What is the difference between filters and interceptors in spring boot?

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In Spring Boot, both filters and interceptors are used to manipulate HTTP requests and responses, but they operate at different levels and have distinct purposes.

Filters:

  • Definition:
  • Filters are part of the Servlet API and are used to preprocess and postprocess HTTP requests and responses. They are defined in the javax.servlet package.
  • Scope:
  • Operate at the servlet level, meaning they can affect all requests and responses passing through a servlet, regardless of the framework in use.
  • Usage:
  • Typically used for tasks such as logging, authentication, input validation, and modifying request and response objects.
  • Configuration:
  • Filters are configured in the web.xml file or via Java configuration using FilterRegistrationBean in Spring Boot.
  • Order:
  • Filters are executed in the order defined in the configuration. You can specify the order using the @Order annotation or by setting the order in FilterRegistrationBean.
  • Example:

```java

@Component

@Order(1)

public class MyFilter implements Filter {

@Override

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)

throws IOException, ServletException {

// Pre-processing logic

System.out.println("Request received at: " + new Date());

  // Pass the request and response to the next filter or servlet
  chain.doFilter(request, response);
// Post-processing logic  

System.out.println("Response sent at: " + new Date());

}

@Override

public void init(FilterConfig filterConfig) throws ServletException {

// Initialization logic

}

@Override

public void destroy() {

// Cleanup logic

}

}

```

Interceptors:

  • Definition:
  • Interceptors are part of the Spring framework and are used to intercept HTTP requests and responses within the Spring MVC context. They are defined in the org.springframework.web.servlet package.
  • Scope:
  • Operate specifically within the Spring MVC framework, allowing for pre-processing and post-processing of requests handled by Spring MVC controllers.
  • Usage:
  • Typically used for tasks such as handling cross-cutting concerns like logging, authentication, authorization, and modifying or inspecting the model and view objects.
  • Configuration:
  • Interceptors are configured in Spring’s application context through Java configuration or XML configuration by implementing HandlerInterceptor and registering it via WebMvcConfigurer.
  • Order:
  • Interceptors are executed in the order specified in the addInterceptors method in the WebMvcConfigurer implementation.
  • Example:

```java

@Component

public class MyInterceptor implements HandlerInterceptor {

@Override

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

throws Exception {

// Pre-processing logic before the handler method is invoked

System.out.println("Pre-handle logic");

return true; // Continue processing

}

@Override

public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,

ModelAndView modelAndView) throws Exception {

// Post-processing logic after the handler method is invoked

System.out.println("Post-handle logic");

}

@Override

public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)

throws Exception {

// Cleanup logic after the request has been completed

System.out.println("After completion logic");

}

}

@Configuration

public class WebConfig implements WebMvcConfigurer {

@Override

public void addInterceptors(InterceptorRegistry registry) {

registry.addInterceptor(new MyInterceptor());

}

}

```

Summary of Differences:

  • Level of Operation:
  • Filters: Operate at the servlet level and are part of the Servlet API.
  • Interceptors: Operate within the Spring MVC framework.
  • Usage Context:
  • Filters: Can be used with any servlet-based application, not limited to Spring.
  • Interceptors: Specifically designed for handling requests and responses in Spring MVC applications.
  • Configuration:
  • Filters: Configured via web.xml or FilterRegistrationBean.
  • Interceptors: Configured via WebMvcConfigurer in Spring Boot.
  • Order and Scope:
  • Filters: Configured globally and executed in the order defined in the configuration.
  • Interceptors: Configured specifically for Spring MVC and executed based on the order defined in the addInterceptors method.

Both filters and interceptors serve different purposes and can be used together to achieve comprehensive request and response handling in a Spring Boot application.