path: root/src/interfaces/jdbc/org/postgresql/util/Serialize.java

package org.postgresql.util;

import java.io.*;
import java.lang.*;
import java.lang.reflect.*;
import java.net.*;
import java.util.*;
import java.sql.*;

/*
 * This class uses PostgreSQL's object oriented features to store Java Objects.<p>
 *
 * It does this by mapping a Java Class name to a table in the database. Each
 * entry in this new table then represents a Serialized instance of this
 * class. As each entry has an OID (Object IDentifier), this OID can be
 * included in another table.<p>
 *
 * Serialize depends on a feature of Postgres that allows
 * a table to be used as a data type. However, Postgres support of
 * this feature is incomplete. The basic ability to create and use
 * a table as a field type in another table exists:<br>
 *	  CREATE TABLE myclass( var1 TEXT, var2 INTEGER );<br>
 *	  CREATE TABLE othertable( field1 TEXT, field2 myclass );<br>
 *	  INSERT INTO myclass VALUES ('Hello', 1);<br>
 *	  INSERT INTO othertable VALUES ('World', xxxx::myclass);<br>
 *	  where xxxx is the OID of a row in myclass<br>
 * This lets othertable reference a myclass instance but
 * the support to actually make any use of the myclass data type
 * is not there. For instance, you cannot compare the myclass field
 * with ANY other data type, not even with other myclass values.
 * Casting to and from the myclass type will also not work.
 * From the limited testing done, only the literal xxxx::myclass
 * syntax appears to work.<p>
 *
 * Queries like:<br>
 *	  SELECT othertable.field2.var1 FROM othertable;<br>
 * will not work but were suggested in the original Postgres
 * design documents.<p>
 * Because support is incomplete for table data types, tables
 * such as othertable that hold java instances should also
 * hold an oid field for the same java instance:<br>
 *	  CREATE othertable( field1 TEXT, field2 myclass, myclassOID oid);<br>
 * This oid-type field would be set with setInt() immediately after
 * setting the myclass-type field with setObject(). The order of these
 * set calls matters since the oid is not available until after
 * setting the object when inserting a new object. With the oid,
 * queries and comparisons etc. can be done to locate a myclass.
 * Read below about how to include an int oid field in your java class
 * that is updated by setObject() when it is inserted.<p>
 *
 * The myclass table represents a java class. This table is created
 * by Serialize.create(). Serialize.create() must be called before
 * the first use of the myclass java class in PreparedStatement.setObject()
 * calls. This is a one-time initialization step.<p>
 *
 * There are a number of limitations placed on the java class to be
 * used by Serialize:
 * <ul>
 * <li>The class name must be less than 32 chars long and must be all lowercase.
 * This is due to limitations in Postgres about the size of table names.
 * The name must be all lowercase since table names in Postgres are
 * case insensitive and the relname is stored in lowercase. Unless some
 * additional table were to be maintained about the names of java classes,
 * there is no way to know how to go from a Postgres table name back to
 * a java class name with knowledge of case of the letters in the name.
 * <li>The class name must not contain the underscore '_' character since
 * any dots in a java class name are converted to an underscore in
 * its table name and vice versa going back.
 * <li>The class should only contain java primitive types and String.
 * Support for recursively "serializing" a class is not tested but
 * some code for this does exist and you may wish to take a look at it.
 * <li>Only the public fields of the class will be stored in and fetched from
 * the database. Protected and private fields are ignored.
 * <li>Must have a no-arg constructor so that Class.newInstance() may
 * instantiate the class in fetch().
 * <li>Should implement the Serializable interface. This interface
 * may be used more in future releases or in providing an alternative
 * method of storing the java classes in the database. The Serializable
 * interface allows a class instance to be written out as a binary
 * stream of data and is a standard java feature.
 * <li>The class should contain a field defined as:<br>
 * int oid = 0;<br>
 * This field is actually optional and its use by jdbc2.PreparedStatement.setObject()
 * is as follows:<br>
 * If oid does not exist in the class, the class instance is stored in a new table row
 * everytime setObject() is called on it. If oid field exists and is 0, then the class
 * instance is stored into a new row in the table and that row's oid is set in the class by setObject().
 * If oid field exists and is > 0, then the existing table row for the class instance is
 * updated. The oid field should be thought of as read-only unless you want to set it to 0
 * so that a new instance is created in the database rather than doing an update.<p>
 * </ul>
 *
 * Suggested usage:
 * <ol>
 * <li>Create your javaclass and include an int oid = 0; field.
 * <li>Run Serialize.create( conn, javaclass ) to create the table for javaclass (once).
 * <li>Create mytable in the database with fields like: jclassoid INTEGER, jclass JAVACLASS<br>
 * <li>Use a jdbc2.PreparedStatement to insert, update, or select from mytable.
 * Use setObject(2, jclass), followed by setInt(1, jclass.oid) to setup an insert.
 * <li>Use jclass.oid and jclassoid to do queries since the jclass field cannot be used
 * for anything but fetching the javaclass instance with getObject("jclass").
 * </ol>
 * Finally, Serialize is a work in progress and being a utility class, it is not supported.
 * You are "on your own" if you use it. If you use it and make any enhancements,
 * please consider joining the email lists pgsql-jdbc@postgresql.org and pgsql-patches@postgresql.org
 * and contributing your additions.
 */
public class Serialize
{
	// This is the connection that the instance refers to
	protected org.postgresql.Connection conn;

