2.3 Data Types in JDBC

2.3 Data Types in JDBC

-          Generally, Oracle datatypes and host language datatypes are not the same.

-          Values are passed from Oracle to Java and vice versa, they need to be cast from one datatype to the other. 

-          The JDBC driver can automatically convert values of Oracle datatypes to values of some of the Java datatypes. 

-          The "Using Prepared Statements" section will cover conversions in the other direction.

-          The JDBC driver converts the Java data type to the appropriate JDBC type before sending it to the database.

-          It uses a default mapping for most data types.

-          For example, a Java int is converted to an SQL INTEGER.

-          Default mappings were created to provide consistency (reliability/stability)  between drivers.

-          The following table summarizes the default JDBC data type

-          That the Java data type is converted to when we call :

1)      the setXXX() method of the PreperedStatement or

2)      CallableStatement object or

3)      the ResultSet.

4)      updateXXX() method.

-          the setXXX() method of the PreparedStatement or CallableStatement object or the ResultSet.updateXXX() method.

SQL	JDBC/Java	setXXX	updateXXX
VARCHAR	java.lang.String	setString	updateString
CHAR	java.lang.String	setString	updateString
LONGVARCHAR	java.lang.String	setString	updateString
BIT	Boolean	setBoolean	updateBoolean
NUMERIC	java.math.BigDecimal	setBigDecimal	updateBigDecimal
TINYINT	Byte	setByte	updateByte
SMALLINT	Short	setShort	updateShort
INTEGER	Int	setInt	updateInt
BIGINT	Long	setLong	updateLong
REAL	Float	setFloat	updateFloat
FLOAT	Float	setFloat	updateFloat
DOUBLE	Double	setDouble	updateDouble
VARBINARY	byte[ ]	setBytes	updateBytes
BINARY	byte[ ]	setBytes	updateBytes
DATE	java.sql.Date	setDate	updateDate
TIME	java.sql.Time	setTime	updateTime
TIMESTAMP	java.sql.Timestamp	setTimestamp	updateTimestamp
CLOB	java.sql.Clob	setClob	updateClob
BLOB	java.sql.Blob	setBlob	updateBlob
ARRAY	java.sql.Array	setARRAY	updateARRAY
REF	java.sql.Ref	SetRef	updateRef
STRUCT	java.sql.Struct	SetStruct	updateStruct

-         JDBC 3.0 has enhanced support for BLOB, CLOB, ARRAY, and REF data types.

-         The ResultSet object now has updateBLOB(), updateCLOB(), updateArray(), and updateRef() methods that enable we to directly manipulate the respective data on the server.

-         The setXXX() and updateXXX() methods enable we to convert specific Java types to specific JDBC data types.

-         The methods, setObject() and updateObject(), enable we to map almost any Java type to a JDBC data type.

-         ResultSet object provides corresponding getXXX() method for each data type to retrieve column value.

-         Each method can be used with column name or by its ordinal position.

-        Date & Time Data Types:

-          The java.sql.Date class maps to the SQL DATE type, and the java.sql.

-          Time and java.sql.Timestamp classes map to the SQL TIME and SQL TIMESTAMP data types, respectively.

-          Following examples shows how the Date and Time classes format standard Java date and time values to match the SQL data type requirements.

-          import java.sql.Date;

-          import java.sql.Time;

-          import java.sql.Timestamp;

-          import java.util.*;

-           

-          public class SqlDateTime

-          {

-             public static void main(String[] args)

-             {

-                //Get standard date and time

-                java.util.Date javaDate = new java.util.Date();

-                long javaTime = javaDate.getTime();

-                System.out.println("The Java Date is:" +

-                       javaDate.toString());

-           

-                //Get and display SQL DATE

-                java.sql.Date sqlDate = new java.sql.Date(javaTime);

-                System.out.println("The SQL DATE is: " +

-                       sqlDate.toString());

-           

-                //Get and display SQL TIME

-                java.sql.Time sqlTime = new java.sql.Time(javaTime);

-                System.out.println("The SQL TIME is: " +

-                       sqlTime.toString());

-                //Get and display SQL TIMESTAMP

-                java.sql.Timestamp sqlTimestamp =

-                new java.sql.Timestamp(javaTime);

-                System.out.println("The SQL TIMESTAMP is: " +

-                       sqlTimestamp.toString());

-               }//end main

-          }//end SqlDateTime

-         C:\>javac SqlDateTime.java

-          C:\>

-         C:\>java SqlDateTime

-          The Java Date is:Tue Aug 18 13:46:02 GMT+04:00 2009

-          The SQL DATE is: 2014-06-24

-          The SQL TIME is: 13:46:02

-          The SQL TIMESTAMP is: 2014-06-24 13:46:02.828

-          C:\>

-          Avoid using getXXX( ) methods that return primitive data types.

-          Use wrapper classes for primitive data types.