Implementing Zuul Logging Filter

In the previous section, we have discussed common functionality that is implemented in API Gateway. We have the Zuul server ready that acts as API Gateway.

In this section, we will implement the logging functionality in the Zuul API Gateway.

Let's implement the logging in the Zuul API Gateway.

Step 1: In the netflix-zuul-api-gateway-server project, create a new class file with the name ZuulLoggingFilter.

Step 2: Add an annotation @Componenet.

Step 3: Extend the ZuulFilter class. There are some abstract methods in the ZuulFilter class. These abstract methods must be implemented in the ZuulLoggingFilter class.

Step 4: Move your cursor over the ZuulLoggingFilter class. It suggests two quick fixes, as shown in the following image. Click on the Add unimplemented methods. We get the default implementation of all the abstract methods of the ZuulFilter class.

ZuulFilter class has four abstract methods that are listed below:

shouldFilter(): The shouldFilter() method checks the request and decides whether filter to be executed or not.
run(): The run() method invokes, if both !isFilterDisabled() and shouldFilter() methods returns true.
filterType(): The filterType() method classify a filter by type. There are four types of standard filters in Zuul: pre for pre-routing filtering, route for routing to an origin, post for post-routing filters, and error for error handling. Zuul also supports a static type for static responses. Any filter type can be created or added and run by calling the method runFilters(type).
filterOrder(): The filter order must be defined for a filter. Filters may have the same filter order if the precedence is not important for the filters. The filter order does not need to be sequential.

Step 5: Create the Logger class object and invoke getLogger() method to create a logger.

Remember: Import Logger class of org.slf4j package.

Step 6: Implement the logic in the run() method.

public Object run() throws ZuulException
{
//getting the current HTTP request that is to be handle
HttpServletRequest request=RequestContext.getCurrentContext().getRequest();
//printing the detail of the request
logger.info("request -> {} request uri-> {}", request, request.getRequestURI());
return null;
}

ZuulLoggingFilter.java

package com.javatpoint.microservices.netflixzuulapigatewayserver;
import javax.servlet.http.HttpServletRequest;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
import com.netflix.zuul.ZuulFilter;
import com.netflix.zuul.context.RequestContext;
import com.netflix.zuul.exception.ZuulException;
@Component
public class ZuulLoggingFilter extends ZuulFilter
{
//creating Logger object
private Logger logger=LoggerFactory.getLogger(this.getClass());
@Override
public booleanshouldFilter() 
{
return true; //executing filter for every request
}
//log the content of the request
@Override
public Object run() throws ZuulException
{
//getting the current HTTP request that is to be handle
HttpServletRequest request=RequestContext.getCurrentContext().getRequest();
//prints the detail of the requestin the log
logger.info("request -> {} request uri-> {}", request, request.getRequestURI());
return null;
}
@Override
public String filterType() 
{
return "pre"; //intercept all the request before execution
}
@Override
public intfilterOrder() 
{
return 1; //setting filter order to 1
}
}

In the next step, we will see how to intercept the request using Zuul.

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