能否让集成Paytm的Spring Boot应用分部分运行在JDK1.8与JDK12？

Great question—this is a super common headache when working with legacy dependencies (like older Paytm SDK versions) that haven’t caught up with newer JDK releases. The good news is yes, you absolutely can split your code across JDK versions without downgrading your entire app. Here are the most practical approaches for your Spring Boot + Paytm setup:

1. Use Multi-Release JARs (MRJARs) #

Multi-Release JARs let you include multiple versions of class files in a single JAR, targeting different JDK versions. This is perfect if the issue is isolated to your Paytm integration code or the Paytm SDK itself.

How to implement it: #

• Isolate Paytm-related code: Move all Paytm integration logic (service classes, SDK wrappers) into a separate module or source directory.
• Compile that module with JDK 1.8: Use javac --release 8 to compile only this portion to JDK 1.8-compatible bytecode.
• Configure your build tool for MRJAR:
  • For Maven: Add the maven-jar-plugin configuration to mark the JAR as multi-release, and specify the directory for JDK 8 classes:

    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-jar-plugin</artifactId>
      <version>3.3.0</version>
      <configuration>
        <archive>
          <manifestEntries>
            <Multi-Release>true</Multi-Release>
          </manifestEntries>
        </archive>
        <classesDirectory>${project.build.outputDirectory}</classesDirectory>
        <multiReleaseOutput>true</multiReleaseOutput>
      </configuration>
    </plugin>
    

  • For Gradle: Use the multiRelease flag in the jar task and set the target release for the Paytm module.
• Package everything together: When you build your main app (with JDK 12), the MRJAR will tell the JVM to use the JDK 1.8 classes for Paytm logic, while running the rest of your code on JDK 12.

2. Isolate Paytm Dependencies with a Custom Class Loader #

Spring Boot gives you flexibility to use different class loaders for specific dependencies. You can load the Paytm SDK and related code using a class loader that enforces JDK 1.8 compatibility, while the rest of your app uses the default JDK 12 class loader.

How to implement it: #

• Identify Paytm dependencies: List all Paytm-related JARs in your pom.xml or build.gradle.
• Create a custom class loader: Extend LaunchedURLClassLoader (Spring Boot's default class loader) and load only the Paytm JARs with it. Initialize this class loader during your app's startup.
• Use the custom loader for Paytm logic: When instantiating Paytm service classes, use the custom class loader to load them, ensuring they run in a JDK 1.8-compatible environment.

Note: This approach requires careful handling of class loader hierarchies to avoid conflicts. Test thoroughly to ensure no cross-class-loader issues pop up (like casting exceptions between classes loaded by different loaders).

3. Wrap Paytm Logic in a Separate Microservice #

If the above approaches feel too complex, the cleanest long-term solution is to split your Paytm integration into a standalone Spring Boot service that runs on JDK 1.8. Your main app (JDK 12) can then communicate with this service via REST APIs.

Why this works: #

• Complete isolation: No class loader conflicts or bytecode compatibility issues, since the two apps run on separate JVMs.
• Easier maintenance: You can update the Paytm service independently (e.g., upgrade to a JDK 12-compatible SDK later without touching your main app).
• Better scalability: If payment traffic grows, you can scale the Paytm service separately from your main application.

Pro Tip First: Check for Updated Paytm SDKs #

Before diving into version-splitting work, double-check if Paytm has released a newer SDK version that supports JDK 12. Many legacy dependencies get updated to support newer JDKs over time, and this might be the simplest fix of all.

内容的提问来源于stack exchange，提问作者Surbhi Lalwani