Activiti之act_ge_property表引发的坑（dbSchemaUpdate）

Activiti之act_ge_property表引发的坑（dbSchemaUpdate）

参考文档：

https://blog.csdn.net/lb19921223/article/details/79213851

上篇文章写道，我学习acitiviti的时候，使用mysql的truncate把表中的数据都删除了，然后重新部署流程，结果居然报错了。

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans   http://www.springframework.org/schema/beans/spring-beans.xsd">

    <!-- 流程引擎配置的bean -->
    <bean id="processEngineConfiguration"
        class="org.activiti.engine.impl.cfg.StandaloneProcessEngineConfiguration">
        <property name="jdbcUrl"
            value="jdbc:mysql://localhost:3306/db_activiti?serverTimezone=Asia/Shanghai" />
        <property name="jdbcDriver" value="com.mysql.cj.jdbc.Driver" />
        <property name="jdbcUsername" value="root" />
        <property name="jdbcPassword" value="123456" />
        <property name="databaseSchemaUpdate" value="true" />
    </bean>

</beans>

package com.yuanqiao.first_activiti.deployment;

import java.util.List;

import org.activiti.engine.ProcessEngine;
import org.activiti.engine.ProcessEngines;
import org.activiti.engine.RepositoryService;
import org.activiti.engine.repository.Deployment;
import org.activiti.engine.repository.DeploymentBuilder;
import org.activiti.engine.repository.ProcessDefinition;
import org.junit.Test;

import com.google.gson.Gson;

/**
 * 通过读取bpmn文件，来部署流程图
 * 
 * @author yuanqiao
 *
 */
public class DeploymentProcess {

	@Test
	public void deploymentFirstProcess() {
		ProcessEngine processEngine = ProcessEngines.getDefaultProcessEngine();

		RepositoryService repositoryService = processEngine.getRepositoryService();

		DeploymentBuilder deploymentBuilder = repositoryService.createDeployment().addClasspathResource("first.bpmn");

		Deployment deployment = deploymentBuilder.deploy();
		String deploymentId = deployment.getId();
		System.out.println(deploymentId);
		List<ProcessDefinition> processDefinitionList = repositoryService.createProcessDefinitionQuery()
				.deploymentId(deploymentId).list();
		Gson gson = new Gson();
		System.out.println(gson.toJson(processDefinitionList));

	}
}

　　

java.lang.NullPointerException
at org.activiti.engine.impl.db.DbSqlSession.dbSchemaUpdate(DbSqlSession.java:911)
at org.activiti.engine.impl.db.DbSqlSession.performSchemaOperationsProcessEngineBuild(DbSqlSession.java:1318)
at org.activiti.engine.impl.SchemaOperationsProcessEngineBuild.execute(SchemaOperationsProcessEngineBuild.java:28)
at org.activiti.engine.impl.interceptor.CommandInvoker$1.run(CommandInvoker.java:37)
at org.activiti.engine.impl.interceptor.CommandInvoker.executeOperation(CommandInvoker.java:78)
at org.activiti.engine.impl.interceptor.CommandInvoker.executeOperations(CommandInvoker.java:57)
at org.activiti.engine.impl.interceptor.CommandInvoker.execute(CommandInvoker.java:42)
at org.activiti.engine.impl.interceptor.TransactionContextInterceptor.execute(TransactionContextInterceptor.java:48)
at org.activiti.engine.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:63)
at org.activiti.engine.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:29)
at org.activiti.engine.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:44)
at org.activiti.engine.impl.ProcessEngineImpl.<init>(ProcessEngineImpl.java:81)
at org.activiti.engine.impl.cfg.ProcessEngineConfigurationImpl.buildProcessEngine(ProcessEngineConfigurationImpl.java:665)
at org.activiti.engine.ProcessEngines.buildProcessEngine(ProcessEngines.java:189)
at org.activiti.engine.ProcessEngines.initProcessEngineFromResource(ProcessEngines.java:162)
at org.activiti.engine.ProcessEngines.init(ProcessEngines.java:94)
at org.activiti.engine.ProcessEngines.getProcessEngine(ProcessEngines.java:223)
at org.activiti.engine.ProcessEngines.getDefaultProcessEngine(ProcessEngines.java:212)
at com.yuanqiao.first_activiti.deployment.DeploymentProcess.deploymentFirstProcess(DeploymentProcess.java:25)
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:497)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)

解决办法如下：

最近给客户部署系统，系统中使用Activiti流程引擎，启动Tomcat死活报错，报错如上边信息。真是一头雾水，刚开始以为是程序自身或者服务器环境问题（因为环境都是新装的），没往流程引擎上想。

上边的异常只是截取的最关键的地方，其实在这之前还要报一片异常，把环境和程序配置检查了一便，还是无果，最终把焦点集中在了org.activiti.engine.impl.db.DbSqlSession.dbSchemaUpdate，意思是流程表在更新表结构的时候出现异常，怎么会老是更新呢？查看了Activiti的配置，如上图。

 databaseSchemaUpdate设置为true代表如果没有表，则自动创建表；估计是这里的原因，我重新建了一个空的数据库test1，然后程序连上test1数据库，启动tomcat，竟然成功了。成功了，心里的一块石头落了地。

但是还是感觉很奇怪，不知道真正原因是什么，后来才想到，act_ge_property表，该表是流程引擎的属性表，里面的三条数据是基础数据，不可以删除。而我看了一下数据库初始化sql，竟然没有这三条数据，我这才恍然大悟，我准备程序包的时候，为了不把流程里面的数据带过来，我只是导出的表结构，没有导出数据。也就是说还原到服务器数据库的时候，act_ge_property表里面压根没有数据，这就造成了当前这个问题。聪明反被聪明误。。以后引以为戒吧。

总结：部署程序准备数据库初始化sql时，对于流程表，以后就不要导出来，只导出业务表，流程表让系统启动时自己生成去。