Spring MVC (Servlet) Filter
Below are the Servlet Filter methods.
ServletFilter methods:
- destroy(): When the filter is removed from the service, the destruct() function is only called once.
- init(FilterConfig config): This function, init(FilterConfig config), is only used once. It serves as the filter’s initialization.
- doFilter method (): Every time a user sends a request to any resource that the filter is mapped to, the doFilter method () is called. It is applied to jobs involving filtration.
Setting Up a (Servlet)Filter
First, we need to develop a class that implements the javax.servlet in order to establish a filter.Interface for filters:
Java
import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.stereotype.Component; import javax.servlet.Filter; import javax.servlet.FilterChain; import javax.servlet.FilterConfig; import javax.servlet.ServletException; import javax.servlet.ServletRequest; import javax.servlet.ServletResponse; import java.io.IOException; @Componentpublic class LogFilter implements Filter { private Logger logger = LoggerFactory.getLogger(LogFilter.class); @Override public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { // Log information about the incoming request logger.info("Hello from: " + request.getLocalAddr()); // Continue with the filter chain chain.doFilter(request, response); } // Other methods of the Filter interface (init, destroy) can be implemented if needed. } |
Spring MVC – Servlet Filter vs Handler Interceptor
Filter is a Java class that is executed by the Servlet Container for each incoming HTTP request and each HTTP response. Filter is associated with the Servlet API, while HandlerIntercepter is unique to Spring. Only after Filters will Interceptors begin to operate. HandlerInterceptors are appropriate for fine grained pre-processing duties (authorization checks, etc.).
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