Where is defination of inbuilt interfaces are written?

[Azrael Noor]

As questioned above, I am slight confused with it when i tracked classes

let me take example of JDBC Connection (i have not posted it in JDBC because asking it in general sense)

Example :

DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());  
Connection gConn = DriverManager.getConnection("jdbc:oracle:thin:@12.16.5.1:11:vqa", "en", "e123");  

Register Driver is called within driver manager and the driver given in Argument is registered shown code below:

  
//In Class DriverManager.java

public static synchronized void registerDriver(java.sql.Driver driver)
        throws SQLException {

        /* Register the driver if it has not already been added to our list */
        if(driver != null) {
            registeredDrivers.addIfAbsent(new DriverInfo(driver));
        } else {
            // This is for compatibility with the original DriverManager
            throw new NullPointerException();
        }

        println("registerDriver: " + driver);

    }

then getConnection is called and in procedure of getConnection it calls CONNECT() method if

//In Class DriverManager.java

  if(isDriverAllowed(aDriver.driver, callerCL)) { 
                try {
                    println("    trying " + aDriver.driver.getClass().getName());
                    Connection con = aDriver.driver.connect(url, info); //<------------------------- This thing
                    if (con != null) {
                        // Success!
                        println("getConnection returning " + aDriver.driver.getClass().getName());
                        return (con);
                    }
                } catch (SQLException ex) {
                    if (reason == null) {
                        reason = ex;
                    }
                }

When i see CONNECT method, i found it in DRIVER interface as shown below:

Connection connect(String url, java.util.Properties info)
throws SQLException; <----------- Picture ends here amd Connection type is returned....unable to find further role and control of "jdbc:oracle:thin:@12.16.5.1:11:vqa", "en", "e123"


Question is how connect acted internally(connect to db) ?
As it is interface, where is it's definition of connection?
Does JVM holds that internally? or JVM takes control?
i mean how it executes?

I hope you understand my question......sly i found for many things in java....

please respond

[Sumit Patil]

Specific to your question, the Driver Interface would be implemented by the provider of the driver, in your case it would be Oracle, since you are using Oracle driver. The implementation is never present in the JVM. The implementation needs to be provided by the vendors.

Hope this helps.

[Azrael Noor]

Sumit ok I am getting into Oracle Driver Class now which is registered above

It contains following overridden on Driver.....please see below

 public OracleDriver() {
        //compiled code
        throw new RuntimeException("Compiled Code");
    }

    public static void registerMBeans() {
        //compiled code
        throw new RuntimeException("Compiled Code");
    }

    public Connection connect(String string, Properties prprts) throws SQLException { 
//<------------------------ HERE only this is defination given,,,,,,,STILL UNABLE TO GET CONTROL FLOW
        //compiled code
        throw new RuntimeException("Compiled Code");
    }

    public Connection defaultConnection() throws SQLException {
        //compiled code
        throw new RuntimeException("Compiled Code");
    }

    static final int oracleDriverExtensionTypeFromURL(String string) {
        //compiled code
        throw new RuntimeException("Compiled Code");
    }

    public boolean acceptsURL(String string) {
        //compiled code
        throw new RuntimeException("Compiled Code");
    }

    public DriverPropertyInfo[] getPropertyInfo(String string, Properties prprts) throws SQLException {
        //compiled code
        throw new RuntimeException("Compiled Code");
    }

    public int getMajorVersion() {
        //compiled code
        throw new RuntimeException("Compiled Code");
    }

    public int getMinorVersion() {
        //compiled code
        throw new RuntimeException("Compiled Code");
    }

    public boolean jdbcCompliant() {
        //compiled code
        throw new RuntimeException("Compiled Code");
    }

    public String processSqlEscapes(String string) throws SQLException {
        //compiled code
        throw new RuntimeException("Compiled Code");
    }

    public static String getCompileTime() {
        //compiled code
        throw new RuntimeException("Compiled Code");
    }

    public static String getSystemPropertyFastConnectionFailover(String string) {
        //compiled code
        throw new RuntimeException("Compiled Code");
    }

    protected OracleConnection getConnectionDuringExceptionHandling() {
        //compiled code
        throw new RuntimeException("Compiled Code");
    }

I am unable to find control here too

[Sumit Patil]

This class will have compiled code, where they have implemented it.
You can use a decompiler to see the implementation details.

