import org.activiti.engine.history.HistoricDetail; //导入依赖的package包/类
/**
 * 读取历史变量并封装到Map中
 */
private Map<String, Object> packageVariables(ProcessInstance processInstance) {
    Map<String, Object> historyVariables = new HashMap<String, Object>();
    List<HistoricDetail> list = historyService.createHistoricDetailQuery().processInstanceId(processInstance.getId()).list();
    for (HistoricDetail historicDetail : list) {
        if (historicDetail instanceof HistoricFormProperty) {
            // 表单中的字段
            HistoricFormProperty field = (HistoricFormProperty) historicDetail;
            historyVariables.put(field.getPropertyId(), field.getPropertyValue());
            System.out.println("form field: taskId=" + field.getTaskId() + ", " + field.getPropertyId() + " = " + field.getPropertyValue());
        } else if (historicDetail instanceof HistoricVariableUpdate) {
            HistoricVariableUpdate variable = (HistoricVariableUpdate) historicDetail;
            historyVariables.put(variable.getVariableName(), variable.getValue());
            System.out.println("variable: " + variable.getVariableName() + " = " + variable.getValue());
        }
    }
    return historyVariables;
}