It would be really helpful if you could furnish details about why the husband is not happy, inorder to provide specific laws applicable. Nonetheless, please find below the grounds for divorce:
Under the Hindu Marriage Act, 1955 - S. 13 (1) states 9 grounds of divorce that can pleaded by either the husband or the wife in a solemnized marriage. They can file a petiton arguing that the other party-
(i) is living in adultery; or
(ii) has ceased to be a Hindu by conversion to another religion; or
(iii) has been incurably of unsound mind for a continuous period of not less than three years immediately preceding the presentation of the petition; or
(iv) has, for a period of not less than three years immediately preceding the presentation of the petition, been
(v) had, for a period of not less than three years immediately preceding the presentation of the petition, been suffering from venereal disease in a communicable form; or
(vi) has renounced the world by entering any religious order; or
(vii) has not been heard of as being alive for a period of seven years or more by those persons who would naturally have heard of it, had that party been alive; or
(viii) has not resumed cohabitation for a space of two years or upwards after the passing of a decree for judicial separation against that party; or
(ix) has failed to comply with a decree for restitution of conjugal rights for a period of two years or upwards after the passing of the decree.
If it is Divorce by mutual consent, then as per S. 13 B of the Hindu Marriage Act, 1955 and S. 28 of the Special Marriage Act, 1954 - for atelast one year the coupld should be living seperately before the instituion of proceedings, whereas under S. 10A of the Divorce Act, 1869 the time span is of 2 years. There must also be reasoning for why the divorce is being filed. Living separately here means they have not been living together like husabnd and wife.