1 files changed, 176 insertions, 0 deletions
diff --git a/feature-server-pool/src/test/java/org/onap/policy/drools/serverpooltest/BlockingClassLoader.java b/feature-server-pool/src/test/java/org/onap/policy/drools/serverpooltest/BlockingClassLoader.java
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--- /dev/null
+++ b/feature-server-pool/src/test/java/org/onap/policy/drools/serverpooltest/BlockingClassLoader.java
@@ -0,0 +1,176 @@
+/*
+ * ============LICENSE_START=======================================================
+ * feature-server-pool
+ * ================================================================================
+ * Copyright (C) 2020 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * 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.
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.drools.serverpooltest;
+
+import java.net.URL;
+import java.util.ArrayList;
+import java.util.Enumeration;
+import java.util.HashSet;
+import java.util.NoSuchElementException;
+
+/**
+ * Ordinarily, a 'ClassLoader' first attempts to load a class via the
+ * parent 'ClassLoader'. If that fails, it attempts to load it "locally"
+ * by whatever mechanism the class loader supports.
+ * This 'ClassLoader' instance blocks attempts to load specific classes,
+ * throwing a 'ClassNotFoundException'. This doesn't seem useful on the
+ * surface, but it forces all child 'ClassLoader' instances to do the lookup
+ * themselves. In addition, each child 'ClassLoader' will have their own
+ * copy of the classes they load, providing a way to have multiple copies of
+ * the same class running within the same JVM. Each child 'ClassLoader' can
+ * be viewed as having a separate name space.
+ */
+public class BlockingClassLoader extends ClassLoader {
+    // these are the set of packages to block
+    private HashSet<String> packages;
+
+    // these are the prefixes of class names to block
+    private ArrayList<String> prefixes;
+
+    // these specific classes will not be blocked, even if they are in one
+    // of the packages indicated by 'packages'
+    private HashSet<String> excludes = new HashSet<String>();
+
+    // these are the prefixes of class names to exclude
+    private ArrayList<String> excludePrefixes = new ArrayList<>();
+
+    /**
+     * Constructor -- initialize the 'ClassLoader' and 'packages' variable.
+     *
+     * @param parent the parent ClassLoader
+     * @param packages variable number of packages to block
+     */
+    public BlockingClassLoader(ClassLoader parent, String... packages) {
+        super(parent);
+        this.packages = new HashSet<>();
+        this.prefixes = new ArrayList<>();
+        for (String pkg : packages) {
+            if (pkg.endsWith("*")) {
+                prefixes.add(pkg.substring(0, pkg.length() - 1));
+            } else {
+                this.packages.add(pkg);
+            }
+        }
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    protected Class<?> findClass(String name) throws ClassNotFoundException {
+        // throws a 'ClassNotFoundException' if we are blocking this one
+        testClass(name);
+
+        // not blocking this one -- pass it on to the superclass
+        return super.findClass(name);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public Enumeration<URL> getResources(String name) {
+        // in order to avoid replicated resources, we return an empty set
+        return new Enumeration<URL>() {
+            public boolean hasMoreElements() {
+                return false;
+            }
+
+            public URL nextElement() {
+                throw new NoSuchElementException("'BlockingClassLoader' blocks duplicate resources");
+            }
+        };
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public Class<?> loadClass(String name) throws ClassNotFoundException {
+        // throws a 'ClassNotFoundException' if we are blocking this one
+        testClass(name);
+
+        // not blocking this one -- pass it on to the superclass
+        return super.loadClass(name);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    protected Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {
+        // throws a 'ClassNotFoundException' if we are blocking this one
+        testClass(name);
+
+        // not blocking this one -- pass it on to the superclass
+        return super.loadClass(name, resolve);
+    }
+
+    /**
+     * Add an entry to the list of classes that should NOT be blocked.
+     *
+     * @param name the full name of a class that shouldn't be blocked
+     */
+    public void addExclude(String name) {
+        if (name.endsWith("*")) {
+            excludePrefixes.add(name.substring(0, name.length() - 1));
+        } else {
+            excludes.add(name);
+        }
+    }
+
+    /**
+     * This method looks at a class name -- if it should be blocked, a
+     * 'ClassNotFoundException' is thrown. Otherwise, it does nothing.
+     *
+     * @param name the name of the class to be tested
+     * @throws ClassNotFoundException if this class should be blocked
+     */
+    private void testClass(String name) throws ClassNotFoundException {
+        if (excludes.contains(name)) {
+            // allow this one
+            return;
+        }
+
+        for (String prefix : excludePrefixes) {
+            if (name.startsWith(prefix)) {
+                // allow this one
+                return;
+            }
+        }
+
+        // extract the package from the class name -- throw a
+        // 'ClassNotFoundException' if the package is in the list
+        // being blocked
+        int index = name.lastIndexOf('.');
+        if (index >= 0) {
+            if (packages.contains(name.substring(0,index))) {
+                throw(new ClassNotFoundException(name));
+            }
+
+            for (String prefix : prefixes) {
+                if (name.startsWith(prefix)) {
+                    throw(new ClassNotFoundException(name));
+                }
+            }
+        }
+    }
+}