session.java

hsqldb是100％java实现的数据库,是一个开放源代码的JAVA数据库 l 具有标准的SQL语法和JAVA接口 l HSQLDB可以自由使用和分发 l 非常简洁和快速的

    /**
     * Rolls back any uncommited transaction this Session may have open.
     *
     * @throws  HsqlException
     */
    public void rollback() {

        if (isClosed) {
            return;
        }

        synchronized (database) {
            if (rowActionList.size() != 0) {
                try {
                    database.logger.writeToLog(this, Token.T_ROLLBACK);
                } catch (HsqlException e) {}
            }

            database.txManager.rollback(this);
            clearIndexRoots();
        }
    }

    /**
     * No-op in this implementation
     */
    public void resetSession() throws HsqlException {
        throw new HsqlException("", "", 0);
    }

    /**
     *  Implements a transaction SAVEPOINT. A new SAVEPOINT with the
     *  name of an existing one replaces the old SAVEPOINT.
     *
     * @param  name of the savepoint
     * @throws  HsqlException if there is no current transaction
     */
    void savepoint(String name) throws HsqlException {

        savepoints.remove(name);
        savepoints.add(name, ValuePool.getInt(rowActionList.size()));

        try {
            database.logger.writeToLog(this, Token.T_SAVEPOINT + " " + name);
        } catch (HsqlException e) {}
    }

    /**
     *  Implements a partial transaction ROLLBACK.
     *
     * @param  name Name of savepoint that was marked before by savepoint()
     *      call
     * @throws  HsqlException
     */
    void rollbackToSavepoint(String name) throws HsqlException {

        if (isClosed) {
            return;
        }

        try {
            database.logger.writeToLog(this,
                                       Token.T_ROLLBACK + " " + Token.T_TO
                                       + " " + Token.T_SAVEPOINT + " "
                                       + name);
        } catch (HsqlException e) {}

        database.txManager.rollbackSavepoint(this, name);
    }

    /**
     * Implements release of named SAVEPOINT.
     *
     * @param  name Name of savepoint that was marked before by savepoint()
     *      call
     * @throws  HsqlException if name does not correspond to a savepoint
     */
    void releaseSavepoint(String name) throws HsqlException {

        // remove this and all later savepoints
        int index = savepoints.getIndex(name);

        Trace.check(index >= 0, Trace.SAVEPOINT_NOT_FOUND, name);

        while (savepoints.size() > index) {
            savepoints.remove(savepoints.size() - 1);
        }
    }

    /**
     * Starts a nested transaction.
     *
     * @throws  HsqlException
     */
    void beginNestedTransaction() throws HsqlException {

        if (isNestedTransaction) {
            Trace.doAssert(false, "beginNestedTransaction");
        }

        nestedOldTransIndex = rowActionList.size();
        isNestedTransaction = true;

        if (isAutoCommit) {
            try {
                database.logger.writeToLog(this, "SET AUTOCOMMIT FALSE");
            } catch (HsqlException e) {}
        }
    }

    /**
     * @todo -- fredt 20050604 - if this method is called after an out of memory
     * error during update, the next block might throw out of memory too and as
     * a result inNestedTransaction remains true and no further update
     * is possible. The session must be closed at that point by the user
     * application.
     */

    /**
     * Ends a nested transaction.
     *
     * @param  rollback true to roll back or false to commit the nested transaction
     * @throws  HsqlException
     */
    void endNestedTransaction(boolean rollback) throws HsqlException {

        if (!isNestedTransaction) {
            Trace.doAssert(false, "endNestedTransaction");
        }

        if (rollback) {
            database.txManager.rollbackTransactions(this,
                    nestedOldTransIndex, true);
        }

        // reset after the rollback
        isNestedTransaction = false;

        if (isAutoCommit) {
            database.txManager.commit(this);

            try {
                database.logger.writeToLog(this, "SET AUTOCOMMIT TRUE");
            } catch (HsqlException e) {}
        }
    }

    /**
     * Setter for readonly attribute.
     *
     * @param  readonly the new value
     */
    public void setReadOnly(boolean readonly) throws HsqlException {

        if (!readonly && database.databaseReadOnly) {
            throw Trace.error(Trace.DATABASE_IS_READONLY);
        }

        isReadOnly = readonly;
    }

    /**
     *  Getter for readonly attribute.
     *
     * @return the current value
     */
    public boolean isReadOnly() {
        return isReadOnly;
    }

