如何从另一个 Spring Boot 应用程序访问一个 Spring Boot 应用程序的内存 H2 数据库

Question

在我的项目中，我创建了 3 个 spring boot 应用程序。第一个 Spring Boot 应用程序具有 h2 嵌入式数据库。现在我想直接从我的第二个和第三个 spring boot 应用程序访问这个数据库，而不需要编写任何服务来获取这些数据。那么谁能告诉我如何才能做到这一点？

Answer 1

您可以将 H2 服务器设置为 Spring Bean。

首先编辑 pom.xml - 从 h2 依赖中删除 <scope>runtime</scope>：

<dependency>
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
</dependency>

然后将H2服务器bean添加到SpringBootApplication或Configuration类：

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    /**
     * Start internal H2 server so we can query the DB from IDE
     *
     * @return H2 Server instance
     * @throws SQLException
     */
    @Bean(initMethod = "start", destroyMethod = "stop")
    public Server h2Server() throws SQLException {
        return Server.createTcpServer("-tcp", "-tcpAllowOthers", "-tcpPort", "9092");
    }
}

最后 - 编辑application.properties - 设置数据库名称：

spring.datasource.url=jdbc:h2:mem:dbname
spring.datasource.driverClassName=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=
spring.jpa.hibernate.ddl-auto=create

然后您可以使用此连接从外部连接到此 H2 服务器（例如，使用 H2 DB 连接到您的应用程序）：

jdbc:h2:tcp://localhost:9092/mem:dbname

使用此网址作为奖励，您可以直接从您的 IDE 连接到应用程序的数据库。

更新

尝试连接到 H2 for Spring Boot app 1.5.x 版本时可能会出错。在这种情况下，只需将 H2 的版本更改为以前的版本，例如：

<dependency>
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
    <version>1.4.193</version>
</dependency>

更新 2

如果您需要在同一主机上同时运行多个带有 H2 的应用程序，您应该在 Server.createTcpServer 方法中为它们设置不同的 H2 端口，例如：9092、9093 等。

// First App
@Bean(initMethod = "start", destroyMethod = "stop")
public Server h2Server() throws SQLException {
    return Server.createTcpServer("-tcp", "-tcpAllowOthers", "-tcpPort", "9092");
}

// Second App
@Bean(initMethod = "start", destroyMethod = "stop")
public Server h2Server() throws SQLException {
    return Server.createTcpServer("-tcp", "-tcpAllowOthers", "-tcpPort", "9093");
}

然后您可以使用以下 url 连接到这些应用程序的 H2 DB：

App1 H2: jdbc:h2:tcp://localhost:9092/mem:dbname
App2 H2: jdbc:h2:tcp://localhost:9093/mem:dbname

Answer 2

您可以在服务器模式下运行H2。

import org.h2.tools.Server;
...
// start the TCP Server
server = Server.createTcpServer("-tcpAllowOthers").start();
...
// stop the TCP Server
server.stop();

Usage: java org.h2.tools.Server 
When running without options, -tcp, -web, -browser and -pg are started.
Options are case sensitive. Supported options are:
[-help] or [-?]         Print the list of options
[-web]                  Start the web server with the H2 Console
[-webAllowOthers]       Allow other computers to connect - see below
[-webDaemon]            Use a daemon thread
[-webPort ]       The port (default: 8082)
[-webSSL]               Use encrypted (HTTPS) connections
[-browser]              Start a browser connecting to the web server
[-tcp]                  Start the TCP server
[-tcpAllowOthers]       Allow other computers to connect - see below
[-tcpDaemon]            Use a daemon thread
[-tcpPort ]       The port (default: 9092)
[-tcpSSL]               Use encrypted (SSL) connections
[-tcpPassword ]    The password for shutting down a TCP server
[-tcpShutdown ""]  Stop the TCP server; example: tcp://localhost
[-tcpShutdownForce]     Do not wait until all connections are closed
[-pg]                   Start the PG server
[-pgAllowOthers]        Allow other computers to connect - see below
[-pgDaemon]             Use a daemon thread
[-pgPort ]        The port (default: 5435)
[-properties ""]   Server properties (default: ~, disable: null)
[-baseDir ]        The base directory for H2 databases (all servers)
[-ifExists]             Only existing databases may be opened (all servers)
[-trace]                Print additional trace information (all servers)
The options -xAllowOthers are potentially risky.
For details, see Advanced Topics / Protection against Remote Access.
See also http://h2database.com/javadoc/org/h2/tools/Server.html

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