数据存储引擎是本项目里比较有特色的模块。

特色一，使用接口来对应不同的数据库。数据库可以是Oracle、Sqlserver、MogoDB、甚至是XML文件。采用接口进行对应：

1     public interface IWorkflowDB 2     { 3         List
      
        GetFlows(); 4         bool SaveFlow(Flow flow); 5         bool DeleteFlow(Guid flowId); 6  7         FlowInstance GetFlowInstanceByInstanceId(Guid flowInstanceId); 8         List
       
         GetFlowInstanceByFlowId(Guid flowId);  9         bool SaveFlowInstance(FlowInstance flowInstance);10         List
        
          GetFlowInstancesListByUser(Person person = null);11         bool DeleteFlowInstanceByInstanceId(Guid flowInstanceId);12 13         bool SaveForm(Form form);14         bool DeleteForm(Guid formId);15         List
         
           GetFormList();16 17         bool AddStep(WorkflowStep workflowStep);18         bool DeleteStep(Guid stepId);19         List
          
            GetStepList();20 21         bool AddBaseTable(WorkflowConstant.BaseTable baseTable, Dictionary
           
             values);22 Dictionary
            
              GetBaseTableData(WorkflowConstant.BaseTable baseTable);23 bool DeleteBaseTableValue(WorkflowConstant.BaseTable baseTable, int key);24 }
            
           
          
         
        
       
      

特色二，使用Oracle的SYS.XMLTYPE来存储数据，查询时使用辅助方法，或者XML查询表达式

这样系统里一共只用了四个表，包括一个临时表，每个表不超过三个字段。

WORKFLOW_SETTINGS表：（存储系统设置参数、流程等）

WORKFLOW_FORM表：（存储系统表单）

WORKFLOW_FLOW表：（存储流程实例）

还有一个temp表，一行一列，字段为CLOB类型。

XMLType里面存储的是什么呢？不错，正是各个类的实例，序列化后的字符：

实际存储的方式：

保存时：类的实例-->XML序列化-->直接用Oracle的XMLtype存储；

读取时：读出数据-->反序列化-->类的实例直接可用。

这样就能方便的解决实体模型或领域模型与数据库存储之间“阻抗不匹配的”的问题。而且XMLType可以被SQLServer等主流数据库支持，所以迁移到其他数据库也很方便；如果你要使用常规的建表规则进行存储，只要实现IWorkflowDB接口即可。

序列化反序列化的方法，使用了扩展方法，可以放在项目里任何一个静态类里：

1         public static string ToSerializableXML
      
       (this T t) 2         { 3             XmlSerializer mySerializer = new XmlSerializer(typeof (T)); 4             StringWriter sw = new StringWriter(); 5             mySerializer.Serialize(sw, t); 6             return sw.ToString(); 7         } 8  9         public static T ToEntity
       
        (this string xmlString)10         {11             var xs = new XmlSerializer(typeof (T));12             var srReader = new StringReader(xmlString);13             var steplist = (T) xs.Deserialize(srReader);14             return steplist;15         }
       
      

注意：有些类不能被序列化，比如Dictionary<TKey,TValue>，需要自己写可序列化的类。

好啦，接下来是实现IWorkflowDB接口的OracleWorkFlowDBUtility类，以存储工作流表单为例：

存储：

1         public bool SaveForm(Form form) 2         { 3             var formContent = form.FormContent; 4             var formId = form.FormId; 5             form.FormContent = string.Empty; 6              7             var sql = string.Empty; 8  9             DbHelperOra.ExecuteSql("truncate table WORKFLOW_TEMP");10             var para = new OracleParameter("formInfo", OracleType.Clob);11             para.Value = form.ToSerializableXML();12             DbHelperOra.ExecuteSql("insert into WORKFLOW_TEMP(content) values (:formInfo)", para);13             14             var paras = new[]15             {16                 new OracleParameter("formId", formId.ToString()),17                 new OracleParameter("formContent", formContent)18             };19             if (DbHelperOra.GetSingle("select count(*) from WORKFLOW_FORM where form_id = :formId",20                 new OracleParameter("formId", formId.ToString())).ToString() == "1")21             {22                 sql =23                     "update WORKFLOW_FORM set FORM_INFO = (select sys.xmlType.createXML(WORKFLOW_TEMP.content) from WORKFLOW_TEMP), FORM_CONTENT = :formContent where FORM_ID = :formId";24             }25             else26             {27                 sql =28                     "insert into WORKFLOW_FORM(FORM_ID,FORM_INFO,FORM_CONTENT) values (:formId,(select sys.xmlType.createXML(WORKFLOW_TEMP.content) from WORKFLOW_TEMP),:formContent)";29             }30 31             return DbHelperOra.ExecuteSql(sql, paras).ToString() == "1";32         }

