判断用户名是否被占用

1.首先在index.jsp中写上

案例1-检查用户名是否占用

2.新建demo11.jsp

在body中写上

2.1继续写上

3.创建servlet&＃xff0c;包名自己随便顶一下&＃xff0c;servlet名明为&＃xff1a;CheckUsername4AjaxServlet     mapping为&＃xff1a;checkUsername4Ajax  如下

CheckUsername4AjaxServlet/checkUsername4Ajax

4. 在  CheckUsername4AjaxServlet 中的doget方法中写入

//0.设置编码

//1.接受用户

String username&＃61;request.getParameter("username");
String password&＃61;request.getParameter("password");
username&＃61;new String(username.getBytes("iso8859-1"),"utf-8");
System.out.println(username);

//2.调用service 完成查询 返回user

User user &＃61; null;
try {user &＃61; new UserService().checkUsername4Ajax(username);
} catch (SQLException e) {// TODO 自动生成的 catch 块e.printStackTrace();
}
//3.判断user是否为空
if(user &＃61;&＃61; null){response.getWriter().println("1");
}else{response.getWriter().println("0");}
}

5.定义一个UserService.java类&＃xff0c;包名自己随意定&＃xff0c;写上checkUsername4Ajax(username)的方法&＃xff0c;如下

public class UserService {/**
* 检测用户名是否被占用
* &＃64;param username
* &＃64;return
* &＃64;throws SQLException 
*/
public User checkUsername4Ajax(String username) throws SQLException {
// TODO 自动生成的方法存根
return new UserDao().getUserByUsername4Ajax(username);
}}

6.定义一个Userdao.java类&＃xff0c;包名自己随意定&＃xff0c;写上getUserByUsername4Ajax(username)的方法&＃xff0c;如下

public class UserDao {/**
* 通过用户名获取一个用户
* &＃64;param username
* &＃64;return
* &＃64;throws SQLException 
*/
public User getUserByUsername4Ajax(String username) throws SQLException {
// TODO 自动生成的方法存根
QueryRunner qr&＃61; new QueryRunner(DataSourceUtils.getDataSource());
String sql&＃61;"select * from user where username&＃61;?";return qr.query(sql, new BeanHandler<>(User.class), username);
}
}

7.定义一个User,java类&＃xff0c;包名随便定

public class User {
private String username;
private String password;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username &＃61; username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password &＃61; password;
}

8.链接数据库的文件dataSourceUtils.java(以文件方式上传)

9.c3p0-config.xml&＃xff08;文件上传&＃xff09;

附件&＃xff1a;

1.c3p0-config.xml里面的内容&＃xff1a;

com.mysql.jdbc.Driver
jdbc:mysql://502Sharepc:3306/day1501
root
123456



30000
30
10
30
100
10
200
 




com.mysql.jdbc.Driver
jdbc:mysql://127.0.0.1:3306/xxxx
root
1234



5
20
10
40
20
5