---
title: "JSR223 Groovy Playground & Code Builder"
description: "Lint JMeter-specific Groovy anti-patterns, inspect JSR223 bindings, and generate ready-to-paste JMX elements from curated recipes or custom scripts."
url: https://docs.jmeter.ai/tools/groovy-builder/
lastUpdated: 2026-10-01
source: docs.jmeter.ai
---

# JSR223 Groovy Playground & Code Builder

## Why Groovy over BeanShell

JMeter supports Groovy through JSR223 compilation caching, while BeanShell is interpreted and substantially slower in a hot sampling path. Groovy also provides modern Java interoperability, mature JSON support, and access to JMeter’s documented script bindings.

This page is a **builder and static analyzer**. Groovy cannot execute in the browser. The tool inspects source text for JMeter-specific pitfalls and generates files for you to review and run in JMeter; it does not validate runtime types, external classes, network access, or script behavior.

## Binding availability

Every JSR223 element exposes the common bindings `log`, `Label`, `FileName`, `Parameters`, `args`, `ctx`, `vars`, `props`, and `OUT`. Element-specific bindings differ:

| Element | Available bindings |
| --- | --- |
| `JSR223 Sampler` | `log`, `Label`, `FileName`, `Parameters`, `args`, `ctx`, `vars`, `props`, `OUT`, `SampleResult`, `sampler` |
| `JSR223 PreProcessor` | `log`, `Label`, `FileName`, `Parameters`, `args`, `ctx`, `vars`, `props`, `OUT`, `sampler` |
| `JSR223 PostProcessor` | `log`, `Label`, `FileName`, `Parameters`, `args`, `ctx`, `vars`, `props`, `OUT`, `sampler`, `prev` |
| `JSR223 Assertion` | `log`, `Label`, `FileName`, `Parameters`, `args`, `ctx`, `vars`, `props`, `OUT`, `SampleResult`, `AssertionResult`, `prev`, `sampler` |
| `JSR223 Timer` | `log`, `Label`, `FileName`, `Parameters`, `args`, `ctx`, `vars`, `props`, `OUT`, `sampler` |
| `JSR223 Listener` | `log`, `Label`, `FileName`, `Parameters`, `args`, `ctx`, `vars`, `props`, `OUT`, `sampleResult`, `prev`, `sampleEvent`, `sampler` |

Binding names are case-sensitive. For example, `SampleResult` is available in a Sampler or Assertion, while lowercase `sampleResult` and `sampleEvent` belong to a Listener. `prev` is available to PostProcessors, Assertions, and Listeners, but not PreProcessors or Timers; `sampler` is available to all six element types, including Listeners.

## Anti-patterns this linter catches

| Rule ID | Severity | What it catches |
| --- | --- | --- |
| `EMPTY_SCRIPT` | Error | Blank code |
| `THREAD_SLEEP` | Error | `Thread.sleep(...)` or `sleep(...)` blocking a JMeter worker thread |
| `JMETER_VAR_INTERPOLATION` | Warning | `${name}` expansion without a preceding Groovy local declaration |
| `SYSTEM_OUT` | Warning | `System.out`, `System.err`, or statement-level `println(...)` |
| `NEW_RANDOM_PER_CALL` | Info | A new `Random` instance created on each invocation |
| `REGEX_COMPILE_IN_SCRIPT` | Info | `Pattern.compile(...)` in the hot script path |
| `UNAVAILABLE_BINDING` | Error | A known binding used by the wrong JSR223 element type |
| `BEANSHELL_IMPORT` | Error | BeanShell imports or API references inside Groovy |
| `LEGACY_JSONSLURPER_CLASSIC` | Info | `JsonSlurperClassic` instead of `JsonSlurper` |
| `PROPS_MUTATION_IN_LOOP_HOT_PATH` | Info | Writes to shared JMeter properties with `props.put(...)` |
| `SCRIPT_TOO_LONG` | Warning | Inline code over 200,000 characters that belongs in a `.groovy` file |

For dynamic JMeter values, prefer `vars.get("name")` or `props.get("name")`. Substitution such as `${token}` happens before Groovy compilation, can create a new compiled script for each value, and can break syntax when data contains quotes or other special characters.

## How to use the generated JMX snippet

1. Select the JSR223 element that matches where the script should run.
2. Fix error-level binding or scripting findings.
3. Copy the generated element and its following `<hashTree/>`.
4. Paste it under the target element’s `<hashTree>` in the `.jmx`, or use **JMeter GUI → Edit → Paste**.
5. Open the plan in JMeter, confirm the tree location, and run a one-user smoke test with assertions before applying load.

The generated element uses `TestBeanGUI`, Groovy, and a non-empty `cacheKey` so JMeter can cache compiled scripts. Downloading the `.groovy` variant is useful when scripts are shared across plans or maintained in source control; set that file through the JSR223 **FileName** field in JMeter.

## Use via MCP

Connect an MCP-compatible agent:

```bash
claude mcp add jmeter-docs https://docs.jmeter.ai/api/mcp --transport http
```

Ask the agent to call `get_jsr223_recipe` by recipe name or category to retrieve the curated JWT, HMAC, dynamic header, JSON extraction, and custom logging examples used by this builder. For your own script, call `lint_groovy_script` with the code and JSR223 element type to receive the same findings, binding analysis, and optional ready-to-paste JMX element XML.