使用Camunda流程引擎开发,如何读取流程图中配制的参数及参数值?
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2022-04-01 20:56
在使用开源 Camunda 流程引擎框架做二次开发,有时候会在固定节点添加固定的参数及参数值,流程在流转到此节点时,我们如何运用Camunda从中取出配制的参数呢?
下面首先介绍 Camunda 支持配制哪些参数:
String
Map
List
Script
String or Expression
在Camunda中,除开1类型之外,其它四种都是以对象的方式保存在流程中(解析出来保存在 ACT_GE_BYTEARRAY 表中)。配制String类型的是在 Extensions ;其它4种是在 Input/Output
上面介绍了使用 Camunda Modeler 流程图工具配制参数,下面来看下流程图是如何取到这些值的。
读取这些值的方法还是很简单,只有一句代码:
Map<String, Object> map = runtimeService.getVariables(task.getExecutionId());
读取配制的值很简单,那有没有想过这些值是怎么取到的呢?
大胆猜想一下,就是在部署流程解析XML文件的时候,这些值就解析出来了,然后在保存在缓存中。
有了猜想,下面再来验证我们的猜想。
protected DeploymentWithDefinitions doExecute(final CommandContext commandContext) {
DeploymentManager deploymentManager = commandContext.getDeploymentManager();
// load deployment handler
ProcessEngine processEngine = commandContext.getProcessEngineConfiguration().getProcessEngine();
deploymentHandler = commandContext.getProcessEngineConfiguration()
.getDeploymentHandlerFactory()
.buildDeploymentHandler(processEngine);
Set<String> deploymentIds = getAllDeploymentIds(deploymentBuilder);
if (!deploymentIds.isEmpty()) {
String[] deploymentIdArray = deploymentIds.toArray(new String[deploymentIds.size()]);
List
ensureDeploymentsWithIdsExists(deploymentIds, deployments);
}
checkCreateAndReadDeployments(commandContext, deploymentIds);
// set deployment name if it should retrieved from an existing deployment
String nameFromDeployment = deploymentBuilder.getNameFromDeployment();
setDeploymentName(nameFromDeployment, deploymentBuilder, commandContext);
// get resources to re-deploy
List
// .. and add them the builder
addResources(resources, deploymentBuilder);
Collection<String> resourceNames = deploymentBuilder.getResourceNames();
if (resourceNames == null || resourceNames.isEmpty()) {
throw new NotValidException("No deployment resources contained to deploy.");
}
// perform deployment
DeploymentWithDefinitions deployment = commandContext.runWithoutAuthorization(() -> {
acquireExclusiveLock(commandContext);
DeploymentEntity deploymentToRegister = initDeployment();
Map<String, ResourceEntity> resourcesToDeploy =
resolveResourcesToDeploy(commandContext, deploymentToRegister);
Map<String, ResourceEntity> resourcesToIgnore = new HashMap<>(deploymentToRegister.getResources());
resourcesToIgnore.keySet().removeAll(resourcesToDeploy.keySet());
// save initial deployment resources before they are replaced with only the deployed ones
CandidateDeployment candidateDeployment =
CandidateDeploymentImpl.fromDeploymentEntity(deploymentToRegister);
if (!resourcesToDeploy.isEmpty()) {
LOG.debugCreatingNewDeployment();
deploymentToRegister.setResources(resourcesToDeploy);
deploy(commandContext, deploymentToRegister);
} else {
// if there are no resources to be deployed, find an existing deployment
String duplicateDeploymentId =
deploymentHandler.determineDuplicateDeployment(candidateDeployment);
deploymentToRegister =
commandContext.getDeploymentManager().findDeploymentById(duplicateDeploymentId);
}
