swing 组合框（下拉框）获取选中的值

//获取下拉框的值

BookType bookType=(BookType) this.jcb_bookType.getSelectedItem();
int bookTypeId=bookType.getId();

Book book=new Book(bookName,bookAuthor,sex,bookPriceFloat,bookDesc,bookTypeId);
Connection conn=null;
try {
conn=dbUtil.getConn();
int bookNumber=bookDao.bookAdd(conn, book);
if(bookNumber==1){
JOptionPane.showMessageDialog(null, "图书新增成功");

}else{
JOptionPane.showMessageDialog(null, "图书失败成功");
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
JOptionPane.showMessageDialog(null, "图书失败成功");
} finally{
try {
dbUtil.closeConn(conn);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();

}
}