## Building Tomcat

### Table of Contents

- Introduction
- Download a Java Development Kit (JDK)
- Install Apache Ant
- Obtain the Tomcat source code
- Configure download area
- Building Tomcat
- Building with Eclipse
- Building with other IDEs

### Introduction

Building Apache Tomcat from source is very easy, and is the first step to contributing to Tomcat. The complete and comprehensive instructions are provided in the file BUILDING.txt. The following is a quick step by step guide.

### Download a Java Development Kit (JDK)

Building Apache Tomcat requires a JDK (version 17) or later to be installed. You can download one from https://adoptium.net/temurin/releases or another JDK vendor.

IMPORTANT: Set an environment variable JAVA_HOME to the pathname of the directory into which you installed the JDK release.

### Install Apache Ant

Download a binary distribution of Ant 1.10.2 or later from here.

Unpack the binary distribution into a convenient location so that the Ant release resides in its own directory (conventionally named `apache-ant-[version]`). For the remainder of this guide, the symbolic name `${ant.home}` is used to refer to the full pathname of the Ant installation directory.

IMPORTANT: Create an ANT_HOME environment variable to point the directory `${ant.home}`, and modify the PATH environment variable to include directory `${ant.home}/bin` in its list. This makes the `ant` command line script available, which will be used to actually perform the build.

### Obtain the Tomcat source code

Tomcat Git repository URL: https://github.com/apache/tomcat

Tomcat source packages: https://tomcat.apache.org/download-10.cgi.

Clone the source repository using Git, selecting a tag for released version or main for the current development code, or download and unpack a source package. For the remainder of this guide, the symbolic name `${tomcat.source}` is used to refer to the location where the source has been placed.

### Configure download area

Building Tomcat involves downloading a number of libraries that it depends on. It is strongly recommended to configure download area for those libraries.

By default the build is configured to download the dependencies into the `${user.home}/tomcat-build-libs` directory. You can change this (see below) but it must be an absolute path.

The build is controlled by creating a `${tomcat.source}/build.properties` file. It can be used to redefine any property that is present in `build.properties.default` and `build.xml` files. The `build.properties` file does not exist by default. You have to create it.

The download area is defined by property `base.path`. For example:

    # ----- Default Base Path for Dependent Packages -----
    # Replace this path with the directory path where
    # dependencies binaries should be downloaded.
    base.path=/home/me/some-place-to-download-to

Different versions of Tomcat are allowed to share the same download area.

Another example:

    base.path=${user.dir}/../libraries-tomcat10.1

Users who access the Internet through a proxy must use the properties file to indicate to Ant the proxy configuration:

    # ----- Proxy setup -----
    proxy.host=proxy.domain
    proxy.port=8080
    proxy.use=on

### Building Tomcat

Use the following commands to build Tomcat:

`cd ${tomcat.source}`
`ant`

Once the build has completed successfully, a usable Tomcat installation will have been produced in the `${tomcat.source}/output/build` directory, and can be started and stopped with the usual scripts.

### Building with Eclipse

IMPORTANT: This is not a supported means of building Tomcat; this information is provided without warranty :-). The only supported means of building Tomcat is with the Ant build described above. However, some developers like to work on Java code with a Java IDE, and the following steps have been used by some developers.

NOTE: This will not let you build everything under Eclipse; the build process requires use of Ant for the many stages that aren't simple Java compilations. However, it will allow you to view and edit the Java code, get warnings, reformat code, perform refactorings, run Tomcat under the IDE, and so on.

WARNING: Do not forget to create and configure `${tomcat.source}/build.properties` file as described above before running any Ant targets.

Sample Eclipse project files and launch targets are provided in the `res/ide-support/eclipse` directory of the source tree. The instructions below will automatically copy these into the required locations.

An Ant target is provided as a convenience to download all binary dependencies, and to create the Eclipse project and classpath files in the root of the source tree.

`cd ${tomcat.source}`
`ant ide-eclipse`

Start Eclipse and create a new Workspace.

Use File->Import and choose Existing Projects into Workspace. From there choose the root directory of the Tomcat source tree (`${tomcat.source}`) and import the Tomcat project located there.

`start-tomcat` and `stop-tomcat` launch configurations are provided in `res/ide-support/eclipse` and will be available in the Run->Run Configurations dialog. Use these to start and stop Tomcat from Eclipse. If you want to configure these yourself (or are using a different IDE) then use `org.apache.catalina.startup.Bootstrap` as the main class, `start`/`stop` etc. as program arguments, and specify `-Dcatalina.home=...` (with the name of your build directory) as VM arguments.

Tweaking a few formatting preferences will make it much easier to keep consistent with Tomcat coding conventions (and have your contributions accepted):

Java -> Code Style -> Formatter -> Edit... | Tab policy: Spaces only Tab and Indentation size: 4
General -> Editors -> Text Editors | Displayed tab width: 2 Insert spaces for tabs Show whitespace characters (optional)
XML -> XML Files -> Editor | Indent using spaces Indentation size: 2
Ant -> Editor -> Formatter | Tab size: 2 Use tab character instead of spaces: unchecked

The recommended configuration of Compiler Warnings is documented in `res/ide-support/eclipse/java-compiler-errors-warnings.txt` file.

### Building with other IDEs

The same general approach should work for most IDEs; it has been reported to work in IntelliJ IDEA, for example.