0
点赞
收藏
分享

微信扫一扫

记一次activiti监听器无法实例化的错误解决过程(SpringBoot Listener)

问题场景

SpringBoot项目中,activiti某个流程节点需要配置监听器,当前节点任务提交完成之后触发方法更改远程表单的状态,具体流程监听设计如下:

feignClient代码:MyService.java

@FeignClient(value = "xxxxx")
public interface MyService {

   /**
    * 修改状态
    * @param inId
    * @return
    */
   @PutMapping("/myTest/updateState")
   Boolean updateState(@RequestParam("id") Integer id);

}

监听器代码:MyTaskListener.java,此处使用Lombok @AllArgConstructor注解通过全参构造器注入MyService

@AllArgsConstructor
public class MyTaskListener implements TaskListener {

    private MyService myService;

   /**
    * 任务监听修改表单状态
    * @param delegateTask 当前执行提交的任务
    */
   @Override
   public void notify(DelegateTask delegateTask) {
       。。。。。//获取到表单id
       myService.updateState(id);
   }
}

任务提交完成触发监听器的报错信息:couldn't instantiate class com.xxx.activiti.listener.MyTaskListener

2019-04-16 19:01:45.592 ERROR [xxx-activiti,b4057cc762e15e24,b4057cc762e15e24,true] 224 --- [  XNIO-1 task-1] o.a.e.impl.interceptor.CommandContext    : Error while closing command context

org.activiti.engine.ActivitiException: Exception while invoking TaskListener: couldn't instantiate class com.xxx.activiti.listener.MyTaskListener
    at org.activiti.engine.impl.persistence.entity.TaskEntity.fireEvent(TaskEntity.java:742)
    at org.activiti.engine.impl.persistence.entity.TaskEntity.complete(TaskEntity.java:184)
    at org.activiti.engine.impl.cmd.CompleteTaskCmd.execute(CompleteTaskCmd.java:52)
    at org.activiti.engine.impl.cmd.CompleteTaskCmd.execute(CompleteTaskCmd.java:24)
    at org.activiti.engine.impl.cmd.NeedsActiveTaskCmd.execute(NeedsActiveTaskCmd.java:59)
    at org.activiti.engine.impl.interceptor.CommandInvoker.execute(CommandInvoker.java:24)
    at org.activiti.engine.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:57)
    at org.activiti.spring.SpringTransactionInterceptor$1.doInTransaction(SpringTransactionInterceptor.java:47)
    at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:140)
    at org.activiti.spring.SpringTransactionInterceptor.execute(SpringTransactionInterceptor.java:45)
    at org.activiti.engine.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:31)
    at org.activiti.engine.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:40)
    at org.activiti.engine.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:35)
    at org.activiti.engine.impl.TaskServiceImpl.complete(TaskServiceImpl.java:182)
    at xxx.activiti.controller.TaskController.submit(TaskController.java:181)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframewor

原因猜想

对比项目自带的请假流程监听类

@Slf4j
public class LeaveProcessTaskListener implements TaskListener {

   /**
    * 查询提交人的上级
    *
    * @param delegateTask
    */
   @Override
   public void notify(DelegateTask delegateTask) {
     。。。。。
   }
}

发现,两者区别在于 MyTaskListener引入了一个Spring的Bean,猜想应该是Bean注入失败导致的

猜想认证

将MyTaskListener中的Bean注入暂时去除:

public class MyTaskListener implements TaskListener {

   /**
    * 任务监听修改表单状态
    * @param delegateTask 当前执行提交的任务
    */
   @Override
   public void notify(DelegateTask delegateTask) {
       。。。。。//获取到表单id
       System.out.println("执行任务完成=========");
   }
}

再次执行任务提交触发监听器输出:

执行任务完成=========

猜想正确

资料查询

Listener中无法通过构造函数进行Bean注入,必须通过setter方法注入

更改MyTaskListener中的Bean注入方式

public class MyTaskListener implements TaskListener {
    @Autowired
    private MyService myService;

   /**
    * 任务监听修改表单状态
    * @param delegateTask 当前执行提交的任务
    */
   @Override
   public void notify(DelegateTask delegateTask) {
       。。。。。//获取到表单id
       myService.updateState(id);
   }
}

执行任务提交报错:Exception while invoking TaskListener: null,错误NullPointException源于MyService空

2019-04-16 19:14:59.049 ERROR [xxx-activiti,b88f0f9fd6ab86e1,b88f0f9fd6ab86e1,true] 14508 --- [  XNIO-1 task-2] t.t.c.s.c.GlobalExceptionHandlerResolver : 全局异常信息 ex=Exception while invoking TaskListener: Exception while invoking TaskListener: null

