Where are the implementation of java.sql.Connection interface?

Question

I am using the Interface Connection from the package java.sql Actually I though it a Class but when I tried to look at the source code I figured out that it is an Interface. In the source of the Connection interface there are only single line for each method without any implementation!! What makes this interface works as it? Database to connect to: MySql Connection source code page: http://www.docjar.com/html/api/java/sql/Connection.java.html

Accepted Answer

It is not the interface that "works" but one of its implementations, which is specific to your particular RDBMS vendor. In fact, it is typically the vendor who provides the implementation of the `Connection` interface.

When you call

```
Connection conn = DriverManager.getConnection(
    "jdbc:jdbc:mysql://localhost:3306/
,    connectionProps);
```

driver manager searches through registered JDBC drivers, finds the one for MySQL (it knows it's MySQL from the connection string), passes connection properties to the constructor of the class inside MySQL JDBC driver that implements `Connection`, and returns the resultant `Connection` instance back to you. For example, the driver may return an instance of a package-private class `MySqlConnection` that implements `Connection`, and your program would use it to interact with RDBMS without knowing any details about the class, other than the fact that it implements `Connection`.

Where are the implementation of java.sql.Connection interface?

Solution

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