达梦数据库整合流程，mybatis-plus踩坑记录
从mysql迁移到达梦数据库可以使用达梦的迁移工具进行迁移，具体可以参考
https://www.cnblogs.com/zywu-king/p/12337382.html 这篇文章；
本次项目使用主要架构为
- mybatis-plus 3.14
- 达梦数据库版本8
数据库驱动问题
使用数据库驱动如下
<dependency>
<groupId>com.dameng</groupId>
<artifactId>Dm8JdbcDriver18</artifactId>
<version>8.1.1.49</version>
</dependency>
注意点 ： DmJdbcDriver18 这类依赖不能使用，否则mybatis 查询数据库会出现类型转换错误；其次 达梦版本为8 就使用 Dm8JdbcDriver18, 如果达梦版本为7 ，就使用 Dm7JdbcDriver17 以此类推；
如果使用 jpa 那么 达梦8 对应的 hibernate 依赖如下
<dependency>
<groupId>com.dameng</groupId>
<artifactId>DmDialect-for-hibernate4.0</artifactId>
<version>8.1.2.79</version>
</dependency>
附方言配置(按需配置)
#方言
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.DmDialect
spring.jpa.database-platform=org.hibernate.dialect.DmDialect
spring.jpa.properties.hibernate.hbm2ddl.auto=update
spring.jpa.properties.hibernate.show_sql=true
spring配置文件问题
达梦数据库类似oracl，其数据库方式为模式方式。一个模式就是一个数据库；如果数据库名称和模式名称不一致，那么使用类似原始的数据库url 就会出问题, 谨慎起见，url后面都配置模式名称；
错误示范
url: jdbc:dm://localhost:5236/mydb
正确示范
url: jdbc:dm://localhost:5236?schema=mydb
mysql 有 longtext, text blog 等大数据库类型，迁移到达梦数据库 一般会转为clob 类型；查询时会报类型转换异常在url后面添加配置,将 clob当作 string处理；
&clobAsString=true
完整的JDBC连接
url: jdbc:dm://localhost:5236?schema=mydb&compatibleMode=mysql&characterEncoding=UTF-8&useUnicode=true&useSSL=false&tinyInt1isBit=false&allowPublicKeyRetrieval=true&serverTimezone=Asia/Shanghai
username: SYSDBA
password: mypassword
driver-class-name: dm.jdbc.driver.DmDriver
activiti支持达梦数据库
方案一： 寻找已经整合好的jar包 ； 获取方式 关注gong众号知识追寻者：回复 dm 获取；
方案二： 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；
具体如下：
- 在org.activiti.engine.impl.cfg.ProcessEngineConfigurationImpl，增加成员变量
public static final String DATABASE_TYPE_DM = "dm";
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";
- 在org.activiti.engine.impl.cfg.ProcessEngineConfigurationImpl，修改getDefaultDatabaseTypeMappings()
protected static Properties getDefaultDatabaseTypeMappings() {
Properties databaseTypeMappings = new Properties();
databaseTypeMappings.setProperty("DM DBMS", DATABASE_TYPE_DM);
databaseTypeMappings.setProperty("H2", DATABASE_TYPE_H2);
- 在org.activiti.engine.impl.db.DbSqlSessionFactory，修改initBulkInsertEnabledMap(String databaseType)
if ("oracle".equals(databaseType) || "dm".equals(databaseType)) {
bulkInsertableMap.put(EventLogEntryEntity.class, Boolean.FALSE);
}
- 在org.activiti.engine.impl.db.DbSqlSessionFactory，修改static{}
// dm
databaseSpecificLimitBeforeStatements.put("dm", "");
databaseSpecificLimitAfterStatements.put("dm", "LIMIT #{maxResults} OFFSET #{firstResult}");
databaseSpecificLimitBetweenStatements.put("dm", "");
databaseOuterJoinLimitBetweenStatements.put("dm", "");
databaseSpecificOrderByStatements.put("dm", defaultOrderBy);
// h2
databaseSpecificLimitBeforeStatements.put("h2", "");
databaseSpecificLimitAfterStatements.put("h2", "LIMIT #{maxResults} OFFSET #{firstResult}");
databaseSpecificLimitBetweenStatements.put("h2", "");
databaseOuterJoinLimitBetweenStatements.put("h2", "");
databaseSpecificOrderByStatements.put("h2", defaultOrderBy);
- 在 org.activiti.engine.impl.AbstractQuery，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_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;
}
}
同时需要引入外部依赖支持流程引擎
<dependency>
<groupId>javax.persistence</groupId>
<artifactId>persistence-api</artifactId>
<version>1.0</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>javax.enterprise.concurrent</groupId>
<artifactId>javax.enterprise.concurrent-api</artifactId>
<version>1.0</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.codehaus.groovy</groupId>
<artifactId>groovy-all</artifactId>
<version>2.4.5</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.drools</groupId>
<artifactId>drools-core</artifactId>
<version>5.5.0.Final</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.drools</groupId>
<artifactId>drools-compiler</artifactId>
<version>5.5.0.Final</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>com.fasterxml.uuid</groupId>
<artifactId>java-uuid-generator</artifactId>
<version>3.1.3</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>javax.transaction</groupId>
<artifactId>javax.transaction-api</artifactId>
<version>1.2</version>
<scope>provided</scope>
</dependency>
删除源码 test 包内容；
完成以上重新编译
数据库手册，达梦数据库连接工具统一关注 gong众号知识追寻者：回复 dm 获取；