读取：

1         public List
      
        GetFormList() 2         { 3             var ds = 4                 DbHelperOra.Query( 5                     "select t.form_info.getclobval() form_info, form_content from WORKFLOW_FORM t"); 6             if (ds != null) 7             { 8                 var forms = new List(ds.Tables[0].Rows.Count); 9                 foreach (DataRow dr in ds.Tables[0].Rows)10                 {11                     var str = dr["form_info"].ToString();12                     var form = str.ToEntity();13                     form.FormContent = dr["form_content"].ToString();14                     forms.Add(form);15                 }16                 return forms;17             }18             return null;19         }
      

删除：

1         public bool DeleteForm(Guid formId) 2         { 3             try 4             { 5                 if(DbHelperOra.ExecuteSql("delete from WORKFLOW_FORM where form_id = :formid", 6                     new OracleParameter("formid", formId.ToString())).ToString(CultureInfo.InvariantCulture)=="1") 7                 return true; 8                 return false; 9             }10             catch (Exception ex)11             {12                 return false;13             }14         }

一切都很简单，没有恼人的一列列字段名，也不用ORM、代码生成器等，开发、维护效率大幅度提高。

数据访问类实例化在WorkflowService类里面

先定义私有变量：

private readonly IWorkflowDB _iWorkflowDb;

然后在类的构造函数里这么写：

1        public WorkflowService(IWorkflowDB workflowDb, IWorkflowMethods workflowMethods)2         {3             _iWorkflowDb = workflowDb;4             _iWorkflowMethods = workflowMethods;5          6         }

使用简单工厂返回类的实例：

1         /// 
 2         /// 程序主调用方法 3         /// 
 4         /// 
       5         public static WorkflowService GetWorkflowService() 6         { 7             IWorkflowDB iWorkflowDb; 8             try 9             {10             string dbSavingProvider = WorkFlowUtility.GetConfiguration("DataBaseProvider").ToLower();11                 switch (dbSavingProvider)12                 {13                     case "oracle":14                         iWorkflowDb = new OracleWorkFlowDBUtility();15                         break;16                     case "sqlserver":17                         //iWorkflowDb = new SqlServerWorkFlowDBUtility();18                         //break;19                     default:20                         iWorkflowDb = (IWorkflowDB) Assembly.Load(dbSavingProvider).CreateInstance(dbSavingProvider);21                         break;22                 }23 24             }25             catch (Exception)26             {27                 throw new WorkFlowConfigurationNotImplementException("数据库配置失败！");28             }

这样能在不同的项目中自由配置数据存储方式了。

如果要提高查询效率，比如报表，就可以这么写查询：

1 select rownum "序号", t.dw "单位",vt.groupname || vs.groupname "团支部",t.xh "学号",t.xm "姓名",t.xb "性别",t.csrq "出生年月", t.zzmm "政治面貌", t.zc "职称", t.gzsj "工作时间", t.lxdh "联系电话" from 2 (select f.instance_id,  3 f.instance_content.extract('//FlowInstance/Creator/@PersonId').getstringval() xh, 4 max(decode(x.key,'c57e4eb1-834c-491f-a1b5-b8b67f1ed160',x.value,null)) dw, 5 max(decode(x.key,'6008c07f-617b-4607-8fe2-6a384c75ea8a',x.value,null)) xm, 6 max(decode(x.key,'1153c641-7567-44ce-85c8-fcb0230d5cf7',x.value,null)) xb, 7 max(decode(x.key,'76936043-17e0-40b7-9adc-22e88d461082',x.value,null)) csrq, 8 max(decode(x.key,'22c6f1c5-d07b-45ba-9752-1118fdafee4c',x.value,null)) zzmm, 9 max(decode(x.key,'47b32ce0-828e-4179-bf11-2ace0028fda5',x.value,null)) zc,10 max(decode(x.key,'a5cd9229-c8f9-4fb4-ba4f-e8157eeefa04',x.value,null)) gzsj,11 max(decode(x.key,'9d2984f9-a5c5-474d-807a-cd756b961615',x.value,null)) lxdh12 from WORKFLOW_FLOW f,13 XMLTable( '/FlowInstance/FlowStepInstances/FlowInstanceStep/WriteValues/SerializableDictionary'14 passing f.instance_content15 COLUMNS key VARCHAR2(40) PATH 'key',16 value VARCHAR2(100) PATH 'value') x17 where f.instance_content.extract('//FlowInstance/Flow/@FlowId').getstringval() = 'e2f35ac0-d5aa-4413-af54-2cf4fe3759ef'18 and to_date(substr(f.instance_content.extract('//FlowInstance/@CreateDate').getstringval(), 0, 10), 'YYYY-MM-DD')19 between  to_date('2015-01-01','yyyy-mm-dd') and to_date('2015-06-01','yyyy-mm-dd')20 group by f.instance_id, f.instance_content.extract('//FlowInstance/Creator/@PersonId').getstringval()) t21 left outer join vm_tuanwei_teachergr vt on t.xh = vt.gh22 left outer join vm_tuanwei_studentgr vs on t.xh = vs.xh

查出来的结果如下图：

好啦，大家对我数据存储方式有什么意见，可以就此进行讨论。

 

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