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)。怎么看?参考 创建数据库和表 中示例。

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
YEARYEAR(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


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