Spring 多个数据库（数据源）之间的引导切换

Question

I have a spring boot REST API application for a project with 2 different setups ( =2 different jars). Both need to be realized, but I have no idea on how to do it or what the best way would be.

Both setups need to have a connection with an online database (on a server; AWS) and a connection with an offline or local database (running on the machine/pc itself). It is the offline or local connection that is different between both setups.

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Setup 1:
When the application is started it needs to connect to the online database. When an error occurs or connection to the online database is lost, it needs to connect to the offline/local database.

It is not required that that it will reconnect with the online database after an error occurred or the connection was lost.

Setup 2:
When the application is started it needs to connect to both the online and the offline database. So when the user does a post to the REST API, both the online and the offline database need to be updated (unless an error occurs or the connection to the online database is lost). If the user just does a get request, it is preferred to get the data from the online database, unless an error occurs or the connection to the online database is lost, than it can use the offline database.

It is not required that that it will reconnect with the online database after an error occurred or the connection was lost, but in this setup it would be nice. Synchronizing the data after connection has been established again isn't required either (but would maybe be a nice feature).

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I have seen a similar post where the solution was to use ha-jdbc but it is an old post... Maven just doesn't find the dependency when I try adding it to my pom.xml file.

After some more searching and trying I was able to add ha-jdbc to my pom.xml. What I had to do was add a repository that contained ha-jdbc.

 <project> <repositories> <repository> <id>jbossrepository</id> <name>jbossrepository</name> <url>https://repository.jboss.org/nexus/content/repositories/thirdparty-releases/</url> </repository> </repositories> <dependency> <dependency> <groupId>net.sf.ha-jdbc</groupId> <artifactId>ha-jdbc</artifactId> <version>3.0.3</version> </dependency> </dependency> </project>

Yet to see if I can get it to work and if it is what I am looking for...
ha-jdbc isn't worth trying, one error or problem after the other, it's just old java too...

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Versions:
- java: 1.8
- org.springframework.boot (spring-boot-starter-parent): 2.1.8.RELEASE
- Database (online & offline): PostgreSQL 11.5

Answer 1

Take a look this example code . There you can find already implemented a working solution. The logic behind it is EnableJpaRepositories which enables it based on packages ( basePackages )