    /**
     *  Getter for nestedTransaction attribute.
     *
     * @return the current value
     */
    boolean isNestedTransaction() {
        return isNestedTransaction;
    }

    /**
     *  Getter for autoCommit attribute.
     *
     * @return the current value
     */
    public boolean isAutoCommit() {
        return isAutoCommit;
    }

    /**
     *  A switch to set scripting on the basis of type of statement executed.
     *  A method in DatabaseCommandInterpreter.java sets this value to false
     *  before other  methods are called to act on an SQL statement, which may
     *  set this to true. Afterwards the method reponsible for logging uses
     *  getScripting() to determine if logging is required for the executed
     *  statement. (fredt@users)
     *
     * @param  script The new scripting value
     */
    void setScripting(boolean script) {
        this.script = script;
    }

    /**
     * Getter for scripting attribute.
     *
     * @return  scripting for the last statement.
     */
    boolean getScripting() {
        return script;
    }

    public String getAutoCommitStatement() {
        return isAutoCommit ? "SET AUTOCOMMIT TRUE"
                            : "SET AUTOCOMMIT FALSE";
    }

    /**
     * Retrieves an internal Connection object equivalent to the one
     * that created this Session.
     *
     * @return  internal connection.
     */
    jdbcConnection getInternalConnection() throws HsqlException {

        if (intConnection == null) {
            intConnection = new jdbcConnection(this);
        }

        return intConnection;
    }

// boucherb@users 20020810 metadata 1.7.2
//----------------------------------------------------------------
    private final long connectTime = System.currentTimeMillis();

// more effecient for MetaData concerns than checkAdmin

    /**
     * Getter for admin attribute.
     *
     * @ return the current value
     */
    boolean isAdmin() {
        return user.isAdmin();
    }

    /**
     * Getter for connectTime attribute.
     *
     * @return the value
     */
    long getConnectTime() {
        return connectTime;
    }

    /**
     * Getter for transactionSise attribute.
     *
     * @return the current value
     */
    int getTransactionSize() {
        return rowActionList.size();
    }

    /**
     * Retrieves whether the database object identifier by the dbobject
     * argument is accessible by the current Session User.
     *
     * @return true if so, else false
     */
    boolean isAccessible(String dbobject) throws HsqlException {
        return user.isAccessible(dbobject);
    }

    boolean isAccessible(HsqlName dbobject) throws HsqlException {
        return user.isAccessible(dbobject);
    }

// boucherb@users 20030417 - patch 1.7.2 - compiled statement support
//-------------------------------------------------------------------
    DatabaseCommandInterpreter dbCommandInterpreter;
    CompiledStatementExecutor  compiledStatementExecutor;
    CompiledStatementManager   compiledStatementManager;

    CompiledStatement sqlCompileStatement(String sql) throws HsqlException {

        parser.reset(sql);

        CompiledStatement cs;
        int               brackets = 0;
        String            token    = tokenizer.getString();
        int               cmd      = Token.get(token);

        switch (cmd) {

            case Token.OPENBRACKET : {
                brackets = parser.parseOpenBracketsSelect() + 1;
            }
            case Token.SELECT : {
                cs = parser.compileSelectStatement(brackets);

                break;
            }
            case Token.INSERT : {
                cs = parser.compileInsertStatement();

                break;
            }
            case Token.UPDATE : {
                cs = parser.compileUpdateStatement();

                break;
            }
            case Token.DELETE : {
                cs = parser.compileDeleteStatement();

                break;
            }
            case Token.CALL : {
                cs = parser.compileCallStatement();

                break;
            }
            default : {

                // DDL statements
                cs = new CompiledStatement(currentSchema);

                break;
            }
        }

        // In addition to requiring that the compilation was successful,
        // we also require that the submitted sql represents a _single_
        // valid DML or DDL statement. We do not check the DDL yet.
        // fredt - now accepts semicolon and whitespace at the end of statement
        // fredt - investigate if it should or not for prepared statements
        if (cs.type != CompiledStatement.DDL) {
            while (tokenizer.getPosition() < tokenizer.getLength()) {
                token = tokenizer.getString();

                if (token.length() != 0 &&!token.equals(Token.T_SEMICOLON)) {
                    throw Trace.error(Trace.UNEXPECTED_TOKEN, token);
                }
            }
        }

