JDBC 中数据库字段类型与Java类型的映射

在使用JDBC从 MySQL 查询数据时，使用 PreparedStatement 向 SQL 指定位置的占位符设置数据时，我们要考虑一个问题：数据库中的字段类型，对应 Java 中的什么类型 ？

以查询数据为例，查询结果会放在 ResultSet 中。ResultSet 不止有查询结果，还有每个字段的元信息（比如对应的Java类型）。

下表摘自 Java, JDBC and MySQL Types ，第1列是 MySQL中的类型，第3列是对应的 Java 类型。

MySQL Type Name	Return value of GetColumnTypeName	Return value of GetColumnClassName
BIT(1) (new in MySQL-5.0)	BIT	java.lang.Boolean
BIT( > 1) (new in MySQL-5.0)	BIT	byte[]
TINYINT	TINYINT	java.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, BOOLEAN	TINYINT	See TINYINT, above as these are aliases for TINYINT(1), currently.
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)] [UNSIGNED]	INTEGER [UNSIGNED]	java.lang.Integer, if UNSIGNED java.lang.Long
BIGINT[(M)] [UNSIGNED]	BIGINT [UNSIGNED]	java.lang.Long, if UNSIGNED java.math.BigInteger
FLOAT[(M,D)]	FLOAT	java.lang.Float
DOUBLE[(M,B)]	DOUBLE	java.lang.Double
DECIMAL[(M[,D])]	DECIMAL	java.math.BigDecimal
DATE	DATE	java.sql.Date
DATETIME	DATETIME	java.sql.Timestamp
TIMESTAMP[(M)]	TIMESTAMP	java.sql.Timestamp
TIME	TIME	java.sql.Time
YEAR、YEAR(2)、YEAR(4)	YEAR	If yearIsDateType configuration property is set to false, then the returned object type is java.sql.Short. If set totrue (the default), then the returned object is of type java.sql.Date with the date set to January 1st, at midnight.
CHAR(M)	CHAR	java.lang.String (unless the character set for the column is BINARY, then byte[] is returned.
VARCHAR(M) [BINARY]	VARCHAR	java.lang.String (unless the character set for the column is BINARY, then byte[] is returned.
BINARY(M)	BINARY	byte[]
VARBINARY(M)	VARBINARY	byte[]
TINYBLOB	TINYBLOB	byte[]
TINYTEXT	VARCHAR	java.lang.String
BLOB	BLOB	byte[]
TEXT	VARCHAR	java.lang.String
MEDIUMBLOB	MEDIUMBLOB	byte[]
MEDIUMTEXT	VARCHAR	java.lang.String
LONGBLOB	LONGBLOB	byte[]
LONGTEXT	VARCHAR	java.lang.String
ENUM('value1','value2',...)	CHAR	java.lang.String
SET('value1','value2',...)	CHAR	java.lang.String