	// This is the table name
	protected String tableName;

	// This is the class name
	protected String className;

	// This is the Class for this serialzed object
	protected Class ourClass;

	/*
	 * This creates an instance that can be used to serialize or deserialize
	 * a Java object from a PostgreSQL table.
	 */
	public Serialize(org.postgresql.Connection c, String type) throws SQLException
	{
		try
		{
			conn = c;
			DriverManager.println("Serialize: initializing instance for type: " + type);
			tableName = toPostgreSQL(type);
			className = type;
			ourClass = Class.forName(className);
		}
		catch (ClassNotFoundException cnfe)
		{
			DriverManager.println("Serialize: " + className + " java class not found");
			throw new PSQLException("postgresql.serial.noclass", type);
		}

		// Second check, the type must be a table
		boolean status = false;
		ResultSet rs = conn.ExecSQL("select typname from pg_type,pg_class where typname=relname and typname='" + tableName + "'");
		if (rs != null)
		{
			if (rs.next())
			{
				status = true;
				DriverManager.println("Serialize: " + tableName + " table found");
			}
			rs.close();
		}
		// This should never occur, as org.postgresql has it's own internal checks
		if (!status)
		{
			DriverManager.println("Serialize: " + tableName + " table not found");
			throw new PSQLException("postgresql.serial.table", type);
		}
		// Finally cache the fields within the table
	}

	/*
	 * Constructor when Object is passed in
	 */
	public Serialize(org.postgresql.Connection c, Object o) throws SQLException
	{
		this(c, o.getClass().getName());
	}

	/*
	 * Constructor when Class is passed in
	 */
	public Serialize(org.postgresql.Connection c, Class cls) throws SQLException
	{
		this(c, cls.getName());
	}

	/*
	 * This fetches an object from a table, given it's OID
	 * @param oid The oid of the object
	 * @return Object relating to oid
	 * @exception SQLException on error
	 */
	public Object fetch(int oid) throws SQLException
	{
		try
		{
			DriverManager.println("Serialize.fetch: " + "attempting to instantiate object of type: " + ourClass.getName() );
			Object obj = ourClass.newInstance();
			DriverManager.println("Serialize.fetch: " + "instantiated object of type: " + ourClass.getName() );

			// NB: we use java.lang.reflect here to prevent confusion with
			// the org.postgresql.Field

			// used getFields to get only public fields. We have no way to set values
			// for other declarations. Maybe look for setFieldName() methods?
			java.lang.reflect.Field f[] = ourClass.getFields();
			boolean hasOID = false;
			int oidFIELD = -1;

