Resolving @ RequestBody Conversion Issues with AES Encrypted Strings in Spring Boot

Learn how to efficiently handle `@ RequestBody` when dealing with AES encrypted strings in Spring Boot. Implement custom filters and optimize code for smooth conversions.
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Handling @ RequestBody Conversion Issues with AES Encrypted Strings in Spring Boot

In the world of modern web applications, sending sensitive data securely is crucial. One common practice is using AES encryption to send secure strings from the client side. However, a frequent challenge developers encounter is the inability to convert this encrypted data back to a usable Java object in a Spring Boot application. This guide addresses how to efficiently handle incoming AES encrypted strings through a well-implemented filter, ensuring they can be properly converted for use in a controller.

The Problem

When passing an AES encrypted string with a content type of text/plain, the Spring Boot application fails to convert it into an object using the @ RequestBody annotation. This typically results in an error message indicating that the required request body is missing:

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The challenge lies in managing the encrypted string and performing the suitable conversion in a way that Spring Boot can understand.

The Solution

Understanding the Filter Mechanism

To solve the problem, we utilize a custom filter that decrypts the incoming AES encrypted string and manipulates the request body before it reaches the controller.

Step 1: Create a Custom Filter

The CustomEncryptedFilter class is responsible for decrypting the AES encrypted string. Here’s how it works:

The filter reads the incoming request and decrypts the AES string using an AES encryption class.

It then wraps the decrypted string within a custom request wrapper that substitutes the content type from text/plain to application/json, allowing Spring to interpret and process it accordingly.

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Step 2: Modify the HttpServletRequestWrapper

The CustomHttpServletRequestWrapper is crucial to changing the media type and providing a valid request body to the controller. It essentially modifies the request headers to reflect that the body content is now JSON:

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Step 3: Implement a Controller

Here’s an example of how your controller might look, expecting a LoginForm object as request body. The controller should now successfully process the decrypted string.

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Ensure InputStream Can Be Read Multiple Times

A critical point to consider is that an InputStream can only be read once. In your custom filter, if you attempt to log the request body straight after reading it into IOUtils, Spring Boot won’t be able to read it again in the controller.

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Alternative Approach: Using RequestBodyAdvice

For better extensibility, consider implementing RequestBodyAdvice. This allows you to centralize the decryption and content type modification without needing a filter. It ensures the request body is decrypted before reaching the controller method.

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Benefits of Using RequestBodyAdvice

Centralized Logic: You facilitate cleaner and reusable code.

Conditional Logic: You can easily implement checks to see if certain conditions or annotations are met before decryption.

For instance, you can create a custom annotation to signal that a specific parameter requires decryption:

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Conclusion

In conclusion, handling AES encrypted strings efficiently in Spring Boot requires a thoughtful approach involving request filtering, stream handling, and possibly implementing RequestBodyAdvice. By ado