242)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1230)
at com.masaike.yama.bootstrap.BootStrapApplication.main(BootStrapApplication.java:36)
這個一個使用JPA時常見問題:延遲加載的時候session不存在
關(guān)于延遲加載no-session問題，可以看如何解決JPA延遲加載no Session報錯
從日志定位到拋出異常的方法為
@Override
@Transactional(rollbackFor = Exception.class)
public List<XXDTO> getAllXX() {
List<XXEntity> result = xXQueryRepository.findAll();
//下面的converter會觸發(fā)延遲加載
return XXConverter.INSTANCE.entityListToDTOList(result);
}
這邊存在兩個迷惑性行為
- 啟動的時候怎么調(diào)用了getAllXX方法
- getAllXX我加了@Transactional捣染，理論上是有session的
問題排查
精簡上面的異常棧
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.masaike.yama.platform.domain.model.product.ProductServiceEntity.properties, could not initialize proxy - no Session
at com.masaike.yama.platform.infrastructure.converter.ProductServiceConverterImpl.productServicePropertyVOListToProductServicePropertyDTOList(ProductServiceConverterImpl.java:139)
at com.masaike.yama.platform.infrastructure.converter.ProductServiceConverterImpl.map(ProductServiceConverterImpl.java:50)
at com.masaike.yama.platform.infrastructure.converter.ProductServiceConverterImpl.entityListToDTOList(ProductServiceConverterImpl.java:32)
at com.masaike.yama.platform.query.ProductServiceQueryServiceImpl.getAllProductService(ProductServiceQueryServiceImpl.java:43)
at com.alibaba.fastjson.JSON.toJSONString(JSON.java:648)
at com.alibaba.dubbo.config.masaikehttp.ExportedInterfaceManager.addInterface(ExportedInterfaceManager.java:104)//關(guān)鍵點
at com.alibaba.dubbo.config.ServiceConfig.doExport(ServiceConfig.java:321)
at com.alibaba.dubbo.config.ServiceConfig.export(ServiceConfig.java:218)
可以復(fù)盤出問題發(fā)生的現(xiàn)場
dubbo服務(wù)進行export的時候調(diào)用了ExportedInterfaceManager.addInterface方法骄瓣，而在addInterface方法中調(diào)用的JSON.toJSONString方法觸發(fā)了ProductServiceQueryServiceImpl.getAllProductService方法
在看了ExportedInterfaceManager.addInterface源碼之后，問題的起因浮出水面
ExportedInterfaceManager這個類是用來針對接口暴露http服務(wù)時收集元數(shù)據(jù)使用
public synchronized void addInterface(Class<?> interfaceCls, Object obj) {
//如果是代理類獲取代理類對象
obj = getObjectTarget(obj);//獲取原始對象
//...
InterfaceInfo interfaceInfo = new InterfaceInfo();
interfaceInfo.setInterfaceName(interfaceName);
interfaceInfo.setRef(obj);//致命之處
//...
logger.info(String.format("start to addInterface into interfaceMap,interfaceName[%s],interfaceInfo[%s]",interfaceName, JSON.toJSONString(interfaceInfo)));//致命之處
// add interface info to map
interfaceMap.put(interfaceName, interfaceInfo);
}
對于第一個問題耍攘，InterfaceInfo的ref指向ProductServiceQueryServiceImpl榕栏，在打印日志的時候，JSON.toJSONString觸發(fā)了ProductServiceQueryServiceImpl中的get方法
而對于第二個問題蕾各，obj = getObjectTarget(obj);這段代碼會獲取代理的原始對象扒磁，導(dǎo)致事務(wù)失效。
問題危害
拋開獲取原始對象這個邏輯不說式曲，這個bug的致命之處在于妨托，他會調(diào)用所暴露dubbo接口中所有get*()格式的方法
問題解決
解決方式很簡單，有以下兩種
- 不要序列化ref(加fastjson注解或字段加transient)
- 去掉打印日志邏輯
在反饋這個問題后吝羞，中間件團隊的改動如下
