Activiti6.0.0拓展支持的数据库，以达梦为例子
起因
工作流基本环境的搭建在此就不做过多的赘述了，在达梦的官微也介绍了如何在activiti上如何结合，但是结合的方式过于死板，如果想通过xml来配置使用何种数据库，正好你又看到了这篇文章，那么可能会节省你半天的时间。
注意，这里所有从jar包中copy出来的源码，仍然需要放在一个新建的重复路径下，方便编译的时候覆盖jar中的class文件
首先
org.activiti.engine.impl.cfg.ProcessEngineConfigurationImpl这个类，从它的jar包中copy出来，然后在
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";
public static final String DATABASE_TYPE_POSTGRES = "postgres";
public static final String DATABASE_TYPE_MSSQL = "mssql";
public static final String DATABASE_TYPE_DB2 = "db2";
下面加上要支持的数据库简称，方便在xml中配置datasourceType
public static final String DATABASE_TYPE_DM = "dm";
当然还得继续在getDefaultDatabaseTypeMappings()方法中加上如下这句话：
databaseTypeMappings.setProperty("dm", DATABASE_TYPE_DM);
接着
接下来，这些配好了，如何映射sql文件呢，请看org.activiti.engine.impl.db.DbSqlSessionFactory类中的initBulkInsertEnabledMap(String databaseType)方法，发现下面有
// Only Oracle is making a fuss in one specific case right now
if ("oracle".equals(databaseType)) {
bulkInsertableMap.put(EventLogEntryEntityImpl.class, Boolean.FALSE);
}
这样一句代码，而且还标识是oracle独有的，由于我适配的是达梦，所以在这里修改为
if ("oracle".equals(databaseType) || "dm".equals(databaseType)) {
bulkInsertableMap.put(EventLogEntryEntityImpl.class, Boolean.FALSE);
}
还有
org.activiti.engine.impl.AbstractQuery类中也需要把addOrder(String column, String sortOrder, NullHandlingOnOrder nullHandlingOnOrder)中
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)) {
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)) {
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;
}
}
修改为
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_DM.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_DM.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;
}
}
接下来
接下来需要把sql建表脚本放好，由于我是web项目，放置于resources的org.activiti.db下，按照acitivit-engine包下的结构放置，原因是这句话：
properties.load(getResourceAsStream("org/activiti/db/properties/"+databaseType+".properties"));
找不到会报空指针异常。
如果
如果发生noSuchMethod的异常，要记住把org.activiti.engine.impl.ProcessEngineImpl沾出来一份，重新给它写一下
this.formEngineFormService = processEngineConfiguration.getFormEngineFormService();
这句话，可能会报错，修改为
this.formEngineFormService = (org.activiti.form.api.FormService) processEngineConfiguration.getFormEngineFormService();