driverrdb.java

jena2.5.4推理机系统的一种最基本实现 HP实验室出品

/*
  (c) Copyright 2003, 2004, 2005, 2006, 2007 Hewlett-Packard Development Company, LP
  [See end of file]
*/

package com.hp.hpl.jena.db.impl;

import java.sql.*;
import java.util.*;
import java.util.zip.CRC32;
import java.io.UnsupportedEncodingException;
import java.lang.Thread;

import com.hp.hpl.jena.datatypes.RDFDatatype;
import com.hp.hpl.jena.datatypes.TypeMapper;
import com.hp.hpl.jena.db.GraphRDB;
import com.hp.hpl.jena.db.IDBConnection;
import com.hp.hpl.jena.db.RDFRDBException;
import com.hp.hpl.jena.graph.*;
import com.hp.hpl.jena.graph.query.ExpressionFunctionURIs; 

import com.hp.hpl.jena.rdf.model.AnonId;
import com.hp.hpl.jena.shared.*;

import com.hp.hpl.jena.vocabulary.RDF;
import com.hp.hpl.jena.vocabulary.DB;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.xerces.util.XMLChar;

//=======================================================================
/**
* Base database driver for implementing SpecializedGraphs.
* Different drivers are needed for different databases and different
* layout schemes.
* <p>
* This driver is a base implemention from which database-specific
* drivers can inherit. It is not generic in the sense that it will work
* on any minimal SQL store and so should be treated as if it were
* an abstract class.
* <p>The SQL statements which implement each of the functions are
* loaded in a separate file etc/[layout]_[database].sql from the classpath.
*
* @author hkuno modification of Jena1 code by Dave Reynolds (der)
* @version $Revision: 1.68 $ on $Date: 2007/06/28 12:46:53 $
*/

public abstract class DriverRDB implements IRDBDriver {

//=======================================================================
// Cutomization variables
// =======================================================================
   /**
    * This Graph's db properties
    */
   protected DBPropDatabase m_dbProps;
    
   /**
   * Name of this class's PSet_TripleStore_XXX class
   */
  protected String m_psetClassName;

  /**
  * Name of this class's PSet_TripleStore_XXX class
  */
 protected String m_psetReifierClassName;

   /**
	* Cached name of this class's SpecializedGraph_XXX class
	*/
   protected String m_lsetClassName;
   
   /**
	* Cached name of this class's SpecializedGraphReifer_XXX class
	*/
   protected String m_lsetReifierClassName;
   
   /** The class name of the database driver (e.g. jdbc.sql.class)*/
   protected  String DRIVER_NAME;     
   // Dummy - needs replacing when instantiated?

   /** The name of the database type this driver supports */
   protected String DATABASE_TYPE;

   /** The maximum size of index key (or a component of a key) */
   protected int INDEX_KEY_LENGTH;

   /** The maximum possible value for INDEX_KEY_LENGTH (db-dependent) */
   protected int INDEX_KEY_LENGTH_MAX;

   /** true if graphs using this database instance supports transactions.
    * this is a user settable parameter. the underlying db engine may support
    * transactions but an application may prefer to run without transactions
    * for better performance. this can only be set before the db is formatted.
    */
   protected boolean IS_XACT_DB;

   
   protected boolean STRINGS_TRIMMED;
   /** true if the database engine will trim trailing spaces in strings. to
    *  prevent this, append EOS to strings that should not be trimmed.
    */
   
   protected String EOS = "";
   protected char	EOS_CHAR = ':';
   protected int	EOS_LEN = 0;
   /** EOS is appended to most RDB strings to deal with string trimming. if
    *  STRINGS_TRIMMED is false, EOS is null. otherwise, EOS is EOS_CHAR.
    *  EOS_LEN is the length of EOS (0 or 1).
    */
   
   protected char	QUOTE_CHAR = '\"';
   /** the quote character used to delimit characters and strings.
    */
   
   /**
    * Indicates whether search pattern used to select system objects by name should be upper-case.
    */
   protected  boolean DB_NAMES_TO_UPPER = false;
  

   /** true if URI's are to be compressed by storing prefixes (an approximation
    *  of a namespace) in the JENA_PREFIX table. note that "short" prefixes are
    *  not stored, i.e., the prefix length not more than URI_COMPRESS_LENGTH.
    */
   protected boolean URI_COMPRESS;

   
   protected int URI_COMPRESS_LENGTH = 100;
   /** if URI_COMPRESS is true, compress prefixes that are longer than this.

