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SpringBoot配置拦截器的示例

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在SpringBoot中配置拦截器,主要有下面两个步骤:

1、继承接口 HandlerInterceptor,根据需要重写其中的三个类。

2、在配置类中注入该类。

public class MyInterceptor implements HandlerInterceptor {

  //controller执行之前
  @Override
  public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
    System.out.println("preHandler......");
    return true;
  }

  //执行完controller执行之后、视图渲染前调用,可以在该方法里获取或者修改model
  @Override
  public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
    System.out.println("postHandler......");
  }

  //一般用于清理资源
  @Override
  public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
    System.out.println("afterCompletion......");
  }
}
@Configuration
public class WebMvcConfig implements WebMvcConfigurer {

  @Override
  public void addInterceptors(InterceptorRegistry registry) {
    //1、全部拦截
//    registry.addInterceptor(myInterceptor()).addPathPatterns("/**");
    //2、拦截指定路径
    registry.addInterceptor(myInterceptor()).addPathPatterns("/hello");
  }

  @Bean
  MyInterceptor myInterceptor(){
    return new MyInterceptor();
  }

}

写个controller测试一下

@RestController
public class HelloController {

  @RequestMapping("/hello")
  public String hello(){
    System.out.println("hello");
    return "hello";
  }

  @RequestMapping("/world")
  public String world(){
    System.out.println("world");
    return "world";
  }
}

测试结果:

preHandler......
hello
postHandler......
afterCompletion......
world

SpringBoot中还有一终拦截器,WebRequestInterceptor

public class MyWebRequestInterceptor implements WebRequestInterceptor {
  @Override
  public void preHandle(WebRequest webRequest) throws Exception {

  }

  @Override
  public void postHandle(WebRequest webRequest, ModelMap modelMap) throws Exception {

  }

  @Override
  public void afterCompletion(WebRequest webRequest, Exception e) throws Exception {

  }
}

和HandlerInterceptor比较相似,但是可以发现,该拦截器的preHandler返回值为空,说明该方法并不影响后面方法的执行。那么这个拦截器存在的目的是什么呐?

点进WebRequest:

public interface WebRequest extends RequestAttributes {
  @Nullable
  String getHeader(String var1);

  @Nullable
  String[] getHeaderValues(String var1);

  Iterator<String> getHeaderNames();

  @Nullable
  String getParameter(String var1);

  @Nullable
  String[] getParameterValues(String var1);

  Iterator<String> getParameterNames();

  Map<String, String[]> getParameterMap();

  Locale getLocale();

  String getContextPath();

  @Nullable
  String getRemoteUser();

  @Nullable
  Principal getUserPrincipal();

  boolean isUserInRole(String var1);

  boolean isSecure();

发现对reques请求中参数做了进一步处理(@Nullable表示可以为空),更加的方便调用。所以两个拦截器的侧重点不同,HandlerInterceptor功能较为强大,可以拦截请求,可以实现WebRequestInterceptor的所有功能,只是要写的逻辑代码要多一点。更而WebRequestInterceptor倾向于简化获取request参数的过程以及预设参数供后面的流程使用。

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