Add example that implements the Metadata SPI for third-party JDBC pools

[linghengqian]

Feature Request

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Is your feature request related to a problem?

No.

Describe the feature you would like.

In ShardingSphere 5.1.0, using the JDBC pool is required to have multiple classes that implements its corresponding metadata SPI. This is available at https://shardingsphere.apache.org/document/current/en/dev-manual/data-source/ manifested, but not obvious.

Under the org.apache.shardingsphere.infra.datasource.pool.metadata.type package, three JDBC pools such as DBCP, HikariCP, Tomcat DBCP (Not Tomcat JDBC Pool) are integrated by default, and implements the corresponding org.apache.shardingsphere.infra.datasource.pool.metadata.DataSourcePoolMetaData and org.apache.shardingsphere.infra.datasource.pool.metadata.DataSourceJdbcUrlMetaData interfaces. In addition, for HikariCP, it also implements the org.apache.shardingsphere.infra.datasource.pool.destroyer.DataSourcePoolDestroyer interface.

In the case of using a third-party JDBC pool that does not implement the metadata SPI (using Alibaba Druid as an example), the information the user gets is not clear. The user is likely to get something like this.

Caused by: java.lang.NoClassDefFoundError: org/apache/tomcat/dbcp/dbcp2/BasicDataSource
	at org.apache.shardingsphere.infra.datasource.pool.metadata.type.dbcp.TomcatDBCPDataSourcePoolMetaData.getType(TomcatDBCPDataSourcePoolMetaData.java:67) ~[shardingsphere-infra-common-5.1.0.jar:5.1.0]
	at org.apache.shardingsphere.spi.typed.TypedSPIRegistry.lambda$findRegisteredService$0(TypedSPIRegistry.java:44) ~[shardingsphere-spi-5.1.0.jar:5.1.0]
	at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:174) ~[na:1.8.0_312]
	at java.util.ArrayList$ArrayListSpliterator.tryAdvance(ArrayList.java:1361) ~[na:1.8.0_312]
	at java.util.stream.ReferencePipeline.forEachWithCancel(ReferencePipeline.java:126) ~[na:1.8.0_312]
	at java.util.stream.AbstractPipeline.copyIntoWithCancel(AbstractPipeline.java:499) ~[na:1.8.0_312]
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:486) ~[na:1.8.0_312]
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:472) ~[na:1.8.0_312]
	at java.util.stream.FindOps$FindOp.evaluateSequential(FindOps.java:152) ~[na:1.8.0_312]
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[na:1.8.0_312]
	at java.util.stream.ReferencePipeline.findFirst(ReferencePipeline.java:531) ~[na:1.8.0_312]
	at org.apache.shardingsphere.spi.typed.TypedSPIRegistry.findRegisteredService(TypedSPIRegistry.java:44) ~[shardingsphere-spi-5.1.0.jar:5.1.0]
	at org.apache.shardingsphere.infra.datasource.pool.metadata.DataSourcePoolMetaDataFactory.newInstance(DataSourcePoolMetaDataFactory.java:46) ~[shardingsphere-infra-common-5.1.0.jar:5.1.0]
	at org.apache.shardingsphere.infra.datasource.props.DataSourceProperties.<init>(DataSourceProperties.java:53) ~[shardingsphere-infra-common-5.1.0.jar:5.1.0]
	at org.apache.shardingsphere.spring.boot.datasource.DataSourceMapSetter.getDataSource(DataSourceMapSetter.java:92) ~[shardingsphere-jdbc-spring-boot-starter-infra-5.1.0.jar:5.1.0]
	at org.apache.shardingsphere.spring.boot.datasource.DataSourceMapSetter.getDataSourceMap(DataSourceMapSetter.java:65) ~[shardingsphere-jdbc-spring-boot-starter-infra-5.1.0.jar:5.1.0]
	at org.apache.shardingsphere.spring.boot.ShardingSphereAutoConfiguration.setEnvironment(ShardingSphereAutoConfiguration.java:122) ~[shardingsphere-jdbc-core-spring-boot-starter-5.1.0.jar:5.1.0]
	at org.springframework.context.support.ApplicationContextAwareProcessor.invokeAwareInterfaces(ApplicationContextAwareProcessor.java:110) ~[spring-context-5.3.15.jar:5.3.15]
	at org.springframework.context.support.ApplicationContextAwareProcessor.postProcessBeforeInitialization(ApplicationContextAwareProcessor.java:102) ~[spring-context-5.3.15.jar:5.3.15]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsBeforeInitialization(AbstractAutowireCapableBeanFactory.java:440) ~[spring-beans-5.3.15.jar:5.3.15]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1796) ~[spring-beans-5.3.15.jar:5.3.15]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:620) ~[spring-beans-5.3.15.jar:5.3.15]
	... 29 common frames omitted
Caused by: java.lang.ClassNotFoundException: org.apache.tomcat.dbcp.dbcp2.BasicDataSource
	at java.net.URLClassLoader.findClass(URLClassLoader.java:387) ~[na:1.8.0_312]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:418) ~[na:1.8.0_312]
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:352) ~[na:1.8.0_312]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:351) ~[na:1.8.0_312]
	... 51 common frames omitted

I think an example can be added at https://github.com/apache/shardingsphere/tree/master/examples to provide users with reference. I believe this is also helpful to users of C3P0 and BeeCP.

[linghengqian]

Because the Example module looks like it's being refactored, and a number of related issues are being addressed. Therefore, I think this issue should be postponed. (Uncertain about the placement and format of the integration content related to the JDBC Pools)

[linghengqian]

I created a simple test case to help locate this situation. It's at https://github.com/linghengqian/shardingsphere-jdbc-pools-test

[zhaojinchao95]

I created a simple test case to help locate this situation. It's at https://github.com/linghengqian/shardingsphere-jdbc-pools-test

Thx.

[linghengqian]

Maybe the content description on the first floor is wrong. After referring to the operation of the website #15563 , I noticed that import org.apache.commons:commons-dbcp2:2.9.0 still reported an error , you must import org.apache.tomcat:tomcat-dbcp to be normal (regardless of the version of this component is 9.0.58 or 10.0.16 ), which seems strange.

[linghengqian]

@ZjcNB

• If this related issue is a bug rather than a feature, I should close this issue and specify in the FAQ that ShardingSphere JDBC 5.1.0 uses a non-hikaricp JDBC Pool that needs to import org.apache.tomcat:tomcat-dbcp ?
• points to Fixed ShardingSphere-JDBC start up fail when use non-HikariCP pool. #15611

[linghengqian]

@ZjcNB

• The bugs involved in this issue have been fixed for a long time, and the description does not point to a discussion. Adding an example of the required SPI doesn't make much sense for consumers at this point.

• I think closing this issue is a good choice？

[linghengqian]

I think #19607 would provide a reasonable example for the c3p0 JDBC pool. So I don't think there's more to do with this issue.