springboot——security实现验证码：使用自定义认证

在使用Spring Security的自定义认证之前，有必要了解Spring Security是如何灵活集成多种认证方式的。在spring Security中用户被称为主体(principal)，主体包含了所有能够验证而获得系统访问权限的用户、设备或其他系统。主体的概念来自Java Security，自定义认证的基类是Authentication

public interface Authentication extends Principal, Serializable {
   
   
	// ~ Methods
	// ========================================================================================================

	/**
	 * Set by an <code>AuthenticationManager</code> to indicate the authorities that the
	 * principal has been granted. Note that classes should not rely on this value as
	 * being valid unless it has been set by a trusted <code>AuthenticationManager</code>.
	 * <p>
	 * Implementations should ensure that modifications to the returned collection array
	 * do not affect the state of the Authentication object, or use an unmodifiable
	 * instance.
	 * </p>
	 *
	 * @return the authorities granted to the principal, or an empty collection if the
	 * token has not been authenticated. Never null.
	 */
	 // 权限列表
	Collection<? extends GrantedAuthority> getAuthorities();

	/**
	 * The credentials that prove the principal is correct. This is usually a password,
	 * but could be anything relevant to the <code>AuthenticationManager</code>. Callers
	 * are expected to populate the credentials.
	 *
	 * @return the credentials that prove the identity of the <code>Principal</code>
	 */
	 // 密码
	Object getCredentials();

	/**
	 * Stores additional details about the authentication request. These might be an IP
	 * address, certificate serial number etc.
	 *
	 * @return additional details about the authentication request, or <code>null</code>
	 * if not used
	 */
	 // 其他信息
	Object getDetails();

	/**
	 * The identity of the principal being authenticated. In the case of an authentication
	 * request with username and password, this would be the username. Callers are
	 * expected to populate the principal for an authentication request.
	 * <p>
	 * The <tt>AuthenticationManager</tt> implementation will often return an
	 * <tt>Authentication</tt> containing richer information as the principal for use by
	 * the application. Many of the authentication providers will create a
	 * {@code UserDetails} object as the principal.
	 *
	 * @return the <code>Principal</code> being authenticated or the authenticated
	 * principal after authentication.
	 */
	 // 用户名
	Object getPrincipal();

	/**
	 * Used to indicate to {@code AbstractSecurityInterceptor} whether it should present
	 * the authentication token to the <code>AuthenticationManager</code>. Typically an
	 * <code>AuthenticationManager</code> (or, more often, one of its
	 * <code>AuthenticationProvider</code>s) will return an immutable authentication token
	 * after successful authentication, in which case that token can safely return
	 * <code>true</code> to this method. Returning <code>true</code> will improve
	 * performance, as calling the <code>AuthenticationManager</code> for every request
	 * will no longer be necessary.
	 * <p>
	 * For security reasons, implementations of this interface should be very careful
	 * about returning <code>true</code> from this method unless they are either
	 * immutable, or have some way of ensuring the properties have not been changed since
	 * original creation.
	 *
	 * @return true if the token has been authenticated and the
	 * <code>AbstractSecurityInterceptor</code> does not need to present the token to the
	 * <code>AuthenticationManager</code> again for re-authentication.
	 */
	 // 是否验证成功
	boolean isAuthenticated();

	/**
	 * See {@link #isAuthenticated()} for a full description.
	 * <p>
	 * Implementations should <b>always</b> allow this method to be called with a
	 * <code>false</code> parameter, as this is used by various classes to specify the
	 * authentication token should not be trusted. If an implementation wishes to reject
	 * an invocation with a <code>true</code> parameter (which would indicate the
	 * authentication token is trusted - a potential security risk) the implementation
	 * should throw an {@link IllegalArgumentException}.
	 *
	 * @param isAuthenticated <code>true</code> if the token should be trusted (which may
	 * result in an exception) or <code>false</code> if the token should not be trusted
	 *
	 * @throws IllegalArgumentException if an attempt to make the authentication token
	 * trusted (by passing <code>true</code> as the argument) is rejected due to the
	 * implementation being immutable or implementing its own alternative approach to
	 * {@link #isAuthenticated()}
	 */
	void setAuthenticated(boolean isAuthenticated) throws IllegalArgumentException;
}

一、分析UsernamePasswordAuthenticationFilter#attemptAuthentication源码

public Authentication attemptAuthentication(HttpServletRequest request,
			HttpServletResponse response) throws AuthenticationException {
   
   
		if (postOnly && !request.getMethod().equals("POST")) {
   
   
			throw new AuthenticationServiceException(
					"Authentication method not supported: " + request.getMethod());
		}
		
		// 获取用户名和密码
		String username = obtainUsername(request);
		String password = obtainPassword(request);

		if (username == null) {
   
   
			username = "";
		}

		if (password == null) {
   
   
			password = "";
		}

		username = username.trim();
	
		Userna