mysql+jsp+servlet 增删改查实例

痛定思痛。 2022-07-16 05:59 243阅读 0赞

**采用简单的MVC设计模式，M(模型层) -> Address.java 里面包含id，name,street,city,state,zip 等相关属性和set，get方法**

**     V(视图层) -> 主要指jsp页面，包含list.jsp,add.jsp,edit.jsp**

**     C(控制层) -> 这里只用一个servlet实现其增删改查(简单明了，方便理解)，并没有用业务层的那套          service+serviceImp**

**项目目录：![Center][]**

**相关的mysql数据库代码：**

**create database addr;  
use addr;  
create table address(  
id int primary key auto\_increment,  
name varchar(20),  
street varchar(20),  
city varchar(20),  
state varchar(20),  
zip varchar(20)  
);  
  
insert into address(name,street,city,state,zip) values ('AAA','永宁街','西安','aa','1101');  
insert into address(name,street,city,state,zip) values ('BBB','嘉定街','上海','bb','1102');  
insert into address(name,street,city,state,zip) values ('CCC','福寿街','天津','cc','1103');  
insert into address(name,street,city,state,zip) values ('DDD','回民街','北京','dd','1104');  
insert into address(name,street,city,state,zip) values ('EEE','健康街','武汉','ee','1105');**

**根据数据库表，我们首先创建一个实体(domain)类:Address.java, 。这里我们就不贴图展示了**

**然后创建JdbcUtil.java 主要用来连接mysql数据库：**

public class JdbcUtil \{  
static\{  
try \{  
Class.forName("com.mysql.jdbc.Driver");  
\} catch (Exception e) \{  
e.printStackTrace();  
\}  
\}  
public static Connection getConnection() throws SQLException\{  
  
String dbUrl="jdbc:mysql://localhost:3306/addr?useUnicode=true&characterEncoding=utf8";  
String dbUser="root";  
String dbPassword="1101";  
  
return DriverManager.getConnection(dbUrl,dbUser,dbPassword);  
  
\}  
  
public static void close(Statement stmt,Connection conn) throws SQLException\{  
stmt.close();  
conn.close();  
\}  
\}

当然代码**JdbcUtil的代码**可进行适当优化

**注意**：要修改成你们mysql的用户名和密码，

**Dao层（数据访问层）代码编写**

public class AddressDao \{  
//增加  
public void add(Address address)\{  
try \{  
   Connection conn = JdbcUtil.getConnection();  
   PreparedStatement pstmt = conn.prepareStatement("insert into address(name,street,city,state,zip) values(?,?,?,?,?)");  
   pstmt.setString(1,address.getName());  
   pstmt.setString(2,address.getStreet());  
   pstmt.setString(3,address.getCity());  
   pstmt.setString(4,address.getState() );  
   pstmt.setString(5,address.getZip() );  
   pstmt.executeUpdate();  
  JdbcUtil.close(pstmt, conn);  
  
   \} catch (SQLException e) \{  
  e.printStackTrace();  
  \}  
\}  
  
//删除  
public void delete(int id)\{  
try\{  
    Connection conn = JdbcUtil.getConnection();  
    PreparedStatement pstmt = conn.prepareStatement("delete from address where id = ?");  
    pstmt.setInt(1, id);  
    pstmt.executeUpdate();  
   JdbcUtil.close(pstmt, conn);  
   \}catch(SQLException e)\{  
   e.printStackTrace();  
   throw new RuntimeException();  
  \}  
\}  
  
//修改  
public void update(Address address)\{  
try \{  
   Connection conn = JdbcUtil.getConnection();  
   PreparedStatement pstmt = conn.prepareStatement("update address set name = ?,street = ?,city =? ,state =?,zip= ? where id = ?");  
   pstmt.setInt(6, address.getId());  
   pstmt.setString(1,address.getName());  
   pstmt.setString(2,address.getStreet());  
   pstmt.setString(3,address.getCity());  
   pstmt.setString(4,address.getState());  
   pstmt.setString(5,address.getZip());  
  
   pstmt.executeUpdate();  
  JdbcUtil.close(pstmt, conn);  
  
  \} catch (SQLException e) \{  
 e.printStackTrace();  
 throw new RuntimeException();  
 \}  
\}  
  
//查询  
public List<Address> findAll()\{  
List<Address> list = new ArrayList<Address>();  
try\{  
  Connection conn = JdbcUtil.getConnection();  
   PreparedStatement pstmt = conn.prepareStatement("select \* from address");  
   ResultSet rs = pstmt.executeQuery();  
   while(rs.next())\{  
   Address address = new Address();  
   address.setId(rs.getInt(1));  
   address.setCity(rs.getString(4));  
   address.setStreet(rs.getString(3));  
   address.setState(rs.getString(5));  
   address.setName(rs.getString(2));  
   address.setZip(rs.getString(6));  
   list.add(address);  
  \}  
   JdbcUtil.close(pstmt, conn);  
  \}catch(SQLException e)\{  
  e.printStackTrace();  
   throw new RuntimeException();  
  \}  
 return list;  
\}  
  
//根据id查询  
public Address findById(int id)\{  
Address address = new Address();  
try\{  
   Connection conn = JdbcUtil.getConnection();  
   PreparedStatement pstmt = conn.prepareStatement("select \* from address where id="+id);  
   ResultSet rs = pstmt.executeQuery();  
  if(rs.next())\{  
   address.setId(rs.getInt(1));  
   address.setCity(rs.getString(4));  
   address.setStreet(rs.getString(3));  
   address.setState(rs.getString(5));  
   address.setName(rs.getString(2));  
   address.setZip(rs.getString(6));  
  \}  
  JdbcUtil.close(pstmt, conn);  
  \}catch(SQLException e)\{  
  e.printStackTrace();  
  throw new RuntimeException();  
   \}  
   return address;  
 \}  
\}

