---
title: "Binding rules"
slug: "oapps-iga-binding-rules-8-4-1"
updated: 2026-10-20T11:53:02Z
published: 2026-10-20T11:53:02Z
canonical: "docs.onespan.com/oapps-iga-binding-rules-8-4-1"
excludeFromSearch: true
---

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

# Binding rules

The Shielding Tool rule files support the following binding-related options:

| Option | Description |
| --- | --- |
| `bind` | Select classes or members to include in the binding process. |
| `unbind` | Select classes or members to exclude from binding (i.e., leave their values in the app code). |
| `untouchable` | Alias of `unbind`. |
| `bindingStyle` | Define a binding configuration to use in conjunction with `bind`. |
| `bindingCache` | Specify the percentage of pull bindings to keep in a Least Recently Used cache. |

Note that you would rarely need to include a specific value in the binding process, as App Shielding will most likely bind the value, regardless. If you are using reflection, however, the affected classes and members could cause issues and should be manually marked as `untouchable` or `unbind`.

Binding can also affect performance, especially for classes and methods that are frequently called during runtime. If performance becomes an issue, consider excluding heavily used classes/methods from the binding process.

## Examples

The following example excludes binding in `MyClass`:

```plaintext
unbind class com.example.MyClass;
```

The following example excludes binding in any class under the `com.example` package:

```plaintext
unbind class com.example.*;
```

The following example excludes binding in any class that implements `MyInterface`:

```plaintext
unbind class * implements com.example.MyInterface;
```

The following example excludes binding in any class that extends `MyBaseClass`:

```plaintext
unbind class * extends com.example.MyBaseClass;
```

The following example excludes binding to the `myField` field under `MyClass`:

```plaintext
match class com.example.MyClass {
    unbind java.lang.String myField;
}
```

The following example excludes binding in any static constructor (i.e., `clinit`):

```plaintext
match * {
    unbind method <clinit>;
}
```

The following example excludes binding in any constructor:

```plaintext
match * {
    unbind <init>;
    unbind <clinit>(...);
}
```

## Binding Styles

The `bindingStyle` option is used to configure a set of pull and push binding rules to apply with the `bind` keyword. The syntax looks like the following:

```plaintext
bindingStyle my-rules {
    pull { ... }

    push { ... }
}

bind:my-rules *;
```

In the above example, the binding style has a custom name of `my-rules` and is applied to all classes and methods (`*`). Styles can also be applied to more specific selectors (e.g., `bind:my-rules com.example.*;`).

### Pull Bindings

Pull bindings rewrite the app code to retrieve values from native calls to App Shielding. Binding styles can control the number of pull bindings to use for integers and strings. The default configuration looks like the following:

```plaintext
bindingStyle default-bindings {
    pull {
        max-integers 0
        max-strings all
    }
}

bind:default-bindings *;
```

The `max-integers` and `max-strings` options can be set to one of the following:

| Value | Description |
| --- | --- |
| `0` | Disable bindings. |
| `all` | Enable bindings for all in-scope integers or strings. |
| Any positive integer | Explicitly set the number of bindings (e.g., `100`). |

Pull bindings make it more difficult to remove App Shielding from the app, but they also add a performance overhead. Generally, it is good to keep the default string pull bindings and then add integer pull bindings, if you specifically want coverage for numeric values.

### Push Bindings

Push bindings remove values from static class fields. Shield then re-inserts the values on first usage of the Java class. For example:

Currently, binding styles are only used to disable push bindings. For push bindings, binding styles only support disabling them altogether. For example:

```plaintext
bindingStyle no-push-bindings {
    push {
        max 0
    }
}

bind:no-push-bindings *;
```

This might speed up application launch time at the cost of security degradation and should only be used if the application launch is extremely slow.

## Least Recently Used Cache

To improve performance, you can use the `bindingCache` option to specify which percentage of pull binding strings to store in a Least Recently Used (LRU) cache. For example:

```plaintext
bindingCache { max-size 4% }
```

Without an LRU cache in place, every retrieval of a pull binding string requires a call to a native method. This is more secure but comes with a performance cost. With the LRU cache enabled, the most recently used strings are stored on the Java side after their initial retrieval, reducing the number of native calls.

A good cache size depends on the application and how it uses strings, but 4% is a good starting point. If you integrate a debug version of App Shielding (using the `--debug` command line option), then you can monitor the cache activity in the logs and adjust the `max-size` based on your findings.

A cache log looks like the following example:

```plaintext
03-10 12:57:53.033 26159 26184 D ShieldSDK: Pull bindings LruCache[maxSize=185,hits=416,misses=110,hitRate=79%]
```

The logs contain the following information:

| Data | Description |
| --- | --- |
| `maxSize` | The size of the cache, which depends on the number of pull bindings and the configured `max-size` percentage . |
| `hits` | The number of strings found in the cache. |
| `misses` | The number of times the cache needed to ask the native code for a string. |
| `hitRate` | The percentage of calls that were `hits`. This should be neither too high (i.e., too much is being cached) nor too low (i.e., there is no performance gain). |