        // - need to be able to key cs against its sql in statement pool
        // - also need to be able to revalidate its sql occasionally
        cs.sql = sql;

        return cs;
    }

    /**
     * Executes the command encapsulated by the cmd argument.
     *
     * @param cmd the command to execute
     * @return the result of executing the command
     */
    public Result execute(Result cmd) {

        try {
            if (isClosed) {
                Trace.check(false, Trace.ACCESS_IS_DENIED,
                            Trace.getMessage(Trace.Session_execute));
            }
        } catch (Throwable t) {
            return new Result(t, null);
        }

        synchronized (database) {
            int type = cmd.mode;

            if (sessionMaxRows == 0) {
                currentMaxRows = cmd.updateCount;
            }

            // we simply get the next system change number - no matter what type of query
            actionTimestamp = database.txManager.nextActionTimestamp();

            JavaSystem.gc();

            switch (type) {

                case ResultConstants.SQLEXECUTE : {
                    Result resultout = sqlExecute(cmd);

                    resultout = performPostExecute(resultout);

                    return resultout;
                }
                case ResultConstants.BATCHEXECUTE : {
                    Result resultout = sqlExecuteBatch(cmd);

                    resultout = performPostExecute(resultout);

                    return resultout;
                }
                case ResultConstants.SQLEXECDIRECT : {
                    Result resultout =
                        sqlExecuteDirectNoPreChecks(cmd.getMainString());

                    resultout = performPostExecute(resultout);

                    return resultout;
                }
                case ResultConstants.BATCHEXECDIRECT : {
                    Result resultout = sqlExecuteBatchDirect(cmd);

                    resultout = performPostExecute(resultout);

                    return resultout;
                }
                case ResultConstants.SQLPREPARE : {
                    CompiledStatement cs;

                    try {
                        cs = compiledStatementManager.compile(
                            this, cmd.getMainString());
                    } catch (Throwable t) {
                        return new Result(t, cmd.getMainString());
                    }

                    Result rmd = cs.describeResult();
                    Result pmd = cs.describeParameters();

                    return Result.newPrepareResponse(cs.id, rmd, pmd);
                }
                case ResultConstants.SQLFREESTMT : {
                    compiledStatementManager.freeStatement(
                        cmd.getStatementID(), sessionId, false);

                    return emptyUpdateCount;
                }
                case ResultConstants.GETSESSIONATTR : {
                    return getAttributes();
                }
                case ResultConstants.SETSESSIONATTR : {
                    return setAttributes(cmd);
                }
                case ResultConstants.SQLENDTRAN : {
                    switch (cmd.getEndTranType()) {

                        case ResultConstants.COMMIT :
                            commit();
                            break;

                        case ResultConstants.ROLLBACK :
                            rollback();
                            break;

                        case ResultConstants.SAVEPOINT_NAME_RELEASE :
                            try {
                                String name = cmd.getMainString();

                                releaseSavepoint(name);
                            } catch (Throwable t) {
                                return new Result(t, null);
                            }
                            break;

                        case ResultConstants.SAVEPOINT_NAME_ROLLBACK :
                            try {
                                rollbackToSavepoint(cmd.getMainString());
                            } catch (Throwable t) {
                                return new Result(t, null);
                            }
                            break;

                        // not yet
                        // case ResultConstants.COMMIT_AND_CHAIN :
                        // case ResultConstants.ROLLBACK_AND_CHAIN :
                    }

                    return emptyUpdateCount;
                }
                case ResultConstants.SQLSETCONNECTATTR : {
                    switch (cmd.getConnectionAttrType()) {

                        case ResultConstants.SQL_ATTR_SAVEPOINT_NAME :
                            try {
                                savepoint(cmd.getMainString());
                            } catch (Throwable t) {
                                return new Result(t, null);
                            }

                        // case ResultConstants.SQL_ATTR_AUTO_IPD
                        //   - always true
                        // default: throw - case never happens
                    }

                    return emptyUpdateCount;
                }
                case ResultConstants.SQLDISCONNECT : {
                    close();