SOLR-16903: Migrate off java.io.File to java.nio.file.Path from core files

solr/core/src/java/org/apache/solr/cloud/ZkSolrResourceLoader.java

@@ -20,6 +20,7 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.lang.invoke.MethodHandles;
+import java.nio.file.FileSystems;
 import java.nio.file.Path;
 import org.apache.solr.common.SolrException.ErrorCode;
 import org.apache.solr.common.cloud.ZooKeeperException;
@@ -120,8 +121,9 @@ public InputStream openResource(String resource) throws IOException {
 
     try {
       // delegate to the class loader (looking into $INSTANCE_DIR/lib jars)
-      // Use Path to normalize path separator
-      is = classLoader.getResourceAsStream(Path.of(resource).toString());
+      is =
+          classLoader.getResourceAsStream(
+              resource.replace(FileSystems.getDefault().getSeparator(), "/"));
     } catch (Exception e) {
       throw new IOException("Error opening " + resource, e);
     }

solr/core/src/java/org/apache/solr/core/CoreDescriptor.java

@@ -20,6 +20,7 @@
 import java.io.Reader;
 import java.lang.invoke.MethodHandles;
 import java.nio.charset.StandardCharsets;
+import java.nio.file.FileSystems;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.HashMap;
@@ -62,7 +63,8 @@ public class CoreDescriptor {
   public static final String CORE_CONFIGSET_PROPERTIES = "configSetProperties";
   public static final String SOLR_CORE_PROP_PREFIX = "solr.core.";
 
-  public static final Path DEFAULT_EXTERNAL_PROPERTIES_FILE = Path.of("conf/solrcore.properties");
+  public static final String DEFAULT_EXTERNAL_PROPERTIES_FILE =
+      "conf" + FileSystems.getDefault().getSeparator() + "solrcore.properties";
 
   /**
    * Whether this core was configured using a configSet that was trusted. This helps in avoiding the
@@ -94,7 +96,7 @@ public Properties getPersistableUserProperties() {
           CORE_CONFIG, "solrconfig.xml",
           CORE_SCHEMA, "schema.xml",
           CORE_CONFIGSET_PROPERTIES, ConfigSetProperties.DEFAULT_FILENAME,
-          CORE_DATADIR, Path.of("data").toString(),
+          CORE_DATADIR, "data" + FileSystems.getDefault().getSeparator(),
           CORE_TRANSIENT, "false",
           CORE_LOADONSTARTUP, "true");
 
@@ -238,8 +240,7 @@ public CoreDescriptor(
    * <p>File paths are taken as read from the core's instance directory if they are not absolute.
    */
   protected void loadExtraProperties() {
-    String filename =
-        coreProperties.getProperty(CORE_PROPERTIES, DEFAULT_EXTERNAL_PROPERTIES_FILE.toString());
+    String filename = coreProperties.getProperty(CORE_PROPERTIES, DEFAULT_EXTERNAL_PROPERTIES_FILE);
     Path propertiesFile = instanceDir.resolve(filename);
     if (Files.exists(propertiesFile)) {
       try (Reader r = Files.newBufferedReader(propertiesFile, StandardCharsets.UTF_8)) {

solr/core/src/java/org/apache/solr/core/SolrResourceLoader.java

@@ -372,12 +372,16 @@ public InputStream openResource(String resource) throws IOException {
 
     // Delegate to the class loader (looking into $INSTANCE_DIR/lib jars).
     // We need a ClassLoader-compatible (forward-slashes) path here!
-    InputStream is = classLoader.getResourceAsStream(resource);
+    InputStream is =
+        classLoader.getResourceAsStream(
+            resource.replace(FileSystems.getDefault().getSeparator(), "/"));
 
     // This is a hack just for tests (it is not done in ZKResourceLoader)!
     // TODO can we nuke this?
     if (is == null && System.getProperty("jetty.testMode") != null) {
-      is = classLoader.getResourceAsStream(Path.of("conf").resolve(resource).toString());
+      is =
+          classLoader.getResourceAsStream(
+              ("conf/" + resource).replace(FileSystems.getDefault().getSeparator(), "/"));
     }
 
