H2數(shù)據庫配置為類似jdbc:h2:tcp://localhost/~/test/database的形式，就是Server Mode，如果沒有單獨啟動H2服務器，那么會導致如下錯誤：

org.h2.jdbc.JdbcSQLException: Connection is broken: "java.net.ConnectException: Connection refused: connect: localhost" [90067-196]

Caused by: java.net.ConnectException: Connection refused: connect

org.springframework.jdbc.support.MetaDataAccessException: Could not get Connection for extracting meta data; nested exception is org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is org.h2.jdbc.JdbcSQLException: Connection is broken: "java.net.ConnectException: Connection refused: connect: localhost" [90067-196]

Caused by: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is org.h2.jdbc.JdbcSQLException: Connection is broken: "java.net.ConnectException: Connection refused: connect: localhost" [90067-196]

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaAutoConfiguration.class]: Invocation of init method failed; nested exception is org.hibernate.service.spi.ServiceException: Unable to create requested service [org.hibernate.engine.jdbc.env.spi.JdbcEnvironment]

Caused by: org.hibernate.service.spi.ServiceException: Unable to create requested service [org.hibernate.engine.jdbc.env.spi.JdbcEnvironment]

Caused by: org.hibernate.HibernateException: Access to DialectResolutionInfo cannot be null when 'hibernate.dialect' not set

大概就是連接失敗一類的問題，網上說是因為springboot比h2服務器啟動更早，然后導致這個錯誤的，具體原因還有待查證，解決方案是：

1. 創(chuàng)建類Starters（類名無所謂，后面引用就可以）

import org.h2.tools.Server;

public class Starters {

    private static final Logger logger = LoggerFactory.getLogger(Starters.class);

    public static void startH2Server() {
        try {
            Server h2Server = Server.createTcpServer().start(); // 關鍵代碼
            if (h2Server.isRunning(true)) {
                logger.info("H2 server was started and is running.");
            } else {
                throw new RuntimeException("Could not start H2 server.");
            }
        } catch (SQLException e) {
            throw new RuntimeException("Failed to start H2 server: ", e);
        }
    }
}

注意：Springboot默認設置h2的依賴范圍是runtime，需要刪除那句代碼才能編譯時調用org.h2.tools.Server。

2. 分別在SpringBoot啟動類ServletInitializer和Application中調用H2 server的啟動代碼

public class ServletInitializer extends SpringBootServletInitializer {

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        Starters.startH2Server(); // 關鍵代碼
        return application.sources(Application.class);
    }
}

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        Starters.startH2Server(); // 關鍵代碼
        SpringApplication.run(Application.class, args);
    }
}

這樣修改之后，就可以正常啟動了！

參考：How to start H2 TCP server on Spring Boot application startup?