Скачать или смотреть Understanding the Sequence of antMatcher in Spring Security: Why Stricter Patterns Should Come First

Learn how to effectively use `antMatcher` in Spring Security to control access to your REST APIs. This guide explains the sequence of URL patterns and why more specific matches may be ignored if not placed correctly.
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This video is based on the question https://stackoverflow.com/q/63138148/ asked by the user 'krtkush' ( https://stackoverflow.com/u/1102691/ ) and on the answer https://stackoverflow.com/a/63138332/ provided by the user 'Kavithakaran Kanapathippillai' ( https://stackoverflow.com/u/7875623/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Sequence of antMatcher in Spring Security

When it comes to securing REST APIs using Spring Security, it's essential to understand how to appropriately configure your access rules. One common issue developers face is the unexpected behavior of the antMatcher sequence when setting up authorization. In this post, we'll explore a specific case where the sequence of specified URL patterns seemingly causes permissions to be ignored and explain the proper way to configure them.

The Problem: Unexpected antMatcher Behavior

In our scenario, we initially configured our security settings as follows:

[[See Video to Reveal this Text or Code Snippet]]

In this configuration, we intended to allow GET requests to /podcast/details/** for everyone, while requiring an admin role for any other podcast-related endpoints (like /podcast/**). However, upon testing the endpoint http://localhost:8080/podcast/details/all, we found that the authorization rules didn’t behave as expected: the permitAll() case was completely ignored.

The Solution: Reordering Your Patterns

After some experimentation, switching the order of our antMatcher rules provided a solution. Here’s the adjusted configuration that worked:

[[See Video to Reveal this Text or Code Snippet]]

With this configuration, accessing http://localhost:8080/podcast/details/all was successful without requiring an admin role.

Why Does This Happen?

Understanding why the order of patterns matters is key to solving these types of issues. Here are some important points to consider:

Pattern Specificity: The order of antMatcher rules is crucial because Spring Security matches incoming requests to patterns from top to bottom. A more general pattern (like "/podcast/**") can overshadow more specific ones (like "/podcast/details/**"). So when a request comes in for a specific endpoint, if a more general match is checked first and succeeds, Spring Security will not evaluate the subsequent rules. In simpler terms:

"/podcast/details/**" is more specific than "/podcast/**".

Request Matching: For a request to "/podcast/details/123", if "/podcast/**" is evaluated first, it will match and therefore stop checking before it reaches the specific pattern "/podcast/details/**". Consequently, the permitAll() will never be applied.

Key Takeaways

Always place more specific patterns before broader ones when configuring antMatchers in Spring Security.

Understand that Spring Security matches request patterns in the order they are defined.

Test your configurations thoroughly to ensure the desired permissions are functioning as expected.

By following these guidelines, you can avoid common pitfalls and ensure that your REST APIs are secured correctly while respecting the intended roles and permissions.