6.5 Java, JDBC, and MySQL Types

MySQL Connector/J is flexible in the way it handles conversions between MySQL data types and Java data types.

In general, any MySQL data type can be converted to a java.lang.String, and any numeric type can be converted to any of the Java numeric types, although round-off, overflow, or loss of precision may occur.

Connector/J issues warnings or throws DataTruncation exceptions as is required by the JDBC specification, unless the connection was configured not to do so by using the property jdbcCompliantTruncation and setting it to false.

The conversions that are always guaranteed to work are listed in the following table. The first column lists one or more MySQL data types, and the second column lists one or more Java types to which the MySQL types can be converted.

Table 6.19 Possible Conversions Between MySQL and Java Data Types

These MySQL Data Types	Can always be converted to these Java types
CHAR, VARCHAR, BLOB, TEXT, ENUM, and SET	java.lang.String, java.io.InputStream, java.io.Reader, java.sql.Blob, java.sql.Clob
FLOAT, REAL, DOUBLE PRECISION, NUMERIC, DECIMAL, TINYINT, SMALLINT, MEDIUMINT, INTEGER, BIGINT	java.lang.String, java.lang.Short, java.lang.Integer, java.lang.Long, java.lang.Double, java.math.BigDecimal
DATE, TIME, DATETIME, TIMESTAMP	java.lang.String, java.sql.Date, java.sql.Timestamp

Note

Round-off, overflow or loss of precision may occur if you choose a Java numeric data type that has less precision or capacity than the MySQL data type you are converting to/from.

The ResultSet.getObject() method uses the type conversions between MySQL and Java types, following the JDBC specification where appropriate. The values returned by ResultSetMetaData.GetColumnTypeName()and ResultSetMetaData.GetColumnClassName() are shown in the table below. For more information on the JDBC types, see the reference on the java.sql.Types class.

Table 6.20 MySQL Types and Return Values for ResultSetMetaData.GetColumnTypeName()and ResultSetMetaData.GetColumnClassName()

MySQL Type Name	Return value of GetColumnTypeName	Return value of GetColumnClassName
BIT(1)	BIT	java.lang.Boolean
BIT( > 1)	BIT	byte[]
TINYINT(1) SIGNED, BOOLEAN	If tinyInt1isBit=true and transformedBitIsBoolean=false: BIT If tinyInt1isBit=true and transformedBitIsBoolean=true: BOOLEAN If tinyInt1isBit=false: TINYINT	If tinyInt1isBit=true and transformedBitIsBoolean=false: java.lang.Boolean If tinyInt1isBit=true and transformedBitIsBoolean=true: java.lang.Boolean If tinyInt1isBit=false: java.lang.Integer
TINYINT( > 1) SIGNED	TINYINT	java.lang.Integer
TINYINT( any ) UNSIGNED	TINYINT UNSIGNED	java.lang.Integer
SMALLINT[(M)] [UNSIGNED]	SMALLINT [UNSIGNED]	java.lang.Integer (regardless of whether it is UNSIGNED or not)
MEDIUMINT[(M)] [UNSIGNED]	MEDIUMINT [UNSIGNED]	java.lang.Integer (regardless of whether it is UNSIGNED or not)
INT,INTEGER[(M)]	INTEGER	java.lang.Integer
INT,INTEGER[(M)] UNSIGNED	INTEGER UNSIGNED	java.lang.Long
BIGINT[(M)]	BIGINT	java.lang.Long
BIGINT[(M)] UNSIGNED	BIGINT UNSIGNED	java.math.BigInteger
FLOAT[(M,D)]	FLOAT	java.lang.Float
DOUBLE[(M,B)] [UNSIGNED]	DOUBLE	java.lang.Double (regardless of whether it is UNSIGNED or not)
DECIMAL[(M[,D])] [UNSIGNED]	DECIMAL	java.math.BigDecimal (regardless of whether it is UNSIGNED or not)
DATE	DATE	java.sql.Date
DATETIME	DATETIME	java.time.LocalDateTime
TIMESTAMP[(M)]	TIMESTAMP	java.sql.Timestamp
TIME	TIME	java.sql.Time
YEAR[(2|4)]	YEAR	If yearIsDateType configuration property is set to false, then the returned object type is java.sql.Short. If set to true (the default), then the returned object is of type java.sql.Date.
CHAR(M)	CHAR	java.lang.String
VARCHAR(M)	VARCHAR	java.lang.String
BINARY(M), CHAR(M) BINARY	BINARY	byte[]
VARBINARY(M), VARCHAR(M) BINARY	VARBINARY	byte[]
BLOB	BLOB	byte[]
TINYBLOB	TINYBLOB	byte[]
MEDIUMBLOB	MEDIUMBLOB	byte[]
LONGBLOB	LONGBLOB	byte[]
TEXT	TEXT	java.lang.String
TINYTEXT	TINYTEXT	java.lang.String
MEDIUMTEXT	MEDIUMTEXT	java.lang.String
LONGTEXT	LONGTEXT	java.lang.String
JSON	JSON	java.lang.String
GEOMETRY	GEOMETRY	byte[]
ENUM('value1','value2',...)	CHAR	java.lang.String
SET('value1','value2',...)	CHAR	java.lang.String