现在人们已经认识到Hibernate等ORM有一定的局限性，在CQRS读写分离的架构中，ORM主要用于命令写操作，进行复杂的增删改查CRUD；而SQL用于查询读操作。
Hibernate ORM, jOOQ, HikariCP, Transactions, and S一文分享了他们在自己的NeighborLink项目中如何实践这个原则。
经验如下：
1.使用明确的读写分离. 实体用于CRUD, 简单DTO用于查询结果.
2.读写两边使用同样对象，而不是维护多个模型，经常会在SQL结果中复用实体对象。
2.通过继承实现分层目标，对象的基础层包含对象的基本必要字段，然后分别有实体和DTO继承它。或者使用DTO作为基础，实体继承DTO。
在具体技术上，CRUD采取Hibernate，查询是JOOQ，JOOQ能够以Java方式编写SQL(DSL)，而且可以根据数据库中数据表结构自动产生元模型，如果数据表结构变化，产生的元模型会随着改变，这样编译时会出错。元模型和DSL都会以数据库本地语言优化地和数据库打交道。
具体代码如下，前端使用的Spring。 将DataSource 和 HibernateTransactionManager 分享给所有DB交互, 包括ORM, jOOQ, 和直接的JDBC!
Maven配置的库包如下：
<build>
<plugins>
...
<plugin>
<groupId>org.jooq</groupId>
<artifactId>jooq-codegen-maven</artifactId>
<version>${jooq.version}</version>
<executions>
<execution>
<goals>
<goal>generate</goal>
</goals>
</execution>
</executions>
<dependencies>
<dependency>
<groupId>org.jooq</groupId>
<artifactId>jooq-codegen</artifactId>
<version>${jooq.version}</version>
</dependency>
</dependencies>
<configuration>
<jdbc>
<driver>com.mysql.jdbc.Driver</driver>
<url>jdbc:mysql://[HOST]:[PORT]/[DB NAME]</url>
<user>[USER]</user>
<password>[PASSWORD]</password>
</jdbc>
<generator>
<name>org.jooq.util.DefaultGenerator</name>
<database>
<name>org.jooq.util.mysql.MySQLDatabase</name>
<includes>.*</includes>
<excludes></excludes>
<inputSchema>[DB NAME]</inputSchema>
</database>
<target>
<packageName>org.threeriverdev.neighborlink.query</packageName>
<directory>target/generated-sources/jooq</directory>
</target>
</generator>
</configuration>
</plugin>
...
</build>
<dependencies>
<!-- Spring framework -->
...
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-orm</artifactId>
<version>${spring.version}</version>
</dependency>
...
<!-- Hibernate -->
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>${hibernate.version}</version>
</dependency>
<!-- DataSource -->
<dependency>
<groupId>com.zaxxer</groupId>
<artifactId>HikariCP</artifactId>
<version>2.4.6</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.39</version>
</dependency>
<!-- jOOQ -->
<dependency>
<groupId>org.jooq</groupId>
<artifactId>jooq</artifactId>
<version>${jooq.version}</version>
</dependency>
<dependency>
<groupId>org.jooq</groupId>
<artifactId>jooq-meta</artifactId>
<version>${jooq.version}</version>
</dependency>
...
</dependencies>
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下面是Spring代码部分：
@Configuration
@EnableWebMvc
@EnableTransactionManagement
@ComponentScan
public class AppConfig {
@Autowired
private Environment env;
@Autowired
private ConfigService configService;
...
@Bean(destroyMethod = "close")
public DataSource dataSource() {
String dbHost;
String dbPort;
String dbName;
String dbUsername;
String dbPassword;
if (configService.isProduction()) {
// We're in a production environment.
dbHost = "localhost";
dbPort = "3306";
dbName = configService.getConfig().getDatabase().getName();
dbUsername = configService.getConfig().getDatabase().getUsername();
dbPassword = configService.getConfig().getDatabase().getPassword();
} else {
// Local dev or unit test.
dbHost = "[HOST]";
dbPort = "[PORT]";
dbName = "[DB NAME]";
dbUsername = "[USER]";
dbPassword = "[PASSWORD]";
}
final String url = new StringBuilder()
.append("jdbc:mysql://")
.append(dbHost)
.append(":")
.append(dbPort)
.append("/")
.append(dbName)
.toString();
HikariDataSource dataSource = new HikariDataSource();
...[HikariCP options]
MysqlDataSource mysqlDataSource = new MysqlDataSource();
mysqlDataSource.setURL(url);
mysqlDataSource.setUser(dbUsername);
mysqlDataSource.setPassword(dbPassword);
...[MySQL-specific options]
dataSource.setDataSource(mysqlDataSource);
return dataSource;
}
// HIBERNATE
@Bean
public LocalSessionFactoryBean sessionFactory() {
LocalSessionFactoryBean sessionFactory = new LocalSessionFactoryBean();
sessionFactory.setDataSource(dataSource());
sessionFactory.setHibernateProperties(hibernateProperties());
List<String> packages = new ArrayList<String>();
packages.add("org.threeriverdev.neighborlink.entity.core");
...
sessionFactory.setPackagesToScan(packages.toArray(new String[packages.size()]));
return sessionFactory;
}
@Bean
public HibernateTransactionManager transactionManager() {
HibernateTransactionManager txManager = new HibernateTransactionManager();
txManager.setSessionFactory(sessionFactory().getObject());
txManager.setDataSource(dataSource());
return txManager;
}
private Properties hibernateProperties() {
final Properties properties = new Properties();
...[Add all "hibernate.*" specific properties -- dialect, etc.]
return properties;
}
// JOOQ
@Bean
public TransactionAwareDataSourceProxy transactionAwareDataSource() {
return new TransactionAwareDataSourceProxy(dataSource());
}
@Bean
public DataSourceConnectionProvider connectionProvider() {
return new DataSourceConnectionProvider(transactionAwareDataSource());
}
@Bean()
public DSLContext jooq() {
// Generated source assumes the development DB. Dynamically change it to the production DB name.
String dbName;
if (configService.isProduction()) {
// We're in a production environment.
dbName = configService.getConfig().getDatabase().getName();
} else {
// Local dev or unit test.
dbName = "[SANDBOX DB NAME]";
}
// The DB name used in the generated DSL (see the Maven plugin use) will not be the same as
// the production DB, unless running in a local dev env! withSchemata allows us
// to override that during runtime.
Settings settings = new Settings().withRenderMapping(
new RenderMapping().withSchemata(new MappedSchema().withInput("[SANDBOX DB NAME]").withOutput(dbName)));
return DSL.using(connectionProvider(), SQLDialect.MYSQL, settings);
}
}
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