The Apache JServ Protocol (AJP) is a

binary protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchroniza ...

that can

proxy Proxy may refer to: * Proxy or agent (law), a substitute authorized to act for another entity or a document which authorizes the agent so to act * Proxy (climate), a measured variable used to infer the value of a variable of interest in climate ...

inbound requests from a

web server A web server is computer software and underlying hardware that accepts requests via HTTP (the network protocol created to distribute web content) or its secure variant HTTPS. A user agent, commonly a web browser or web crawler, initiate ...

through to an

application server An application server is a server that hosts applications or software that delivers a business application through a communication protocol. An application server framework is a service layer model. It includes software components available to a ...

that sits behind the web server. AJP is a highly trusted protocol and should never be exposed to untrusted clients, which could use it to gain access to sensitive information or execute code on the application server. It also supports some monitoring in that the web server can

ping Ping may refer to: Arts and entertainment Fictional characters * Ping, a domesticated Chinese duck in the illustrated book '' The Story about Ping'', first published in 1933 * Ping, a minor character in ''Seinfeld'', an NBC sitcom * Ping, a c ...

the application server. Web implementors typically use AJP in a load-balanced deployment where one or more front-end web servers feed requests into one or more application servers. Sessions are redirected to the correct application server using a routing mechanism wherein each application server instance gets a name (called a ''route''). In this scenario the web server functions as a

reverse proxy In computer networks, a reverse proxy is the application that sits in front of back-end applications and forwards client (e.g. browser) requests to those applications. Reverse proxies help increase scalability, performance, resilience and securi ...

for the application server. Lastly, AJP supports request attributes which, when populated with environment-specific settings in the reverse proxy, provides for secure communication between the reverse proxy and application server. AJP runs in

Apache HTTP Server The Apache HTTP Server ( ) is a free and open-source cross-platform web server software, released under the terms of Apache License 2.0. Apache is developed and maintained by an open community of developers under the auspices of the Apache So ...

1.x using the plugin and in Apache 2.x using , and proxy balancer modules together. Other web server implementations exist for:

lighttpd lighttpd (pronounced "lighty") is an open-source web server optimized for speed-critical environments while remaining standards-compliant, secure and flexible. It was originally written by Jan Kneschke as a proof-of-concept of the c10k problem � ...

1.4.59,

nginx Nginx (pronounced "engine x" ) is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache. The software was created by Igor Sysoev and publicly released in 2004. Nginx is free and open-source software ...

Grizzly The grizzly bear (''Ursus arctos horribilis''), also known as the North American brown bear or simply grizzly, is a population or subspecies of the brown bear inhabiting North America. In addition to the mainland grizzly (''Ursus arctos horri ...

2.1, and the

Internet Information Services Internet Information Services (IIS-pronounced 2S, formerly Internet Information Server) is an extensible web server software created by Microsoft for use with the Windows NT family. IIS supports HTTP, HTTP/2, HTTPS, FTP, FTPS, SMTP and NNTP. ...

Web container A web container (also known as a servlet container; and compare "webcontainer" ) is the component of a web server that interacts with Jakarta Servlets. A web container is responsible for managing the lifecycle of servlets, mapping a URL to a par ...

application servers supporting AJP include:

Apache Tomcat Apache Tomcat (called "Tomcat" for short) is a free and open-source implementation of the Jakarta Servlet, Jakarta Expression Language, and WebSocket technologies. It provides a "pure Java" HTTP web server environment in which Java code can also ...

WildFly WildFly, formerly known as JBoss AS, or simply JBoss, is an application server written by JBoss, now developed by Red Hat. WildFly is written in Java and implements the Java Platform, Enterprise Edition (Java EE) specification. It runs on multip ...

(formerly JBoss AS), and

GlassFish GlassFish is an open-source Jakarta EE platform application server project started by Sun Microsystems, then sponsored by Oracle Corporation, and now living at the Eclipse Foundation and supported by Payara, Oracle and Red Hat. The supported v ...

History

Alexei Kosut originally developed the Apache JServ Protocol in July 1997 but the version 1.0 specification was published later on July 29, 1998. He also wrote the first implementations of it in the same month, with the releases of the Apache JServ servlet engine 0.9 and the Apache mod_jserv 0.9a (released on July 30, 1997). The specification was updated to version 1.1 on September 9, 1998. Also in 1998, a revamped protocol was created and published in specification versions 2 and 2.1, however it was never adopted. In 1999,

Sun Microsystems Sun Microsystems, Inc. (Sun for short) was an American technology company that sold computers, computer components, software, and information technology services and created the Java programming language, the Solaris operating system, ZFS, the ...

donated their JavaServer Web Development Kit (JSWDK; codenamed Tomcat) reference implementation to

Apache Software Foundation The Apache Software Foundation (ASF) is an American nonprofit corporation (classified as a 501(c)(3) organization in the United States) to support a number of open source software projects. The ASF was formed from a group of developers of the A ...

. This became

version 3.0, the successor to JSWDK 2.1, and derailed further development of Apache JServ servlet engine and AJP towards support of

Java servlet A Jakarta Servlet (formerly Java Servlet) is a Java software component that extends the capabilities of a server. Although servlets can respond to many types of requests, they most commonly implement web containers for hosting web application ...

API version 2.1. The current specification remains at version 1.3, however there is a published extension proposal as well as an archived experimental 1.4 proposal.

References

External links

The Apache Tomcat Connector - AJP Protocol Reference
AJPv13

Dan Milstein, December 2000. * BonCode IIS implementation of AJP {{Web interfaces JServ

History

See also

References

External links