接上一篇文章，咱们探索了execution的运行机制，activiti里变量的作用域就是通过execution实现，activiti里变量按作用域有以下几种

  • 执行变量(variable)
  • 本地变量(LocalVariable)
  • 长期变量(TransVariable)

执行变量作用域在execution上，本地变量作用域在task上，长期变量不存储数据库，流程进入期待节点（比方UserTask）变量主动革除。

须要应用变量的是RuntimeService和TaskService，本文次要对这两个service中变量的应用做具体阐明，防止在不理解变量应用范畴的状况下，谬误的应用变量，导致流程出错。

变量表构造

变量存储在表ACT_RU_VARIABLE上，

mysql> describe ACT_RU_VARIABLE;+---------------+---------------+------+-----+---------+-------+| Field         | Type          | Null | Key | Default | Extra |+---------------+---------------+------+-----+---------+-------+| ID_           | varchar(64)   | NO   | PRI | NULL    |       || REV_          | int(11)       | YES  |     | NULL    |       || TYPE_         | varchar(255)  | NO   |     | NULL    |       || NAME_         | varchar(255)  | NO   |     | NULL    |       || EXECUTION_ID_ | varchar(64)   | YES  | MUL | NULL    |       || PROC_INST_ID_ | varchar(64)   | YES  | MUL | NULL    |       || TASK_ID_      | varchar(64)   | YES  | MUL | NULL    |       || BYTEARRAY_ID_ | varchar(64)   | YES  | MUL | NULL    |       || DOUBLE_       | double        | YES  |     | NULL    |       || LONG_         | bigint(20)    | YES  |     | NULL    |       || TEXT_         | varchar(4000) | YES  |     | NULL    |       || TEXT2_        | varchar(4000) | YES  |     | NULL    |       |+---------------+---------------+------+-----+---------+-------+12 rows in set (0.00 sec)

NAME_是变量名称，TYPE_是变量类型，依据TYPE_类型会将数据保留到不同的字段里，如TYPE_为string则保留到TEXT_或者TEXT_2中，如果是二进制数据，数据存储到表ACT_GE_BYTEARRAY中，并将id存储到BYTEARRAY_ID_字段上。EXECUTION_ID_、PROC_INST_ID_、TASK_ID_控制变量的作用域，如果TASK_ID_为null则为执行变量，如果不为null则为本地变量。

TaskService变量

TaskService有两个设置变量相干的API（理论有四个，但另外两个性能相似），定义如下：

/** * set variable on a task. If the variable is not already existing, it will be created in the most outer scope. This means the process instance in case this task is related to an execution. */void setVariable(String taskId, String variableName, Object value);/** * set variable on a task. If the variable is not already existing, it will be created in the task. */void setVariableLocal(String taskId, String variableName, Object value);

setVariable设置的是全局变量，也就是instance的变量，设置完后流程全局可见，setVariableLocal设置的是本地变量，设置完后只有该task可见。

执行如下示例代码：

taskService.setVariable(task.getId(), "variable", "this is Variable");taskService.setVariableLocal(task.getId(), "localVariable", "this is Local Variable");
mysql> select * from activiti.ACT_RU_VARIABLE t where t.proc_inst_id_=100001 and name_='variable' or name_='localVariable'\G;*************************** 1. row ***************************          ID_: 100024         REV_: 1        TYPE_: string        NAME_: variableEXECUTION_ID_: 100001PROC_INST_ID_: 100001     TASK_ID_: NULLBYTEARRAY_ID_: NULL      DOUBLE_: NULL        LONG_: NULL        TEXT_: this is Variable       TEXT2_: NULL*************************** 2. row ***************************          ID_: 100025         REV_: 1        TYPE_: string        NAME_: localVariableEXECUTION_ID_: 100008PROC_INST_ID_: 100001     TASK_ID_: 100015BYTEARRAY_ID_: NULL      DOUBLE_: NULL        LONG_: NULL        TEXT_: this is Local Variable       TEXT2_: NULL2 rows in set (0.00 sec)

variable变量EXECUTION_ID_和PROC_INST_ID_都是100001，100001是流程的实例id（instance_id)，阐明该变量作用域在整个instance上，整个流程周期内都能够应用，localVariable设置了TASK_ID，并且设置了所在的EXECUTION_ID_，阐明只能在指定的Task上应用。

既然有设置变量，那必定有获取变量，能够先试着想想上面几行代码的输入会是什么?

