多数据源回退

Question

根据建议更新：

我有一个 Springboot Java 应用程序和两个在 application.properties 中定义的数据源：

spring.jpa.hibernate.ddl-auto=update

#online
spring.datasource.url=jdbc:mysql://172.17.0.2:3306/gcdb?allowPublicKeyRetrieval=true&useSSL=false
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.driverClassName=com.mysql.jdbc.Driver 

#offline
spring.secondDatasource.url=jdbc:h2:mem:gcdboff
spring.secondDatasource.username=root
spring.secondDatasource.password=root
spring.secondDatasource.driverClassName=org.h2.Driver

# Enabling H2 Console
spring.h2.console.enabled=true
spring.h2.console.path=/h2

手动将凭据从 "datasource" 更改为 "secondDatasource" 后，两个连接都正常工作。

但现在我想添加一个后备。如果"datasource"不可用，请取"secondDatasource".

我找到了以下解决方案。

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.jdbc.DataSourceBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Primary;

import javax.sql.DataSource;

@SpringBootApplication
public class GCApplication {

    public static void main(String[] args) {
        SpringApplication.run(GCApplication.class, args);
    }
/**/
    @Bean
    @Primary
    @ConfigurationProperties(prefix="spring.datasource")
    public DataSource primaryDataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean
    @ConfigurationProperties(prefix="spring.secondDatasource")
    public DataSource secondaryDataSource() {
        return DataSourceBuilder.create().build();
    }
/**/
}

但现在没有人会运行。该应用程序以以下错误结束，我不知道如何更正该错误。

2018-07-06 09:52:30.805 ERROR 28073 --- [           main]     o.s.boot.SpringApplication               : Application run failed

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]: Unsatisfied dependency expressed through method 'entityManagerFactory' parameter 0; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'entityManagerFactoryBuilder' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]: Unsatisfied dependency expressed through method 'entityManagerFactoryBuilder' parameter 0; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'jpaVendorAdapter' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.orm.jpa.JpaVendorAdapter]: Factory method 'jpaVendorAdapter' threw exception; nested exception is java.lang.IllegalArgumentException: dataSource or dataSourceClassName or jdbcUrl is required.
at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:732) ~[spring-beans-5.0.7.RELEASE.jar:5.0.7.RELEASE]
[...]

感谢您的帮助！

Answer 1

嗯，异常很简单，说：

java.lang.IllegalArgumentException: dataSource or dataSourceClassName or jdbcUrl is required

所以这意味着您缺少其中一个数据源的配置属性。

如果我们查看您的属性文件，我们可以看到 spring.datasource.driverClassName 配置属性。

因此您缺少 MySQL 数据库的 driverClassName，您需要指定它。

Answer 2

我找到了解决问题的方法。我希望它也能帮助你。使用以下代码，在第一个连接失败后选择第二个数据连接：

在 GC 应用程序中：

import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.jdbc.DataSourceProperties;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Primary;

import javax.sql.DataSource;

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

    @Primary
    @Bean
    public DataSource getDataSource(
        @Qualifier("first") DataSourceProperties first,
        @Qualifier("second") DataSourceProperties second)
    {
        int i = 0;
        final DataSource firstDataSource = first.initializeDataSourceBuilder().build();
        final DataSource secondDataSource = second.initializeDataSourceBuilder().build();
        try
        {
            firstDataSource.getConnection();
            return firstDataSource;
        } 
        catch (Exception e) 
        {
            return secondDataSource;
        }
    }

    @Primary
    @Bean("first")
    @ConfigurationProperties(prefix = "spring.datasource")
    public DataSourceProperties primaryDataSource()     
    {
        final DataSourceProperties dataSourceProperties = new DataSourceProperties();
        dataSourceProperties.setUrl("jdbc:mysql://172.17.0.2:3306/gcdb?allowPublicKeyRetrieval=true&useSSL=false");
        dataSourceProperties.setDriverClassName("com.mysql.jdbc.Driver");
        dataSourceProperties.setUsername("root");
        dataSourceProperties.setPassword("root");
        return dataSourceProperties;
    }

