function.java

Java写的含有一个jdbc驱动的小型数据库数据库引擎

/*
 * Function.java
 *
 * Copyright (c) 2001, The HSQL Development Group
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 *
 * Neither the name of the HSQL Development Group nor the names of its
 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * This package is based on HypersonicSQL, originally developed by Thomas Mueller.
 *
 */
package org.hsqldb;

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

/**
 * Function class declaration
 *
 *
 * @version 1.0.0.1
 */
class Function {
    private Channel    cChannel;
    private String     sFunction;
    private Method     mMethod;
    private int	       iReturnType;
    private int	       iArgCount;
    private int	       iArgType[];
    private boolean    bArgNullable[];
    private Object     oArg[];
    private Expression eArg[];
    private boolean    bConnection;

    /**
     * Constructor declaration
     *
     *
     * @param function
     * @param channel
     */
    Function(String function, Channel channel) throws SQLException {
	cChannel = channel;
	sFunction = function;

	int i = function.lastIndexOf('.');

	Trace.check(i != -1, Trace.UNEXPECTED_TOKEN, function);

	String classname = function.substring(0, i);

	channel.check("CLASS \"" + classname + "\"", Access.ALL);

	String methodname = function.substring(i + 1);
	Class  classinstance = null;

	try {
	    classinstance = Class.forName(classname);
	} catch (Exception e) {
	    throw Trace.error(Trace.ERROR_IN_FUNCTION, classname + " " + e);
	}

	Method method[] = classinstance.getMethods();

	for (i = 0; i < method.length; i++) {
	    Method m = method[i];

	    if (m.getName().equals(methodname)) {
		Trace.check(mMethod == null, Trace.UNKNOWN_FUNCTION,
			    methodname);

		mMethod = m;
	    }
	}

	Trace.check(mMethod != null, Trace.UNKNOWN_FUNCTION, methodname);

	Class returnclass = mMethod.getReturnType();

	iReturnType = Column.getTypeNr(returnclass.getName());

	Class arg[] = mMethod.getParameterTypes();

	iArgCount = arg.length;
	iArgType = new int[iArgCount];
	bArgNullable = new boolean[iArgCount];

	for (i = 0; i < arg.length; i++) {
	    Class  a = arg[i];
	    String type = a.getName();

	    if (i == 0 && type.equals("java.sql.Connection")) {

		// only the first parameter can be a Connection
		bConnection = true;
	    } else {
		if (type.equals("[B")) {
		    type = "byte[]";
		}

		iArgType[i] = Column.getTypeNr(type);
		bArgNullable[i] = !a.isPrimitive();
	    }
	}

	eArg = new Expression[iArgCount];
	oArg = new Object[iArgCount];
    }

    /**
     * Method declaration
     *
     *
     * @return
     *
     * @throws SQLException
     */
    Object getValue() throws SQLException {
	int i = 0;

	if (bConnection) {
	    oArg[i] = new jdbcConnection(cChannel);
	    i++;
	}

	for (; i < iArgCount; i++) {
	    Expression e = eArg[i];
	    Object     o = null;

	    if (e != null) {

		// no argument: null
		o = e.getValue(iArgType[i]);
	    }

	    if (o == null &&!bArgNullable[i]) {

		// null argument for primitive datatype: don't call & return null
		return null;
	    }

	    oArg[i] = o;
	}

	try {
	    return mMethod.invoke(null, oArg);
	} catch (Exception e) {
	    String s = sFunction + ": " + e.toString();

	    throw Trace.getError(Trace.FUNCTION_NOT_SUPPORTED, s);
	}
    }

    /**
     * Method declaration
     *
     *
     * @return
     */
    int getArgCount() {
	return iArgCount - (bConnection ? 1 : 0);
    }

    /**
     * Method declaration
     *
     *
     * @param f
     *
     * @throws SQLException
     */
    void resolve(TableFilter f) throws SQLException {
	for (int i = 0; i < iArgCount; i++) {
	    if (eArg[i] != null) {
		eArg[i].resolve(f);
	    }
	}
    }

    /**
     * Method declaration
     *
     *
     * @throws SQLException
     */
    void checkResolved() throws SQLException {
	for (int i = 0; i < iArgCount; i++) {
	    if (eArg[i] != null) {
		eArg[i].checkResolved();
	    }
	}
    }

    /**
     * Method declaration
     *
     *
     * @param i
     *
     * @return
     */
    int getArgType(int i) {
	return iArgType[i];
    }

    /**
     * Method declaration
     *
     *
     * @return
     */
    int getReturnType() {
	return iReturnType;
    }

    /**
     * Method declaration
     *
     *
     * @param i
     * @param e
     */
    void setArgument(int i, Expression e) {
	if (bConnection) {
	    i++;
	}

	eArg[i] = e;
    }

}