			StringBuffer sb = new StringBuffer("select");
			char sep = ' ';
			// build a select for the fields. Look for the oid field to use in the where
			for (int i = 0;i < f.length;i++)
			{
				String n = f[i].getName();
				if (n.equals("oid"))
				{
					hasOID = true;
					oidFIELD = i;
				}
				sb.append(sep);
				sb.append(n);
				sep = ',';
			}
			sb.append(" from ");
			sb.append(tableName);
			sb.append(" where oid=");
			sb.append(oid);

			DriverManager.println("Serialize.fetch: " + sb.toString());
			ResultSet rs = conn.ExecSQL(sb.toString());

			if (rs != null)
			{
				if (rs.next())
				{
					for (int i = 0;i < f.length;i++)
					{
						if ( !Modifier.isFinal(f[i].getModifiers()) )
						{
							if ( f[i].getType().getName().equals("short") )
								f[i].setShort(obj, rs.getShort(i + 1));
							else if ( f[i].getType().getName().equals("char") )
								f[i].setChar(obj, rs.getString(i + 1).toCharArray()[0]);
							else if ( f[i].getType().getName().equals("byte"))
								f[i].setByte(obj, rs.getByte(i + 1));
							else if ( f[i].getType().getName().equals("boolean") )
							{
								// booleans come out of pgsql as a t or an f
								if ( rs.getString(i + 1).equals("t") )
									f[i].setBoolean(obj, true);
								else
									f[i].setBoolean(obj, false);
							}
							else
								f[i].set(obj, rs.getObject(i + 1));
						}
					}
				}
				rs.close();
			}
			else
				throw new PSQLException("postgresql.unexpected");

			return obj;

		}
		catch (IllegalAccessException iae)
		{
			throw new SQLException(iae.toString());
		}
		catch (InstantiationException ie)
		{
			throw new SQLException(ie.toString());
		}
	}

	/*
	 * This stores an object into a table, returning it's OID.<p>
         * This method was deprecated in 7.2 because the value of an OID
         * can be larger than a java signed int.
	 * @deprecated Replaced by storeObject() in 7.2
	 */
	public int store(Object o) throws SQLException
	{
	    return (int) storeObject(o);
	}

	/*
	 * This stores an object into a table, returning it's OID.<p>
	 *
	 * If the object has an int called OID, and it is > 0, then
	 * that value is used for the OID, and the table will be updated.
	 * If the value of OID is 0, then a new row will be created, and the
	 * value of OID will be set in the object. This enables an object's
	 * value in the database to be updateable.
	 *
	 * If the object has no int called OID, then the object is stored. However
	 * if the object is later retrieved, amended and stored again, it's new
	 * state will be appended to the table, and will not overwrite the old
	 * entries.
	 *
	 * @param o Object to store (must implement Serializable)
	 * @return oid of stored object
	 * @exception SQLException on error
         * @since 7.2
	 */
	public long storeObject(Object o) throws SQLException
	{
		try
		{
			// NB: we use java.lang.reflect here to prevent confusion with
			// the org.postgresql.Field

			// don't save private fields since we would not be able to fetch them
			java.lang.reflect.Field f[] = ourClass.getFields();

			boolean hasOID = false;
			int oidFIELD = -1;
			boolean update = false;

			// Find out if we have an oid value
			for (int i = 0;i < f.length;i++)
			{
				String n = f[i].getName();
				if (n.equals("oid"))
				{
					hasOID = true;
					oidFIELD = i;
					// Do update if oid != 0
					update = f[i].getInt(o) > 0;
				}
			}

