面向接口编程

定义CustomerDAO接口

public interface CustomerDAO {
    public List<Customer> getForListWithCriteriaCustomer(CriteriaCustomer cc);
    public List<Customer> getAll();
    public void save(Customer customer);
    public Customer get(Integer id);
    public void delete(Integer id);
    public void update(Customer customer);
    /**
     * 返回和name相等的记录数
     * @param name
     * @return
     */
    public long getCountWithName(String name);
}

定义两个实现类CustomerDAOJdbcImpl，CustomerDAOXMLImpl

public class CustomerDAOJdbcImpl extends DAO<Customer> implements CustomerDAO{

    @Override
    public List<Customer> getAll() {
        String sql = "select * from customer";
        return getForList(sql);
    }

    @Override
    public void save(Customer customer) {
        String sql = "insert into customer values (null,?,?,?)";
        update(sql, customer.getName(), customer.getAddress(),customer.getPhone());
    }

    @Override
    public Customer get(Integer id) {
        String sql = "select id, name,address,phone from customer where id=?";

        return get(sql, id);
    }

    @Override
    public void delete(Integer id) {
        String sql = "delete from customer where id = ?";
        update(sql, id);
    }

    @Override
    public long getCountWithName(String name) {
        String sql = "select count(id) from customer where name = ?";
        return getForValue(sql, name);
    }

    @Override
    public List<Customer> getForListWithCriteriaCustomer(CriteriaCustomer cc) {
        String sql = "select * from customer where name LIKE ? AND address LIKE ? AND phone LIKE ?";
        return getForList(sql,cc.getName(),cc.getAddress(), cc.getPhone());
    }

    @Override
    public void update(Customer customer) {
        String sql = "update customer set name = ?, address = ?, phone = ? where id = ?";
        update(sql, customer.getName(), customer.getAddress(), customer.getPhone(), customer.getId());
    }

}

CustomerDAOXMLImpl类

public class CustomerDAOXMLImpl implements CustomerDAO{

    @Override
    public List<Customer> getForListWithCriteriaCustomer(CriteriaCustomer cc) {
        System.out.println("getForListWithcriteriaCustomer");
        return null;
    }

    @Override
    public List<Customer> getAll() {
        System.out.println("getAll");
        return null;
    }

    @Override
    public void save(Customer customer) {
        System.out.println("save");
    }

    @Override
    public Customer get(Integer id) {
        System.out.println("get");
        return null;
    }

    @Override
    public void delete(Integer id) {
        System.out.println("delete");

    }

    @Override
    public void update(Customer customer) {
        System.out.println("update");
    }

    @Override
    public long getCountWithName(String name) {
        System.out.println("getCountWithName");
        return 0;
    }

}

面向接口编程。定义一个接口，多个实现类可以有不同的具体实现
用的时间这样：
// private CustomerDAO customerDAO = new CustomerDAOJdbcImpl();
private CustomerDAO customerDAO = new CustomerDAOXMLImpl();
只改变这个地方就ok。
调用的类CustomerServlet

@WebServlet(urlPatterns="*.do",name="CustomerServlet")
public class CustomerServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
//  private CustomerDAO customerDAO = new CustomerDAOJdbcImpl();
    private CustomerDAO customerDAO = new CustomerDAOXMLImpl();
    public CustomerServlet() {
        super();
    }


    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

//    @Override
//    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//      String method = req.getParameter("method");
//      System.out.println("para:" + method);
//      switch(method) {
//      case "add":
//          addCustomer(req, resp);
//          break;
//      case "query":
//          query(req, resp);
//          break;
//      case "delete":
//          delete(req, resp);
//          break;
//      }
//    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String servletPath = request.getServletPath();
        System.out.println("servletPath:" + servletPath);
        String methodName = servletPath.substring(1);
        methodName = methodName.substring(0, methodName.length()-3);
        System.out.println("methodName:" + methodName);

        Method method;
        try {
            //啊，啊，嗯。。。嗯。。。银家是反射。。。。呃，我擦，好恶心
            method = getClass().getDeclaredMethod(methodName,   HttpServletRequest.class, HttpServletResponse.class);
            method.invoke(this, request, response);
        } catch (Exception e) {
            e.printStackTrace();
            response.sendRedirect("error.jsp");
        } 

    }

    @SuppressWarnings("unused")
    private void delete(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        System.out.println("delete");
        String idStr = req.getParameter("id");
        int id = 0;
        try {
            id = Integer.valueOf(idStr);
            customerDAO.delete(id);
        } catch (NumberFormatException e) {
            e.printStackTrace();
        }

        resp.sendRedirect("query.do");

    }

    @SuppressWarnings("unused")
    private void update(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException {
        String id = req.getParameter("id");
        String name = req.getParameter("name");
        String oldName = req.getParameter("oldName");
        String phone = req.getParameter("phone");
        String address = req.getParameter("address");

        if(!oldName.equalsIgnoreCase(name)) {
            long count = customerDAO.getCountWithName(name);
            if(count > 0) {
                req.setAttribute("message", "用戶名" + name + "已经被占用，请重新选择");
                req.getRequestDispatcher("/updatecustomer.jsp").forward(req, resp);
                return;
            }
        }

        Customer customer = new Customer(name, address, phone);
        customer.setId(Integer.valueOf(id));
        customerDAO.update(customer);

        resp.sendRedirect("query.do");
    }

    @SuppressWarnings("unused")
    private void edit(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException {
        System.out.println("edit");
        String forwordPath = "/error.jsp";
        String idStr = req.getParameter("id");
        int id = -1;
        try {
            Customer customer = customerDAO.get(Integer.valueOf(idStr));
            if(customer != null) {
                forwordPath = "/updatecustomer.jsp";
                req.setAttribute("customer", customer);
            }
        } catch (Exception e) {}

        req.getRequestDispatcher(forwordPath).forward(req, resp);

    }


    @SuppressWarnings("unused")
    private void query(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("query");
        String name = req.getParameter("name");
        String address = req.getParameter("address");
        String phone = req.getParameter("phone");
        CriteriaCustomer cc = new CriteriaCustomer(name, address, phone);
        List<Customer> customers = customerDAO.getForListWithCriteriaCustomer(cc);
        req.setAttribute("customers", customers);
        req.getRequestDispatcher("/index.jsp").forward(req, resp);
    }


    @SuppressWarnings("unused")
    private void addCustomer(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("addCustomer");
        String name = req.getParameter("name");
        String address = req.getParameter("address");
        String phone = req.getParameter("phone");
        System.out.println("name:" + name + "...address:" + address + "...phone:" + phone);

        long count = customerDAO.getCountWithName(name);
        if(count > 0) {
            req.setAttribute("message", "用户名" + name + "已被占用，请重新选择");
            req.getRequestDispatcher("/newcustomer.jsp").forward(req, resp);
            return;
        }

        Customer customer = new Customer(name, address, phone);
        customerDAO.save(customer);
        resp.sendRedirect("success.jsp");
    }
}