> ## Building your software when using the SDK

> Learn how to build and instrument Java applications with the Antithesis SDK.

> Fetch the complete documentation index at: https://antithesis.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

---

When you use the Antithesis Java SDK, you may want to adjust your build/deploy process as follows:

1. Enable [assertion cataloging](/docs/reference/instrumentation/coverage_instrumentation/) and [coverage instrumentation](/docs/reference/instrumentation/coverage_instrumentation/) for your software.
2. [Start your JARs](#starting-your-jars) in a specific way.

### Enable assertion cataloging

Assertion cataloging is required when using SDK assertions.

Place directories, files, or symlinks to the code you want cataloged in the directory `/opt/antithesis/catalog/` within your container image. Generally, this means any `.jar` and/or `.war` files.

Antithesis will recursively instrument and catalog all the code in this directory, including any JARs or WARs. Instrumentation and cataloging for separate `.class` files is not currently supported.

> **Note**
>
> Antithesis will follow symlinks one level deep while resolving the path to the cataloging directory. Do not symlink to a symlink.

### Enable coverage instrumentation

Antithesis can automatically instrument compiled Java code by means of bytecode weaving. No changes to your source code or build system are required.

Instrumentation is enabled the same way as assertion cataloging, so if you enabled assertion cataloging, no additional steps are required.

Just remember Antithesis will follow only one symlink deep into each item in `/opt/antithesis/catalog/`.

#### Example cataloging directory:

```bash
> ln -s /usr/share/my_app /opt/antithesis/catalog

> ls -lAh /opt/antithesis/catalog
lrwxrwxrwx  1 me users 4 Apr  8 17:32 /opt/antithesis/catalog -> /usr/share/my_app

> ls -lAh /opt/antithesis/catalog/
-rwxr-xr-x  1 me users  20K Apr  8 17:33 dotnet_file.dll
lrwxrwxrwx  1 me users 27 Apr  8 17:52 more_files -> /opt/my_project/java_files
-rwxr-xr-x  1 me users  10K Apr  8 17:33 python_script.py

> ls -lA /opt/antithesis/catalog/more_files/
-rw-r--r--  1 me users  16K Apr  8 17:51 main.jar
lrwxrwxrwx  1 me users  16K Apr  8 17:51 my_other.jar -> /some/other/place.jar
```

Based on the example above, the following files would be instrumented:

- `dotnet_file.dll`
- `python_script.py`
- `main.jar`

Ignored files:

- `my_other.jar` - this will be ignored as we already encountered one symlink when traversing down from `opt/antithesis/catalog/more_files`.

> **Note**
>
> Antithesis will, by default, act upon every language it supports in the cataloging directory: ([Java](/docs/reference/sdk/java/how_to_build_with_sdk/#enable-assertion-cataloging), [Python](/docs/reference/sdk/python/), [JavaScript](/docs/reference/sdk/javascript_sdk/), [.NET](/docs/reference/sdk/dotnet/instrumentation/)), not just Java.

If you need help with instrumentation, contact us at support@antithesis.com or [ask on our Discord](https://discord.com/invite/antithesis).

### Enable symbolization

Antithesis automatically gathers the symbol information from your code. You don't need to separately provide symbol files.

### Starting your JARs

When running assertion cataloging and instrumentation, Antithesis create a additional dependencies for the application, and inject the dependency JARs at the same path as the main application JAR, so you will need to add that folder to your classpath.

For example, if you are starting the app in `/opt/app/bin/sample_app.jar`, then we will require `/opt/app/bin/*` to be on the classpath.

This means invoking your app JAR like:

```bash
java -ea -cp "/opt/app/bin/*" com.your_org.sample_app.controller.Method
```

This ensures that you are scanning the classpath that includes the Antithesis-injected dependencies, as well as invoking the main program method.

The following invocation will not work:

```bash
java -jar /opt/app/bin/sample_app.jar
```