     if (is == null) {

solr/core/src/java/org/apache/solr/core/backup/BackupManager.java

@@ -23,7 +23,7 @@
 import java.lang.invoke.MethodHandles;
 import java.net.URI;
 import java.nio.charset.StandardCharsets;
-import java.nio.file.Path;
+import java.nio.file.FileSystems;
 import java.time.Instant;
 import java.util.Collections;
 import java.util.List;
@@ -343,7 +343,8 @@ private void downloadConfigToRepo(ConfigSetService configSetService, String conf
     // getAllConfigFiles always separates file paths with '/'
     for (String filePath : filePaths) {
       // Replace '/' to ensure that propre file is resolved for writing.
-      URI uri = repository.resolve(dir, Path.of(filePath).toString());
+      URI uri =
+          repository.resolve(dir, filePath.replace("/", FileSystems.getDefault().getSeparator()));
       // checking for '/' is correct for a directory since ConfigSetService#getAllConfigFiles
       // always separates file paths with '/'
       if (!filePath.endsWith("/")) {

solr/core/src/java/org/apache/solr/filestore/DistribFileStore.java

@@ -84,14 +84,15 @@ public Path getRealPath(String path) {
     return _getRealPath(path, solrHome);
   }
 
-  private static Path _getRealPath(String path, Path solrHome) {
-    Path dir = Path.of(path);
-    SolrPaths.assertNotUnc(dir);
+  private static Path _getRealPath(String dir, Path solrHome) {
+    Path path = Path.of(dir);
+    SolrPaths.assertNotUnc(path);
 
-    // Strip the path of from being absolute to become relative to resolve with SolrHome
-    while (path.startsWith("/")) {
-      path = path.substring(1);
+    if (path.isAbsolute()) {
+      // Strip the path of from being absolute to become relative to resolve with SolrHome
+      path = path.subpath(0, path.getNameCount());
     }
+
     var finalPath = getFileStoreDirPath(solrHome).resolve(path);
 
     // Guard against path traversal by asserting final path is sub path of filestore
@@ -432,8 +433,7 @@ public void get(String path, Consumer<FileEntry> consumer, boolean fetchmissing)
     Path file = getRealPath(path);
     String simpleName = file.getFileName().toString();
     if (isMetaDataFile(simpleName)) {
-      // TODO SOLR-8282 Move to Files.newInputStream
-      try (InputStream is = new FileInputStream(file.toString())) {
+      try (InputStream is = Files.newInputStream(file)) {
         consumer.accept(
             new FileEntry(null, null, path) {
               // no metadata for metadata file

solr/core/src/java/org/apache/solr/handler/IndexFetcher.java

@@ -1494,11 +1494,10 @@ private void copyTmpConfFiles2Conf(Path tmpconfDir) {
       if (Files.exists(oldPath)) {
         try {
           Path backupFile =
-              Path.of(
-                  oldPath
+              oldPath.resolveSibling(
+                  oldPath.getFileName()
                       + "."
                       + getDateAsStr(new Date(Files.getLastModifiedTime(oldPath).toMillis())));
-          Files.createDirectories(backupFile.getParent());
           Files.move(oldPath, backupFile);
         } catch (Exception e) {
           throw new SolrException(

solr/core/src/java/org/apache/solr/schema/ManagedIndexSchemaFactory.java

@@ -410,7 +410,9 @@ private void upgradeToManagedSchema() {
               "nor under SolrConfig.getConfigDir() or the current directory. ",
               "PLEASE REMOVE THIS FILE.");
         } else {
-          Path upgradedSchemaFile = Path.of(nonManagedSchemaFile + UPGRADED_SCHEMA_EXTENSION);
+          Path upgradedSchemaFile =
+              nonManagedSchemaFile.resolveSibling(
+                  nonManagedSchemaFile.getFileName() + UPGRADED_SCHEMA_EXTENSION);
           try {
             Files.move(nonManagedSchemaFile, upgradedSchemaFile);
             // Set the resource name to the managed schema so that the CoreAdminHandler returns a

solr/core/src/java/org/apache/solr/spelling/AbstractLuceneSpellChecker.java

@@ -84,9 +84,7 @@ public String init(NamedList<?> config, SolrCore core) {
 
     // If indexDir is relative then create index inside core.getDataDir()
     if (indexDir != null) {
-      if (!indexDir.isAbsolute()) {
-        indexDir = Path.of(core.getDataDir(), indexDir.toString());
-      }
+      indexDir = Path.of(core.getDataDir()).resolve(indexDir);
     }
 
     sourceLocation = (String) config.get(LOCATION);

solr/core/src/java/org/apache/solr/spelling/suggest/fst/AnalyzingInfixLookupFactory.java

