共同学习，共同进步。QQ:240814476
面对对象编程这门课，我刚开始都不知道干什么的，后来慢慢明白了，就是抽象包装，最终达到把代码像是叠衣服一样，一块一块的。
我复习一下以前学的JSP，废话不说了，上图：
package com.DataBase.Dao;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
import com.DataBase.connect.JDBCconnect;
import com.DataBase.entity.contacts;
/**
* @author cantacts 增删改差
*
*/
public class contactsDAO {
public boolean addcontacts(contacts contacts) {
boolean flag=false;
//增加功能需要执行两个sql语句，一个语句用于获取唯一值做为主键，还有一个语句才是增加语句；
//String sql_1 = "select SEQ_T_USER.nextVal as id from dual";
String sql_2 = "insert into tb_contacts(con_id, con_name, con_phone, con_telephone, con_email,com_id)" +
"values( (select nvl(max(con_id),0)+1 id2 from tb_contacts), ?, ?, ?, ?,?)";
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
try{
conn = JDBCconnect.getConnection();
ps = conn.prepareStatement(sql_2);
ps.setString(1,contacts.getCon_id());
ps.setString(2, contacts.getCon_name());
ps.setString(3, contacts.getCon_phone());
ps.setString(4, contacts.getCon_telephone());
ps.setString(5, contacts.getCon_email());
ps.setString(6, contacts.getCom_id());
//System.out.println(cz.getAmount());
//System.out.println(""+sql_2);
ps.executeUpdate();
flag=true;
}catch(SQLException e){
e.printStackTrace();
}finally{
JDBCconnect.closeAll(conn, ps, rs);
}
return flag;
}
//删除
public int deletecontacts(String con_id) {
int result = 0;
Connection con = null;
PreparedStatement pstm = null;
String sql = "delete from tb_contacts where con_id=?";
try {
con = JDBCconnect.getConnection();
pstm = con.prepareStatement(sql);
pstm.setString(1, con_id);
result = pstm.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
} finally{
JDBCconnect.closeAll(con, pstm, null);
}
return result ;
}
//查询联系人by com_id
public List<contacts> querycontacts(String com_id) {
StringBuffer sql = new StringBuffer(
"select * from tb_contacts where com_id=?");
Statement st = null;
ResultSet rs = null;
Connection con = null;
List<contacts> list=new ArrayList<contacts>();
try{
con = JDBCconnect.getConnection();
System.out.println("---------------sql="+sql);
st = con.createStatement();
rs = st.executeQuery(sql.toString()+com_id);
while(rs.next())
{
contacts temp=new contacts();
temp.setCon_id(rs.getString("con_id"));
temp.setCon_name(rs.getString("con_name"));
temp.setCon_phone(rs.getString("con_phone"));
temp.setCon_telephone(rs.getString("con_telephone"));
temp.setCon_email(rs.getString("con_email"));
temp.setCom_id(rs.getString("com_id"));
list.add(temp);
}
}catch (SQLException e) {
e.printStackTrace();
}finally{
JDBCconnect.closeAll(con, st, rs);
}
return list;
}
public int updatecontacts(contacts contacts) {
String sql = "update tb_contacts " +
" set con_name=?, con_phone=?, con_telephone=?, con_email=?, com_id=?" +
" where con_id=?";
PreparedStatement pstm = null;
Connection con = null;
int result = 0;
try {
con = JDBCconnect.getConnection();
pstm = con.prepareStatement(sql);
pstm.setString(1, contacts.getCon_name());
pstm.setString(2, contacts.getCon_phone());
pstm.setString(3, contacts.getCon_telephone());
pstm.setString(4, contacts.getCon_email());
pstm.setString(5, contacts.getCom_id());
pstm.setString(6, contacts.getCon_id());
result = pstm.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
} finally{
JDBCconnect.closeAll(con, pstm, null);
}
return result;
}
}这是对联系人的增删改查。但是在前台调用的时候并没有直接从DAO这个类里提取方法，而是通过对servlet类调用方法。
代码如下
package com.DataBase.servlet;
import java.io.IOException;
import java.util.List;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.DataBase.Dao.contactsDAO;
import com.DataBase.Dao.customDAO;
import com.DataBase.Dao.orderDAO;
import com.DataBase.Dao.pro_detailDAO;
import com.DataBase.Dao.productDAO;
import com.DataBase.Dao.purchaseDAO;
import com.DataBase.entity.contacts;
import com.DataBase.entity.custom;
import com.DataBase.entity.order;
import com.DataBase.entity.pro_detail;
import com.DataBase.entity.product;
import com.DataBase.entity.purchase;
import com.DataBase.service.contactsService;
import com.DataBase.service.customService;
import com.DataBase.service.orderService;
import com.DataBase.service.pro_detailService;
import com.DataBase.service.productService;
import com.DataBase.service.purchaseService;
public class contactsServlet extends HttpServlet{
/**
*
*/
private static final long serialVersionUID = 1L;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
req.setCharacterEncoding("UTF-8");
String actionDo = req.getParameter("actionDo");
if("query".equals(actionDo)){//表示进行查询操作
query(req, resp);
}else if("add".equals(actionDo)){//表示进行增加操作
add(req, resp);
}else if("delete".equals(actionDo)){//表示进行删除操作
delete(req, resp);
}else if("toUpdate".equals(actionDo)){//表示进行修改操作
toUpdate(req, resp);
}else if("update".equals(actionDo)){//表示进行修改操作
update(req, resp);
}
}
//查询操作
protected void query(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
String con_id = req.getParameter("con_id");
String con_name = req.getParameter("con_name");
String con_phone= req.getParameter("con_phone");
String con_telephone = req.getParameter("con_telephone");
String con_email= req.getParameter("con_email");
String com_id = req.getParameter("com_id");
//System.out.
