java DAO 增删改查功能

第四步:写个DAO,里面包括增删改查的操作

package cn.itcast.webapp.dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import cn.itcast.webapp.db.DBManager;
import cn.itcast.webapp.domain.Customer;

public class CustomerDAO {

public static void updateCustomer(Customer cust){
//1. 获取数据库连接
Connection conn = DBManager.getConnection();
//2. 准备 sql 文
String sql = "UPDATE customers SET name = ?, address = ?, phone = ? WHERE id = ?";

PreparedStatement ps = null;

try {
//3. 获取 PreparedStatement 对象
ps = conn.prepareStatement(sql);
ps.setString(1, cust.getName());
ps.setString(2, cust.getAddress());
ps.setString(3, cust.getPhone());
ps.setInt(4, cust.getId());

//4. 进行更改操作
ps.executeUpdate();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
throw new RuntimeException("修改用户信息异常");
}finally{
//5. 关闭数据库资源
DBManager.releaseDBSource(null, ps, conn);
}
}

public static Customer getCustomerById(int id){
Customer cust = null;

Connection conn = DBManager.getConnection();
PreparedStatement ps = null;
ResultSet rs = null;

String sql = "SELECT id, name, address, phone FROM customers WHERE id = ?";
try {
ps = conn.prepareStatement(sql);
ps.setInt(1, id);

rs = ps.executeQuery();
if(rs.next()){
String name = rs.getString(2);
String address = rs.getString("address");
String phone = rs.getString("phone");

cust = new Customer();
cust.setName(name);
cust.setId(id);
cust.setAddress(address);
cust.setPhone(phone);
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
throw new RuntimeException("根据 id: " + id + " 查询用户信息异常.");
}

return cust;
}

public static void deleteCustomerById(int id){
//1. 获取连接
Connection conn = null;
PreparedStatement ps = null;

conn = DBManager.getConnection();

//2. 准备 sql
String sql = "DELETE FROM customers WHERE id = ?";

try {
//3. 获取 PreparedStatement
ps = conn.prepareStatement(sql);
ps.setInt(1, id);

//4. 删除操作
ps.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
}finally{
//5. 关闭数据库资源
DBManager.releaseDBSource(null, ps, conn);
}
}

//根据 customer 对象查找符合条件的 customer 记录, 将它们放到 List 中, 并返回
public static List searchCustomers(Customer customer){
List customers = new ArrayList();

//1. 不考虑条件, 全部查出来, 并返回
//a. 获取数据库连接
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;

conn =
DBManager.getConnection();

//b.

准备 sql 语句
String sql = "SELECT id, name, address, phone FROM customers WHERE name LIKE ? AND address LIKE

? AND phone LIKE ?";

try {
//c. 获取执行 sql 语句的 PreparedStatement 对象
ps = conn.prepareStatement(sql);
ps.setString(1, "%" + (customer.getName() == null ? "" : customer.getName()) + "%");
ps.setString(2, "%" + (customer.getAddress() == null ? "" : customer.getAddress()) + "%");
ps.setString(3, "%" + (customer.getPhone() == null ? "" : customer.getPhone()) + "%");

//d. 执行查询
rs = ps.executeQuery();

//e. 对 ResultSet 进行遍历

Customer cust = null;
while(rs.next()){
int id = 0;
String name = null;
String address = null;
String phone = null;

id = rs.getInt(1);
name = rs.getString(2);
address = rs.getString(3);
phone = rs.getString(4);

cust = new Customer();

cust.setId(id);
cust.setAddress(address);
cust.setName(name);
cust.setPhone(phone);

customers.add(cust);
}
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException("查询用户异常");
}finally{
//f. 关闭数据库资源
DBManager.releaseDBSource(rs, ps, conn);
}


return customers;
}

public static void saveCustomer(Customer customer){
Connection conn = null;
PreparedStatement ps = null;

String sql = "INSERT INTO customers(name, address, phone) VALUES(?, ?, ?)";
String name = customer.getName();
String address = customer.getAddress();
String phone = customer.getPhone();

conn = DBManager.getConnection();

try {
ps = conn.prepareStatement(sql);
ps.setString(1, name);
ps.setString(2, address);
ps.setString(3, phone);

ps.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
if(e.getMessage().equals("Duplicate entry '" + customer.getName() + "' for key 2"))
throw new RuntimeException("该用户名已经存在, 请重新选择!");
throw new RuntimeException("插入新客户信息异常");
}finally{
DBManager.releaseDBSource(null, ps, conn);
}
}
}


下面写的是视图界面程序:

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="https://www.doczj.com/doc/bb15367258.html,/jsp/jstl/core" prefix="c" %>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'addCustomer.jsp' starting page</title>
<script type="text/javascript" src="js/check.js"></script>
</head>

<body>
<c:if test="${requestScope.errorInfo != null}">
<font color="red">${requestScope.errorInfo}</font>
<br><br>
</c:if>
<form action="addCustomerServlet" method="post">
<table>
<tr>
<td>Name: &l

t;/td>
<td><input type="text" name="name" value="${https://www.doczj.com/doc/bb15367258.html, }" /></td>
</tr>
<tr>
<td>Address: </td>
<td><i
nput type="text" name="address" value="${param.address }" /></td>
</tr>
<tr>
<td>Phone: </td>
<td><input type="text" name="phone" value="${param.phone }" /></td>
</tr>
<tr>
<td colspan="2">
<input type="submit" value="Submit" id="submitButton" />
</td>
</tr>
</table>
</form>
</body>
</html>


