java/src/main/com/google/apphosting/utils/config/DispatchXmlReader.java

   1 package com.google.apphosting.utils.config;
   2
   3 import com.google.apphosting.utils.config.DispatchXml.DispatchEntry;
   4
   5 import org.mortbay.xml.XmlParser.Node;
   6
   7 import java.io.File;
   8 import java.io.InputStream;
   9 import java.util.Stack;
  10
  11 /**
  12  * Creates a {@link DispatchXml} from dispatch.yaml.
  13  */
  14 public class DispatchXmlReader extends AbstractConfigXmlReader<DispatchXml> {
  15
  16   public static final String DEFAULT_RELATIVE_FILENAME = "WEB-INF" + File.separatorChar
  17       + "dispatch.xml";
  18
  19   private final String relativeFilename;
  20
  21   public DispatchXmlReader(String warDirectory, String relativeFilename) {
  22     super(warDirectory, false);
  23     this.relativeFilename = relativeFilename;
  24   }
  25
  26   /**
  27    * Parses the dispatch.xml file if one exists into an {@link DispatchXml} and otherwise
  28    * returns null.
  29    */
  30   public DispatchXml readDispatchXml() {
  31     return readConfigXml();
  32   }
  33
  34   @Override
  35   protected DispatchXml processXml(InputStream is) {
  36     DispatchXmlParserCallback dispatchParserCallback = new DispatchXmlParserCallback();
  37     parse(dispatchParserCallback, is);
  38     return dispatchParserCallback.getDispatchXml();
  39   }
  40
  41   @Override
  42   protected String getRelativeFilename() {
  43     return relativeFilename;
  44   }
  45
  46   private class DispatchXmlParserCallback implements ParserCallback {
  47     private final DispatchXml.Builder dispatchXmlBuilder = DispatchXml.builder();
  48
  49     private static final String DISPATCH_ENTRIES_TAG = "dispatch-entries";
  50     private static final String DISPATCH_TAG = "dispatch";
  51     private static final String URL_TAG = "url";
  52     private static final String MODULE_TAG = "module";
  53
  54     private boolean first = true;
  55
  56     private boolean dispatchComplete;
  57     private String url = null;
  58     private String module = null;
  59
  60     DispatchXml getDispatchXml() {
  61       if (first) {
  62         throw new IllegalStateException(
  63             "getDispatchXml() called before parsing a valid dispatch.xml");
  64       }
  65       checkForIncompleteDispatchElement();
  66       return dispatchXmlBuilder.build();
  67     }
  68
  69     @Override
  70     public void newNode(Node node, Stack<Node> ancestors) {
  71       switch (ancestors.size()) {
  72         case 0:
  73           if (!DISPATCH_ENTRIES_TAG.equalsIgnoreCase(node.getTag())) {
  74             throwExpectingTag(DISPATCH_ENTRIES_TAG, node.getTag());
  75           }
  76           if (!first) {
  77             throwDuplicateTag(DISPATCH_ENTRIES_TAG, null);
  78           }
  79           first = false;
  80           break;
  81
  82         case 1:
  83           if (DISPATCH_TAG.equalsIgnoreCase(node.getTag())) {
  84             checkForIncompleteDispatchElement();
  85             dispatchComplete = false;
  86           } else {
  87             throwExpectingTag(DISPATCH_TAG, node.getTag());
  88           }
  89           break;
  90
  91         case 2:
  92           if (URL_TAG.equalsIgnoreCase(node.getTag())) {
  93             if (dispatchComplete || url != null) {
  94               throwDuplicateTag(URL_TAG, DISPATCH_TAG);
  95             } else if (node.size() == 1 && node.get(0) instanceof String) {
  96               url = (String) node.get(0);
  97             } else {
  98               throwBadElementContents(URL_TAG);
  99             }
 100           } else if (MODULE_TAG.equalsIgnoreCase(node.getTag())) {
 101             if (dispatchComplete || module != null) {
 102               throwDuplicateTag(MODULE_TAG, DISPATCH_TAG);
 103             } else if (node.size() == 1 && node.get(0) instanceof String) {
 104               module = (String) node.get(0);
 105             } else {
 106               throwBadElementContents(MODULE_TAG);
 107             }
 108           } else {
 109             throwUnsupportedTag(node.getTag(), DISPATCH_TAG);
 110           }
 111           if (url != null && module != null) {
 112             dispatchXmlBuilder.addDispatchEntry(new DispatchEntry(url, module));
 113             url = null;
 114             module = null;
 115             dispatchComplete = true;
 116           }
 117           break;
 118
 119         default:
 120           throw new AppEngineConfigException(
 121               String.format("Syntax error; node <%s> is too deeply nested in file %s",
 122                  node.getTag(), getFilename()));
 123       }
 124     }
 125
 126     private void checkForIncompleteDispatchElement() {
 127       if (module != null) {
 128         throwExpectingTag("url", "/dispatch");
 129       }
 130       if (url != null) {
 131         throwExpectingTag("module", "/dispatch");
 132       }
 133     }
 134
 135     private void throwExpectingTag(String expecting, String got) {
 136       throw new AppEngineConfigException(String.format("Expecting <%s> but got <%s> in file %s",
 137           expecting, got, getFilename()));
 138     }
 139
 140     private void throwUnsupportedTag(String tag, String parent) {
 141       throw new AppEngineConfigException(String.format(
 142           "Tag <%s> not supported in element <%s> in file %s", tag, parent, getFilename()));
 143     }
 144
 145     private void throwDuplicateTag(String duplicateTag, String parentTag) {
 146       if (parentTag == null) {
 147         throw new AppEngineConfigException(String.format("Duplicate <%s> in file %s",
 148             duplicateTag, getFilename()));
 149       } else {
 150         throw new AppEngineConfigException(String.format("Duplicate <%s> inside <%s> in file %s",
 151             duplicateTag, parentTag, getFilename()));
 152       }
 153     }
 154
 155     private void throwBadElementContents(String badTag) {
 156       throw new AppEngineConfigException(String.format(
 157           "Invalid contents in element <%s> in file %s", badTag, getFilename()));
 158     }
 159   }
 160 }