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.

Starting with Connector/J 3.1.0, the JDBC driver will issue warnings or throw 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:

Connection Properties - Miscellaneous. 

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


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 value returned by ResultSetMetaData.GetColumnClassName() is also shown below. For more information on the java.sql.Types classes see Java 2 Platform Types.

MySQL Types to Java Types for ResultSet.getObject(). 

MySQL Type NameReturn value of GetColumnClassNameReturned as Java Class
BIT(1) (new in MySQL-5.0)BITjava.lang.Boolean
BIT( > 1) (new in MySQL-5.0)BITbyte[]
TINYINTTINYINTjava.lang.Boolean if the configuration property tinyInt1isBit is set to true (the default) and the storage size is 1, or java.lang.Integer if not.
BOOL, BOOLEANTINYINTSee TINYINT, above as these are aliases for TINYINT(1), currently.
SMALLINT[(M)] [UNSIGNED]SMALLINT [UNSIGNED]java.lang.Integer (regardless if UNSIGNED or not)
MEDIUMINT[(M)] [UNSIGNED]MEDIUMINT [UNSIGNED]java.lang.Integer, if UNSIGNED java.lang.Long (C/J 3.1 and earlier), or java.lang.Integer for C/J 5.0 and later
INT,INTEGER[(M)] [UNSIGNED]INTEGER [UNSIGNED]java.lang.Integer, if UNSIGNED java.lang.Long
BIGINT[(M)] [UNSIGNED]BIGINT [UNSIGNED]java.lang.Long, if UNSIGNED java.math.BigInteger
YEAR[(2|4)]YEARIf yearIsDateType configuration property is set to false, then the returned object type is java.sql.Short. If set to true (the default) then an object of type java.sql.Date (with the date set to January 1st, at midnight).
CHAR(M)CHARjava.lang.String (unless the character set for the column is BINARY, then byte[] is returned.
VARCHAR(M) [BINARY]VARCHARjava.lang.String (unless the character set for the column is BINARY, then byte[] is returned.

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