前言

目前国内部分公司做的项目要求去ioe使用国产的替代方案。数据从异构数据库中迁移到GBase，应用中使用Activiti工作流在替换了数据库驱动后启动过程报错如下：

nested exception is org.activiti.engine.ActivitiException: couldn’t deduct database type from database product name ‘Gbase 8s Server’

原因是：activiti5.22.0内置的数据库类型不支持GBase数据库。

解决方案

将activiti-engine-5.22.0相关源码拷贝到工程src下，保持包路径不变，并做相应修改以支持达梦数据库。
源码地址:https://github.com/Activiti/Activiti/tree/activiti-5.22.0/modules/activiti-engine

具体如下：

1.新建与源文件一模一样的类，包路径也要与源文件一样,新建org.activiti.engine.impl.cfg.ProcessEngineConfigurationImpl的源码内容全部复制过来，然后增加成员变量

此时会报错，因为缺少依赖，然后去github把他的pom文件拷贝过来,放到本项目下面。
https://github.com/Activiti/Activiti/tree/activiti-5.22.0/modules/activiti-engine


在刚刚拷贝的org.activiti.engine.impl.cfg.ProcessEngineConfigurationImpl，增加成员变量

public static final String DATABASE_TYPE_GBASE = "gbase";
public static final String DATABASE_TYPE_H2 = "h2";
public static final String DATABASE_TYPE_HSQL = "hsql";
public static final String DATABASE_TYPE_MYSQL = "mysql";
public static final String DATABASE_TYPE_ORACLE = "oracle";

2.在org.activiti.engine.impl.cfg.ProcessEngineConfigurationImpl，修改getDefaultDatabaseTypeMappings()

protected static Properties getDefaultDatabaseTypeMappings() {
Properties databaseTypeMappings = new Properties();
databaseTypeMappings.setProperty(“GBase 8s Server”, DATABASE_TYPE_GBASE);
databaseTypeMappings.setProperty(“H2”, DATABASE_TYPE_H2);

3. 在新建org.activiti.engine.impl.db.DbSqlSessionFactory，把源文件内容拷贝过来，然后修改initBulkInsertEnabledMap(String databaseType)

if (“oracle”.equals(databaseType) || “gbase”.equals(databaseType)) {
bulkInsertableMap.put(EventLogEntryEntity.class, Boolean.FALSE); }

4.在org.activiti.engine.impl.db.DbSqlSessionFactory，修改static{}

// gbase
databaseSpecificLimitBeforeStatements.put("gbase ", “”);
databaseSpecificLimitAfterStatements.put("gbase ", “LIMIT #{maxResults}
OFFSET #{firstResult}”);
databaseSpecificLimitBetweenStatements.put("gbase ", “”);
databaseOuterJoinLimitBetweenStatements.put("gbase ", “”);
databaseSpecificOrderByStatements.put("gbase ", defaultOrderBy);

// h2
databaseSpecificLimitBeforeStatements.put(“h2”, “”);
databaseSpecificLimitAfterStatements.put(“h2”, “LIMIT #{maxResults}
OFFSET #{firstResult}”);
databaseSpecificLimitBetweenStatements.put(“h2”, “”);
databaseOuterJoinLimitBetweenStatements.put(“h2”, “”);
databaseSpecificOrderByStatements.put(“h2”, defaultOrderBy);

5. 在新建 org.activiti.engine.impl.AbstractQuery类，把源文件的内容拷贝过来，修改addOrder(String column, String sortOrder, NullHandlingOnOrder nullHandlingOnOrder)

if (nullHandlingOnOrder.equals(NullHandlingOnOrder.NULLS_FIRST)) {

    if (ProcessEngineConfigurationImpl.DATABASE_TYPE_H2.equals(databaseType) 
            || ProcessEngineConfigurationImpl.DATABASE_TYPE_HSQL.equals(databaseType)
            || ProcessEngineConfigurationImpl.DATABASE_TYPE_POSTGRES.equals(databaseType) 
            || ProcessEngineConfigurationImpl.DATABASE_TYPE_ORACLE.equals(databaseType)
            || ProcessEngineConfigurationImpl.DATABASE_TYPE_GBASE.equals(databaseType)) {
        orderBy = orderBy + defaultOrderByClause + " NULLS FIRST";
    } else if (ProcessEngineConfigurationImpl.DATABASE_TYPE_MYSQL.equals(databaseType)) {
        orderBy = orderBy + "isnull(" + column + ") desc," + defaultOrderByClause;
    } else if (ProcessEngineConfigurationImpl.DATABASE_TYPE_DB2.equals(databaseType) 
            || ProcessEngineConfigurationImpl.DATABASE_TYPE_MSSQL.equals(databaseType)) {
        orderBy = orderBy + "case when " + column + " is null then 0 else 1 end," + defaultOrderByClause;
    } else {
        orderBy = orderBy + defaultOrderByClause;
    }

} else if (nullHandlingOnOrder.equals(NullHandlingOnOrder.NULLS_LAST)) {

    if (ProcessEngineConfigurationImpl.DATABASE_TYPE_H2.equals(databaseType) 
            || ProcessEngineConfigurationImpl.DATABASE_TYPE_HSQL.equals(databaseType)
            || ProcessEngineConfigurationImpl.DATABASE_TYPE_POSTGRES.equals(databaseType) 
            || ProcessEngineConfigurationImpl.DATABASE_TYPE_ORACLE.equals(databaseType)
            || ProcessEngineConfigurationImpl.DATABASE_TYPE_GBASE.equals(databaseType)) {
        orderBy = orderBy + column + " " + sortOrder + " NULLS LAST";
    } else if (ProcessEngineConfigurationImpl.DATABASE_TYPE_MYSQL.equals(databaseType)) {
        orderBy = orderBy + "isnull(" + column + ") asc," + defaultOrderByClause;
    } else if (ProcessEngineConfigurationImpl.DATABASE_TYPE_DB2.equals(databaseType) 
            || ProcessEngineConfigurationImpl.DATABASE_TYPE_MSSQL.equals(databaseType)) {
        orderBy = orderBy + "case when " + column + " is null then 1 else 0 end," + defaultOrderByClause;
    } else {
        orderBy = orderBy + defaultOrderByClause;
    }
}

6.右击项目，选择构建模块

7. 构建成功就会在target目录下面生成class文件，然后去jar包里面替换即可。