[SPARK-4613][Core] Java API for JdbcRDD

[liancheng]

This PR introduces a set of Java APIs for using JdbcRDD:

1. Trait (interface) JdbcRDD.ConnectionFactory: equivalent to the getConnection: () => Connection parameter in JdbcRDD constructor.
2. Two overloaded versions of Jdbc.create: used to create JavaRDD that wraps a JdbcRDD.

[SparkQA]

Test build #23888 has started for PR 3478 at commit ffcdf2e.

• This patch merges cleanly.

[SparkQA]

Test build #23888 has finished for PR 3478 at commit ffcdf2e.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • trait ConnectionFactory extends Serializable

[AmplabJenkins]

Test FAILed.
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Test FAILed.

[pwendell]

@liancheng this appears to have failed its own test :P

[liancheng]

@pwendell Yea, I don't see why it can't find Derby driver, and I can't reproduce it locally :(

[mateiz]

Maybe it got it from the Java or Hadoop version. You can add a test dep on Derby.

[SparkQA]

Test build #23912 has started for PR 3478 at commit d4cedc5.

• This patch merges cleanly.

[liancheng]

@mateiz The thing puzzles me is that Derby has already been added as a test dependency in Spark core, otherwise the Scala JdbcRDDSuite couldn't pass.

[SparkQA]

Test build #23912 has finished for PR 3478 at commit d4cedc5.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • trait ConnectionFactory extends Serializable

[AmplabJenkins]

Test FAILed.
Refer to this link for build results (access rights to CI server needed):
https://amplab.cs.berkeley.edu/jenkins//job/SparkPullRequestBuilder/23912/
Test FAILed.

[liancheng]

Found the cause. JdbcRDDSuite deletes the temporary Derby database with shutdown=true, but didn't specify a database name. In this way, the whole Derby driver is shut down. Thus, when executing JavaJdbcRDDSuite after JdbcRDDSuite, it fails.

[SparkQA]

Test build #23917 has started for PR 3478 at commit 9a54625.

• This patch merges cleanly.

[SparkQA]

Test build #23917 has finished for PR 3478 at commit 9a54625.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • trait ConnectionFactory extends Serializable

[AmplabJenkins]

Test PASSed.
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Test PASSed.

[mateiz]

Looks good to me; going to merge it.