    @Bean("second")
    public DataSourceProperties secondaryDataSource() {
        final DataSourceProperties dataSourceProperties = new DataSourceProperties();
        dataSourceProperties.setUrl("jdbc:h2:mem:gcdboff");
        dataSourceProperties.setDriverClassName("org.h2.Driver");
        dataSourceProperties.setUsername("root");
        dataSourceProperties.setPassword("root");
        return dataSourceProperties;
    }
}

在application.properties中：

spring.jpa.hibernate.ddl-auto=update
spring.jpa.database=default

# Enabling H2 Console
spring.h2.console.enabled=true
spring.h2.console.path=/h2

Answer 3

只是为了添加到@Tagamoga 的回答中，您可以将三个 bean：getDataSource、primaryDataSource 和 secondaryDataSource 添加到一个单独的 class 中，并使用 @Configuration 对其进行注释。在那种情况下，您有一个单独的配置，您仍然可以使用属性文件来配置数据库连接。像这样：

import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.autoconfigure.jdbc.DataSourceProperties;
import org.springframework.boot.jdbc.DataSourceInitializationMode;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;

import javax.sql.DataSource;

@Configuration
public class DatabaseConfig {

    @Value("${datasource.primary.url}")
    String primaryDSUrl;

    @Value("${datasource.primary.platform}")
    String primaryDSPlatform;

    @Value("${datasource.primary.username}")
    String primaryDSUsername;

    @Value("${datasource.primary.password}")
    String primaryDSPassword;

    @Value("${datasource.secondary.url}")
    String secondaryDSUrl;

    @Value("${datasource.secondary.platform}")
    String secondaryDSPlatform;

    @Value("${datasource.secondary.username}")
    String secondaryDSUsername;

    @Value("${datasource.secondary.password}")
    String secondaryDSPassword;

    @Primary
    @Bean
    public DataSource getDataSource(
            @Qualifier("first") DataSourceProperties first,
            @Qualifier("second") DataSourceProperties second) {
        final DataSource firstDataSource = first.initializeDataSourceBuilder().build();
        final DataSource secondDataSource = second.initializeDataSourceBuilder().build();
        try {
            firstDataSource.getConnection();
            return firstDataSource;
        } catch (Exception e) {
            return secondDataSource;
        }
    }

    @Primary
    @Bean("first")
    public DataSourceProperties primaryDataSource() {
        final DataSourceProperties dataSourceProperties = new DataSourceProperties();
        dataSourceProperties.setUrl(primaryDSUrl);
        dataSourceProperties.setPlatform(primaryDSPlatform);
        dataSourceProperties.setUsername(primaryDSUsername);
        dataSourceProperties.setPassword(primaryDSPassword);
        dataSourceProperties.setInitializationMode(DataSourceInitializationMode.ALWAYS);
        return dataSourceProperties;
    }

    @Bean("second")
    public DataSourceProperties secondaryDataSource() {
        final DataSourceProperties dataSourceProperties = new DataSourceProperties();
        dataSourceProperties.setUrl(secondaryDSUrl);
        dataSourceProperties.setPlatform(secondaryDSPlatform);
        dataSourceProperties.setUsername(secondaryDSUsername);
        dataSourceProperties.setPassword(secondaryDSPassword);
        dataSourceProperties.setInitializationMode(DataSourceInitializationMode.ALWAYS);
        return dataSourceProperties;
    }
}

和属性文件：

#Datasource Primary
datasource.primary.platform=oracle
datasource.primary.url=jdbc:oracle:thin:@localhost:1521:orcl
datasource.primary.username=LCO2TL
datasource.primary.password=LCO2TL2020

#Datasource Secondary
datasource.secondary.platform=h2
datasource.secondary.url=jdbc:h2:mem:test"
datasource.secondary.username=root
datasource.secondary.password=root

多数据源回退

Multiple Datasources fallback

java

datasource

spring-boot