Fix #248

pf4j/src/main/java/org/pf4j/BasePluginRepository.java

@@ -23,7 +23,9 @@ import java.io.IOException;
 import java.nio.file.NoSuchFileException;
 import java.nio.file.Path;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collections;
+import java.util.Comparator;
 import java.util.List;
 
 /**
@@ -33,21 +35,43 @@ import java.util.List;
 public class BasePluginRepository implements PluginRepository {
 
     protected final Path pluginsRoot;
+
     protected FileFilter filter;
+    protected Comparator<File> comparator;
 
     public BasePluginRepository(Path pluginsRoot) {
-        this.pluginsRoot = pluginsRoot;
+        this(pluginsRoot, null);
     }
 
     public BasePluginRepository(Path pluginsRoot, FileFilter filter) {
         this.pluginsRoot = pluginsRoot;
         this.filter = filter;
+
+        // last modified file is first
+        this.comparator = new Comparator<File>() {
+
+            @Override
+            public int compare(File o1, File o2) {
+                return (int) (o2.lastModified() - o1.lastModified());
+            }
+
+        };
     }
 
     public void setFilter(FileFilter filter) {
         this.filter = filter;
     }
 
+    /**
+     * Set a {@link File} {@link Comparator} used to sort the listed files from {@code pluginsRoot}.
+     * This comparator is used in {@link #getPluginPaths()} method.
+     * By default is used a file comparator that returns the last modified files first.
+     * If you don't want a file comparator, then call this method with {@code null}.
+     */
+    public void setComparator(Comparator<File> comparator) {
+        this.comparator = comparator;
+    }
+
     @Override
     public List<Path> getPluginPaths() {
         File[] files = pluginsRoot.toFile().listFiles(filter);
@@ -56,6 +80,10 @@ public class BasePluginRepository implements PluginRepository {
             return Collections.emptyList();
         }
 
+        if (comparator != null) {
+            Arrays.sort(files, comparator);
+        }
+
         List<Path> paths = new ArrayList<>(files.length);
         for (File file : files) {
             paths.add(file.toPath());

pf4j/src/test/java/org/pf4j/LoadPluginsTest.java

@@ -92,7 +92,9 @@ public class LoadPluginsTest {
 
     @Test
     public void upgrade() throws Exception {
-        new PluginZip.Builder(pluginsFolder.newFile("my-plugin-1.2.3.zip"), "myPlugin")
+        String pluginId = "myPlugin";
+
+        new PluginZip.Builder(pluginsFolder.newFile("my-plugin-1.2.3.zip"), pluginId)
             .pluginVersion("1.2.3")
             .build();
 
@@ -102,18 +104,19 @@ public class LoadPluginsTest {
         assertEquals(1, pluginManager.getPlugins().size());
         assertEquals(1, pluginManager.getStartedPlugins().size());
 
-        PluginZip pluginZip2 = new PluginZip.Builder(pluginsFolder.newFile("my-plugin-2.0.0.ZIP"), "myPlugin")
+        PluginZip pluginZip2 = new PluginZip.Builder(pluginsFolder.newFile("my-plugin-2.0.0.ZIP"), pluginId)
             .pluginVersion("2.0.0")
             .build();
 
-        assertEquals("1.2.3", pluginManager.getPlugin(pluginZip2.pluginId()).getDescriptor().getVersion());
+        assertEquals("1.2.3", pluginManager.getPlugin(pluginId).getDescriptor().getVersion());
 
-        pluginManager.loadPlugins();
-        pluginManager.startPlugin(pluginZip2.pluginId());
+        pluginManager.unloadPlugin(pluginId);
+        pluginManager.loadPlugin(pluginZip2.path()); // or `pluginManager.loadPlugins();`
+        pluginManager.startPlugin(pluginId);
 
         assertEquals(1, pluginManager.getPlugins().size());
-        assertEquals("2.0.0", pluginManager.getPlugin(pluginZip2.pluginId()).getDescriptor().getVersion());
-        assertEquals("2.0.0", pluginManager.getStartedPlugins().get(1).getDescriptor().getVersion());
+        assertEquals("2.0.0", pluginManager.getPlugin(pluginId).getDescriptor().getVersion());
+        assertEquals("2.0.0", pluginManager.getStartedPlugins().get(0).getDescriptor().getVersion());
     }
 
     @Test