   /** The maximum size of an object that can be stored in a Statement table */
   protected int LONG_OBJECT_LENGTH;
   
   /** The maximum possible value for LONG_OBJECT_LENGTH (db-dependent) */
   protected int LONG_OBJECT_LENGTH_MAX;

   /** The SQL type to use for storing ids (compatible with wrapDBID) */
   protected String ID_SQL_TYPE;
   
   /** Set to true if the insert operations already check for duplications */
   protected boolean SKIP_DUPLICATE_CHECK;

   /** Set to true if IDs are allocated prior to insert */
   protected boolean PRE_ALLOCATE_ID;
	
   /** The name of the sql definition file for this database/layout combo */
   protected String SQL_FILE;
   
   /** The name of the sql definition file for this database/layout combo */
   protected String DEFAULT_SQL_FILE = "etc/generic_generic.sql";
      
   
// =======================================================================
//	Common variables
// =======================================================================
   /**
	* Holds prefix for names of Jena database tables.
	*/
   protected String TABLE_NAME_PREFIX = "jena_";
   
   /**
	* Holds maximum length of table and index names in database.
	*/
   protected int TABLE_NAME_LENGTH_MAX;
      
   /** Suffixes for asserted and reified table names. */
   protected String STMT_TABLE_NAME_SUFFIX = "_stmt";
   protected String REIF_TABLE_NAME_SUFFIX = "_reif";
   
   /** Maximum number of index columns. can be changed. */
   protected int MAXIMUM_INDEX_COLUMNS = 3;
  
   /** Number of required system tables. */
   protected int SYSTEM_TABLE_CNT = 0;
   
   /** Names of jena system tables. */
   public String [] SYSTEM_TABLE_NAME;
  
   /** Set to true to enable cache of pre-prepared statements */
   protected boolean CACHE_PREPARED_STATEMENTS = true;

   /** The name of the layout type this driver supports */
   protected String LAYOUT_TYPE = "TripleStore";

   /** Default name of the table that holds system property graph asserted statements **/
   protected String SYSTEM_STMT_TABLE;
   
   /** Name of the long literal table **/
   protected String LONG_LIT_TABLE;
   
   /** Name of the long URI table **/
   protected String LONG_URI_TABLE;

   /** Name of the prefix table **/
   protected String PREFIX_TABLE;

      /** Name of the graph table **/
   protected String GRAPH_TABLE;
    
   /** Name of the mutex table **/
   protected String MUTEX_TABLE;
    
	/** If not null, newly-created graphs share tables with the identified graph **/
   protected String STORE_WITH_MODEL = null;
    
   /** Name of the graph holding default properties (the one's that a newly-created
	*  graph will have by default **/
   protected final String DEFAULT_PROPS = "JENA_DEFAULT_GRAPH_PROPERTIES";
   
   /** Unique numeric identifier of the graph holding default properties **/
   protected final int DEFAULT_ID = 0;

        
   /** Driver version number */
   protected final String VERSION = "2.0alpha";
   
   /** Database layout version */
   protected String LAYOUT_VERSION = "2.0";
   
   protected static Log logger = LogFactory.getLog( DriverRDB.class );
    
// =======================================================================
//	Instance variables
// =======================================================================

	/**
	 * Instance of SQLCache used by Driver for hard-coded db commands
	 */
	protected SQLCache m_sql = null;

    /** Cache a reference to the system property graph (java) **/
    protected SpecializedGraph m_sysProperties = null;
    
    protected IDBConnection m_dbcon = null;
    
    protected LRUCache prefixCache = null;
    
    public static final int PREFIX_CACHE_SIZE = 50;
    
    //===================================
    // for transaction support
    //===================================
    
    
    // caches whether or not underlying connection supports transactions
    private Boolean m_transactionsSupported;
    
	/** flag to indicate that there is a transaction active on the associated connection */
	private boolean inTransaction = false;



//	=======================================================================
//	 Constructor
//	=======================================================================


    /**
     * Create a bare instance of the driver. It is not functional until a
     * database connection has been supplied via setConnection.
     */
    public DriverRDB() {
    }
    
//	=======================================================================
//	 Methods
//	=======================================================================
	
	/**
	 * Return the connection
	 */
	public IDBConnection getConnection() {
		return m_dbcon;
	}
	
