Avoid UUID.randomUUID() in file system related startup code

This is done because bootstrapping the plumbing
needed by the JDK to produce a UUID value
is expensive, it thus doesn't make sense to
pay this cost when the property isn't actually
needed

Author: geoand

vertx-core/src/main/generated/io/vertx/core/file/FileSystemOptionsConverter.java

@@ -29,6 +29,11 @@ static void fromJson(Iterable<java.util.Map.Entry<String, Object>> json, FileSys
             obj.setFileCacheDir((String)member.getValue());
           }
           break;
+        case "exactFileCacheDir":
+          if (member.getValue() instanceof String) {
+            obj.setExactFileCacheDir((String)member.getValue());
+          }
+          break;
       }
     }
   }
@@ -43,5 +48,8 @@ static void toJson(FileSystemOptions obj, java.util.Map<String, Object> json) {
     if (obj.getFileCacheDir() != null) {
       json.put("fileCacheDir", obj.getFileCacheDir());
     }
+    if (obj.getExactFileCacheDir() != null) {
+      json.put("exactFileCacheDir", obj.getExactFileCacheDir());
+    }
   }
 }

vertx-core/src/main/java/io/vertx/core/file/FileSystemOptions.java

@@ -45,9 +45,17 @@ public class FileSystemOptions {
    */
   public static final String DEFAULT_FILE_CACHING_DIR = SysProps.FILE_CACHE_DIR.get();
 
+  /**
+   * The default exact file caching dir, which is {@code null} as {@link FileSystemOptions#setExactFileCacheDir}
+   * is meant to be used by advanced integrations that can guarantee on their own that the cache dir
+   * will be unique
+   */
+  public static final String DEFAULT_EXACT_FILE_CACHING_DIR = null;
+
   private boolean classPathResolvingEnabled = DEFAULT_CLASS_PATH_RESOLVING_ENABLED;
   private boolean fileCachingEnabled = DEFAULT_FILE_CACHING_ENABLED;
   private String fileCacheDir = DEFAULT_FILE_CACHING_DIR;
+  private String exactFileCacheDir = DEFAULT_EXACT_FILE_CACHING_DIR;
 
   /**
    * Default constructor
@@ -128,7 +136,7 @@ public FileSystemOptions setFileCachingEnabled(boolean fileCachingEnabled) {
   }
 
   /**
-   * @return the configured file cache dir
+   * @return the base name of the configured file cache dir. Vert.x will append a random value to this when determining the effective value
    */
   public String getFileCacheDir() {
     return this.fileCacheDir;
@@ -147,13 +155,34 @@ public FileSystemOptions setFileCacheDir(String fileCacheDir) {
     return this;
   }
 
+  /**
+   * @return the configured exact file cache dir to be used as is
+   */
+  public String getExactFileCacheDir() {
+    return this.exactFileCacheDir;
+  }
+
+  /**
+   * When vert.x reads a file that is packaged with the application it gets
+   * extracted to this directory first and subsequent reads will use the extracted
+   * file to get better IO performance.
+   *
+   * @param exactFileCacheDir the value
+   * @return a reference to this, so the API can be used fluently
+   */
+  public FileSystemOptions setExactFileCacheDir(String exactFileCacheDir) {
+    this.exactFileCacheDir = exactFileCacheDir;
+    return this;
+  }
+
 
   @Override
   public String toString() {
     return "FileSystemOptions{" +
     "classPathResolvingEnabled=" + classPathResolvingEnabled +
     ", fileCachingEnabled=" + fileCachingEnabled +
     ", fileCacheDir=" + fileCacheDir +
+    ", exactFileCacheDir=" + exactFileCacheDir +
     '}';
   }
 }

vertx-core/src/main/java/io/vertx/core/file/impl/FileCache.java

@@ -18,7 +18,6 @@
 import java.io.InputStream;
 import java.nio.file.FileAlreadyExistsException;
 import java.nio.file.Files;
-import java.nio.file.Path;
 import java.nio.file.StandardCopyOption;
 import java.nio.file.attribute.PosixFilePermission;
 import java.nio.file.attribute.PosixFilePermissions;
@@ -27,8 +26,8 @@
 
 public class FileCache {
 
-  static FileCache setupCache(String fileCacheDir) {
-    FileCache cache = new FileCache(setupCacheDir(fileCacheDir));
+  static FileCache setupCache(String fileCacheDir, boolean isEffectiveValue) {
+    FileCache cache = new FileCache(setupCacheDir(fileCacheDir, isEffectiveValue));
     // Add shutdown hook to delete on exit
     cache.registerShutdownHook();
     return cache;
@@ -37,16 +36,15 @@ static FileCache setupCache(String fileCacheDir) {
   /**
    * Prepares the cache directory to be used in the application.
    */
-  static File setupCacheDir(String fileCacheDir) {
+  static File setupCacheDir(String fileCacheDir, boolean isEffectiveValue) {
     // ensure that the argument doesn't end with separator
     if (fileCacheDir.endsWith(File.separator)) {
       fileCacheDir = fileCacheDir.substring(0, fileCacheDir.length() - File.separator.length());
     }
 
     // the cacheDir will be suffixed a unique id to avoid eavesdropping from other processes/users
     // also this ensures that if process A deletes cacheDir, it won't affect process B
-    String cacheDirName = fileCacheDir + "-" + UUID.randomUUID();
-    File cacheDir = new File(cacheDirName);
+    File cacheDir = isEffectiveValue ? new File(fileCacheDir) : new File(fileCacheDir + "-" + UUID.randomUUID());
     // Create the cache directory
     try {
       if (Utils.isWindows()) {

vertx-core/src/main/java/io/vertx/core/file/impl/FileResolverImpl.java

@@ -68,7 +68,12 @@ public FileResolverImpl(FileSystemOptions fileSystemOptions) {
     enableCPResolving = fileSystemOptions.isClassPathResolvingEnabled();
 
     if (enableCPResolving) {
-      cache = FileCache.setupCache(fileSystemOptions.getFileCacheDir());
+      String exactFileCacheDir = fileSystemOptions.getExactFileCacheDir();
+      if (exactFileCacheDir != null) {
+        cache = FileCache.setupCache(exactFileCacheDir, true);
+      } else {
+        cache = FileCache.setupCache(fileSystemOptions.getFileCacheDir(), false);
+      }
     } else {
       cache = null;
     }

vertx-core/src/test/java/io/vertx/tests/file/FileResolverTestBase.java

@@ -22,6 +22,8 @@
 import io.vertx.core.internal.VertxInternal;
 import io.vertx.test.core.VertxTestBase;
 import io.vertx.test.http.HttpTestBase;
+import java.nio.file.Path;
+import java.nio.file.Paths;
 import org.junit.Assert;
 import org.junit.Assume;
 import org.junit.Test;
@@ -486,4 +488,16 @@ public void testGetTheCacheDirWithoutHacks() {
       }
     }
   }
+
+  @Test
+  public void testGetTheExactCacheDirWithoutHacks() {
+    String cacheDir = new FileResolverImpl(new FileSystemOptions().setExactFileCacheDir(cacheBaseDir + "-exact")).cacheDir();
+    if (cacheDir != null) {
+      System.out.println(cacheDir);
+      assertTrue(cacheDir.startsWith(cacheBaseDir + "-"));
+      // strip the remaining
+      String remaining = cacheDir.substring(cacheBaseDir.length() + 1);
+      assertEquals(remaining, "exact");
+    }
+  }
 }