net.sourceforge.jtds.jdbc

Class Support

java.lang.Object

net.sourceforge.jtds.jdbc.Support

public class Support
extends java.lang.Object

This class contains static utility methods designed to support the main driver classes.

Implementation notes:

1. The methods in this class incorporate some code from previous versions of jTDS to handle dates, BLobs etc.
2. This class contains routines to generate runtime messages from the resource file.
3. The key data conversion logic used in Statements and result sets is implemented here.
4. There is nothing here which is TDS specific.

Version:

$Id: Support.java,v 1.56.2.6 2010-05-17 09:36:57 ickzon Exp $

Author:

Mike Hutchinson, jTDS project

Field Summary

Fields

Modifier and Type	Field and Description
private static java.math.BigDecimal	BIG_DECIMAL_ONE
private static java.math.BigDecimal	BIG_DECIMAL_ZERO
private static java.sql.Date	DATE_ZERO
private static java.lang.Double	DOUBLE_ONE
private static java.lang.Double	DOUBLE_ZERO
private static java.lang.Float	FLOAT_ONE
private static java.lang.Float	FLOAT_ZERO
private static char[]	hex Hex constants to use in conversion routines.
private static java.lang.Integer	INTEGER_ONE
private static java.lang.Integer	INTEGER_ZERO
private static java.lang.Long	LONG_ONE
private static java.lang.Long	LONG_ZERO
private static java.math.BigInteger	MAX_VALUE_28
private static java.math.BigInteger	MAX_VALUE_38
private static java.math.BigDecimal	MAX_VALUE_LONG_BD
private static java.math.BigInteger	MAX_VALUE_LONG_BI
private static java.math.BigDecimal	MIN_VALUE_LONG_BD
private static java.math.BigInteger	MIN_VALUE_LONG_BI
private static java.sql.Time	TIME_ZERO
private static java.util.HashMap	typeMap Convert java clases to java.sql.Type constant.

Constructor Summary

Constructors

Modifier	Constructor and Description
private	Support()

Method Summary

Methods

Modifier and Type	Method and Description
(package private) static int	calculateNamedPipeBufferSize(int tdsVersion, int packetSize) Calculate the buffer size to use when buffering the InputStream for named pipes.
(package private) static java.lang.Object	castNumeric(java.lang.Object orig, int sourceType, int targetType)
(package private) static java.lang.Object	convert(java.lang.Object callerReference, java.lang.Object x, int jdbcType, java.lang.String charSet) Convert an existing data object to the specified JDBC type.
static java.lang.Object	convertLOB(java.lang.Object value) Converts a LOB to the equivalent Java type, i.e.
static int	convertLOBType(int type) Converts a LOB type constant to the equivalent Java type constant, i.e.
(package private) static void	embedData(java.lang.StringBuilder buf, java.lang.Object value, boolean isUnicode, JtdsConnection connection) Embed the data object as a string literal in the buffer supplied.
(package private) static byte[]	encodeString(java.lang.String cs, java.lang.String value) Encode a string into a byte array using the specified character set.
(package private) static java.lang.String	getClassName(int jdbcType) Retrieve the fully qualified java class name for the supplied JDBC Types constant.
private static JtdsConnection	getConnection(java.lang.Object callerReference) Returns the connection for a given ResultSet, Statement or Connection object.
(package private) static int	getJdbcType(java.lang.Class typeClass) Get the JDBC type constant which matches the supplied Class.
(package private) static int	getJdbcType(java.lang.Object value) Get the JDBC type constant which matches the supplied Object type.
(package private) static java.lang.String	getJdbcTypeName(int jdbcType) Get a String describing the supplied JDBC type constant.
(package private) static java.lang.String	getParameterDefinitions(ParamInfo[] parameters) Constructs a parameter definition string for use with sp_executesql, sp_prepare, sp_prepexec, sp_cursoropen, sp_cursorprepare and sp_cursorprepexec.
(package private) static java.lang.String	getStatementKey(java.lang.String sql, ParamInfo[] params, int serverType, java.lang.String catalog, boolean autoCommit, boolean cursor) Generates a unique statement key for a given SQL statement.
static boolean	isWindowsOS() Checks the os.name system property to see if it starts with "windows".
static java.lang.Throwable	linkException(java.lang.Exception exception, java.lang.Throwable cause) Link the original cause to an Exception.
static java.sql.SQLException	linkException(java.sql.SQLException sqle, java.lang.Throwable cause) Link the original cause to an SQLException.
static java.sql.SQLWarning	linkException(java.sql.SQLWarning sqle, java.lang.Throwable cause) Link the original cause to an SQLWarning.
(package private) static java.math.BigDecimal	normalizeBigDecimal(java.math.BigDecimal value, int maxPrecision) Normalize a BigDecimal value so that it fits within the available precision.
(package private) static java.lang.String	substituteParameters(java.lang.String sql, ParamInfo[] list, JtdsConnection connection) Substitute actual data for the parameter markers to simulate parameter substitution in a PreparedStatement.
(package private) static java.lang.String	substituteParamMarkers(java.lang.String sql, ParamInfo[] list) Update the SQL string and replace the ?
static long	timeFromZone(java.util.Date value, java.util.Calendar target) Convert a timestamp from a different Timezone.
static long	timeToZone(java.util.Date value, java.util.Calendar target) Convert a timestamp to a different Timezone.
static java.lang.String	toHex(byte[] bytes) Convert a byte[] object to a hex string.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