System.out.println("getVariable(variable) ==>"+taskService.getVariable(taskId,"variable"));System.out.println("getVariable(localVariable) ==>"+taskService.getVariable(taskId,"localVariable"));System.out.println("getVariableLocal(variable) ==>"+taskService.getVariableLocal(taskId,"variable"));System.out.println("getVariableLocal(localVariable) ==>"+taskService.getVariableLocal(taskId,"localVariable"));

输入的后果如下：

getVariable(variable) ==>this is VariablegetVariable(localVariable) ==>this is Local VariablegetVariableLocal(variable) ==>nullgetVariableLocal(localVariable) ==>this is Local Variable

通过getVariable既可能获取到执行变量，也能获取到本地变量，通过getVariableLocal只能获取到本地变量。至于为什么Local的变量用getVariable能获取到，咱们能够看下getVariable执行的sql过程

#1. 尝试用名称和taskid进行查问（即查问本地变量）==>  Preparing: select * from ACT_RU_VARIABLE where TASK_ID_ = ? and NAME_= ? ==> Parameters: 100015(String), variable(String)<==      Total: 0#2. 如果没有查问到尝试查问执行变量（指定TASK_ID_为NULL，设置EXECUTION_ID_和NAME_）==>  Preparing: select * from ACT_RU_EXECUTION where ID_ = ? ==> Parameters: 100008(String)<==      Total: 1==>  Preparing: select * from ACT_RU_VARIABLE where EXECUTION_ID_ = ? and NAME_= ? and TASK_ID_ is null ==> Parameters: 100008(String), variable(String)<==      Total: 0#3. 如果没有查问到尝试查问以后EXECUTION的父EXECUTION的变量，直至顶级EXECUTION，也就是instance了==>  Preparing: select * from ACT_RU_EXECUTION where ID_ = ? ==> Parameters: 100003(String)<==      Total: 1==>  Preparing: select * from ACT_RU_VARIABLE where EXECUTION_ID_ = ? and NAME_= ? and TASK_ID_ is null ==> Parameters: 100003(String), variable(String)<==      Total: 0==>  Preparing: select * from ACT_RU_EXECUTION where ID_ = ? ==> Parameters: 100001(String)<==      Total: 1==>  Preparing: select * from ACT_RU_VARIABLE where EXECUTION_ID_ = ? and NAME_= ? and TASK_ID_ is null ==> Parameters: 100001(String), variable(String)<==      Total: 1

getVariable会尝试从本地变量到执行变量到实例变量层层往上找，直到找到为止。getVariableLocal的执行过程如下：

==>  Preparing: select * from ACT_RU_VARIABLE where TASK_ID_ = ? and NAME_= ? ==> Parameters: 100015(String), variable(String)<==      Total: 1

getVariableLocal间接依据TASK_ID_和NAME_进行查找，如果没找到就没找到，不会持续往上执行。

基于以上后果，咱们能够得出如下论断

  • TaskService.getVariable能够获取该EXECUTION链上的任意变量
  • TaskService.getVariableLocal只能获取本地变量，也就是定义在TASK的变量
  • TaskService.getVariable因为存在递归调用，性能没有getVariableLocal好，所以在流程里应该优先思考应用本地变量

RuntimeService变量

流程发动

流程发动时传入的变量，保留到流程实例里在整个流程流转周期内都能够拜访到，上面是一个带参数的流程发动代码示例：

public String start() {    Map<String, Object> params = new HashMap<>();    params.put("startVariable", "this is startVariable");    ProcessInstance instance = runtimeService.startProcessInstanceByKey("myProcess1", params);    return instance.getId();}

存储到数据库中的变量如下

mysql> select * from activiti.ACT_RU_VARIABLE t where t.proc_inst_id_=100001 and name_='startVariable'\G;*************************** 1. row ***************************          ID_: 100002         REV_: 1        TYPE_: string        NAME_: startVariableEXECUTION_ID_: 100001PROC_INST_ID_: 100001     TASK_ID_: NULLBYTEARRAY_ID_: NULL      DOUBLE_: NULL        LONG_: NULL        TEXT_: this is startVariable       TEXT2_: NULL1 row in set (0.00 sec)