org.activiti.engine.ActivitiException: Exception while invoking TaskListener: Exception while invoking TaskListener: null
    at org.activiti.engine.impl.persistence.entity.TaskEntity.fireEvent(TaskEntity.java:742)
    at org.activiti.engine.impl.persistence.entity.TaskEntity.complete(TaskEntity.java:184)
    at org.activiti.engine.impl.cmd.CompleteTaskCmd.execute(CompleteTaskCmd.java:52)
    at org.activiti.engine.impl.cmd.CompleteTaskCmd.execute(CompleteTaskCmd.java:24)
    at org.activiti.engine.impl.cmd.NeedsActiveTaskCmd.execute(NeedsActiveTaskCmd.java:59)
    at org.activiti.engine.impl.interceptor.CommandInvoker.execute(CommandInvoker.java:24)
    at org.activiti.engine.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:57)
    at org.activiti.spring.SpringTransactionInterceptor$1.doInTransaction(SpringTransactionInterceptor.java:47)
    at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:140)
    at org.activiti.spring.SpringTransactionInterceptor.execute(SpringTransactionInterceptor.java:45)
    at org.activiti.engine.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:31)
    at org.activiti.engine.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:40)
    at org.activiti.engine.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:35)
    at org.activiti.engine.impl.TaskServiceImpl.complete(TaskServiceImpl.java:182)
    at com.xxx.activiti.controller.TaskController.submit(TaskController.java:181)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at or

以上述结果为基础进行查询,一说Listener未被Spring容器进行管理,所以注入为空,我们可以在MyTaskListener上添加@Component注解,将MyTaskListener装配到Spring容器中

@Component
public class MyTaskListener implements TaskListener {
    @Autowired
    private MyService myService;

   /**
    * 任务监听修改表单状态
    * @param delegateTask 当前执行提交的任务
    */
   @Override
   public void notify(DelegateTask delegateTask) {
       。。。。。//获取到表单id
       myService.updateState(id);
   }
}

执行任务提交报错:Exception while invoking TaskListener: null

一样的结果

此时怀疑是否MyTaskListener没有成功装配到Spring容器中,所以编写一个工具类输出当前ApplicationContext所有被装配的类

@Component
public class SpringUtil implements ApplicationContextAware {

   /**
    * 当前IOC
    */
   private static ApplicationContext applicationContext;

   @Override
   public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
      this.applicationContext = applicationContext;
   }

   /**
    * 输出当前容器中所有被装配的类的id/bean名称
    */
   public static void showClass(){
      String[] beanDefinitionNames = applicationContext.getBeanDefinitionNames();
      for(String beanDefinitionName : beanDefinitionNames){
         System.out.println(beanDefinitionName);
      }
   }
}

任务提交后调用SpringUtil.showClass(),输出结果:

。
。
。
myTaskListener
。
。
。
com.xxx.activiti.feign.MyService
。

证明MyTaskListener及MyService都被装配成功

④继续查找,得到下述解释:

个人理解,上述过程中MyTaskListenre虽然存在于Spring容器中,但未被Spring容器所管理,所以@Autowired失效

尝试解决,既然注解方式不可以,那么可以考虑使用xml配置的传统方式,但是SpringBoot早已抛弃了xml配置方式,所以可以使用JAVA配置的老方法,手动从容器中取出Bean

改写SpringUtil,提供手动获取Bean的方法

 @Component
public class SpringUtil implements ApplicationContextAware {

   /**
    * 当前IOC
    *
    */
   private static ApplicationContext applicationContext;
    /**
     * 设置applicationContext
     */
   @Override
   public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
      this.applicationContext = applicationContext;
   }

   /**
    * 从当前IOC获取bean
    */
   public static <T> T getObject(Class<T> clazz){
       return applicationContext.getBean(clazz);
   }

   public static void showClass(){
      String[] beanDefinitionNames = applicationContext.getBeanDefinitionNames();
      for(String beanDefinitionName : beanDefinitionNames){
         System.out.println(beanDefinitionName);
      }
   }
}

改写监听器,更改MyService的获取方式:

@Component
public class MyTaskListener implements TaskListener {

   /**
    * 任务监听修改表单状态
    * @param delegateTask 当前执行提交的任务
    */
   @Override
   public void notify(DelegateTask delegateTask) {
       MyService myService= SpringUtil.getObject(MyService.class);
       。。。。。//获取到表单id
       myService.updateState(id);
   }
}

测试运行,问题解决

解决方案

手动获取Bean(如上):

 @Component
public class SpringUtil implements ApplicationContextAware {

   /**
    * 当前IOC
    *
    */
   private static ApplicationContext applicationContext;

    /**
     * 设置applicationContext
     */
   @Override
   public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
      this.applicationContext = applicationContext;
   }

   public static <T> T getObject(Class<T> clazz){
       return applicationContext.getBean(clazz);
   }
 }

思路推演

|------activiti执行任务触发监听器报错:couldn't instantiate class com.xxx.activiti.listener.MyTaskListener
|
|------比对正常监听类,发现区别在于注入的Bean
|
|------确认问题所在,第一次尝试使用@Autowired方式注入失败,新报错:Exception while invoking TaskListener: null,错误NullPointException源于MyService空
|
|-----问题定位转移:SpringBoot中监听器注入Spring Bean空?
|
|-----获得解决方案且知悉原理,手动获取Bean

备注

当初考虑过是否因为MyService在Spring容器中注册的ID为:com.xxx.activiti.feign.MyService 而不是myService从而导致无法注入。而后一想,controller中可以正常注入且变量命名随意,证明@Autowired并不是根据Bean的id进行,而是默认根据类型去获取bean(Spring基础知识)

举报

相关推荐

0 条评论