Hibernate通过串联表和属性名称来生成约束名称，并将结果转换为
MD5。由于某些数据库中的约束名称长度限制，因此需要它。例如，在Oracle数据库中，外键名称的长度不能超过30个符号长度。
Hibernate源org.hibernate.mapping.Constraint中的此代码段
public static String generateName(String prefix, Table table, Column... columns) { // Use a concatenation that guarantees uniqueness, even if identical names // exist between all table and column identifiers. StringBuilder sb = new StringBuilder( "table`" + table.getName() + "`" ); // Ensure a consistent ordering of columns, regardless of the order // they were bound. // Clone the list, as sometimes a set of order-dependent Column // bindings are given. Column[] alphabeticalColumns = columns.clone(); Arrays.sort( alphabeticalColumns, ColumnComparator.INSTANCE ); for ( Column column : alphabeticalColumns ) { String columnName = column == null ? "" : column.getName(); sb.append( "column`" ).append( columnName ).append( "`" ); } return prefix + hashedName( sb.toString() );}public static String hashedName(String s) { try { MessageDigest md = MessageDigest.getInstance( "MD5" ); md.reset(); md.update( s.getBytes() ); byte[] digest = md.digest(); BigInteger bigInt = new BigInteger( 1, digest ); // By converting to base 35 (full alphanumeric), we guarantee // that the length of the name will always be smaller than the 30 // character identifier restriction enforced by a few dialects. return bigInt.toString( 35 ); } catch ( NoSuchAlgorithmException e ) { throw new HibernateException( "Unable to generate a hashed Constraint name!", e ); }}您可以使用生成自己的约束名称（唯一键和外键）
ImplicitNamingStrategy。您可以参考Hibernate5NamingStrategy作为示例。
