Executing javax.servlet.Filters in aws-serverless-java-container Jersey Apps

I work with a few Jersey web applications that are built on top of the aws-serverless-java-container.

We have a lot of shared libraries that solve things in a central way, and for a lot of our Java web services, these are built with java.servlet.Filters. To allow us to continue using these across multiple types of web services, we wanted to be able to integrate the Filters in, but couldn't quite work out how using Stefano Buliani's comment on this GitHub thread.

In the interest of Blogumentation, I've created jamietanna/jersey-servlet-filter-example to show how to do this.

We can do this by replacing the existing logic in StreamLambdaHandler and, as per Stefano's comment, we can construct the JerseyLambdaContainerHandler ourselves, and register our Filter for the URLs it needs to handle.

import com.amazonaws.serverless.proxy.AwsProxyExceptionHandler;
import com.amazonaws.serverless.proxy.AwsProxySecurityContextWriter;
import com.amazonaws.serverless.proxy.internal.servlet.AwsProxyHttpServletRequestReader;
import com.amazonaws.serverless.proxy.internal.servlet.AwsProxyHttpServletResponseWriter;
import com.amazonaws.serverless.proxy.internal.testutils.Timer;
import com.amazonaws.serverless.proxy.jersey.JerseyLambdaContainerHandler;
import com.amazonaws.serverless.proxy.model.AwsProxyRequest;
import com.amazonaws.serverless.proxy.model.AwsProxyResponse;
import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.runtime.RequestStreamHandler;

import org.glassfish.jersey.jackson.JacksonFeature;
import org.glassfish.jersey.server.ResourceConfig;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.EnumSet;
import javax.servlet.DispatcherType;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.FilterRegistration;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;

public class StreamLambdaHandler implements RequestStreamHandler {
    private static final ResourceConfig jerseyApplication = new ResourceConfig()
                                                             .packages("com.amazonaws.serverless.sample.jersey")
                                                             .register(JacksonFeature.class);
    private static final JerseyLambdaContainerHandler<AwsProxyRequest, AwsProxyResponse> handler
            = getAwsProxyHandler(); // required to simplify setup

    private static JerseyLambdaContainerHandler<AwsProxyRequest, AwsProxyResponse> getAwsProxyHandler() {
        // allow us to inject Filter(s) before we `initialize`
        JerseyLambdaContainerHandler<AwsProxyRequest, AwsProxyResponse> newHandler = new JerseyLambdaContainerHandler(
                AwsProxyRequest.class, AwsProxyResponse.class,
                new AwsProxyHttpServletRequestReader(),
                new AwsProxyHttpServletResponseWriter(), new AwsProxySecurityContextWriter(),
                new AwsProxyExceptionHandler(), jerseyApplication);
        // register all the filters we need
        addFilter(newHandler, new ExampleFilter(), "FilterName");
        // finalise setup
        newHandler.initialize();
        return newHandler;
    }

    private static void addFilter(JerseyLambdaContainerHandler<?, ?> handler, String filterName, Filter filterToAdd) {
        FilterRegistration.Dynamic registered = handler.getServletContext().addFilter(filterName, filterToAdd);
        registered.addMappingForUrlPatterns(EnumSet.of(DispatcherType.REQUEST), true, "/*"); // you could do something different here
    }

    // ...
}

Written by Jamie Tanna's profile image Jamie Tanna on , and last updated on .

Content for this article is shared under the terms of the Creative Commons Attribution Non Commercial Share Alike 4.0 International, and code is shared under the Apache License 2.0.

#java #jersey #blogumentation #aws #serverless.

This post was filed under articles.

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