Common usage scenarios for JNI include improving the execution efficiency of performance-sensitive parts, accessing operating system or hardware-specific features, reusing existing local library resources, and enhancing security and anti-reverse protection. 1. For high-performance tasks such as image processing, encryption and decryption, C/C can be used to implement key logic to improve efficiency through JNI, but attention should be paid to cross-language call overhead; 2. When accessing device drivers, sensor data or system APIs is required, it can be implemented with the help of the JNI call platform-related local libraries, and compatibility issues must be considered; 3. In order to reuse existing C/C code assets, it can be encapsulated through JNI for Java application calls to reduce duplicate development, but a reasonable interface should be designed; 4. Placing the key logic at the native layer can increase the reverse difficulty, and is suitable for payment, authorization verification and other scenarios, but cannot be used as the only security means. Although JNI is powerful, it also brings debugging difficulties and cross-platform complexity, which need to be traded down.

JNI (Java Native Interface) is part of the Java platform, which allows Java code to interact with local code (such as C, C). Many people are exposed to JNI because they need to call non-Java-implemented features in Java, or want to improve the performance of certain critical paths. The following common usage scenarios can help you understand when JNI will be used.

Improve the execution efficiency of performance-sensitive parts

For some operations that require extremely high performance, such as image processing, encryption and decryption, or high-frequency computing tasks, pure Java implementations may not meet the requirements. At this time, this part of the logic can be implemented in C/C through JNI and then called in Java to obtain higher execution efficiency.

• Suitable for hotspot function optimization, rather than rewriting the entire application with local code
• It should be noted that cross-language calls themselves also have overheads and cannot blindly replace all Java code.

For example, an audio and video encoder may implement the core algorithm in C and use it to the upper Java control logic through the JNI exposure interface.

Access operating system or hardware specific features

Although the Java standard library covers a wide range of coverage, not all system-level functions can be directly accessed. For example, when accessing specific device drivers, reading hardware sensor data, and calling Windows APIs or Linux kernel features, it needs to be implemented with the help of JNI.

• This type of scenario usually depends on the platform-related local library
• Pay special attention to compatibility issues when developing and deploying, such as different CPU architectures, operating system versions, etc.

For example, some industrial control software will use JNI to call the underlying hardware interface to obtain real-time data.

Reuse existing local library resources

Many companies have a large number of legacy C/C code assets, which have been proven for a long time and are highly stable. If the cost of rewriting completely in Java is too high, it can be encapsulated through JNI and used for Java application calls.

• Can avoid duplicate development and improve development efficiency
• Consider how to design the appropriate interface to reduce frequent cross-language calls

For example, in some financial risk control systems, the core scoring model may be written in C, and Java front-end services can be accessed through JNI.

Security and reverse protection

Some projects place key logic in the native layer to increase the difficulty of reverse analysis. Although not absolutely safe, native code is harder to understand and modify than Java bytecode.

• Suitable for applications that have certain security requirements, such as payment, authorization verification, etc.
• It is not recommended to rely too much on this method for security protection, it can only be used as one of the auxiliary means.

For example, the anti-cheat module in the game, the license verification logic of commercial software, etc., often use the JNI method to hide key judgment logic.

Basically, these are the more common JNI usage scenarios. Although JNI is powerful, it also brings problems such as debugging difficulties and increasing cross-platform complexity. Therefore, whether to use it needs to weigh the pros and cons, not all situations are suitable for use.

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