INTEGER_ZERO

private static final java.lang.Integer INTEGER_ZERO

INTEGER_ONE

private static final java.lang.Integer INTEGER_ONE

LONG_ZERO

private static final java.lang.Long LONG_ZERO

LONG_ONE

private static final java.lang.Long LONG_ONE

FLOAT_ZERO

private static final java.lang.Float FLOAT_ZERO

FLOAT_ONE

private static final java.lang.Float FLOAT_ONE

DOUBLE_ZERO

private static final java.lang.Double DOUBLE_ZERO

DOUBLE_ONE

private static final java.lang.Double DOUBLE_ONE

BIG_DECIMAL_ZERO

private static final java.math.BigDecimal BIG_DECIMAL_ZERO

BIG_DECIMAL_ONE

private static final java.math.BigDecimal BIG_DECIMAL_ONE

DATE_ZERO

private static final java.sql.Date DATE_ZERO

TIME_ZERO

private static final java.sql.Time TIME_ZERO

MIN_VALUE_LONG_BI

private static final java.math.BigInteger MIN_VALUE_LONG_BI

MAX_VALUE_LONG_BI

private static final java.math.BigInteger MAX_VALUE_LONG_BI

MIN_VALUE_LONG_BD

private static final java.math.BigDecimal MIN_VALUE_LONG_BD

MAX_VALUE_LONG_BD

private static final java.math.BigDecimal MAX_VALUE_LONG_BD

MAX_VALUE_28

private static final java.math.BigInteger MAX_VALUE_28

MAX_VALUE_38

private static final java.math.BigInteger MAX_VALUE_38

typeMap

private static final java.util.HashMap typeMap

Convert java clases to java.sql.Type constant.

hex

private static final char[] hex

Hex constants to use in conversion routines.

Constructor Detail

Support

private Support()

Method Detail

toHex

public static java.lang.String toHex(byte[] bytes)

Convert a byte[] object to a hex string.

Parameters:

bytes - The byte array to convert.

Returns:

The hex equivalent as a String.

normalizeBigDecimal

static java.math.BigDecimal normalizeBigDecimal(java.math.BigDecimal value,
                                       int maxPrecision)
                                         throws java.sql.SQLException

Normalize a BigDecimal value so that it fits within the available precision.

Parameters:

value - The decimal value to normalize.

maxPrecision - The decimal precision supported by the server (assumed to be a value of either 28 or 38).