<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="https://www.doczj.com/doc/bb15367258.html,/jsp/jstl/core" %>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'searchCustomers.jsp' starting page</title>
</head>

<body>
<c:if test="${requestScope.errorInfo != null}">
<font color="red">${requestScope.errorInfo}</font>
<br><br>
</c:if>
<form action="searchCustomerServlet" method="post">
<table>
<tr>
<td>Name: </td>
<td><input type="text" name="name" /></td>
</tr>
<tr>
<td>Address: </td>
<td><input type="text" name="address" /></td>
</tr>
<tr>
<td>Phone: </td>
<td><input type="text" name="phone" /></td>
</tr>
<tr>
<td colspan="2">
<input type="submit" value="Search" />&nbsp;&nbsp;
<a href="addCustomer.jsp">Create New Customer</a>
</td>
</tr>
</table>
</form>

<c:if test="${requestScope.customers != null}">
<br>
<hr>
Search Results: <br>
<c:if test="${!empty requestScope.customers}">
<table border="1" cellpadding="8" cellspacing="0">
<tr>
<td>Name</td>
<td>Address</td>
<td>Phone</td>
<td>Update</td>
<td>Delete</td>
</tr>
<c:forEach items="${requestScope.customers}" var="customer">
<tr>
<td>${https://www.doczj.com/doc/bb15367258.html, }</td>
<td>${customer.address }</td>
<td>${customer.phone }</td>
<td><a href="customerUIServlet?id=${customer.id }&name=${https://www.doczj.com/doc/bb15367258.html, }

&address=${param.address }&phone=${param.phone }">Update</a></td>

<td><a href="deleteCustomerServlet?id=${customer.id }&name=${https://www.doczj.com/doc/bb15367258.html, }

&address=${param.address }&phone=${param.phone }">Delete</a></td>
</tr>
</c:forEach>
</table>
</c:if>
<c:if test="${empty requestScope.customers}">
对不起, 没有满足条件的客户信息.
</c:if>
</c:if>
</body>
</html>
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'updateCustomer.jsp' starting page</title>
</head>

<body>
<form action="updateCustomerServlet" method="post">
<input type="hidden" name="updateid" value="${requestScope.customer.id }" />
<input type="hidden" name="name" value="${https://www.doczj.com/doc/bb15367258.html, }" />
<input type="hid
den" name="address" value="${param.address }" />
<input type="hidden" name="phone" value="${param.phone }" />

<table>
<tr>
<td>Name: </td>
<td><input type="text" name="updatename" value="${https://www.doczj.com/doc/bb15367258.html, }" /></td>
</tr>
<tr>
<td>Address: </td>
<td><input type="text" name="updateaddress" value="${requestScope.customer.address }"

/></td>
</tr>
<tr>
<td>Phone: </td>
<td><input type="text" name="updatephone" value="${requestScope.customer.phone }" /></td>
</tr>
<tr>
<td colspan="2">
<input type="submit" value="Submit" id="submitButton" />
</td>
</tr>
</table>
</form>
</body>
</html>
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'success.jsp' starting page</title>
</head>

<body>
添加成功!<br>
<a href="searchCustomers.jsp">return...</a>
</body>
</html>

现在呢,就需要在配置文件中,将两个不相关联的东西连接起来: web.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
xmlns="https://www.doczj.com/doc/bb15367258.html,/xml/ns/javaee"
xmlns:xsi="https://www.doczj.com/doc/bb15367258.html,/2001/XMLSchema-instance"
xsi:schemaLocation="https://www.doczj.com/doc/bb15367258.html,/xml/ns/javaee
https://www.doczj.com/doc/bb15367258.html,/xml/ns/jav

aee/web-app_2_5.xsd">
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>AddCustomerServlet</servlet-name>
<servlet-class>cn.itcast.webapp.servlet.AddCustomerServlet</servlet-class>
</servlet>
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>SearchCustomersServlet</servlet-name>
<servlet-class>cn.itcast.webapp.servlet.SearchCustomersServlet</servlet-class>
</servlet>
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>DeleteCustomerServlet</servlet-name>
<servlet-class>cn.itcast.webapp.servlet.DeleteCustomerServlet</servlet-class>
</servlet>
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>CustomerUIServlet</servlet-name>
<servlet-class>cn.itcast.webapp.servlet.CustomerUIServlet</servlet-class>
</servlet>
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>UpdateCustomerServlet</servlet-name>
<servlet-class
>cn.itcast.webapp.servlet.UpdateCustomerServlet</servlet-class>
</servlet>





<servlet-mapping>
<servlet-name>AddCustomerServlet</servlet-name>
<url-pattern>/addCustomerServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>SearchCustomersServlet</servlet-name>
<url-pattern>/searchCustomerServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>DeleteCustomerServlet</servlet-name>
<url-pattern>/deleteCustomerServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>CustomerUIServlet</servlet-name>
<url-pattern>/customerUIServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>UpdateCustomerServlet</servlet-name>
<url-pattern>/updateCustomerServlet</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>



这个字一个小的应用程序就写完了.通过这个小例子 ,我们可以很清晰的

了解的MVC 模式的开发流程,当然这个还

算是很简单的程序,今后在做大的应用开发时,MVC 模式的优势将会很明显的显示出来!记着,servlet的编写是一

个很重要的一个过程的!当然,一个WEB程序所有的一切都是密不可分的!但是servlet写的好坏会直接影响到程序

的性能的!我至少现在这么认为!