JavaWeb实现MVC设计模式(实例解析)
本例使用MySQL数据库，实现了简单的用户登录验证
一、创建用户表 login_user ，插入一条数据 insert login_user value(“sa”,”1234”)
create table login_user(
name varchar(20) primary key,
pwd varchar(20) not null
)二、新建web工程ch12，建立四个包：com.bo , com.dao , com.entity , com.control ,在com.entity包下新建User.java实体类,代码如下：
public class User {
private String name;
private String pwd;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPwd() {
return pwd;
}
public void setPwd(String pwd) {
this.pwd = pwd;
}
public User() {
super();
}
public User(String name, String pwd) {
super();
this.name = name;
this.pwd = pwd;
}
}三、在com.dao包下建立数据访问类UserDao.java，定义方法findById,代码如下:
public class UserDao {
public User findById(String name){
User user=null;
Connection conn=null;
PreparedStatement ps=null;
ResultSet rs=null;
try{
conn=DbUtil.getConn();
String sql="select * from login_user where name=?";
ps=conn.prepareStatement(sql);
ps.setString(1, name);
rs=ps.executeQuery();
while(rs.next()){
user=new User();
user.setName(rs.getString("name"));
user.setPwd(rs.getString("pwd"));
}
}catch(Exception ex){
ex.printStackTrace();
}finally{
DbUtil.closeConn(conn,ps,rs);
}
return user;
}
}四、DbUtil类主要提供了数据库连接的基本方法，代码如下:
public class DbUtil {
private static String driver;
private static String url;
private static String userName;
private static String password;
//从properties文件中获取连接数据库所需的参数
static{
try {
Properties prop=new Properties();
InputStream in = DbUtil.class.getClassLoader().getResourceAsStream("jdbc.properties");
prop.load(in);
driver=prop.getProperty("driver");
url=prop.getProperty("url");
userName=prop.getProperty("userName");
password=prop.getProperty("password");
}catch (FileNotFoundException e) {
System.out.println("找不到文件！");
e.printStackTrace();
}catch (IOException e) {
System.out.println("读取properties文件出错!");
e.printStackTrace();
}
}
//获取数据库连接
public static Connection getConn(){
Connection conn=null;
try {
Class.forName(driver);
conn=DriverManager.getConnection(url,userName,password);
} catch (Exception e) {
e.printStackTrace();
}
return conn;
}
//释放资源
public static void closeConn(Connection conn,Statement stmt,ResultSet rs) {
try{
if(rs!=null){rs.close();}
if(stmt!=null){stmt.close();}
if (conn != null) {conn.close();}
}catch (SQLException e) {e.printStackTrace();}
}
}在该类中获取的数据库连接所用的jdbc.properties文件位于src目录下，对其进行的配置如下:
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/oa
userName=root
password=123456五、在com.bo包下编写UserBo.java 业务逻辑类,定义方法checkUser：
public class UserBo {
UserDao dao=new UserDao();
//将用户输入的密码与在数据库中查到的进行匹配
public boolean checkUser(String name,String pwd){
boolean result=false;
User user=dao.findById(name);
if(user!=null&&user.getPwd().equals(pwd)){
result=true;
}
return result;
}
} 六、编写登录页面和登录成功页面(本例的登录成功页面就不弄复杂的，创建名为loginSuccess.jsp的文件，内容随意填，这里就不描述了)
<body>
<center>
<h3>用户登录h3>
<form action="UserLogin" method="post">
用户名:<input type="text" name="username"/><br/>
密 码:<input type="text" name="password"/> <br/>
<input type="submit" value="登录" /><br/>
form>
center>
body>七、在com.control包下编写UserAction.java用于登录验证
public class UserAction extends HttpServlet {
private static final long serialVersionUID = 1L;
public UserAction() {
super();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
UserBo userbo=new UserBo();
String name=request.getParameter("username");
String pwd=request.getParameter("password");
//控制器并不做数据处理，而是调用相应的模型，
boolean validate=userbo.checkUser(name, pwd);
//根据模型的返回结果将符合要求的视图返回给用户
if(validate){
response.sendRedirect("loginSuccess.jsp");
}else{
response.sendRedirect("login.jsp");
}
}
}OK,到此就可以将此例子运行到Web服务器上了，在服务器上运行成功后访问login.jsp，就可以开始完成简单的用户登录验证