public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception

这是一个`LoginInterceptor`类中的`preHandle()`方法的签名，它实现了`HandlerInterceptor`接口的方法。该方法在请求处理之前被调用，用于进行预处理操作。

在`preHandle()`方法中，它接收了三个参数：`HttpServletRequest request`，`HttpServletResponse response`和`Object handler`。这些参数分别表示当前请求的HttpServletRequest对象、HttpServletResponse对象和处理当前请求的处理器对象。

该方法的返回类型是`boolean`，它表示是否允许请求继续进行处理。如果返回`true`，表示允许请求继续进行处理；如果返回`false`，则表示拦截请求，不再继续进行处理。

在实际的方法体内，可以根据具体的业务需求进行相应的预处理操作，如验证用户登录状态、权限控制等。如果有需要拦截请求并进行相应处理的逻辑，可以在该方法中实现。

相关问题

public class LoginInterceptor implements HandlerInterceptor { public LoginInterceptor() { } public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception { return true; } public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception { } public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception { } }

这是一个Java类，实现了Spring MVC框架中的 `HandlerInterceptor` 接口，并且名为 `LoginInterceptor`，用于实现登录拦截器的功能。

在Web应用中，登录拦截器通常用于拦截用户的登录请求，并检查用户是否已经登录。如果用户已经登录，则可以允许用户继续访问指定的页面或资源；否则，可以将用户重定向到登录页面，要求用户先进行登录操作。

在该示例中，实现了三个方法，分别是 `preHandle`、`postHandle` 和 `afterCompletion`，它们的作用如下：

- `preHandle` 方法在请求处理之前调用，可以用于实现登录验证逻辑。如果返回值为 `true`，则表示允许请求继续进行；如果返回值为 `false`，则表示拦截请求，并将用户重定向到登录页面。

- `postHandle` 方法在请求处理之后调用，但在视图被渲染之前调用，可以用于对请求进行处理或修改ModelAndView。

- `afterCompletion` 方法在请求处理之后调用，并在视图已经渲染之后调用，可以用于清理资源或执行一些后续操作。

在实现登录拦截器时，通常会在 `preHandle` 方法中进行登录验证，例如检查用户的session中是否包含登录信息。如果用户未登录，则可以通过 `httpServletResponse.sendRedirect` 方法将用户重定向到登录页面，例如：

public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
    Object user = request.getSession().getAttribute("user");
    if (user == null) {
        response.sendRedirect(request.getContextPath() + "/login");
        return false;
    }
    return true;
}

在上述示例中，通过 `getSession().getAttribute` 方法获取用户的登录信息，如果用户未登录，则通过 `sendRedirect` 方法将用户重定向到登录页面，并返回 `false`。如果用户已经登录，则返回 `true`，允许请求继续进行。

@Slf4j public class LoopCallInterceptor implements HandlerInterceptor { @Override public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { //调用接口 // 头部获取当前请求所经过且没结束请求的path列表 // 判定path列表中是否包含当前path //无则正常访问 并记录到列表中 //有则告警循环调用，并终止调用，返回异常 return true; //return HandlerInterceptor.super.preHandle(request, response, handler); } @Override public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception { //HandlerInterceptor.super.postHandle(request, response, handler, modelAndView); //正常结束接口 //获取头部path列表 //从path列表中删除当前path } }

This is a Java class named `LoopCallInterceptor` that implements the `HandlerInterceptor` interface. The `HandlerInterceptor` interface is part of the Spring MVC framework and provides a way to intercept and handle requests and responses for Spring MVC applications.

The purpose of the `LoopCallInterceptor` class is to prevent circular or recursive calls to a Spring MVC controller method, which can cause infinite loops and consume excessive resources.

The `preHandle` method is called before a request is handled by a controller method. It takes in the `HttpServletRequest` and `HttpServletResponse` objects, as well as the `Object` representing the handler method that will handle the request.

The `preHandle` method first checks if the current request path is already present in the request header path list. If it is not present, it adds the current request path to the path list and returns `true` to indicate that the request can proceed normally. If it is already present, it logs a warning message for the circular or recursive call and returns `false` to indicate that the request should be stopped.

The `postHandle` method is called after a request has been handled by a controller method. It takes in the `HttpServletRequest`, `HttpServletResponse`, `Object` representing the handler method, and the `ModelAndView` object that contains the view and model data returned by the handler method.

The `postHandle` method removes the current request path from the request header path list.

Note that the `HandlerInterceptor` interface has three methods, but the `LoopCallInterceptor` class only implements the `preHandle` and `postHandle` methods. The `afterCompletion` method is called after the response has been rendered, but before the response has been committed.