Returns:

The possibly normalized decimal value as a BigDecimal.

Throws:

java.sql.SQLException - If the number is too big.

castNumeric

static java.lang.Object castNumeric(java.lang.Object orig,
                           int sourceType,
                           int targetType)

convert

static java.lang.Object convert(java.lang.Object callerReference,
                       java.lang.Object x,
                       int jdbcType,
                       java.lang.String charSet)
                         throws java.sql.SQLException

Convert an existing data object to the specified JDBC type.

Parameters:

callerReference - an object reference to the caller of this method; must be a Connection, Statement or ResultSet

x - the data object to convert

jdbcType - the required type constant from java.sql.Types

Returns:

the converted data object

Throws:

java.sql.SQLException - if the conversion is not supported or fails

getJdbcType

static int getJdbcType(java.lang.Object value)

Get the JDBC type constant which matches the supplied Object type.

Parameters:

value - The object to analyse.

Returns:

The JDBC type constant as an int.

getJdbcType

static int getJdbcType(java.lang.Class typeClass)

Get the JDBC type constant which matches the supplied Class.

Parameters:

typeClass - the Class to analyse

Returns:

the JDBC type constant as an int

getJdbcTypeName

static java.lang.String getJdbcTypeName(int jdbcType)

Get a String describing the supplied JDBC type constant.

Parameters:

jdbcType - The constant to be decoded.

Returns:

The text decode of the type constant as a String.

getClassName

static java.lang.String getClassName(int jdbcType)

Retrieve the fully qualified java class name for the supplied JDBC Types constant.

Parameters:

jdbcType - The JDBC Types constant.

Returns:

The fully qualified java class name as a String.

embedData

static void embedData(java.lang.StringBuilder buf,
             java.lang.Object value,
             boolean isUnicode,
             JtdsConnection connection)
               throws java.sql.SQLException

Embed the data object as a string literal in the buffer supplied.

Parameters:

buf - The buffer in which the data will be embedded.

value - The data object.

isUnicode - Set to true if Unicode strings should be used, else false.

connection - The JtdsConnection object.

Throws:

java.sql.SQLException

getStatementKey

static java.lang.String getStatementKey(java.lang.String sql,
                               ParamInfo[] params,
                               int serverType,
                               java.lang.String catalog,
                               boolean autoCommit,
                               boolean cursor)

Generates a unique statement key for a given SQL statement.

Parameters:

sql - the sql statement to generate the key for

params - the statement parameters

serverType - the type of server to generate the key for

catalog - the catalog is required for uniqueness on Microsoft SQL Server

autoCommit - true if in auto commit mode

cursor - true if this is a prepared cursor

Returns:

the unique statement key

getParameterDefinitions

static java.lang.String getParameterDefinitions(ParamInfo[] parameters)

Constructs a parameter definition string for use with sp_executesql, sp_prepare, sp_prepexec, sp_cursoropen, sp_cursorprepare and sp_cursorprepexec.

Parameters:

parameters - Parameters to construct the definition for

Returns:

a parameter definition string

substituteParamMarkers

static java.lang.String substituteParamMarkers(java.lang.String sql,
                                      ParamInfo[] list)

Update the SQL string and replace the ? markers with parameter names eg @P0, @P1 etc.

Parameters:

sql - the SQL containing markers to substitute

list - the parameter list

Returns:

the modified SQL as a String

substituteParameters

static java.lang.String substituteParameters(java.lang.String sql,
                                    ParamInfo[] list,
                                    JtdsConnection connection)
                                      throws java.sql.SQLException

Substitute actual data for the parameter markers to simulate parameter substitution in a PreparedStatement.

Parameters:

sql - The SQL containing parameter markers to substitute.

list - The parameter descriptors.

connection - The current connection.

Returns:

The modified SQL statement.

Throws:

java.sql.SQLException

encodeString

static byte[] encodeString(java.lang.String cs,
                  java.lang.String value)

Encode a string into a byte array using the specified character set.

