.NET/ASP.NET/C#/VB.NET PDF Document SDK

You saw the basic structure of lexer files in the preceding example, which contained a handful of rules only. In general, fslex input files have the following simple structure: // Preamble any user code you need for the lexer, such as opening modules, etc. { [Code] } // Definitions named patterns that you can use in the rules or other definitions let [Ident_1] = [Pattern] let ... // Rules text patterns that trigger certain actions rule [Rule_1] [arg1... argn] = parse | [Pattern] { [Action] } | ... | [Pattern] { [Action] } and [Rule_2] [arg1... argn] = parse ... rule [Rule_3] ... // Epilogue code that can call the lexer rules defined above { [Code] } Each rule defined in the lexer will become an F# function that can be accessed from other modules and the lexer itself. Comments can be placed between (* and *), and you can also use // comments in the actions just like in any other F# code. Patterns can be any of the forms listed in Table 16-2. Lexical actions are pieces of F# code enclosed in braces that are executed when a lexer match is made. You can put any logic here that you like; typically you construct a token. Tokens are specified in the parser definition using the %token directive (you will see this later in this chapter), or if you do not have a parser, any user-defined type will do. If your lexer rules do not construct tokens or if your lexer is simple enough, often you may simply want to put all driver code in the epilogue section to create a stand-alone lexer.

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System.out.println("binary file: num of bytes read: " + numOfBytesRead); System.out.println(""); } } finally { if( in != null ) in.close(); if( bfile != null ) bfile.closeFile(); JDBCUtil.close( pstmt); JDBCUtil.close( orset); } } Reading BFILE Data As ASCII Text Reading BFILE data as ASCII text follows the exact same procedure as presented in the previous section for reading binary data, except that we need to convert the bytes into a String before we use it in our Java code, as shown in the method _readBfileAsTextData: /* demos how to read from a BFILE from the database as an ASCII file. */ private static void _readBfileAsAsciiData( Connection conn ) throws SQLException, IOException { PreparedStatement pstmt = null; OracleResultSet orset = null; BFILE bfile = null; InputStream in = null; try { String stmtString = "select bfile_col from bfile_table "+ " where id = "; pstmt = conn.prepareStatement( stmtString ); pstmt.setInt( 1, 1 ); orset = (OracleResultSet) pstmt.executeQuery(); byte[] buffer = new byte[30]; int numOfCharacersRead = 0; int length = -1; while( orset.next() ) { bfile = orset.getBfile( 1 ); bfile.openFile(); in = bfile.getBinaryStream(); while (( length = in.read( buffer)) != -1 ) { System.out.print( new String( buffer, 0, length ) ); numOfCharacersRead += length;

public void ProcessRequest (HttpContext context) { byte[] b; object id = context.Request.QueryString["BookId"]; b = (byte[])context.Cache[string.Format("Book{0}",id)]; if (b == null) { SqlConnection cn = new SqlConnection(ConfigurationManager. ConnectionStrings["Library_local"].ConnectionString); string sql = "select CoverImage from BookCoverImage"; sql += " where bookid = @BookID"; SqlCommand cm = new SqlCommand(sql, cn); cm.Parameters.Add("@BookId", SqlDbType.Int).Value = id; cn.Open(); SqlDataReader dr = cm.ExecuteReader(); if (!dr.Read()) context.Response.End(); b = (byte[])dr[0]; context.Cache.Insert(string.Format("Book{0}", id), b, null, DateTime.Now.AddSeconds(60), Cache.NoSlidingExpiration); dr.Close(); cn.Close(); } context.Response.OutputStream.Write(b, 0, b.Length - 1); } public bool IsReusable { get { return true; } } } The heart of the IHttpHandler interface is the ProcessRequest method. This is where the main work of a handler implementation goes. The only other method on the interface is the IsReusable method, which simply returns a Boolean indicating whether instances of the handler can be pooled or not. Handlers that can be pooled will perform better under load than ones that cannot, as a new instance of a nonpooled handler will need to be created for each request. To make a handler poolable, do not maintain any field level variables that need to be re-initialized with construction semantics, and return true from the IsReusable method.

'c' ['a' 'b' 'c'] ['a'-'z'] [^'a' 'b' 'c'] "abc" _ eof identifier pattern pattern+ pattern* pattern1 | pattern2 pattern1 pattern2

} System.out.println("\ntext file: num of chars read: " + numOfCharacersRead); } } finally { if( in != null ) in.close(); if( bfile != null ) bfile.closeFile(); JDBCUtil.close( pstmt); JDBCUtil.close( orset); } } }// end of class In the next section, we ll cover how to use temporary LOBs in JDBC. 29.380