1定义一个在方法上作用的注解

@Retention(RetentionPolicy.RUNTIME) // 表示注解在运行时依然存在

@Target(ElementType.METHOD)

@Documented

public @interface noNull {

public String str() default "";

}

2定义一个拦截类，拦截被注解的方法，并验证注解中指定的方法是否为空

public class NoNullInterceptor extends HandlerInterceptorAdapter{

//在请求处理之前进行调用(Controller方法调用之前

@Override

public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {

//如果不是映射到方法直接通过

if (!(o instanceof HandlerMethod)) {

return true;

}

HandlerMethod handlerMethod = (HandlerMethod) o;

Method method = handlerMethod.getMethod();

if (method.getAnnotation(noNull.class) != null) {

noNull noNullAnnotation=method.getAnnotation(noNull.class);

String Str = noNullAnnotation.str();

//从httpServletRequest获取注解上指定的参数

Object obj = httpServletRequest.getParameter(Str);

if(null != obj){

return true;

}else{

httpServletResponse.getWriter().write(JSON.toJSONString(new Result("false","参数缺失")));

return false;

}

}else{

return true;

}

}

//请求处理之后进行调用，但是在视图被渲染之前(Controller方法调用之后)

@Override

public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {

}

//在整个请求结束之后被调用，也就是在DispatcherServlet 渲染了对应的视图之后执行(主要是用于进行资源清理工作)

@Override

public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {

}

}

3将上步定义的拦截类加入到拦截链

@Configuration

public class interceptorConfig extends WebMvcConfigurerAdapter{

public void addInterceptors(InterceptorRegistry registry){

registry.addInterceptor(new NoNullInterceptor())

.addPathPatterns("/**");

//非空字段拦截

super.addInterceptors(registry);

}

}

4将注解和需要验证非空的参数在需要做非空check的方法声明

@noNull(str = "userName")

public Result sysLogin (

@RequestParam(value="userName", required=false) String userName,

@RequestParam(value="passWord", required=false) String passWord

) {

return Service.sysLogin(userName, passWord);

}

5实现效果