SE-146 Helper class added

SVN: 12907

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

+/*
+ * Copyright 2009 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.InputStream;
+import java.io.Reader;
+import java.util.ArrayList;
+import java.util.List;
+
+import javax.xml.XMLConstants;
+import javax.xml.parsers.SAXParser;
+import javax.xml.parsers.SAXParserFactory;
+import javax.xml.transform.stream.StreamSource;
+import javax.xml.validation.Schema;
+import javax.xml.validation.SchemaFactory;
+
+import org.xml.sax.ContentHandler;
+import org.xml.sax.EntityResolver;
+import org.xml.sax.ErrorHandler;
+import org.xml.sax.InputSource;
+import org.xml.sax.SAXException;
+import org.xml.sax.SAXParseException;
+import org.xml.sax.XMLReader;
+
+import com.sun.org.apache.xerces.internal.jaxp.JAXPConstants;
+
+import ch.systemsx.cisd.base.exceptions.CheckedExceptionTunnel;
+
+/**
+ * Helper class providing convenient methods for parsing XML document with and without 
+ * schema validation.
+ *
+ * @author Franz-Josef Elmer
+ */
+public class XMLInfraStructure
+{
+    private static final SchemaFactory SCHEMA_FACTORY =
+            SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
+
+    /**
+     * Creates a Schema from a classpath resource.
+     */
+    public static Schema createSchema(String schemaAsClasspathResource)
+    {
+        return createSchema(XMLInfraStructure.class.getResourceAsStream(schemaAsClasspathResource));
+    }
+
+    /**
+     * Creates a Schema from an input stream
+     */
+    public static Schema createSchema(InputStream schemaAsInputStream)
+    {
+        try
+        {
+            return SCHEMA_FACTORY.newSchema(new StreamSource(schemaAsInputStream));
+        } catch (SAXException ex)
+        {
+            throw CheckedExceptionTunnel.wrapIfNecessary(ex);
+        }
+    }
+
+    private final SAXParserFactory parserFactory;
+    
+    private EntityResolver entityResolver;
+
+    /**
+     * Creates a new instance. 
+     *
+     * @param validating If <code>true</code> Schema validation is enabled. 
+     */
+    public XMLInfraStructure(boolean validating)
+    {
+        parserFactory = SAXParserFactory.newInstance();
+        parserFactory.setNamespaceAware(true);
+        parserFactory.setValidating(validating);
+    }
+    
+    /**
+     * Replaces the default entity resolver by the specified one.
+     */
+    public void setEntityResolver(EntityResolver entityResolver)
+    {
+        this.entityResolver = entityResolver;
+    }
+    
+    /**
+     * Parses the specified XML document and deliver all content event to the specified
+     * content handler. An exception with detailed error messages is thrown in case
+     * of enabled Schema validation. 
+     */
+    public void parse(Reader xmlDocument, ContentHandler contentHandler)
+    {
+        try
+        {
+            SAXParser saxParser = parserFactory.newSAXParser();
+            if (parserFactory.isValidating())
+            {
+                if (parserFactory.getSchema() == null)
+                {
+                    saxParser.setProperty(JAXPConstants.JAXP_SCHEMA_LANGUAGE,
+                            JAXPConstants.W3C_XML_SCHEMA);
+                }
+                XMLReader xmlReader = saxParser.getXMLReader();
+                xmlReader.setEntityResolver(entityResolver);
+                final List<SAXParseException> exceptions = new ArrayList<SAXParseException>();
+                xmlReader.setErrorHandler(new ErrorHandler()
+                    {
+                        public void warning(SAXParseException exception) throws SAXException
+                        {
+                        }
+
+                        public void fatalError(SAXParseException exception) throws SAXException
+                        {
+                            exceptions.add(exception);
+                        }
+
+                        public void error(SAXParseException exception) throws SAXException
+                        {
+                            exceptions.add(exception);
+                        }
+                    });
+                xmlReader.setContentHandler(contentHandler);
+                xmlReader.parse(new InputSource(xmlDocument));
+                if (exceptions.isEmpty() == false)
+                {
+                    StringBuilder builder = new StringBuilder();
+                    for (SAXParseException exception : exceptions)
+                    {
+                        builder.append("\n");
+                        builder.append("Error in line ").append(exception.getLineNumber());
+                        builder.append(" column ").append(exception.getColumnNumber());
+                        builder.append(":").append(exception.getMessage());
+                    }
+                    throw new SAXException("XML validation errors:" + builder);
+                }
+            } else
+            {
+                XMLReader xmlReader = saxParser.getXMLReader();
+                xmlReader.setContentHandler(contentHandler);
+                xmlReader.parse(new InputSource(xmlDocument));
+            }
+        } catch (Exception ex)
+        {
+            throw CheckedExceptionTunnel.wrapIfNecessary(ex);
+        }
+    }
+    
+}
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