Java API Gateways combine high performance with a broad feature set and excellent integration capabilities. They are often faster in real workloads than expected and benefit from the rich Java ecosystem.
This article explains what a Java API Gateway is, why it is special and what are the limitations.
A Java API Gateway is an API gateway built entirely in Java, leveraging the extensive libraries of the Java ecosystem. Unlike gateways based on nginx that use embedded scripting engines for plugins and API functionality, a Java gateway is homogeneously implemented in Java. All components of a Java gateway from the HTTP protocol to OpenAPI validators are made with Java. This unified approach makes the gateway easier to extend, debug, and integrate with enterprise infrastructure. It also allows developers to configure and adapt core behavior without switching between languages or runtimes.
Well-known Java API gateways include Gravitee, Membrane, and Spring Cloud Gateway.
Java provides a mature platform and a vast ecosystem of libraries. Many gateway features can be implemented simply by wrapping existing, battle-tested Java libraries as plugins. This approach is typically faster and less error-prone than writing Lua scripts for a C-based reverse proxy such as Nginx.
Over the last 15+ years, gateways from multiple vendors have proven that Java is both reliable and performant in production.
A key advantage is legacy integration. Large organizations still rely on XML and SOAP-based Web Services, and Java offers a wealth of libraries for handling them. This makes it straightforward for Java API gateways to provide strong support for XML processing and Web Services integration.
Modern JVMs are highly optimized. While raw micro-benchmarks may still favor native C, Rust, or Go implementations, real-world workloads such as OpenAPI validation, authentication, and JSON/XML transformation often allow Java gateways to excel thanks to mature libraries and JIT optimizations.
With features enabled, Java-based gateways can match or even outperform solutions that combine native code with interpreted scripts. Most API gateways rely on C-based reverse proxies for raw HTTP routing, which is indeed fast. However, once you add plugins written in another language such as Lua, the cross-runtime overhead reduces performance. A gateway implemented homogeneously on one platform like Java avoids this overhead and can deliver more consistent throughput.
A higher memory footprint is the trade-off for Java’s ecosystem and extensibility. Typical Java gateways e.g., Membrane need 300–400 MByte for operation. If you deploy hundreds of sidecar micro-gateways, this may be too much overhead, but for a few central gateways it’s negligible.
Native image compilation (e.g., GraalVM) can further reduce startup and memory in specific scenarios.
Question: Can I run a Java API Gateway in Docker?
Answer: Yes. Java gateways run well in containers. Image size and memory usage are manageable for most deployments.
Question: What is the best deployment option for a Java API Gateway?
Answer: There is no single preferred option. A Java API Gateway can run in a container, directly on the Java Virtual Machine, inside a Java web server such as Tomcat, in an OSGi runtime, or on operating systems including Linux, Windows, and macOS.
Question: What is the best deployment for a Java API Gateway
Answer: There is no preference. You can run the gateways in a container, a Java virtual machine, a Java Web Server like Tomcat, an OSGi runtime, on linux, windows, mac...
Question: How do I extend a Java gateway?
Answer: You can extend a Java gateway with Java or JVM languages such as Groovy and Kotlin, or by using expression languages. See the documentation for examples.
Membrane API Gateway is a typical Java-based gateway with API security, OpenAPI validation, and legacy XML/SOAP support. Start with the Quick Start or browse the API Gateway Cookbook.
Java is a registered trademark of Oracle and/or its affiliates. Membrane API Gateway is an open-source project by predic8 and is not affiliated with, endorsed by, or sponsored by Oracle.