@@ -89,9 +89,8 @@ public Lookup create(NamedList<?> params, SolrCore core) {
         params.get(INDEX_PATH) != null
             ? Path.of(params.get(INDEX_PATH).toString())
             : Path.of(DEFAULT_INDEX_PATH);
-    if (!indexPath.isAbsolute()) {
-      indexPath = Path.of(core.getDataDir(), indexPath.toString());
-    }
+
+    indexPath = Path.of(core.getDataDir()).resolve(indexPath);
 
     int minPrefixChars =
         params.get(MIN_PREFIX_CHARS) != null

solr/core/src/java/org/apache/solr/spelling/suggest/fst/BlendedInfixLookupFactory.java

@@ -76,11 +76,12 @@ public Lookup create(NamedList<?> params, SolrCore core) {
 
     // optional parameters
 
-    String indexPath =
-        params.get(INDEX_PATH) != null ? params.get(INDEX_PATH).toString() : DEFAULT_INDEX_PATH;
-    if (!Path.of(indexPath).isAbsolute()) {
-      indexPath = Path.of(core.getDataDir(), indexPath).toString();
-    }
+    Path indexPath =
+        params.get(INDEX_PATH) != null
+            ? Path.of(params.get(INDEX_PATH).toString())
+            : Path.of(DEFAULT_INDEX_PATH);
+
+    indexPath = Path.of(core.getDataDir()).resolve(indexPath);
 
     int minPrefixChars =
         params.get(MIN_PREFIX_CHARS) != null
@@ -109,7 +110,7 @@ public Lookup create(NamedList<?> params, SolrCore core) {
 
     try {
       return new BlendedInfixSuggester(
-          FSDirectory.open(Path.of(indexPath)),
+          FSDirectory.open(indexPath),
           indexAnalyzer,
           queryAnalyzer,
           minPrefixChars,

solr/core/src/java/org/apache/solr/util/SystemIdResolver.java

@@ -19,7 +19,7 @@
 import java.io.IOException;
 import java.net.URI;
 import java.net.URISyntaxException;
-import java.nio.file.Path;
+import java.nio.file.FileSystems;
 import javax.xml.stream.XMLResolver;
 import javax.xml.stream.XMLStreamException;
 import javax.xml.transform.Source;
@@ -167,9 +167,9 @@ public InputSource resolveEntity(String publicId, String systemId) throws IOExce
   }
 
   public static String createSystemIdFromResourceName(String name) {
-    Path pathName = Path.of(name);
+    name = name.replace(FileSystems.getDefault().getSeparator(), "/");
     final String authority;
-    if (pathName.startsWith("/")) {
+    if (name.startsWith("/")) {
       // a hack to preserve absolute filenames and keep them absolute after resolving, we set the
       // URI's authority to "@" on absolute filenames:
       authority = RESOURCE_LOADER_AUTHORITY_ABSOLUTE;

solr/core/src/java/org/apache/solr/util/VersionedFile.java

@@ -16,8 +16,6 @@
  */
 package org.apache.solr.util;
 
-import java.io.FileInputStream;
-import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.nio.file.Files;
@@ -38,9 +36,9 @@ public class VersionedFile {
    * the last fileName.* after being sorted lexicographically.
    * Older versions of the file are deleted (and queued for deletion if
    * that fails).
+   * TODO SOLR-8282 dirName should be a Path instead of string
    */
-  public static InputStream getLatestFile(String dirName, String fileName)
-      throws FileNotFoundException {
+  public static InputStream getLatestFile(String dirName, String fileName) throws IOException {
     Collection<Path> oldFiles = null;
     final String prefix = fileName + '.';
     Path f = Path.of(dirName, fileName);
@@ -66,23 +64,22 @@ public static InputStream getLatestFile(String dirName, String fileName)
                 SolrException.ErrorCode.SERVER_ERROR, "Unable to list files in " + dir, e);
           }
 
-          f = Path.of(dir.toString(), fileList.getLast().getFileName().toString());
+          f = dir.resolve(fileList.getLast());
           oldFiles = new ArrayList<>();
           for (int i = 0; i < fileList.size() - 1; i++) {
-            oldFiles.add(Path.of(dir.toString(), fileList.get(i).toString()));
+            oldFiles.add(dir.resolve(fileList.get(i)));
           }
         }
 
-        // TODO SOLR-8282 Move to Files.newInputStream
-        is = new FileInputStream(f.toString());
+        is = Files.newInputStream(f);
       } catch (Exception e) {
         // swallow exception for now
       }
     }
 
     // allow exception to be thrown from the final try.
     if (is == null) {
-      is = new FileInputStream(f.toString());
+      is = Files.newInputStream(f);
     }
 
     // delete old files only after we have successfully opened the newest