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`