java - Spring Boot 多数据源

Question

我对 Spring Boot 很陌生，我想为我的项目创建一个多数据源。 这是我目前的情况。我有两个用于多个数据库的实体包。比方说

com.test.entity.db.mysql ; for entities that belong to MySql
com.test.entity.db.h2 ; for entities that belong to H2 Databases

所以，目前我有两个实体类

UserMySql.java

@Entity
@Table(name="usermysql")
public class UserMysql{

    @Id
    @GeneratedValue
    public int id;

    public String name;

}

UserH2.java

@Entity
@Table(name="userh2")
public class Userh2 {

    @Id
    @GeneratedValue
    public int id;

    public String name;
}

我想实现一个配置，如果我从 UserMySql 创建用户，它将被保存到 MySql 数据库，如果我从 Userh2 创建用户，它将被保存到 H2 数据库。所以，我也有两个 DBConfig，比如说 MySqlDbConfig 和 H2DbConfig。

(com.test.model 是我将放置我的 Repositories 类的包。它将在下面定义)

MySqlDbConfig.java

@Configuration
@EnableJpaRepositories(
    basePackages="com.test.model",
    entityManagerFactoryRef = "mysqlEntityManager")
public class MySqlDBConfig {

@Bean
@Primary
@ConfigurationProperties(prefix="datasource.test.mysql")
public DataSource mysqlDataSource(){
    return DataSourceBuilder
            .create()
            .build();
}

@Bean(name="mysqlEntityManager")
public LocalContainerEntityManagerFactoryBean mySqlEntityManagerFactory(
        EntityManagerFactoryBuilder builder){       
    return builder.dataSource(mysqlDataSource())                
            .packages("com.test.entity.db.mysql")
            .build();
}   

}

H2DbConfig.java

@Configuration
@EnableJpaRepositories(
    entityManagerFactoryRef = "h2EntityManager")
public class H2DbConfig {

@Bean
@ConfigurationProperties(prefix="datasource.test.h2")
public DataSource h2DataSource(){
    return DataSourceBuilder
            .create()
            .driverClassName("org.h2.Driver")
            .build();
}

@Bean(name="h2EntityManager")
public LocalContainerEntityManagerFactoryBean h2EntityManagerFactory(
        EntityManagerFactoryBuilder builder){
    return builder.dataSource(h2DataSource())
            .packages("com.test.entity.db.h2")
            .build();
}
}

我的 application.properties 文件

#DataSource settings for mysql
datasource.test.mysql.jdbcUrl = jdbc:mysql://127.0.0.1:3306/test
datasource.test.mysql.username = root
datasource.test.mysql.password = root
datasource.test.mysql.driverClassName = com.mysql.jdbc.Driver

#DataSource settings for H2
datasource.test.h2.jdbcUrl = jdbc:h2:~/test
datasource.test.h2.username = sa

# DataSource settings: set here configurations for the database connection
spring.datasource.url = jdbc:mysql://127.0.0.1:3306/test
spring.datasource.username = root
spring.datasource.password = root
spring.datasource.driverClassName = com.mysql.jdbc.Driver
spring.datasource.validation-query=SELECT 1


# Specify the DBMS
spring.jpa.database = MYSQL

# Show or not log for each sql query
spring.jpa.show-sql = true

# Hibernate settings are prefixed with spring.jpa.hibernate.*
spring.jpa.hibernate.ddl-auto = update
spring.jpa.hibernate.dialect = org.hibernate.dialect.MySQL5Dialect
spring.jpa.hibernate.naming_strategy = org.hibernate.cfg.ImprovedNamingStrategy
spring.jpa.hibernate.show_sql = true
spring.jpa.hibernate.format_sql = true

server.port=8080
endpoints.shutdown.enabled=false

然后对于 crud，我有 UserMySqlDao 和 UserH2Dao

UserMySqlDao.java

@Transactional 
@Repository
public interface UserMysqlDao extends CrudRepository<UserMysql, Integer>{

    public UserMysql findByName(String name);
}

UserH2Dao.java

@Transactional
@Repositories
public interface UserH2Dao extends CrudRepository<Userh2, Integer>{

    public Userh2 findByName(String name);
}

最后，我有一个 UserController 作为端点来访问我的服务

UserController.java

@Controller 
@RequestMapping("/user")
public class UserController {


@Autowired
private UserMysqlDao userMysqlDao;

@Autowired
private UserH2Dao userH2Dao;

@RequestMapping("/createM")
@ResponseBody
public String createUserMySql(String name){
    UserMysql user = new UserMysql();
    try{            
        user.name = name;
        userMysqlDao.save(user);
        return "Success creating user with Id: "+user.id;
    }catch(Exception ex){
        return "Error creating the user: " + ex.toString();
    }
}

@RequestMapping("/createH")
@ResponseBody
public String createUserH2(String name){
    Userh2 user = new Userh2();
    try{
        user.name = name;
        userH2Dao.save(user);
        return "Success creating user with Id: "+user.id;
    }catch(Exception ex){
        return "Error creating the user: " + ex.toString();
    }
}   
}

Application.java

@Configuration
@EnableAutoConfiguration(exclude={DataSourceAutoConfiguration.class})
@EntityScan(basePackages="com.test.entity.db")
@ComponentScan
public class Application {

public static void main(String[] args) {
    System.out.println("Entering spring boot");
    ApplicationContext ctx = SpringApplication.run(Application.class, args);

    System.out.println("Let's inspect the beans provided by Spring Boot:");
    String[] beanNames = ctx.getBeanDefinitionNames();
    Arrays.sort(beanNames);
    for (String beanName : beanNames) {
        System.out.print(beanName);
        System.out.print(" ");
    }

    System.out.println("");
}

}

有了这个配置，我的 Spring boot 运行良好，但是当我访问时

http://localhost/user/createM?name=myname it writes an exception

Error creating the user: org.springframework.dao.InvalidDataAccessResourceUsageException:   could not execute statement; SQL [n/a]; nested exception is org.hibernate.exception.SQLGrammarException: could not execute statement

我在谷歌上搜索了一下，还没有找到解决方案。任何想法为什么会发生此异常？这是实现多个数据源以实现上述案例的最佳方式吗？如果需要，我愿意进行全面重构。

谢谢

Answer 1

我认为你会发现它很有用

http://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#howto-two-datasources

它展示了如何定义多个数据源并将其中一个分配为主数据源。

这是一个相当完整的示例，还包含分发事务 - 如果您需要的话。

http://fabiomaffioletti.me/blog/2014/04/15/distributed-transactions-multiple-databases-spring-boot-spring-data-jpa-atomikos/

您需要创建 2 个配置类，分离模型/存储库包等以简化配置。

此外，在上面的示例中，它手动创建数据源。您可以使用 spring doc 上的方法和 @ConfigurationProperties 注释来避免这种情况。这是一个例子:

http://xantorohara.blogspot.com.tr/2013/11/spring-boot-jdbc-with-multiple.html

希望这些有所帮助。