[Azrael Noor]

Yes Bro i am studying it

I have used this J Decompiler: http://java.decompiler.free.fr/?q=jdgui

I found

public Connection connect(String paramString, Properties paramProperties)
    throws SQLException
  {
    if (paramString.regionMatches(0, "jdbc:default:connection", 0, 23))
    {
      String str = "jdbc:oracle:kprb";
      int j = paramString.length();

      if (j > 23)
        paramString = str.concat(paramString.substring(23, paramString.length()));
      else {
        paramString = str.concat(":");
      }
      str = null;
    }

    int i = oracleDriverExtensionTypeFromURL(paramString);

    if (i == -2) {
      return null;
    }
    if (i == -3) {
      DatabaseError.throwSqlException(getConnectionDuringExceptionHandling(), 67);
    }
    OracleDriverExtension localOracleDriverExtension = null;

    localOracleDriverExtension = this.driverExtensions[i];

    if (localOracleDriverExtension == null)
    {
      try
      {
        synchronized (this)
        {
          if (localOracleDriverExtension == null)
          {
            localOracleDriverExtension = (OracleDriverExtension)Class.forName(driverExtensionClassNames[i]).newInstance();

            this.driverExtensions[i] = localOracleDriverExtension;
          }
          else
          {
            localOracleDriverExtension = this.driverExtensions[i];
          }

        }

      }
      catch (Exception localException)
      {
        DatabaseError.throwSqlException(getConnectionDuringExceptionHandling(), localException);
      }

    }

    if (paramProperties == null) {
      paramProperties = new Properties();
    }

    Enumeration localEnumeration = DriverManager.getDrivers();

    while (localEnumeration.hasMoreElements())
    {
      localObject2 = (Driver)(Driver)localEnumeration.nextElement();

      if ((localObject2 instanceof OracleDriver))
      {
        break;
      }
    }
    while (localEnumeration.hasMoreElements())
    {
      localObject2 = (Driver)(Driver)localEnumeration.nextElement();

      if ((localObject2 instanceof OracleDriver)) {
        DriverManager.deregisterDriver((Driver)localObject2);
      }

    }

    Object localObject2 = (PhysicalConnection)localOracleDriverExtension.getConnection(paramString, paramProperties);

    ((PhysicalConnection)localObject2).protocolId = i;

    return (Connection)localObject2;
  }

Let me study, it i will ask question again :p

Thank you for your help......i am reaching to the place where JVM actually takes whole control...i mean where control goes non visible to me :p

will ask again, if any problem occurs

[Sumit Patil]

You are welcome

[Jeff Verdegan]

Azrael Noor wrote:
When i see CONNECT method, i found it in DRIVER interface as shown below:

Connection connect(String url, java.util.Properties info)
throws SQLException; <----------- Picture ends here amd Connection type is returned....unable to find further role and control of "jdbc:oracle:thin:@12.16.5.1:11:vqa", "en", "e123"


Question is how connect acted internally(connect to db) ?
As it is interface, where is it's definition of connection?

When you call DriverManager.getConnection(), it looks at its registered Drivers until it finds one that can understand the particular URL you've passed. In this case, it finds the OracleDriver, and asks it for a Connection. The driver returns an instance of a concrete class that implements the Connection interface. We don't know and we don't care what the specific class is.

(And by the way, you should not be doing DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver()). You shouldn't need to instantiate it. Just call Class.forName("oracle.jdbc.driver.OracleDriver") and it should register itself, and manage its own instantiation.)

Does JVM holds that internally? or JVM takes control?
i mean how it executes?

It executes just like any other code. You call a method, which class another method, and so on. These methods make use of various classes that are on the classpath. The classes may be your own, or part of the core API, or may have come from some third party library. It doesn't matter; it's all executed the same way.

[Jeff Verdegan]

Sumit Patil wrote:The implementation is never present in the JVM.

Yes it it. The implementing class, like any other class, has to be loaded into the JVM at runtime in order to execute its code.