What are ap­plic­a­tion servers?

To provide software to a client in a network, an ap­plic­a­tion server is a good choice for security and com­pat­ib­il­ity reasons. Dis­ad­vant­ages of an ap­plic­a­tion server include ad­di­tion­al costs and more serious con­sequences when bugs or other problems occur.

What is an ap­plic­a­tion server used for?

In ever larger systems, you need solutions that can shoulder data volume while still main­tain­ing the desired speed and serving access volume. In a client-server network, an ap­plic­a­tion server can be one such solution. An ap­plic­a­tion server usually hosts different ap­plic­a­tion programs and makes them available to clients. To do this, it uses server-side business logic to generate dynamic content and serve it to a client. Typical examples of software found on an ap­plic­a­tion server include office programs, address man­age­ment, corporate calendars and database access. Sensitive processes such as trans­ac­tions or au­then­tic­a­tions can also be carried out via an ap­plic­a­tion server.

What are the features of ap­plic­a­tion servers?

Ap­plic­a­tion servers offer various features to simplify and improve processes. A dis­tinc­tion is made between explicit and implicit features. In addition, there are other features that are more or less pro­nounced depending on the type of ap­plic­a­tion server. However, common features include:

Explicit features

• En­cap­su­la­tion of data sources
• In­ter­faces to other higher value services
• Asyn­chron­ous com­mu­nic­a­tion
• Pre­ser­va­tion of per­sist­ence
• Directory services
• Standards for the con­nec­tion of databases

Implicit features

Using a system with an ap­plic­a­tion server creates some implicit features that can provide benefits for all users. These include:

• Better scalab­il­ity without ad­di­tion­al modi­fic­a­tion of in­di­vidu­al ap­plic­a­tions
• Mon­it­or­ing
• Logging functions
• Cal­ib­ra­tion options
• Runtime man­age­ment
• Software lifecycle man­age­ment through patching, upgrading, delivery and de­ploy­ment

How does an ap­plic­a­tion server work?

To better un­der­stand the general function of an ap­plic­a­tion server, it’s important to first un­der­stand its place within a network. It ranks between in­di­vidu­al clients and the database. It receives HTTP requests and responds to them, but it can also issue servlet requests and process the cor­res­pond­ing responses. This is one of the main dif­fer­ences between an ap­plic­a­tion server and a web server. We elaborate on how the two models differ beyond that in our com­par­is­on of web servers and ap­plic­a­tion servers. An ap­plic­a­tion server works together with a web server in the following manner:

1. A user wants to visit a website. They open a browser and navigate to the website.
2. The HTTP request is sent to the web server that processes the request and returns the requested website to the client. This works as long as they’re static requests.
3. If an in­ter­act­ive tool is used instead, the procedure is the same, but the web server won’t output the response directly. Instead, it’s forwarded to the ap­plic­a­tion server.
4. The ap­plic­a­tion server receives the HTTP request and converts it into a servlet request.
5. It’s forwarded to the database.
6. The database server processes the request and sends a servlet response back to the ap­plic­a­tion server.
7. In the final step, the ap­plic­a­tion server sends the servlet format to the web server. This converts the response to HTTP and makes it available to the client.

What are the ad­vant­ages and dis­ad­vant­ages of ap­plic­a­tion servers?

If you’re thinking about using an ap­plic­a­tion server, it’s worth taking a look at the ad­vant­ages and dis­ad­vant­ages of such servers. The table below provides an overview:

What are the ad­vant­ages of ap­plic­a­tion servers?

An ap­plic­a­tion server offers numerous ad­vant­ages. They include:

Com­pat­ib­il­ity

By in­stalling an ap­plic­a­tion server in your network, you ensure all clients work with the same software version. As a result, all exchanged and stored data is com­pat­ible. If you do without an ap­plic­a­tion server, problems may arise due to missed updates or outdated software.

Security

The im­ple­ment­a­tion of an ap­plic­a­tion server can be ad­vant­age­ous for security reasons. For example, it prevents a direct con­nec­tion between a website and its own database. Malware attacks such as SQL injection programs can often be prevented.

Per­form­ance

Ap­plic­a­tion servers can improve overall per­form­ance. Per­form­ance im­prove­ments are par­tic­u­larly no­tice­able for large and/or fre­quently used software. Scaling options can help to improve per­form­ance as well as bundle and control access to the database.

Con­fig­ur­a­tion

Cent­ral­isa­tion via an ap­plic­a­tion server means con­fig­ur­a­tion doesn’t have to be performed on each in­di­vidu­al device. This sim­pli­fies con­fig­ur­a­tion and saves time and resources.

Scalab­il­ity

Due to numerous con­nec­tion pos­sib­il­it­ies with the database, higher scalab­il­ity is possible. This also ensures greater flex­ib­il­ity for users.

What are the dis­ad­vant­ages of ap­plic­a­tion servers?

However, there are a few dis­ad­vant­ages when using an ap­plic­a­tion server. The following are worth men­tion­ing:

Ad­di­tion­al costs

In­stall­a­tion and main­ten­ance of an ap­plic­a­tion server cost money and time. You should carefully consider whether the im­ple­ment­a­tion is necessary. If this is the case, costs should be con­sidered.

Possible delays

Delays may occur during the de­ploy­ment of an ap­plic­a­tion server. This is es­pe­cially true if the in­stall­a­tion is performed behind a firewall.

Demanding pro­gram­ming

Pro­gram­ming re­quire­ments are higher for an ap­plic­a­tion server. A little ex­per­i­ence and prior knowledge are therefore ad­vant­age­ous.

Bandwidth

When several large ap­plic­a­tions are used sim­ul­tan­eously and multiple users access them, this can have a negative impact on speed and overall per­form­ance.

Impact of problems and bugs

While bundling is an advantage of using an ap­plic­a­tion server, problems and bugs are much more pro­nounced as a result. Since numerous clients depend on a single source, problems with one piece of software affect several par­ti­cipants. Solutions for such problems are usually a bit more com­plic­ated.

What are examples of ap­plic­a­tion servers?

You can choose from numerous different ap­plic­a­tion servers. The best-known and most popular vendors and models include:

• Apache Geronimo: Suitable for Java EE
• Apache Tomcat: For Servlets and JavaS­erv­er Pages (JSP)
• Cold­Fu­sion: The oldest ap­plic­a­tion server
• GlassFish: Open-source solution for Java EE
• Jetty: Servlet and JSP container
• Resin: For Java and PHP5
• WEBrick: Solution based on Ruby
• Zope: An ap­plic­a­tion server based on Python