ssm整合（七）：拦截器参数和拦截器链

• 拦截器参数

@Component
//定义拦截器类，实现HandlerInterceptor接口
//注意当前类必须受Spring容器控制
public class ProjectInterceptor implements HandlerInterceptor {

    @Override
    //原始方法调用前执行的内容
    //返回值类型可以拦截控制的执行，true放行，false终止
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        // 获取请求头中的数据
        String contentType = request.getHeader("Content-Type");
        // 获取要操作的那个方法
        HandlerMethod hm = (HandlerMethod)handler;
        System.out.println("preHandle..."+contentType);
        return true;
    }

    @Override
    //原始方法调用后执行的内容
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle...");
    }

    @Override
    //原始方法调用完成后执行的内容
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion...");
    }

}

• 配置多个拦截器

@Component
public class ProjectInterceptor2 implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("preHandle...222");
        return false;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle...222");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion...222");
    }

}

@Configuration
@ComponentScan({"com.itheima.controller"})
@EnableWebMvc
public class SpringMvcConfig implements WebMvcConfigurer {

    @Autowired
    private ProjectInterceptor projectInterceptor;

    @Autowired
    private ProjectInterceptor2 projectInterceptor2;

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        //配置多拦截器
        registry.addInterceptor(projectInterceptor).addPathPatterns("/books","/books/*");
        registry.addInterceptor(projectInterceptor2).addPathPatterns("/books","/books/*");
    }

}

• 拦截器执行顺序

• 当2个拦截器都设置为true时，执行顺序如下
  

• 将第1个拦截器设置为false，第2个拦截器设置为true
  

• 拦截器的运行顺序参照拦截器的添加顺序

• 例如配置3个拦截器，执行顺序如下
  

• 配置3个拦截器，第1个设置为false，第2、3设置为true，则只执行第1个拦截器的preHandle方法

• 当3个拦截器都设置为false时，则执行3个拦截器的前置，3个postHandle都不执行，最后执行第2个和第1个拦截器的afterCompletion
  

• 当第1个和第2个拦截器设置为false时，则执行前2个拦截器的前置，3个postHandle都不执行，最后执行第1个拦截器的afterCompletion
  

• 当第1个拦截器设置为false时，则执行第1个拦截器的前置，3个postHandle都不执行，最后3个拦截器的afterCompletion也都不会执行