碰到个问题，不知道mysql中ENUM到底是对应java中的哪个类型。
因此在mysql-connector-java源码中查了一下代码，顺便和大家分享一下:

mysql-connector-java-6.0.6中的数据类型和java数据类型的转换代码位置.png

几个关注点:

1. mysql中的基本数据类型，例如INT，BOOLEAN….等都对应为java的包装类(Integer，Boolean)

2. mysql中的JSON类型，对应的是java中的String类型

3. mysql中的ENUM类型，对应的是java中的String类型

4. 为什么mysql中的BLOB系列类型，没有java的对应类型，都是null呢？

    DECIMAL("DECIMAL", Types.DECIMAL, BigDecimal.class, MysqlType.FIELD_FLAG_ZEROFILL, MysqlType.IS_DECIMAL, 65L, "[(M[,D])] [UNSIGNED] [ZEROFILL]"),

    DECIMAL_UNSIGNED("DECIMAL UNSIGNED", Types.DECIMAL, BigDecimal.class, MysqlType.FIELD_FLAG_UNSIGNED | MysqlType.FIELD_FLAG_ZEROFILL, MysqlType.IS_DECIMAL,
            65L, "[(M[,D])] [UNSIGNED] [ZEROFILL]"),

    TINYINT("TINYINT", Types.TINYINT, Integer.class, MysqlType.FIELD_FLAG_ZEROFILL, MysqlType.IS_DECIMAL, 3L, "[(M)] [UNSIGNED] [ZEROFILL]"),
 
    TINYINT_UNSIGNED("TINYINT UNSIGNED", Types.TINYINT, Integer.class, MysqlType.FIELD_FLAG_UNSIGNED | MysqlType.FIELD_FLAG_ZEROFILL, MysqlType.IS_DECIMAL, 3L,
            "[(M)] [UNSIGNED] [ZEROFILL]"),

    BOOLEAN("BOOLEAN", Types.BOOLEAN, Boolean.class, 0, MysqlType.IS_NOT_DECIMAL, 3L, ""),

    SMALLINT("SMALLINT", Types.SMALLINT, Integer.class, MysqlType.FIELD_FLAG_ZEROFILL, MysqlType.IS_DECIMAL, 5L, "[(M)] [UNSIGNED] [ZEROFILL]"),

    SMALLINT_UNSIGNED("SMALLINT UNSIGNED", Types.SMALLINT, Integer.class, MysqlType.FIELD_FLAG_UNSIGNED | MysqlType.FIELD_FLAG_ZEROFILL, MysqlType.IS_DECIMAL,
            5L, "[(M)] [UNSIGNED] [ZEROFILL]"),
  
    INT("INT", Types.INTEGER, Integer.class, MysqlType.FIELD_FLAG_ZEROFILL, MysqlType.IS_DECIMAL, 10L, "[(M)] [UNSIGNED] [ZEROFILL]"),
   
    INT_UNSIGNED("INT UNSIGNED", Types.INTEGER, Long.class, MysqlType.FIELD_FLAG_UNSIGNED | MysqlType.FIELD_FLAG_ZEROFILL, MysqlType.IS_DECIMAL, 10L,
            "[(M)] [UNSIGNED] [ZEROFILL]"),
  
    FLOAT("FLOAT", Types.REAL, Float.class, MysqlType.FIELD_FLAG_ZEROFILL, MysqlType.IS_DECIMAL, 12L, "[(M,D)] [UNSIGNED] [ZEROFILL]"),
   
    FLOAT_UNSIGNED("FLOAT UNSIGNED", Types.REAL, Float.class, MysqlType.FIELD_FLAG_UNSIGNED | MysqlType.FIELD_FLAG_ZEROFILL, MysqlType.IS_DECIMAL, 12L,
            "[(M,D)] [UNSIGNED] [ZEROFILL]"),
  
    DOUBLE_UNSIGNED("DOUBLE UNSIGNED", Types.DOUBLE, Double.class, MysqlType.FIELD_FLAG_UNSIGNED | MysqlType.FIELD_FLAG_ZEROFILL, MysqlType.IS_DECIMAL, 22L,
            "[(M,D)] [UNSIGNED] [ZEROFILL]"),

    NULL("NULL", Types.NULL, Object.class, 0, MysqlType.IS_NOT_DECIMAL, 0L, ""),
    
    TIMESTAMP("TIMESTAMP", Types.TIMESTAMP, Timestamp.class, 0, MysqlType.IS_NOT_DECIMAL, 26L, "[(fsp)]"),
   
    BIGINT("BIGINT", Types.BIGINT, Long.class, MysqlType.FIELD_FLAG_ZEROFILL, MysqlType.IS_DECIMAL, 19L, "[(M)] [UNSIGNED] [ZEROFILL]"),
  
