ChildFirstClassLoader (#1873)

* ChildFirstClassLoader

* Lint

* ChildFirstURLClassLoader

* Fix reference

server/src/main/kotlin/suwayomi/tachidesk/manga/impl/util/ChildFirstURLClassLoader.kt

@@ -0,0 +1,90 @@
+package suwayomi.tachidesk.manga.impl.util
+
+import java.io.IOException
+import java.io.InputStream
+import java.net.URL
+import java.net.URLClassLoader
+import java.util.Enumeration
+
+/**
+ * A parent-last class loader that will try in order:
+ * - the system class loader
+ * - the child class loader
+ * - the parent class loader.
+ */
+class ChildFirstURLClassLoader(
+    urls: Array<URL>,
+    parent: ClassLoader? = null,
+) : URLClassLoader(urls, parent) {
+    private val systemClassLoader: ClassLoader? = getSystemClassLoader()
+
+    override fun loadClass(
+        name: String?,
+        resolve: Boolean,
+    ): Class<*> {
+        var c = findLoadedClass(name)
+
+        if (c == null && systemClassLoader != null) {
+            try {
+                c = systemClassLoader.loadClass(name)
+            } catch (_: ClassNotFoundException) {
+            }
+        }
+
+        if (c == null) {
+            c =
+                try {
+                    findClass(name)
+                } catch (_: ClassNotFoundException) {
+                    super.loadClass(name, resolve)
+                }
+        }
+
+        if (resolve) {
+            resolveClass(c)
+        }
+
+        return c
+    }
+
+    override fun getResource(name: String?): URL? =
+        systemClassLoader?.getResource(name)
+            ?: findResource(name)
+            ?: super.getResource(name)
+
+    override fun getResources(name: String?): Enumeration<URL> {
+        val systemUrls = systemClassLoader?.getResources(name)
+        val localUrls = findResources(name)
+        val parentUrls = parent?.getResources(name)
+        val urls =
+            buildList {
+                while (systemUrls?.hasMoreElements() == true) {
+                    add(systemUrls.nextElement())
+                }
+
+                while (localUrls?.hasMoreElements() == true) {
+                    add(localUrls.nextElement())
+                }
+
+                while (parentUrls?.hasMoreElements() == true) {
+                    add(parentUrls.nextElement())
+                }
+            }
+
+        return object : Enumeration<URL> {
+            val iterator = urls.iterator()
+
+            override fun hasMoreElements() = iterator.hasNext()
+
+            override fun nextElement() = iterator.next()
+        }
+    }
+
+    override fun getResourceAsStream(name: String?): InputStream? {
+        return try {
+            getResource(name)?.openStream()
+        } catch (_: IOException) {
+            return null
+        }
+    }
+}

server/src/main/kotlin/suwayomi/tachidesk/manga/impl/util/PackageTools.kt

@@ -156,7 +156,7 @@ object PackageTools {
     ): Any {
         try {
             logger.debug { "loading jar with path: $jarPath" }
-            val classLoader = jarLoaderMap[jarPath] ?: URLClassLoader(arrayOf<URL>(Path(jarPath).toUri().toURL()))
+            val classLoader = jarLoaderMap[jarPath] ?: ChildFirstURLClassLoader(arrayOf<URL>(Path(jarPath).toUri().toURL()))
             val classToLoad = Class.forName(className, false, classLoader)
 
             jarLoaderMap[jarPath] = classLoader