EXECUTION_ID_和PROC_INST_ID_都是100001，而100001正是流程的instanceid，因而该变量是保留到instance中，流程的任意节点都应用到，依据上面对getVariable的剖析咱们晓得，activiti会逐级往上寻找变量，而instance位于最顶级，因而流程内所有的节点都能够应用。

Execution变量

同样，咱们能够通过示例代码察看activiti设置在Execution上的状况。

runtimeService.setVariable(task.getExecutionId(), "runtimeVariable", "this is runtimeVariable");runtimeService.setVariableLocal(task.getExecutionId(), "runtimeLocalVariable", "this is Local runtimeLocalVariable");System.out.println("getVariable(variable) ==>"+runtimeService.getVariable(task.getExecutionId(),"runtimeVariable"));System.out.println("getVariable(localVariable) ==>"+runtimeService.getVariable(task.getExecutionId(),"runtimeLocalVariable"));System.out.println("getVariableLocal(variable) ==>"+runtimeService.getVariableLocal(task.getExecutionId(),"runtimeVariable"));System.out.println("getVariableLocal(localVariable) ==>"+runtimeService.getVariableLocal(task.getExecutionId(),"runtimeLocalVariable"));

输入为：

getVariable(variable) ==>this is runtimeVariablegetVariable(localVariable) ==>this is Local runtimeLocalVariablegetVariableLocal(variable) ==>nullgetVariableLocal(localVariable) ==>this is Local runtimeLocalVariable

getVariable数据库执行过程

#基于以后EXECUTION，依据EXECUTION_ID_和NAME_进行查问，并且非本地变量（TASK_ID_ is null ）==>  Preparing: select * from ACT_RU_EXECUTION where ID_ = ? ==> Parameters: 100009(String)<==      Total: 1==>  Preparing: select * from ACT_RU_VARIABLE where EXECUTION_ID_ = ? and NAME_= ? and TASK_ID_ is null ==> Parameters: 100009(String), runtimeVariable(String)<==      Total: 0#依据父EXECUTION进行查问==>  Preparing: select * from ACT_RU_EXECUTION where ID_ = ? ==> Parameters: 100003(String)<==      Total: 1==>  Preparing: select * from ACT_RU_VARIABLE where EXECUTION_ID_ = ? and NAME_= ? and TASK_ID_ is null ==> Parameters: 100003(String), runtimeVariable(String)<==      Total: 0#持续往上查问==>  Preparing: select * from ACT_RU_EXECUTION where ID_ = ? ==> Parameters: 100001(String)<==      Total: 1==>  Preparing: select * from ACT_RU_VARIABLE where EXECUTION_ID_ = ? and NAME_= ? and TASK_ID_ is null ==> Parameters: 100001(String), runtimeVariable(String)<==      Total: 1

getVariableLocal数据库执行过程

# 基于以后EXECUTION，依据EXECUTION_ID_和NAME_进行查问，并且非本地变量（TASK_ID_ is null ）==>  Preparing: select * from ACT_RU_VARIABLE where EXECUTION_ID_ = ? and NAME_= ? and TASK_ID_ is null ==> Parameters: 100009(String), runtimeVariable(String)<==      Total: 0

基于以上后果，能够得悉，RuntimeService.getVariable基于以后EXECUTION所在的EXECUTION链进行一级级往上找，直到找到符合条件的变量，getVariableLocal只找以后EXECUTION的变量，过程根本和TaskService.getVariable以及TaskService.getVariableLocal相似

长期变量

长期变量不做长久化存储，也就是不存储数据库，TaskService和RuntimeService都能够设置长期变量，设置长期变量api如下：

void setTransientVariable(String variableName, Object variableValue);void setTransientVariableLocal(String variableName, Object variableValue);void setTransientVariables(Map<String, Object> transientVariables);void setTransientVariablesLocal(Map<String, Object> transientVariables);Object getTransientVariable(String variableName);Object getTransientVariableLocal(String variableName);Map<String, Object> getTransientVariables();Map<String, Object> getTransientVariablesLocal();

获取长期变量也能够通过getVariable获取，实际上getVariable首先从长期变量中读取，读不到才进行数据库查问，因而如果长期变量和执行变量或者本地变量名称一样的话，实际上读取到的是长期变量。

长期变量因为是存储在内存中的，因而当流程流到期待状态(wait state)的节点，如UserTask节点，长期变量就生效，基于这个个性，能够将长期变量作为Service两头后果的保留。