swing 组合框（下拉框）填充默认值

public void fillBookType(){
Connection conn=null;

try {
conn=dbUtil.getConn();
ResultSet rs=bookTypeDao.bookTypeList(conn, new BookType());
while (rs.next()){
BookType bookType=new BookType();
bookType.setId(rs.getInt("id"));
bookType.setBookTypeName(rs.getString("bookTypeName"));
this.jcb_bookType.addItem(bookType);      //object传进去会乱码，要重写toString方法
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally{
try {
dbUtil.closeConn(conn);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

--重写bookType的toString方法
@Override
public String toString() {
return bookTypeName;
}