Parameters:

cs - The Charset name.

value - The value to encode.

Returns:

The value of the String as a byte[].

linkException

public static java.sql.SQLWarning linkException(java.sql.SQLWarning sqle,
                                java.lang.Throwable cause)

Link the original cause to an SQLWarning.

This convenience method calls linkException(Exception, Throwable) and casts the result for cleaner code elsewhere.

Parameters:

sqle - The SQLWarning to enhance.

cause - The Throwable to link.

Returns:

The original SQLWarning object.

linkException

public static java.sql.SQLException linkException(java.sql.SQLException sqle,
                                  java.lang.Throwable cause)

Link the original cause to an SQLException.

This convenience method calls linkException(Exception, Throwable) and casts the result for cleaner code elsewhere.

Parameters:

sqle - The SQLException to enhance.

cause - The Throwable to link.

Returns:

The original SQLException object.

linkException

public static java.lang.Throwable linkException(java.lang.Exception exception,
                                java.lang.Throwable cause)

Link the original cause to an Exception.

If running under JVM 1.4+ the Throwable.initCause(Throwable) method will be invoked to chain the exception, else the exception is logged via the Logger class. Modeled after the code written by Brian Heineman.

Parameters:

exception - The Exception to enhance.

cause - The Throwable to link.

Returns:

The original Exception object.

timeToZone

public static long timeToZone(java.util.Date value,
              java.util.Calendar target)

Convert a timestamp to a different Timezone.

Parameters:

value - the timestamp value

target - the Calendar containing the TimeZone

Returns:

the new timestamp value as a long

timeFromZone

public static long timeFromZone(java.util.Date value,
                java.util.Calendar target)

Convert a timestamp from a different Timezone.

Parameters:

value - the timestamp value.

target - the Calendar containing the TimeZone.

Returns:

The new timestamp value as a long.

convertLOB

public static java.lang.Object convertLOB(java.lang.Object value)
                                   throws java.sql.SQLException

Converts a LOB to the equivalent Java type, i.e. Clob to String and Blob to byte[]. If the value passed is not a LOB object, it is left unchanged and no exception is thrown; the idea is to transparently convert only LOBs.

Parameters:

value - an object that may be a LOB

Returns:

if the value was a LOB, the equivalent Java object, otherwise the original value

Throws:

java.sql.SQLException - if an error occurs while reading the LOB contents

convertLOBType

public static int convertLOBType(int type)

Converts a LOB type constant to the equivalent Java type constant, i.e. Types.CLOB to Types.LONGVARCHAR and Types.BLOB to Types.LONGVARBINARY. If the type passed is not that of a LOB, it is left unchanged and no exception is thrown; the idea is to transparently convert only LOB types.

Parameters:

type - a Types constant defining a JDBC type, possibly a LOB

Returns:

if the type was that of a LOB, the equivalent Java object type, otherwise the original type

isWindowsOS

public static boolean isWindowsOS()

Checks the os.name system property to see if it starts with "windows".

Returns:

true if os.name starts with "windows", else false.

getConnection

private static JtdsConnection getConnection(java.lang.Object callerReference)

Returns the connection for a given ResultSet, Statement or Connection object.

Parameters:

callerReference - an object reference to the caller of this method; must be a Connection, Statement or ResultSet

Returns:

a connection

calculateNamedPipeBufferSize

static int calculateNamedPipeBufferSize(int tdsVersion,
                               int packetSize)

Calculate the buffer size to use when buffering the InputStream for named pipes.

The buffer size is tied directly to the packet size because each request to the SmbNamedPipe will send a request for a particular size of packet. In other words, if you only request 1 byte, the SmbNamedPipe will send a request out and only ask for 1 byte back. Buffering the expected packet size ensures that all of the data will be returned in the buffer without wasting any space.

Parameters:

tdsVersion - the TDS version for the connection

packetSize - requested packet size for the connection

Returns:

minimum default packet size if packetSize == 0, else packetSize