HandlerMethodArgumentResolver(四)：自定参数解析器处理特定场景需求，介绍PropertyNamingStrategy的使用【享学Spring MVC】（上）

/**
 * 用于获取当前登陆人信息的注解,配合自定义的参数处理器使用
 *
 * @see CurrUserArgumentResolver
 */
@Target({ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface CurrUser {
}
// 待封装的Vo
@Getter
@Setter
@ToString
public class CurrUserVo {
    private Long id;
    private String name;
}

public class CurrUserArgumentResolver implements HandlerMethodArgumentResolver {
    // 只有标注有CurrUser注解，并且数据类型是CurrUserVo/Map/Object的才给与处理
    @Override
    public boolean supportsParameter(MethodParameter parameter) {
        CurrUser ann = parameter.getParameterAnnotation(CurrUser.class);
        Class<?> parameterType = parameter.getParameterType();
        return (ann != null &&
                (CurrUserVo.class.isAssignableFrom(parameterType)
                        || Map.class.isAssignableFrom(parameterType)
                        || Object.class.isAssignableFrom(parameterType)));
    }
    @Override
    public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer container, NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
        HttpServletRequest request = webRequest.getNativeRequest(HttpServletRequest.class);
        // 从请求头中拿到token
        String token = request.getHeader("Authorization");
        if (StringUtils.isEmpty(token)) {
            return null; // 此处不建议做异常处理，因为校验token的事不应该属于它来做，别好管闲事
        }
        // 此处作为测试：new一个处理（写死的）
        CurrUserVo userVo = new CurrUserVo();
        userVo.setId(1L);
        userVo.setName("fsx");
        // 判断参数类型进行返回
        Class<?> parameterType = parameter.getParameterType();
        if (Map.class.isAssignableFrom(parameterType)) {
            Map<String, Object> map = new HashMap<>();
            BeanUtils.copyProperties(userVo, map);
            return map;
        } else {
            return userVo;
        }
    }
}
// 注册进Spring组件内
@Configuration
@EnableWebMvc
public class WebMvcConfig extends WebMvcConfigurerAdapter {
    @Override
    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) {
        argumentResolvers.add(new CurrUserArgumentResolver());
    }
}

@Controller
@RequestMapping
public class HelloController {
    @ResponseBody
    @GetMapping("/test/curruser")
    public Object testCurrUser(@CurrUser CurrUserVo currUser) {
        return currUser;
    }
    @ResponseBody
    @GetMapping("/test/curruser/map")
    public Object testCurrUserMap(@CurrUser Map<String,Object> currUser) {
        return currUser;
    }
    @ResponseBody
    @GetMapping("/test/curruser/object")
    public Object testCurrUserObject(@CurrUser Object currUser) {
        return currUser;
    }
}

@Configuration
@EnableWebMvc
public class WebMvcConfig extends WebMvcConfigurerAdapter {
    @Bean
    public CurrUserArgumentResolver currUserArgumentResolver(){
        return new CurrUserArgumentResolver();
    }
    @Override
    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) {
        argumentResolvers.add(currUserArgumentResolver());
    }

public class CurrUserArgumentResolver implements HandlerMethodArgumentResolver {
    @Autowired
    HelloService helloService;
    @Autowired
    StringRedisTemplate stringRedisTemplate;
    ...
}

@Configuration
@EnableWebMvc
public class WebMvcConfig extends WebMvcConfigurerAdapter {
    @Autowired
    private ApplicationContext applicationContext;
    @Override
    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) {
        CurrUserArgumentResolver resolver = new CurrUserArgumentResolver();
        // 利用工厂给容器外的对象注入所需组件
        applicationContext.getAutowireCapableBeanFactory().autowireBean(resolver);
        argumentResolvers.add(resolver);
    }
}