在连接到PostgreSQL数据库时需要指定JDBC驱动程序。

    dependencies {
        // specify dependencies here under either 'build', 'compile', 'runtime', 'test' or 'provided' scopes e.g.
        runtime 'postgresql:postgresql:9.1-901.jdbc4'
    }

编写连接到PostgreSQL所需的信息。

dataSource {
    pooled = true
    driverClassName = "org.postgresql.Driver"
    username = [PostgreSQLのユーザ名]
    password = [PostgreSQLのパスワード]

}
hibernate {
    cache.use_second_level_cache = true
    cache.use_query_cache = false
    cache.region.factory_class = 'net.sf.ehcache.hibernate.EhCacheRegionFactory'
}
// environment specific settings
environments {
    development {
        dataSource {
            url = "jdbc:postgresql://[IPアドレスとかホスト名とか]:[ポート番号]/[DB名]"
        }
    }
    test {
        基本的にurlを変えるだけなので省略
    }
    production {
        基本的にurlを変えるだけなので省略
    }

这样就完成了。只需启动Grails，就会自动连接到PostgreSQL。

比如随意创建以下类似的域名…

grails> create-domain-class service-test.Writer
| Created file grails-app/domain/service-test/Writer.groovy
| Created file test/unit/service-test/WriterSpec.groovy
grails> create-domain-class service-test.Book
| Created file grails-app/domain/service-test/Book.groovy
| Created file test/unit/service-test/BookSpec.groovy

如果使用Grails的run-app命令进行启动，表将会自动被生成。

如果Grails启动时输出异常（例如，错误）时间异常长的话。

有时可能会输出类似以下的异常。

| Running Grails application
| Error 2014-01-12 03:59:50,510 [localhost-startStop-1] ERROR context.GrailsContextLoader  - Error initializing the application: Error creating bean with name 'transactionManagerPostProcessor': Initialization of bean failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'transactionManager': Cannot resolve reference to bean 'sessionFactory' while setting bean property 'sessionFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory': Cannot resolve reference to bean 'dataSource' while setting bean property 'dataSource'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource': Cannot resolve reference to bean 'dataSourceLazy' while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSourceLazy': Cannot resolve reference to bean 'dataSourceUnproxied' while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSourceUnproxied': Error setting property values; nested exception is org.springframework.beans.PropertyBatchUpdateException; nested PropertyAccessExceptions (1) are:
PropertyAccessException 1: org.springframework.beans.MethodInvocationException: Property 'driverClassName' threw exception; nested exception is java.lang.IllegalStateException: Could not load JDBC driver class [org.postgresql.Driver]
Message: Error creating bean with name 'transactionManagerPostProcessor': Initialization of bean failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'transactionManager': Cannot resolve reference to bean 'sessionFactory' while setting bean property 'sessionFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory': Cannot resolve reference to bean 'dataSource' while setting bean property 'dataSource'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource': Cannot resolve reference to bean 'dataSourceLazy' while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSourceLazy': Cannot resolve reference to bean 'dataSourceUnproxied' while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSourceUnproxied': Error setting property values; nested exception is org.springframework.beans.PropertyBatchUpdateException; nested PropertyAccessExceptions (1) are:
PropertyAccessException 1: org.springframework.beans.MethodInvocationException: Property 'driverClassName' threw exception; nested exception is java.lang.IllegalStateException: Could not load JDBC driver class [org.postgresql.Driver]
    Line | Method
->>  334 | innerRun  in java.util.concurrent.FutureTask$Sync
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
|    166 | run       in java.util.concurrent.FutureTask
|   1110 | runWorker in java.util.concurrent.ThreadPoolExecutor
|    603 | run       in java.util.concurrent.ThreadPoolExecutor$Worker
^    722 | run . . . in java.lang.Thread
Caused by BeanCreationException: Error creating bean with name 'transactionManager': Cannot resolve reference to bean 'sessionFactory' while setting bean property 'sessionFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory': Cannot resolve reference to bean 'dataSource' while setting bean property 'dataSource'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource': Cannot resolve reference to bean 'dataSourceLazy' while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSourceLazy': Cannot resolve reference to bean 'dataSourceUnproxied' while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSourceUnproxied': Error setting property values; nested exception is org.springframework.beans.PropertyBatchUpdateException; nested PropertyAccessExceptions (1) are:
PropertyAccessException 1: org.springframework.beans.MethodInvocationException: Property 'driverClassName' threw exception; nested exception is java.lang.IllegalStateException: Could not load JDBC driver class [org.postgresql.Driver]
->>  334 | innerRun  in java.util.concurrent.FutureTask$Sync
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
|    166 | run       in java.util.concurrent.FutureTask
|   1110 | runWorker in java.util.concurrent.ThreadPoolExecutor
|    603 | run       in java.util.concurrent.ThreadPoolExecutor$Worker
^    722 | run . . . in java.lang.Thread

まだまだ続くので省略

在这种情况下，首先要确认与连接到PostgreSQL所需的信息（如用户名、密码、URL等）。
如果确认没有问题，可以使用grails clean来清除所有缓存等，如果当前处于Grails的交互模式下，先退出再重新运行grails run-app就可以解决问题。