			StringBuffer sb = new StringBuffer(update ? "update " + tableName + " set" : "insert into " + tableName + " ");
			char sep = update ? ' ' : '(';
			for (int i = 0;i < f.length;i++)
			{
				String n = f[i].getName();
				// oid cannot be updated!
				if ( n.equals("oid") )
					continue;
				sb.append(sep);
				sep = ',';
				sb.append(n);
				if (update)
				{
					sb.append('=');
					// handle unset values
					if (f[i].get(o) == null)
						sb.append("null");
					else if (
						f[i].getType().getName().equals("java.lang.String")
						|| f[i].getType().getName().equals("char") )
					{
						sb.append('\'');
						// don't allow single qoutes or newlines in the string
						sb.append(fixString(f[i].get(o).toString()));
						sb.append('\'');
					}
					else
						sb.append(f[i].get(o).toString());
				}
			}

			if (update)
				sb.append(" where oid = " + f[oidFIELD].getInt(o) );

			if (!update)
			{
				sb.append(") values ");
				sep = '(';
				for (int i = 0;i < f.length;i++)
				{
					String n = f[i].getName();
					// oid cannot be set!
					if ( n.equals("oid") )
						continue;
					sb.append(sep);
					sep = ',';
					// handle unset values
					if (f[i].get(o) == null)
						sb.append("null");
					else if (
						f[i].getType().getName().equals("java.lang.String")
						|| f[i].getType().getName().equals("char"))
					{
						sb.append('\'');
						// don't allow single quotes or newlines in the string
						sb.append(fixString(f[i].get(o).toString()));
						sb.append('\'');
					}
					else
						sb.append(f[i].get(o).toString());
				}
				sb.append(')');
			}

			DriverManager.println("Serialize.store: " + sb.toString() );
			org.postgresql.ResultSet rs = (org.postgresql.ResultSet) conn.ExecSQL(sb.toString());

			// fetch the OID for returning
			if (update)
			{
				// object has oid already, so return it
				if (rs != null)
					rs.close();
				return f[oidFIELD].getInt(o);
			}
			else
			{
				// new record inserted has new oid; rs should be not null
				long newOID = ((org.postgresql.ResultSet)rs).getLastOID();
				rs.close();
				// update the java object's oid field if it has the oid field
				if (hasOID)
					f[oidFIELD].setLong(o, newOID);
				// new object stored, return newly inserted oid
				return newOID;
			}

		}
		catch (IllegalAccessException iae)
		{
			throw new SQLException(iae.toString());
		}
	}

	/*
	* Escape literal single quote and backslashes embedded in strings/chars.
	* Otherwise, postgres will bomb on the single quote and remove the
	* the backslashes.
	*/
	private String fixString(String s)
	{
		int idx = -1;

		// handle null
		if (s == null)
			return "";

		// if the string has single quotes in it escape them as ''
		if ((idx = s.indexOf("'")) > -1)
		{
			StringBuffer buf = new StringBuffer();
			StringTokenizer tok = new StringTokenizer(s, "'");
			// handle quote as 1St charater
			if (idx > 0)
				buf.append(tok.nextToken());

			while (tok.hasMoreTokens())
				buf.append("''").append(tok.nextToken());

			s = buf.toString();
		}

		// if the string has backslashes in it escape them them as \\
		if ((idx = s.indexOf("\\")) > -1)
		{
			StringBuffer buf = new StringBuffer();
			StringTokenizer tok = new StringTokenizer(s, "\\");
			if (idx > 0)
				buf.append(tok.nextToken());

			while (tok.hasMoreTokens())
				buf.append("\\\\").append(tok.nextToken());

			s = buf.toString();
		}

		return s;
	}

	/*
	 * This method is not used by the driver, but it creates a table, given
	 * a Serializable Java Object. It should be used before serializing any
	 * objects.
	 * @param c Connection to database
	 * @param o Object to base table on
	 * @exception SQLException on error
	 */
	public static void create(org.postgresql.Connection con, Object o) throws SQLException
	{
		create(con, o.getClass());
	}

	/*
	 * This method is not used by the driver, but it creates a table, given
	 * a Serializable Java Object. It should be used before serializing any
	 * objects.
	 * @param c Connection to database
	 * @param o Class to base table on
	 * @exception SQLException on error
	 */
	public static void create(org.postgresql.Connection con, Class c) throws SQLException
	{
		if (c.isInterface())
			throw new PSQLException("postgresql.serial.interface");