contacts temp = new contacts();
temp.setCon_id( con_id);
temp.setCon_name(con_name);
temp.setCon_phone(con_phone);
temp.setCon_telephone(con_telephone);
temp.setCon_email(con_email);
temp.setCom_id(com_id);
List<contacts> list=null;
contactsDAO dao=new contactsDAO();
list=dao.querycontacts(com_id);
req.setAttribute("list", list);
//跳转页面
//RequestDispatcher rd = req.getRequestDispatcher("ChuZhang2.jsp");
//rd.forward(req, resp);
}
//增加操作
protected void add(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
String con_id = req.getParameter("con_id");
String con_name = req.getParameter("con_name");
String con_phone= req.getParameter("con_phone");
String con_telephone = req.getParameter("con_telephone");
String con_email= req.getParameter("con_email");
String com_id = req.getParameter("com_id");
//System.out.
contacts temp = new contacts();
temp.setCon_id( con_id);
temp.setCon_name(con_name);
temp.setCon_phone(con_phone);
temp.setCon_telephone(con_telephone);
temp.setCon_email(con_email);
temp.setCom_id(com_id);
contactsDAO dao=new contactsDAO();
boolean flag=dao.addcontacts(temp);
String msg = "";
RequestDispatcher rd = null;
if(flag){//表示增加成功，应该转到查询结果页面，显示最新的所有记录；
//我们这里就提示成功就算了，不继续做查询功能了。
msg = "增加成功";
req.setAttribute("msg", msg);
//rd = req.getRequestDispatcher("ChuZhang2.jsp");
}else{//增加失败，转回到增加页面
msg = "增加失败";
req.setAttribute("msg", msg);
//rd = req.getRequestDispatcher("ChuZhang1.jsp");
}
rd.forward(req, resp);
}
//删除操作
protected void delete(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
String id = req.getParameter("con_id");
contactsService contacts=new contactsService();
contacts.delete(id);
req.getRequestDispatcher("/customServlet?actionDo=query").forward(req, resp);
}
//4、转到修改页面
public void toUpdate(HttpServletRequest request,HttpServletResponse response)
throws ServletException,IOException{
// String id = request.getParameter("com_id");
//
// customService service = new customService();
//
// custom custom = service.getpurchaseById(id);
//
// request.setAttribute("purchase", purchase);
//RequestDispatcher rd = request.getRequestDispatcher("/wangjian/wang_index_update.jsp");
//rd.forward(request, response);
}
//修改操作
protected void update(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
String con_id = req.getParameter("con_id");
String con_name = req.getParameter("con_name");
String con_phone= req.getParameter("con_phone");
String con_telephone = req.getParameter("con_telephone");
String con_email= req.getParameter("con_email");
String com_id = req.getParameter("com_id");
//System.out.
contacts temp = new contacts();
temp.setCon_id( con_id);
temp.setCon_name(con_name);
temp.setCon_phone(con_phone);
temp.setCon_telephone(con_telephone);
temp.setCon_email(con_email);
temp.setCom_id(com_id);
contactsService contacts=new contactsService();
contacts.update(temp);
resp.sendRedirect(req.getContextPath()+"/pro_detailServlet?actionDo=query");
//req.getRequestDispatcher("/CZServlet?actionDo=query").forward(req, resp);
} @Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
doGet(req, resp);
}
}
大家也许能够注意到，在我调用这个类的时候，这个类只是负责把 POST过来的东西收集起来封装起来，但是调用的是service 这个中间类。
service 就像名字一样 服务，什么服务呢 就是把前台接收到的信息 传递给他想要调用的方法的一个中间类。
package com.DataBase.service;
import java.util.List;
import com.DataBase.Dao.contactsDAO;
import com.DataBase.entity.contacts;
public class contactsService {
contactsDAO dao = new contactsDAO();
public contactsService() {
}
public boolean addcontacts(contacts contacts) {
return dao.addcontacts(contacts);
}
public List<contacts> getcontacts(String com_id) {
return dao.querycontacts(com_id);
}
public int update(contacts contacts) {
return dao.updatecontacts(contacts);
}
public int delete(String con_id) {
return dao.deletecontacts(con_id);
}
}
这样 这三个类就完成了一系列的操作。
在写后台的时候要注意一定要注意封装和抽象。这点很重要！做一款真正的软件需要大量的抽象和封装，这样可以大大的减少代码的耦合程度。提高代码的利用率
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