Easiest way to obtain database metadata in Java?

It's easily done using DdlUtils:

import javax.sql.DataSource;import org.apache.ddlutils.Platform;import org.apache.ddlutils.PlatformFactory;import org.apache.ddlutils.model.Database;import org.apache.ddlutils.platform.hsqldb.HsqlDbPlatform;public void readMetaData(final DataSource dataSource) {  final Platform platform = PlatformFactory.createNewPlatformInstance(dataSource);  final Database database = platform.readModelFromDatabase("someName");  // Inspect the database as required; has objects like Table/Column/etc.}

Take a look at SchemaCrawler (free and open source), which is another API designed for this purpose. Some sample SchemaCrawler code:

    // Create the optionsfinal SchemaCrawlerOptions options = new SchemaCrawlerOptions();// Set what details are required in the schema - this affects the// time taken to crawl the schemaoptions.setSchemaInfoLevel(SchemaInfoLevel.standard());options.setShowStoredProcedures(false);// Sorting optionsoptions.setAlphabeticalSortForTableColumns(true);// Get the schema definition // (the database connection is managed outside of this code snippet)final Database database = SchemaCrawlerUtility.getDatabase(connection, options);for (final Catalog catalog: database.getCatalogs()){  for (final Schema schema: catalog.getSchemas())  {    System.out.println(schema);    for (final Table table: schema.getTables())    {      System.out.print("o--> " + table);      if (table instanceof View)      {        System.out.println(" (VIEW)");      }      else      {        System.out.println();      }      for (final Column column: table.getColumns())      {        System.out.println("     o--> " + column + " (" + column.getType()                           + ")");      }    }  }}

http://schemacrawler.sourceforge.net/