	/**
	 * Return the specialized graph used to store system properties.
	 * (Constuct a new one if necessary). if the database is not
	 * properly formatted, then if doInit is true, the database will
	 * be formatted, else null is returned and the (unformatted
	 * database is unchanged).
	 */
	public SpecializedGraph getSystemSpecializedGraph(boolean doInit) {

		SpecializedGraph res = null;
		
		if (m_sysProperties != null) {
			return m_sysProperties;
		}

		if (!isDBFormatOK()) {
			// another thread could be formatting database
			// so get the mutex and try again
			lockDB();
			if (!isDBFormatOK()) {
				if (doInit) {
					try {
						// Format the DB
						// throw new JenaException("The database is not
						// formatted.\n");
						doCleanDB(false);
						prefixCache = new LRUCache(PREFIX_CACHE_SIZE); 
						res = formatAndConstructSystemSpecializedGraph();
					} catch (Exception e) {
						unlockDB();
						// We see an error during format testing, might be
						// a dead connection rather than an unformated
						// database so abort
						throw new JenaException(
						"The database appears to be unformatted or corrupted and\n"
						+ "an attempt to automatically format the database has failed\n", e);
					}
				}
				unlockDB();
				return res;
			}
			// after second try, DB is found to be correctly formatted.
			unlockDB();
		}

		prefixCache = new LRUCache(PREFIX_CACHE_SIZE);
		getDbInitTablesParams(); //this call is a hack. it's needed because
		// it has the side effect of initializing some vars (e.g., EOS).
		IPSet pSet = createIPSetInstanceFromName(m_psetClassName,
				SYSTEM_STMT_TABLE);
		m_sysProperties = createLSetInstanceFromName(m_lsetClassName, pSet,
				DEFAULT_ID);
		m_dbProps = new DBPropDatabase(m_sysProperties);
		
		// need to get initial values for encoding parameters
		String longObjLen = m_dbProps.getInitLongObjectLength();
		String indexKeyLen = m_dbProps.getInitIndexKeyLength();
		String compURI = m_dbProps.getInitDoCompressURI();
		String compURILen = m_dbProps.getInitCompressURILength();

		if (longObjLen == null)
			throwBadFormat("long object length");
		else
			LONG_OBJECT_LENGTH = Integer.parseInt(longObjLen);
		if (indexKeyLen == null)
			throwBadFormat("index key length");
		else
			INDEX_KEY_LENGTH = Integer.parseInt(indexKeyLen);
		if (compURI == null)
			throwBadFormat("compress URIs");
		else
			URI_COMPRESS = Boolean.valueOf(compURI).booleanValue();
		if (compURILen == null)
			throwBadFormat("URI compress length");
		else
			URI_COMPRESS_LENGTH = Integer.parseInt(compURILen);

		// now reset the configuration parameters
		checkEngine(m_dbProps);
		checkDriverVersion(m_dbProps);
		checkLayoutVersion(m_dbProps);
		String val = null;
		val = m_dbProps.getIsTransactionDb();
		if (val == null)
			throwBadFormat("database supports transactions");
		else
			IS_XACT_DB = Boolean.valueOf(val).booleanValue();
		val = m_dbProps.getTableNamePrefix();
		if (val == null)
			throwBadFormat("table name prefix");
		else
			TABLE_NAME_PREFIX = val;

		return m_sysProperties;
	}
	
	private void checkEngine ( DBProp dbProps ) {
		String dbtype = m_dbProps.getEngineType();
		if ( dbtype == null ) throwBadFormat("database type");
		if ( !dbtype.equals(DATABASE_TYPE) ) {
			throw new JenaException(
			"Database created with incompatible database type for this version of Jena: "
			+ dbtype);
		}
	}
	
	private void checkDriverVersion ( DBProp dbProps ) {
		String vers = m_dbProps.getDriverVersion();
		if ( vers == null ) throwBadFormat("database version");
		if ( !vers.equals(VERSION) ) {
			throw new JenaException(
			"Models in the database were created with an incompatible version of Jena: "
			+ vers);
		}
	}
	
	private void checkLayoutVersion ( DBProp dbProps ) {
		String layout = m_dbProps.getLayoutVersion();
		if ( layout == null ) throwBadFormat("database layout");
		if ( !layout.equals(LAYOUT_VERSION) ) {
			throw new JenaException(