    BIGINT_UNSIGNED("BIGINT UNSIGNED", Types.BIGINT, BigInteger.class, MysqlType.FIELD_FLAG_UNSIGNED | MysqlType.FIELD_FLAG_ZEROFILL, MysqlType.IS_DECIMAL, 20L,
            "[(M)] [UNSIGNED] [ZEROFILL]"),

    MEDIUMINT("MEDIUMINT", Types.INTEGER, Integer.class, MysqlType.FIELD_FLAG_ZEROFILL, MysqlType.IS_DECIMAL, 7L, "[(M)] [UNSIGNED] [ZEROFILL]"),
  
    MEDIUMINT_UNSIGNED("MEDIUMINT UNSIGNED", Types.INTEGER, Integer.class, MysqlType.FIELD_FLAG_UNSIGNED | MysqlType.FIELD_FLAG_ZEROFILL, MysqlType.IS_DECIMAL,
            8L, "[(M)] [UNSIGNED] [ZEROFILL]"),
   
    DATE("DATE", Types.DATE, Date.class, 0, MysqlType.IS_NOT_DECIMAL, 10L, ""),
    
    TIME("TIME", Types.TIME, Time.class, 0, MysqlType.IS_NOT_DECIMAL, 16L, "[(fsp)]"),
   
    DATETIME("DATETIME", Types.TIMESTAMP, Timestamp.class, 0, MysqlType.IS_NOT_DECIMAL, 26L, "[(fsp)]"),
    
    YEAR("YEAR", Types.DATE, Date.class, 0, MysqlType.IS_NOT_DECIMAL, 4L, "[(4)]"),
    
    VARCHAR("VARCHAR", Types.VARCHAR, String.class, 0, MysqlType.IS_NOT_DECIMAL, 65535L, "(M) [CHARACTER SET charset_name] [COLLATE collation_name]"),
   
    VARBINARY("VARBINARY", Types.VARBINARY, null, 0, MysqlType.IS_NOT_DECIMAL, 65535L, "(M)"),
 
    BIT("BIT", Types.BIT, Boolean.class, 0, MysqlType.IS_DECIMAL, 1L, "[(M)]"), // TODO maybe precision=8 ?
   
    JSON("JSON", Types.LONGVARCHAR, String.class, 0, MysqlType.IS_NOT_DECIMAL, 1073741824L, ""),
 
    ENUM("ENUM", Types.CHAR, String.class, 0, MysqlType.IS_NOT_DECIMAL, 65535L,
            "('value1','value2',...) [CHARACTER SET charset_name] [COLLATE collation_name]"),
   
    SET("SET", Types.CHAR, String.class, 0, MysqlType.IS_NOT_DECIMAL, 64L, "('value1','value2',...) [CHARACTER SET charset_name] [COLLATE collation_name]"),
   
    TINYBLOB("TINYBLOB", Types.VARBINARY, null, 0, MysqlType.IS_NOT_DECIMAL, 255L, ""),
   
    TINYTEXT("TINYTEXT", Types.VARCHAR, String.class, 0, MysqlType.IS_NOT_DECIMAL, 255L, " [CHARACTER SET charset_name] [COLLATE collation_name]"),
   
    MEDIUMBLOB("MEDIUMBLOB", Types.LONGVARBINARY, null, 0, MysqlType.IS_NOT_DECIMAL, 16777215L, ""),
  
    MEDIUMTEXT("MEDIUMTEXT", Types.LONGVARCHAR, String.class, 0, MysqlType.IS_NOT_DECIMAL, 16777215L, " [CHARACTER SET charset_name] [COLLATE collation_name]"),
    
    LONGBLOB("LONGBLOB", Types.LONGVARBINARY, null, 0, MysqlType.IS_NOT_DECIMAL, 4294967295L, ""),
    
    LONGTEXT("LONGTEXT", Types.LONGVARCHAR, String.class, 0, MysqlType.IS_NOT_DECIMAL, 4294967295L, " [CHARACTER SET charset_name] [COLLATE collation_name]"),
    
    BLOB("BLOB", Types.LONGVARBINARY, null, 0, MysqlType.IS_NOT_DECIMAL, 65535L, "[(M)]"),
   
    TEXT("TEXT", Types.LONGVARCHAR, String.class, 0, MysqlType.IS_NOT_DECIMAL, 65535L, "[(M)] [CHARACTER SET charset_name] [COLLATE collation_name]"),
   
    CHAR("CHAR", Types.CHAR, String.class, 0, MysqlType.IS_NOT_DECIMAL, 255L, "[(M)] [CHARACTER SET charset_name] [COLLATE collation_name]"),
    
    BINARY("BINARY", Types.BINARY, null, 0, MysqlType.IS_NOT_DECIMAL, 255L, "(M)"), 
    GEOMETRY("GEOMETRY", Types.BINARY, null, 0, MysqlType.IS_NOT_DECIMAL, 65535L, ""),
  
    UNKNOWN("UNKNOWN", Types.OTHER, null, 0, MysqlType.IS_NOT_DECIMAL, 65535L, "");