		// See if the table exists
		String tableName = toPostgreSQL(c.getName());

		ResultSet rs = con.ExecSQL("select relname from pg_class where relname = '" + tableName + "'");
		if ( rs.next() )
		{
			DriverManager.println("Serialize.create: table " + tableName + " exists, skipping");
			rs.close();
			return;
		}

		// else table not found, so create it
		DriverManager.println("Serialize.create: table " + tableName + " not found, creating" );
		// No entries returned, so the table doesn't exist

		StringBuffer sb = new StringBuffer("create table ");
		sb.append(tableName);
		char sep = '(';

		// java.lang.reflect.Field[] fields = c.getDeclaredFields();
		// Only store public fields, another limitation!
		java.lang.reflect.Field[] fields = c.getFields();
		for (int i = 0;i < fields.length;i++)
		{
			Class type = fields[i].getType();
			// oid is a special field
			if (!fields[i].getName().equals("oid"))
			{
				sb.append(sep);
				sb.append(fields[i].getName());
				sb.append(' ');
				sep = ',';

				if (type.isArray())
				{
					// array handling
				}
				else
				{
					// convert the java type to org.postgresql, recursing if a class
					// is found
					String n = type.getName();
					int j = 0;
					for (;j < tp.length && !tp[j][0].equals(n);j++)
						;
					if (j < tp.length)
						sb.append(tp[j][1]);
					else
					{
						create(con, type);
						sb.append(toPostgreSQL(n));
					}
				}
			}
		}
		sb.append(")");

		// Now create the table
		DriverManager.println("Serialize.create: " + sb );
		con.ExecSQL(sb.toString());
	}

	// This is used to translate between Java primitives and PostgreSQL types.
	private static final String tp[][] = {
											 //    {"boolean",			"int1"},
											 {"boolean", "bool"},
											 {"double", "float8"},
											 {"float", "float4"},
											 {"int", "int4"},
											 //    {"long",			"int4"},
											 {"long", "int8"},
											 {"short", "int2"},
											 {"java.lang.String", "text"},
											 {"java.lang.Integer", "int4"},
											 {"java.lang.Float", "float4"},
											 {"java.lang.Double", "float8"},
											 {"java.lang.Short", "int2"},
											 {"char", "char"},
											 {"byte", "int2"}
										 };

	/*
	 * This converts a Java Class name to a org.postgresql table, by replacing . with
	 * _<p>
	 *
	 * Because of this, a Class name may not have _ in the name.<p>
	 * Another limitation, is that the entire class name (including packages)
	 * cannot be longer than 32 characters (a limit forced by PostgreSQL).
	 *
	 * @param name Class name
	 * @return PostgreSQL table name
	 * @exception SQLException on error
	 */
	public static String toPostgreSQL(String name) throws SQLException
	{
		name = name.toLowerCase();

		if (name.indexOf("_") > -1)
			throw new PSQLException("postgresql.serial.underscore");

		// Postgres table names can only be 32 character long.
		// Reserve 1 char, so allow only up to 31 chars.
		// If the full class name with package is too long
		// then just use the class name. If the class name is
		// too long throw an exception.
		//
		if ( name.length() > 31 )
		{
			name = name.substring(name.lastIndexOf(".") + 1);
			if ( name.length() > 31 )
				throw new PSQLException("postgresql.serial.namelength", name, new Integer(name.length()));
		}
		return name.replace('.', '_');
	}


	/*
	 * This converts a org.postgresql table to a Java Class name, by replacing _ with
	 * .<p>
	 *
	 * @param name PostgreSQL table name
	 * @return Class name
	 * @exception SQLException on error
	 */
	public static String toClassName(String name) throws SQLException
	{
		name = name.toLowerCase();
		return name.replace('_', '.');
	}

}