scheduleProcessDefinitionActivation(commandContext, deploymentToRegister);
if(deploymentBuilder instanceof ProcessApplicationDeploymentBuilder) {
// for process application deployments, job executor registration
// is managed by the ProcessApplicationManager
ProcessApplicationRegistration registration = registerProcessApplication(
commandContext,
deploymentToRegister,
candidateDeployment,
resourcesToIgnore.values());
return new ProcessApplicationDeploymentImpl(deploymentToRegister, registration);
} else {
registerWithJobExecutor(commandContext, deploymentToRegister);
}
return deploymentToRegister;
});
createUserOperationLog(deploymentBuilder, deployment, commandContext);
return deployment;
}
、********************、
public
CommandContext commandContext = Context.getCommandContext();
boolean authorizationEnabled = commandContext.isAuthorizationCheckEnabled();
try {
commandContext.disableAuthorizationCheck();
return runnable.call();
} catch (RuntimeException e) {
throw e;
} catch (Exception e) {
throw new ProcessEngineException(e);
} finally {
if (authorizationEnabled) {
commandContext.enableAuthorizationCheck();
}
}
}
代码调试发现,上面的代码就是部署流程的核心代码。
代码一步一步跟踪调试,终是没有发现解析参数的地方?上面的猜想失败了
那Camunda 到底是如何处理参数的呢?调试了好几天,都没有发现解析参数的地方!真的都被搞的很点失去信心了。
就在3月17日下午,我重新整理了调整了思路。
是不是直接从表里面查询出来的?
试试跟踪 runtimeService.getVariables(task.getExecutionId()) 这个方法,终于发现了一点眉目,真是从表查询出来的。
public VariableMap execute(CommandContext commandContext) {
ensureNotNull("executionId", executionId);
ExecutionEntity execution = commandContext
.getExecutionManager()
.findExecutionById(executionId);
ensureNotNull("execution " + executionId + " doesn't exist", "execution", execution);
checkGetExecutionVariables(execution, commandContext);
VariableMapImpl executionVariables = new VariableMapImpl();
// collect variables from execution 核心方法
execution.collectVariables(executionVariables, variableNames, isLocal, deserializeValues);
return executionVariables;
}
// selectVariablesByExecutionId 对应执行的SQL语句
SELECT RES.*,
( case when RES.TASK_ID_ is not null and RES.EXECUTION_ID_ is not null then EXECUTION.ACT_INST_ID_
when RES.CASE_EXECUTION_ID_ is not null then RES.CASE_EXECUTION_ID_ when EXECUTION.PARENT_ID_ is null
and RES.IS_CONCURRENT_LOCAL_ = 0 then EXECUTION.ID_ when EXECUTION.IS_SCOPE_ = 1 and EXECUTION.PARENT_ID_ is not null
and RES.IS_CONCURRENT_LOCAL_ = 0 then PARENT_EXECUTION.ACT_INST_ID_ else EXECUTION.ACT_INST_ID_ end ) ACT_INST_ID_
FROM ACT_RU_VARIABLE RES LEFT JOIN ACT_RU_EXECUTION EXECUTION ON RES.EXECUTION_ID_ = EXECUTION.ID_
LEFT JOIN ACT_RU_EXECUTION PARENT_EXECUTION ON EXECUTION.PARENT_ID_ = PARENT_EXECUTION.ID_
WHERE EXECUTION_ID_ = '54854e59-a5c7-11ec-a5f8-92b1d713a145' AND TASK_ID_ is null
执行上面的SQL后,会返回 List<VariableInstanceEntity> 列表对象,在 VariableInstanceEntity 对象中有 ByteArrayField 属性,它保证的是 一条 ACT_GE_BYTEARRAY(保存的对象信息,也就是需要序列化的参数) 表的数据信息。
总结 runtimeService.getVariables 执行过程:
1、根据当前任务ID获取当 executionId,根据 executionId 查询 ACT_RU_VARIABLE 参数表
2、判断 ACT_RU_EXECUTION 表中的 PARENT_ID_ 是否有值,有值就继续根据此值查询 ACT_RU_VARIABLE
3、 根据查询的 ACT_RU_VARIABLE 结果中 BYTEARRAY_ID_ 有值,就根据此ID去查询ACT_GE_BYTEARRAY 资源信息表,反序列化对象