feat: restore configurable hotfile option

Add back the hotfile feature that was removed in commit 588863c.
The hotfile is now configurable and can be disabled by setting
hotFile to false.

The hotfile allows Spring applications to detect when the Vite
dev server is running by checking for the existence of the file,
which contains the dev server URL.

Changes:
- Add hotFile option to VitePluginJavaConfig (string | false)
- Write hotfile on server start with dev server URL
- Clean up hotfile on process exit
- Update .gitignore to ignore hot file
- Update README with hotfile documentation

Closes #2

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: benny123tw

.gitignore

@@ -23,6 +23,9 @@ dist-ssr
 *.sln
 *.sw?
 
+# Plugin hot file
+hot
+
 # Java
 target/
 build/

packages/vite-plugin-java/README.md

@@ -39,6 +39,7 @@ export default defineConfig({
           target: 'es2015'
         }
       },
+      hotFile: 'public/hot',
       transformOnServe: (code, url) => code.replace('__PLACEHOLDER__', url)
     })
   ]
@@ -55,6 +56,7 @@ export default defineConfig({
 | `outputDirectory`  | `string`                                      | `'dist'`        | Directory where the bundle should be written               |
 | `tsCompiler`       | `'esbuild'` \| `'swc'`                        | `'esbuild'`     | @experimental TypeScript compiler to use                                 |
 | `swcOptions`       | `SwcOptions`                                  | `{}`            | @experimental Options to pass to the SWC compiler                        |
+| `hotFile`          | `string` \| `false`                           | `'public/hot'`  | Path to the "hot" file. Set to `false` to disable          |
 | `transformOnServe` | `(code: string, url: DevServerUrl) => string` | `code => code`  | Transform the code while serving                           |
 
 ### Example
@@ -72,6 +74,7 @@ export default {
       publicDirectory: 'static',
       buildDirectory: 'assets',
       outputDirectory: 'build',
+      hotFile: 'static/hot',
       transformOnServe: (code, url) => code.replace('__VITE_URL__', url)
     })
   ]
@@ -96,6 +99,7 @@ export interface VitePluginJavaConfig {
   outputDirectory?: string
   tsCompiler?: SupportedTSCompiler
   swcOptions?: SwcOptions
+  hotFile?: string | false
   transformOnServe?: (code: string, url: DevServerUrl) => string
 }
 

packages/vite-plugin-java/src/index.ts

@@ -32,6 +32,15 @@ export interface VitePluginJavaConfig {
    */
   javaProjectBase?: string
 
+  /**
+   * The path to the "hot" file.
+   *
+   * Set to `false` to disable hot file generation.
+   *
+   * @default `${publicDirectory}/hot`
+   */
+  hotFile?: string | false
+
   /**
    * Transform the code while serving.
    */

packages/vite-plugin-java/src/vite-plugin-java.ts

@@ -126,6 +126,10 @@ function resolveJavaPlugin(pluginConfig: Required<VitePluginJavaConfig>): [JavaP
           if (isAddressInfo(address)) {
             viteDevServerUrl = userConfig.server?.origin ? userConfig.server.origin as DevServerUrl : resolveDevServerUrl(address, server.config)
 
+            if (pluginConfig.hotFile) {
+              fs.writeFileSync(pluginConfig.hotFile, `${viteDevServerUrl}${server.config.base.replace(/\/$/, '')}`)
+            }
+
             setTimeout(() => {
               server.config.logger.info(`\n  ${colors.red(`${colors.bold('JAVA')} ${javaVersion(pluginConfig.javaProjectBase)}`)}  ${colors.dim('plugin')} ${colors.bold(`v${pluginVersion()}`)}`)
               server.config.logger.info('')
@@ -138,6 +142,13 @@ function resolveJavaPlugin(pluginConfig: Required<VitePluginJavaConfig>): [JavaP
         })
 
         if (!exitHandlersBound) {
+          const clean = () => {
+            if (pluginConfig.hotFile && fs.existsSync(pluginConfig.hotFile)) {
+              fs.rmSync(pluginConfig.hotFile)
+            }
+          }
+
+          process.on('exit', clean)
           process.on('SIGINT', () => process.exit())
           process.on('SIGTERM', () => process.exit())
           process.on('SIGHUP', () => process.exit())
@@ -203,6 +214,7 @@ function resolvePluginConfig(config: string | string[] | VitePluginJavaConfig):
     publicDirectory: config.publicDirectory ?? 'public',
     outputDirectory: config.outputDirectory ?? 'dist',
     javaProjectBase: config.javaProjectBase ?? '.',
+    hotFile: config.hotFile === false ? false : (config.hotFile ?? path.join((config.publicDirectory ?? 'public'), 'hot')),
     transformOnServe: config.transformOnServe ?? (code => code),
   }
 }