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 JDBC 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`
`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 to`true` (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`