Hey there! Let's tackle your JDK 1.6 to 1.8 upgrade problem for that legacy Java project—sounds like a big undertaking with 800+ modules and a hodgepodge of frameworks from Struts to Spring. Here's how you can approach this efficiently:

Identifying Frameworks Affected by JDK 1.8 Upgrade #

First, you need to map out which of your frameworks might break or need adjustments when moving to JDK 1.8. Here are practical, actionable steps:

• Dump and analyze your dependency tree
  Use your build tool to get a full list of all direct and transitive dependencies. For Maven, run mvn dependency:tree; for Gradle, use ./gradlew dependencies. This will help you see exactly which versions of Struts, Spring, and other frameworks you're using—since compatibility often depends on the specific version, not just the framework name.

• Cross-check framework version compatibility docs
  Even though it's not fully "automated," official docs are the most reliable source. For example:

  • Struts 1.x: The latest 1.3.x versions (like 1.3.11) support JDK 1.5 to 1.8, so if you're on an older Struts 1 release, you might need to patch it up.
  • Struts 2.x: Versions 2.3.x and above support JDK 1.6+, but 2.5.x requires JDK 1.7+—so if you're on 2.1 or earlier, you'll need to upgrade the framework itself.
  • Spring: Spring 3.2.x supports JDK 1.5-1.8, but Spring 4.x (especially 4.3+) adds full support for JDK 1.8 features like lambdas. If you're on Spring 3.0 or older, you'll likely hit compatibility issues.

• Use static analysis tools for JDK migration
  Tools like Oracle's Java Migration Assistant (JMA) or Eclipse's Migration Toolkit for Java (MTJ) can scan your codebase and dependencies to flag:

  • Deprecated API calls that were removed or changed in JDK 1.8
  • Framework classes that rely on JDK 1.6-specific behavior (like older JDBC implementations or deprecated Date methods)
    SonarQube also has rules that can detect JDK version incompatibilities.

• Run incremental tests with JDK 1.8
  Spin up a test environment with JDK 1.8, run your existing unit and integration tests, and look for runtime errors. Stack traces will point directly to which framework classes are failing (e.g., a Struts action that uses a deprecated JDK method, or a Spring bean that can't initialize due to JDK version checks). This is hands-on but often the fastest way to find edge cases.

Is There an API to Check Framework-JDK Compatibility? #

Unfortunately, there's no universal, official API that lets you query JDK compatibility for any Java framework—each project maintains its own compatibility data. But you have a few workarounds:

• Parse Maven/Gradle metadata
  Most frameworks publish their JDK requirements in their build files. For Maven dependencies, you can use the Maven API or a tool like Apache Ivy to fetch the pom.xml of a framework version and check properties like <maven.compiler.source> or <maven.compiler.target>, which indicate the minimum supported JDK version.

• Build a custom scraper for official docs
  If you need to automate this at scale, you can write a script (using tools like Jsoup) to scrape framework official docs or release notes for compatibility info. For example, Spring's release pages clearly state JDK requirements for each version—you can parse that data into a lookup table.

• Leverage framework runtime checks
  Many frameworks (like Spring) include runtime checks for JDK version. If you try to run a framework version that doesn't support JDK 1.8, it will throw an exception early on with a message indicating the required JDK version. You can use this behavior to test compatibility programmatically if needed.

内容的提问来源于stack exchange，提问作者MohanGV