如何取出clob类型的数据

public String getreadclob(String roleid) throws Exception{
String getinfo = "";
String sql = "select personpublicid from ess_person_right where  roleid='"+roleid+"'";
Session session = null;
Connection conn = null ;
ResultSet rs = null;
session = this.getSession();
conn = session.connection();
Statement st = null;
st = conn.createStatement();
rs = st.executeQuery(sql);
Clob clob = null;
if(rs.next()){
clob = rs.getClob("personpublicid");//MAX：65536
getinfo=clob.getSubString((long)1,(int)clob.length());
}
rs.close();
st.close();
conn.close();
this.closeSession();
if(session!=null){
session.close();
}
return getinfo;

}