1 /*
   2  * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package jdk.nashorn.api.scripting;
  27 
  28 import java.io.CharArrayReader;
  29 import java.io.IOException;
  30 import java.io.Reader;
  31 import java.net.URL;
  32 import java.nio.charset.Charset;
  33 import java.util.Objects;
  34 import jdk.nashorn.internal.runtime.Source;
  35 
  36 /**
  37  * A Reader that reads from a URL. Used to make sure that the reader
  38  * reads content from given URL and can be trusted to do so.
  39  *
  40  * @since 1.8u40
  41  */
  42 public final class URLReader extends Reader {
  43     // underlying URL
  44     private final URL url;
  45     // Charset used to convert
  46     private final Charset cs;
  47 
  48     // lazily initialized underlying reader for URL
  49     private Reader reader;
  50 
  51     /**
  52      * Constructor
  53      *
  54      * @param url URL for this URLReader
  55      * @throws NullPointerException if url is null
  56      */
  57     public URLReader(final URL url) {
  58         this(url, (Charset)null);
  59     }
  60 
  61     /**
  62      * Constructor
  63      *
  64      * @param url URL for this URLReader
  65      * @param charsetName  Name of the Charset used to convert bytes to chars
  66      * @throws NullPointerException if url is null
  67      */
  68     public URLReader(final URL url, final String charsetName) {
  69         this(url, Charset.forName(charsetName));
  70     }
  71 
  72     /**
  73      * Constructor
  74      *
  75      * @param url URL for this URLReader
  76      * @param cs  Charset used to convert bytes to chars
  77      * @throws NullPointerException if url is null
  78      */
  79     public URLReader(final URL url, final Charset cs) {
  80         this.url = Objects.requireNonNull(url);
  81         this.cs  = cs;
  82     }
  83 
  84     @Override
  85     public int read(final char cbuf[], final int off, final int len) throws IOException {
  86         return getReader().read(cbuf, off, len);
  87     }
  88 
  89     @Override
  90     public void close() throws IOException {
  91         getReader().close();
  92     }
  93 
  94     /**
  95      * URL of this reader
  96      * @return the URL from which this reader reads.
  97      */
  98     public URL getURL() {
  99         return url;
 100     }
 101 
 102     /**
 103      * Charset used by this reader
 104      *
 105      * @return the Charset used to convert bytes to chars
 106      */
 107     public Charset getCharset() {
 108         return cs;
 109     }
 110 
 111     // lazily initialize char array reader using URL content
 112     private Reader getReader() throws IOException {
 113         synchronized (lock) {
 114             if (reader == null) {
 115                 reader = new CharArrayReader(Source.readFully(url, cs));
 116             }
 117         }
 118 
 119         return reader;
 120     }
 121 }