Sql type to Java class?

Question

I want to write a utility class to generate a java source file (bean) from out of the metadata of a database table. the metadata returns the column type as a java.sql.Types constant (int value). now, i want to map these int values to Java classes. (e.g. Types.INT => java.lang.Integer). Is there already such a method in the API or do i have to write my own switch ... case Types.INT ... result = Integer.class ... method?

Answer 1

well, i wrote my own utility method to generate such beans:
     * Convert SQL type code to corresponding Java class.
     * @param sqlType One of java.sql.Types.xxx.
     * @return Class that corresponds to the given type.
    public static Class toClass(int sqlType) {
        Class result = null;
        switch (sqlType) {
        case Types.BIGINT :
        case Types.INTEGER :
        case Types.SMALLINT :
        case Types.TINYINT :
            result = Integer.class;
            break;
        case Types.BIT :
        case Types.BOOLEAN :
            result = Boolean.class;
            break;
        case Types.CHAR :
            result = Character.class;
            break;
        case Types.DATE :
        case Types.TIMESTAMP :
            result = java.util.Date.class;
            break;
        case Types.DECIMAL :
        case Types.DOUBLE :
        case Types.FLOAT :
            result = BigDecimal.class;
            break;
        case Types.NULL :
            result = null;
            break;
        case Types.LONGVARCHAR :
        case Types.VARCHAR :
        default :
            result = String.class;
            break;
        return result;
    }//toClass()
     * Create a Java bean (source file) to map a database table. The class name is the table name, the bean
     * properties are the table columns. Each column will result in a property with a corresponding set() and
     * get() method.
     * @param connection Database connection to load table from.
     * @param schema Schema to get tables for.
     * @param tableName Name of table to create the bean for.
     * @param className Name of Java class to create.
     * @param fileName Name of Java source file to create.
     * @throws SQLException, IOException
    public static void createTableBean(Connection connection, String schema, String tableName, String className, String fileName)
            throws SQLException, IOException {
        if (connection != null && tableName != null && fileName != null) {
            //read table columns:
            DatabaseMetaData dmd = connection.getMetaData();
            ResultSet resultSet = dmd.getColumns(null, "%", tableName, null);
            Properties props = new Properties();
            if (resultSet != null) {
                while (resultSet.next()) { //for each table
                    String name = resultSet.getString("COLUMN_NAME");
                    int type = resultSet.getInt("DATA_TYPE");
                    props.setProperty(name, ""+type);
                }//next table
            }//else: resultSet unavailable
            //create source file:
            File file = new File(fileName);
            StringBuffer sb = new StringBuffer();
            sb.append("/* $Header:$ */\n");
            sb.append("package TODO;\n\n");
            sb.append("/**\n");
            sb.append(" * Container class to store data of one record (row) of table '"+tableName+"'.\n");
            sb.append(" *\n");
            sb.append(" * @version $Revision:$ ($Date:$)\n");
            sb.append(" * @author $Author:$\n");
            sb.append(" */\n");
            sb.append("public class ");
            sb.append(className);
            sb.append(" {\n\n");
            Enumeration enum = props.keys();
            StringBuffer sb2 = new StringBuffer(); //methods
            StringBuffer sb3 = new StringBuffer(); //toString()
            while (enum.hasMoreElements()) {
                String columnName = (String) enum.nextElement();
                //change first character of column name to lower case:
                String fieldName = columnName.substring(0, 1).toLowerCase() + columnName.substring(1);
                String stype = props.getProperty(columnName, ""+Types.VARCHAR);
                int type = (new Integer(stype)).intValue();
                Class javaClass = toClass(type);
                String typeName = "String"; //default
                if (javaClass != null) {
                    String javaClassName = javaClass.getName();
                    int lastDot = javaClassName.lastIndexOf('.');
                    if (lastDot >= 0) {
                        typeName = javaClassName.substring(lastDot + 1);
                //field:
                sb.append("    /** ");
                sb.append(columnName);
                sb.append(" */\n");
                sb.append("    private ");
                sb.append(typeName);
                sb.append(" ");
                sb.append(fieldName);
                sb.append(" = null;\n");
                //toString() method:
                sb3.append("        sb.append(\",");
                sb3.append(fieldName);
                sb3.append("=\");\n");
                sb3.append("        sb.append(");
                sb3.append(fieldName);
                sb3.append(");\n");
                //set method:
                sb2.append("    /**\n");
                sb2.append("     * Set ");
                sb2.append(columnName);
                sb2.append(".\n     *\n     * @param value ");
                sb2.append(columnName);
                sb2.append(" to set.\n");
                sb2.append("     */\n");
                sb2.append("    public void set");
                sb2.append(columnName);
                sb2.append("(");
                sb2.append(typeName);
                sb2.append(" value) {\n        ");
                sb2.append(fieldName);
                sb2.append(" = value;\n    }\n\n");
                //get method:
                sb2.append("    /**\n");
                sb2.append("     * Get ");
                sb2.append(columnName);
                sb2.append(".\n     *\n     * @return ");
                sb2.append(columnName);
                sb2.append(".\n     */\n");
                sb2.append("    public ");
                sb2.append(typeName);
                sb2.append(" get");
                sb2.append(columnName);
                sb2.append("() {\n");
                sb2.append("        return ");
                sb2.append(fieldName);
                sb2.append(";\n    }\n\n");
            }//next column
            sb.append("\n\n");
            sb.append(sb2.toString()); //methods
            //overwrite toString() method:
            sb.append("    /**\n");
            sb.append("     * Overwrite super.\n");
            sb.append("     *\n     * @return String representation of the object.\n");
            sb.append("     */\n");
            sb.append("    public String toString() {\n");
            sb.append("        StringBuffer sb = new StringBuffer(super.toString());\n\n");
            sb.append(sb3.toString());
            sb.append("\n        return sb.toString();\n");
            sb.append("    }\n\n");
            sb.append("}//"+className);
            //write to file:
            String text = sb.toString();
            BufferedWriter bw = null;
            try {
                bw = new BufferedWriter(new FileWriter(file));
                bw.write(text, 0, text.length());
            } finally {
                if (bw != null) {
                    try { bw.close(); } catch (IOException ioe) { /* ignore */ }
        }//else: input unavailable
    }//createTableBean()