捕获SpringSecurity异常，进行统一返回

无法捕获SpringSecurity的认证和鉴权中发生异常的原因

使用@ControllerAdvice的全局异常处理器无法捕获到SpringSecurity中的异常，原因如下：

在SpringSecurity中，如果认证或者授权的过程中出现了异常会被ExceptionTranslationFilter捕获到。在ExceptionTranslationFilter中会去判断是认证失败还是授权失败出现的异常：

如果是【认证】过程中出现的异常会被封装成AuthenticationException然后调用AuthenticationEntryPoint对象的方法去进行异常处理。
如果是【授权】过程中出现的异常会被封装成AccessDeniedException然后调用AccessDeniedHandler对象的方法去进行异常处理。

所以如果我们需要自定义异常处理，我们只需要实现AuthenticationEntryPoint和AccessDeniedHandler接口，然后配置给SpringSecurity即可。

代码实现

WebUtils工具类，用来渲染字符串：

public class WebUtils {
    /**
     * 将字符串渲染到客户端
     *
     * @param response 渲染对象
     * @param string   待渲染的字符串
     * @return null
     */
    public static String renderString(HttpServletResponse response, String string) {
        try {
            response.setStatus(200);
            response.setContentType("application/json");
            response.setCharacterEncoding("utf-8");
            response.getWriter().print(string);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }
}

AuthenticationEntryPoint 自定义实现类

@Component
public class AuthenticationEntryPointImpl implements AuthenticationEntryPoint {
    @Override
    public void commence(HttpServletRequest request, HttpServletResponse response, AuthenticationException authException) throws IOException, ServletException {
        ResponseResult result = new ResponseResult(401, authException.getMessage());
        String json = JSON.toJSONString(result);
        WebUtils.renderString(response, json);
    }
}

AccessDeniedHandler 自定义实现类：

@Component
public class AccessDeniedHandlerImpl implements AccessDeniedHandler {
    @Override
    public void handle(HttpServletRequest request, HttpServletResponse response, AccessDeniedException accessDeniedException) throws IOException, ServletException {
        ResponseResult result = new ResponseResult(403, accessDeniedException.getMessage());
        String json = JSON.toJSONString(result);
        WebUtils.renderString(response, json);
    }
}

将自定义异常处理器配置给SpringSecurity

@Configuration
public class SecurityConfig extends WebSecurityConfigurerAdapter {

	//注入
    @Autowired
    private AuthenticationEntryPoint authenticationEntryPoint;
    @Autowired
    private AccessDeniedHandler accessDeniedHandler;

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        //配置自定义异常处理器
        http.exceptionHandling()
                .authenticationEntryPoint(authenticationEntryPoint)
                .accessDeniedHandler(accessDeniedHandler);
    }
}