Java：自定义异常实现登录

一、用户登录功能

public class Login {
    private String userName = "admin";
    private String password = "123456";

    public void loginInfo(String userName, String password){
        if(!userName.equals(this.userName)) {
            // TODO 处理用户名错误
        }
        if(!password.equals(this.password)) {
            // TODO 处理密码错误
        }
    }
    public static void main(String[] args) {
        Login login = new Login();
        login.loginInfo("Admin", "123456");
    }
}

二、自定义异常类

处理用户名密码错误的时候可能就需要抛出两种异常。 可以基于已有的异常类进行扩展（继承），   创建与我们业务相关的异常类。

class UserNameError extends Exception {
    public UserNameError(String message) {
        super(message);
    }
}
class PasswordError extends Exception {
    public PasswordError(String message) {
        super(message);
    }
}

三、Login的代码可以改写为

public void loginInfo(String userName, String password) throws UserNameError, PasswordError{
    if(!userName.equals(this.userName)) {
        throw new UserNameError("用户名错误");
    }
    if(!password.equals(this.password)) {
        throw new PasswordError("密码错误");
    }
}
public static void main(String[] args) {
    try{
        Login login = new Login();
        login.loginInfo("admin", "123456");
    } catch (UserNameError userNameError) {
        userNameError.printStackTrace();
    } catch (PasswordError passwordError) {
        passwordError.printStackTrace();
    }
}

四、完整代码

class UserNameError extends Exception {
    public UserNameError(String message) {
        super(message);
    }
}
class PasswordError extends Exception {
    public PasswordError(String message) {
        super(message);
    }
}
public class Login {
    private String userName = "admin";
    private String password = "123456";

    public void loginInfo(String userName, String password) throws UserNameError, PasswordError{
        if(!userName.equals(this.userName)) {
            throw new UserNameError("用户名错误");
        }
        if(!password.equals(this.password)) {
            throw new PasswordError("密码错误");
        }
    }
    public static void main(String[] args) {
        try{
            Login login = new Login();
            login.loginInfo("admin", "123456");
        } catch (UserNameError userNameError) {
            userNameError.printStackTrace();
        } catch (PasswordError passwordError) {
            passwordError.printStackTrace();
        }
    }
}