升级GWT至2.8.2后JUnit测试失败，请求协助排查

Hey there, let's tackle this issue step by step—your upgrade from GWT 2.4 to 2.8.2 is throwing errors because of a deprecated parameter and Ant version mismatches. Here's how to fix it:

1. Root Cause: The -standardsMode Argument is No Longer Supported #

GWT 2.8+ removed the -standardsMode flag entirely because standards compliance is now the default behavior for the compiler and runtime. Your existing test configuration (either in your IDE run settings or Ant build script) is still passing this obsolete argument, which triggers the Unknown argument: -standardsMode error.

Fix Steps: #

• Locate where this argument is being set:
  • If using Eclipse/IntelliJ run configurations: Open your JUnit test's run settings, look for VM arguments or GWT-specific flags, and delete -standardsMode.
  • If using an Ant script: Check the <gwt:test> task or any custom JUnit launch targets for the -standardsMode parameter, and remove it from the argument list.

2. Resolve Ant Version Conflicts #

GWT 2.8.2 requires a newer Ant version (1.9.3 or later) to work correctly. The build warning about Ant version conflicts means your project is either using an outdated Ant version or has conflicting Ant dependencies in your build setup.

Fix Steps: #

• For pure Ant projects: Upgrade your local Ant installation to 1.9.3+ (grab the latest compatible release from the official Ant project resources).
• For Maven projects using maven-antrun-plugin: Update the plugin configuration to explicitly use a compatible Ant version, like this:

  <plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-antrun-plugin</artifactId>
    <version>3.1.0</version>
    <dependencies>
      <dependency>
        <groupId>org.apache.ant</groupId>
        <artifactId>ant</artifactId>
        <version>1.10.13</version>
      </dependency>
    </dependencies>
  </plugin>
  

• Clean your project's build artifacts (delete target/ or build/ directories) before re-running the build.

3. Additional Checks to Avoid Future Issues #

• Scan for other deprecated GWT parameters: GWT 2.8.x removed several old flags (like -draftCompile was replaced with -draft). Review your build scripts and test configurations for any other outdated arguments.
• Verify test class dependencies: Ensure none of your JUnit tests are using deprecated GWT API classes/methods (check for compiler warnings about deprecated code) — these might break silently after the upgrade.

Once you've applied these fixes, re-run your JUnit test and the build should complete successfully.

内容的提问来源于stack exchange，提问作者Vadiraj