add PasswordInput

SVN: 70

common/source/java/ch/systemsx/cisd/common/utilities/PasswordInput.java

+/*
+ * Copyright 2007 ETH Zuerich, CISD
+ *
+ * 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 ch.systemsx.cisd.common.utilities;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+
+/**
+ * Helper method for reading unvisible characters from <code>System.in</code>.
+ * Code adapted from <a href="http://java.sun.com/developer/technicalArticles/Security/pwordmask/">Password Masking in 
+ * the Java Programming Language</a> by Qusay H. Mahmoud.
+ * 
+ * Note: This is a hack! Sometimes characters become visible.
+ *
+ */
+public class PasswordInput
+{
+    private static class Eraser implements Runnable
+    {
+        private volatile boolean stop;
+
+        public void run()
+        {
+            int priority = Thread.currentThread().getPriority();
+            Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
+            try
+            {
+                stop = true;
+                while (stop)
+                {
+                    System.out.print("\010*");
+                    try
+                    {
+                        Thread.sleep(1);
+                    } catch (InterruptedException e)
+                    {
+                        Thread.currentThread().interrupt();
+                        return;
+                    }
+                }
+            } finally
+            {
+                Thread.currentThread().setPriority(priority);
+            }
+        }
+
+        void stopMasking()
+        {
+            this.stop = false;
+        }
+    }
+    
+    /**
+     * Read non-echoed characters from the console until 'enter' has been pressed.
+     */
+    public static String readPassword()
+    {
+        Eraser eraser = new Eraser();
+        Thread mask = new Thread(eraser);
+        mask.start();
+
+        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
+        String password = "";
+
+        try
+        {
+            password = in.readLine();
+        } catch (IOException ioe)
+        {
+            ioe.printStackTrace();
+        }
+        eraser.stopMasking();
+        return password;
+    }
+
+    public static void main(String[] args)
+    {
+        System.out.print("enter: ");
+        System.out.println(PasswordInput.readPassword());
+    }
+}