change the static ClassFile cache to an instance cache

src/de/inetsoftware/jwebassembly/module/ClassFileLoader.java

@@ -0,0 +1,71 @@
+/*
+   Copyright 2020 Volker Berlin (i-net software)
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+
+*/
+package de.inetsoftware.jwebassembly.module;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+import javax.annotation.Nullable;
+
+import de.inetsoftware.classparser.ClassFile;
+import de.inetsoftware.classparser.WeakValueCache;
+
+/**
+ * Cache and manager for the loaded ClassFiles
+ * 
+ * @author Volker Berlin
+ */
+public class ClassFileLoader {
+
+    private final WeakValueCache<String, ClassFile> CACHE = new WeakValueCache<>();
+
+    private final ClassLoader                       loader;
+
+    /**
+     * Create a new instance
+     * 
+     * @param loader
+     *            the classloader to find the *.class files
+     */
+    public ClassFileLoader( ClassLoader loader ) {
+        this.loader = loader;
+    }
+
+    /**
+     * Get the ClassFile from cache or load it.
+     * 
+     * @param className
+     *            the class name
+     * @return the ClassFile or null
+     * @throws IOException
+     *             If any I/O error occur
+     */
+    @Nullable
+    public ClassFile get( String className ) throws IOException {
+        ClassFile classFile = CACHE.get( className );
+        if( classFile != null ) {
+            return classFile;
+        }
+        InputStream stream = loader.getResourceAsStream( className + ".class" );
+        if( stream != null ) {
+            classFile = new ClassFile( stream );
+            CACHE.put( className, classFile );
+        }
+        return classFile;
+    }
+
+}