Main.java Source code

Introduction

Here is the source code for Main.java

Source

//package com.java2s;
/*
    
 Derby - Class org.apache.derbyDemo.vtis.core.VTIHelper
    
 Licensed to the Apache Software Foundation (ASF) under one or more
 contributor license agreements.  See the NOTICE file distributed with
 this work for additional information regarding copyright ownership.
 The ASF licenses this file to You under the Apache License, Version 2.0
 (the "License"); you may not use this file except in compliance with
 the License.  You may obtain a copy of the License at
    
 http://www.apache.org/licenses/LICENSE-2.0
    
 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
    
 */

import java.lang.reflect.*;
import java.math.BigDecimal;
import java.sql.*;

public class Main {
    private static final boolean DEBUG = true;

    /**
     * <p>
     * Register a VTI.
     * </p>
     */
    public static void registerVTI(Method method, String[] columnNames, String[] columnTypes, boolean readsSqlData)
            throws Exception {
        String methodName = method.getName();
        String sqlName = doubleQuote(methodName);
        Class methodClass = method.getDeclaringClass();
        Class[] parameterTypes = method.getParameterTypes();
        int parameterCount = parameterTypes.length;
        int columnCount = columnNames.length;
        StringBuilder buffer = new StringBuilder();

        buffer.append("create function ");
        buffer.append(sqlName);
        buffer.append("\n( ");
        for (int i = 0; i < parameterCount; i++) {
            if (i > 0) {
                buffer.append(", ");
            }

            String parameterType = mapType(parameterTypes[i]);

            buffer.append("arg");
            buffer.append(i);
            buffer.append(" ");
            buffer.append(parameterType);
        }
        buffer.append(" )\n");

        buffer.append("returns table\n");
        buffer.append("( ");
        for (int i = 0; i < columnCount; i++) {
            if (i > 0) {
                buffer.append(", ");
            }

            buffer.append("\"" + columnNames[i] + "\"");
            buffer.append(" ");
            buffer.append(columnTypes[i]);
        }
        buffer.append(" )\n");

        buffer.append("language java\n");
        buffer.append("parameter style DERBY_JDBC_RESULT_SET\n");
        if (readsSqlData) {
            buffer.append("reads sql data\n");
        } else {
            buffer.append("no sql\n");
        }

        buffer.append("external name ");
        buffer.append("'");
        buffer.append(methodClass.getName());
        buffer.append(".");
        buffer.append(methodName);
        buffer.append("'\n");

        executeDDL(buffer.toString());
    }

    /**
     * <p>
     * Double-quote a name.
     * </p>
     *
     */
    public static String doubleQuote(String name) {
        return '\"' + name + '\"';
    }

    /**
     * <p>
     * Map a Java type to a SQL type.
     * </p>
     */
    private static String mapType(Class javaType) throws Exception {
        if (javaType == Long.class) {
            return "bigint";
        } else if (javaType == Blob.class) {
            return "blob";
        } else if (javaType == String.class) {
            return "varchar( 32672 )";
        } else if (javaType == Clob.class) {
            return "clob";
        } else if (javaType == BigDecimal.class) {
            return "decimal";
        } else if (javaType == Double.class) {
            return "double";
        } else if (javaType == Float.class) {
            return "float";
        } else if (javaType == Integer.class) {
            return "integer";
        } else if (javaType == byte[].class) {
            return "long varchar for bit data";
        } else if (javaType == Short.class) {
            return "smallint";
        } else if (javaType == Timestamp.class) {
            return "timestamp";
        } else {
            throw new Exception("Unsupported type of argument to Table Function: " + javaType.getName());
        }
    }

    /**
     * <p>
     * Execute a DDL statement
     * </p>
     */
    public static void executeDDL(String ddl) throws SQLException {
        Connection conn = getLocalConnection();

        // now register the function
        print(ddl);
        try {
            PreparedStatement createStatement = conn.prepareStatement(ddl);

            createStatement.execute();
            createStatement.close();
        } catch (SQLException t) {
            SQLException s = new SQLException("Could not execute DDL:\n" + ddl);

            s.setNextException(t);

            throw s;
        }
    }

    /**
     * <p>
     * Get the connection to the local database.
     * </p>
     */
    public static Connection getLocalConnection() throws SQLException {
        return DriverManager.getConnection("jdbc:default:connection");
    }

    /**
     * <p>
     * Debug helper method to print a diagnostic.
     * </p>
     */
    public static void print(String text) {
        if (DEBUG) {
            System.out.println(text);
        }
    }
}