**servlet代码编写**

public class AddressServlet extends HttpServlet \{   
// 注入dao  
private AddressDao addressDao = new AddressDao();  
  
protected void doGet(HttpServletRequest request, HttpServletResponse response)   
throws ServletException, IOException \{   
//设置编码，很重要，否则页面提交，中文会出现乱码  
request.setCharacterEncoding("UTF-8");  
response.setCharacterEncoding("utf-8");  
//设置路径  
String path = "list.jsp";  
String method = request.getParameter("method");  
//若请求的url有list  
if (("list").equals(method)) \{   
List<Address> list = addressDao.findAll();  
request.setAttribute("list", list);  
\}  
else if (method.equals("add")) \{

//注入Address实体类  
Address address = new Address();  
//获取参数  
String name = request.getParameter("name");  
String street = request.getParameter("street");  
String city = request.getParameter("city");  
String state = request.getParameter("state");  
String zip = request.getParameter("zip");  
//设置增加的属性  
address.setName(name);  
address.setStreet(street);  
address.setCity(city);  
address.setState(state);  
address.setZip(zip);  
  
addressDao.add(address);  
<!--把新加入的数据重新加载

这点特别重要，否则刷新页面会报空指针异常

\-->  
**path = "AddressServlet?method=list";**  
\}  
  
else if (method.equals("delete")) \{

//根据id来删除  
int id = Integer.parseInt(request.getParameter("id"));  
addressDao.delete(id);  
//要重新查询一遍，否则会报空指针  
path = "AddressServlet?method=list";  
\}  
//跳转编辑页面url请求如下：

![Center 1][]  
else if (method.equals("toedit")) \{   
int id = Integer.parseInt(request.getParameter("id"));  
Address address = addressDao.findById(id);  
path = "edit.jsp";  
request.setAttribute("address", address);  
\}  
  
else if (method.equals("edit")) \{   
  
//根据id修改  
int id = Integer.parseInt(request.getParameter("id"));  
  
String name = request.getParameter("name");  
String street = request.getParameter("street");  
String city = request.getParameter("city");  
String state = request.getParameter("state");  
String zip = request.getParameter("zip");  
  
Address address = new Address();  
address.setId(id);  
address.setName(name);  
address.setStreet(street);  
address.setCity(city);  
address.setState(state);  
address.setZip(zip);  
  
addressDao.update(address);  
//把新加入的数据重新加载  
path = "AddressServlet?method=list";  
 \}  
  request.getRequestDispatcher(path).forward(request, response);  
\}

**add.jsp页面**

<form action="AddressServlet?method=add" method="post">  
      Name:<input type="text" name="name"/><br>  
      Street:<input type="text" name="street"/><br>  
     City:<input type="text" name="city"/><br>  
     State:<input type="text" name="state"/><br>  
     Zip:<input type="text" name="zip"/><br>  
    <input type="submit" name="add"/><br>  
 </form>

**edit.jsp页面**

//获取request中的address对象  
<% Address address = (Address)request.getAttribute("address"); %>  
 <form action="AddressServlet?method=edit" method="post">

<input type="hidden"      name="id"value="<%=address.getId()%>"><br>  
   Name:<input type="text"   name="name" value="<%=address.getName()%>"><br>  
   Street:<input type="text"   name="street"  value="<%=address.getStreet()%>"><br>  
   City:<input type="text"   name="city" value="<%=address.getCity()%>"><br>  
   State:<input type="text"  name="state" value="<%=address.getState()%>"><br>  
   Zip:<input type="text"    name="zip"    value="<%=address.getZip()%>"><br>  
  <input type="submit"  name="Edit" value="编辑"/><br>  
 </form>

**list页面**

<body><br>  
<table border="1">  
<tr>  
<td>Name</td>  
<td>Street</td>  
<td>City</td>  
<td>State</td>  
<td>Zip</td>  
<td><center>Options</center></td>  
<tr>  
<%  
List<Address> list = (List<Address>)request.getAttribute("list");  
for(Address a :list)\{  
  
%>  
<tr>  
<td><%=a.getName()%></td>  
<td><%=a.getStreet() %></td>  
<td> <%=a.getCity()%></td>  
<td><%=a.getState()%></td>  
<td><%=a.getZip() %></td>  
<td>  
<a href="AddressServlet?method=delete&id=<%=a.getId() %>">Delete</a>&nbsp;  
<a href="AddressServlet?method=toedit&id=<%=a.getId() %>">Edit</a>  
</td>  
  
</tr>  
<%\}%>  
</table>  
<a href="add.jsp">Add</a>

**最后若觉得请求url名字过长，可在index.jsp页面设置默认跳转<jsp:forward page="AddressServlet?method=list"></jsp:forward>**

**主要重点在于增删改查的逻辑，方便对这些知识掌握不牢的同学进行理解，当然有兴趣的同学代可以继续优化代码，使之更加符合项目要求的MVC设计思想，增加service以及serviceImp，daoImp等等，以后会出基于ssh三层架构的javaWeb，欢迎批评指正**

## [源代码下载][Link 1] ##

[Center]: /images/20220716/1b7a37d6a0884563a83610d4bba5ddea.png
[Center 1]: /images/20220716/a3a7e359bc7e4aa6ac9427eee45f3a67.png
[Link 1]: https://download.csdn.net/download/u013215018/10585317