View Javadoc

1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *     http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  
18  package org.apache.commons.pipeline.stage;
19  
20  import java.io.IOException;
21  import java.io.InputStream;
22  import java.net.MalformedURLException;
23  import java.net.URL;
24  import java.util.ArrayList;
25  import java.util.List;
26  import java.util.Queue;
27  import org.apache.commons.logging.Log;
28  import org.apache.commons.logging.LogFactory;
29  import org.apache.commons.pipeline.stage.BaseStage;
30  import org.apache.commons.pipeline.StageException;
31  
32  /**
33   * Converts a URL into an InputStream.  This stage keeps track of all
34   * input streams that are created and closes them at the release step.
35   */
36  public class URLToInputStreamStage extends BaseStage {
37      private final Log log = LogFactory.getLog(URLToInputStreamStage.class);
38      private List<InputStream> inputStreams = new ArrayList<InputStream>();
39      
40      /** Creates a new instance of URLToInputStreamStage */
41      public URLToInputStreamStage() {    }
42      
43      /** 
44       * Takes a String or a URL object representing a URL and exqueues the input 
45       * stream returned by opening that URL.
46       *
47       * @param obj A String or URL object
48       */    
49      public void process(Object obj) throws org.apache.commons.pipeline.StageException {        
50          URL url = null;
51          if (obj instanceof URL){
52              url = (URL) obj;
53          } else if (obj instanceof String) {
54              String urlString = (String) obj;
55              try {
56                  url = new URL(urlString);
57              } catch (MalformedURLException e){
58                  throw new StageException(this, "Error converting url String:" + urlString, e);
59              }
60          }
61          
62          try {
63              InputStream inputStream = url.openStream();
64              this.inputStreams.add(inputStream);
65              log.info("enqueing input stream");
66              this.emit(inputStream);
67          } catch (IOException e){
68              throw new StageException(this, "Error with stream from url:" + url, e);
69          }
70      }
71      
72      /**
73       * Ensure that all opened input streams are closed.
74       */
75      public void release() {
76          log.info("running post process number of streams:" + inputStreams.size());
77          while(inputStreams.size() > 0){
78              InputStream is = (InputStream) inputStreams.remove(0);
79              try {
80                  is.close();
81                  log.info("closed stream");
82              } catch (IOException e){
83                  log.warn("Error closing stream",e);
84              }
85          }
86      }
87  }