activitiservice.java_Activiti的Java服务任务（ServiceTask）属性用法

Java服务任务是自动任务，不用人为，调用外部Java类。

Type为Class的情况

开始演示

Type选class

Class填com.plancode.ThrowErrorDelegate

Result Variable Name不允许填，因为只有type为Expression才有效

Fields为参数列表，这些参数就是通过ThrowErrorDelegate类的Expression属性注入的，我这里定义了两个参数，fieldA的type为String是静态参数写死的，另一个参数fieldB的type为Expression是表达式，里面可以使用流程变量动态给ThrowErrorDelegate类的Expression属性赋值

(1)流程图

(2)ThrowErrorDelegate类代码

package com.plancode;

import org.activiti.engine.delegate.*;

import org.springframework.stereotype.Service;

public class ThrowErrorDelegate implements JavaDelegate {

private Expression fieldA;

private Expression fieldB;

public void execute(DelegateExecution execution) throws Exception {

String result = fieldA.getValue(execution).toString() + fieldB.getValue(execution).toString();

execution.setVariable("resultVar", result);

}

}

(3)流程启动代码

Map variableMap = new HashMap();

variableMap.put("fieldB","valueB");

ProcessInstance pi = runtimeService.startProcessInstanceByKey("myProcess_1", variableMap);

Object resultVar = historyService.createHistoricVariableInstanceQuery().processInstanceId(pi.getId()).variableName("resultVar").singleResult().getValue();

(4)结果

在流程启动代码中的resultVar的值为：valueAvalueB

Type为Delegate Expression的情况

开始演示

Type选Delegate Expression

Delegate Expression填${throwErrorDelegate}，注入spring管理的bean

Result Variable Name不允许填，因为只有type为Expression才有效

Fields为参数列表，这些参数就是通过ThrowErrorDelegate类的Expression属性注入的，我这里定义了两个参数，fieldA的type为String是静态参数写死的，另一个参数fieldB的type为Expression是表达式，里面可以使用流程变量动态给ThrowErrorDelegate类的Expression属性赋值

(2)流程图

(2)ThrowErrorDelegate类代码，多了一个@Service注解

```

package com.plancode;

import org.activiti.engine.delegate.*;

import org.springframework.stereotype.Service;

@Service

public class ThrowErrorDelegate implements JavaDelegate {

private Expression fieldA;

private Expression fieldB;

public void execute(DelegateExecution execution) throws Exception {

String result = fieldA.getValue(execution).toString() + fieldB.getValue(execution).toString();

execution.setVariable("resultVar", result);

}