三方：
1、入口地址 /oauth2Login被filter拦截
org.springframework.security.oauth2.client.filter.OAuth2ClientContextFilter       FilterChain
    org.springframework.security.oauth2.client.filter.OAuth2ClientAuthenticationProcessingFilter
       如果没有token    OAuth2ClientContextFilter.redirectUser(redirect, request, response);  302到授权服务器的/oauth/authorize
3、回调地址 /oauth2Login?code=vzPM3K&state=g3vW7k
4、请求token  /oauth/token 后台调用

服务器：
2、/oauth/authorize org.springframework.security.oauth2.provider.endpoint.AuthorizationEndpoint
    获取code 302到三方的回调地址 前端重定向
/oauth/token  org.springframework.security.oauth2.provider.endpoint.TokenEndpoint


三方第一次oauth登录流程
org.springframework.security.oauth2.client.filter.OAuth2ClientAuthenticationProcessingFilter.attemptAuthentication()
-->org.springframework.security.oauth2.client.OAuth2RestTemplate.getAccessToken()
---->acquireAccessToken()
------>org.springframework.security.oauth2.client.token.AccessTokenProviderChain.obtainAccessToken
------->obtainNewAccessTokenInternal
---------->org.springframework.security.oauth2.client.token.grant.code.AuthorizationCodeAccessTokenProvider.obtainAccessToken 上面都是要尽力获取token，如果获取到则重定向的授权服务器授权码接口
---------------->getRedirectForAuthorization 填充UserRedirectRequiredException
------------------>org.springframework.security.oauth2.client.token.grant.redirect.AbstractRedirectResourceDetails.getRedirectUri 确定获取code url中redirect参数
-------------------->org.springframework.security.oauth2.client.filter.OAuth2ClientContextFilter.doFilter 过滤器链捕获异常，302到授权码接口

为什么集成security的三方oauth登录地址和回调地址默认是一样的，答案就在AbstractRedirectResourceDetails.getRedirectUri
    public String getRedirectUri(AccessTokenRequest request) {
		String redirectUri = request.getFirst("redirect_uri");
		// 这里redirect回调地址默认取的就是当前的url，也就是oauth的入口地址
		if (redirectUri == null && request.getCurrentUri() != null && useCurrentUri) {
			redirectUri = request.getCurrentUri();
		}
		// 如果要自定义oauth回调地址 就要将useCurrentURI设置false，preEstablishedRedirectUri设置为自定义的回调地址
		if (redirectUri == null && getPreEstablishedRedirectUri() != null) {
			// Override the redirect_uri if it is pre-registered
			redirectUri = getPreEstablishedRedirectUri();
		}
		return redirectUri;
	}