ALF-11031: Persist object graph to file

Implemented so that the graph can actually be rendered to XML as a OutputStream, File, Writer.



git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/HEAD/root@31548 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261

source/java/org/alfresco/util/schemacomp/DbObjectXMLTransformer.java

@@ -0,0 +1,211 @@
+/*
+ * Copyright (C) 2005-2011 Alfresco Software Limited.
+ *
+ * This file is part of Alfresco
+ *
+ * Alfresco is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Alfresco is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with Alfresco. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.alfresco.util.schemacomp;
+
+import java.util.Collection;
+
+import org.alfresco.util.schemacomp.model.Column;
+import org.alfresco.util.schemacomp.model.DbObject;
+import org.alfresco.util.schemacomp.model.ForeignKey;
+import org.alfresco.util.schemacomp.model.Index;
+import org.alfresco.util.schemacomp.model.PrimaryKey;
+import org.alfresco.util.schemacomp.model.Schema;
+import org.alfresco.util.schemacomp.model.Table;
+import org.xml.sax.Attributes;
+import org.xml.sax.ContentHandler;
+import org.xml.sax.SAXException;
+import org.xml.sax.helpers.AttributesImpl;
+
+/**
+ * Converts DbObject instances into an XML output stream.
+ * 
+ * @author Matt Ward
+ */
+public class DbObjectXMLTransformer
+{
+    private static final Attributes EMPTY_ATTRIBUTES = new AttributesImpl();
+    private ContentHandler xmlOut;
+    
+    
+    public DbObjectXMLTransformer(ContentHandler contentHandler)
+    {
+        this.xmlOut = contentHandler;
+    }
+    
+    public void output(DbObject dbObject)
+    {
+        try
+        {
+            attemptOutput(dbObject);
+        }
+        catch (SAXException e)
+        {
+            throw new RuntimeException("Unable to output " + dbObject, e);
+        }
+    }
+    
+    private void attemptOutput(DbObject dbObject) throws SAXException
+    {
+        // All DbObjects result in an XML element with the DbObject's class name as the tag
+        // and a name attribute corresponding to the value of getName(),
+        // e.g. For an instance of a Column: <column name="the_column_name"/>
+        String tagName = dbObject.getClass().getSimpleName().toLowerCase();   
+        final AttributesImpl attribs = new AttributesImpl();
+        attribs.addAttribute("", "", "name", "CDATA", dbObject.getName());
+        xmlOut.startElement("", "", tagName, attribs);
+        
+        // The element's contents can optionally be populated with class-specific content.
+        transformDbObject(dbObject);
+        
+        // Provide the end tag, or close an empty element.
+        xmlOut.endElement("", "", tagName);
+    }
+    
+    private void transformDbObject(DbObject dbObject) throws SAXException
+    {
+        if (dbObject instanceof Schema)
+        {
+            transformSchema((Schema) dbObject);
+        }
+        else if (dbObject instanceof Table)
+        {
+            transformTable((Table) dbObject);
+        }
+        else if (dbObject instanceof Column)
+        {
+            transformColumn((Column) dbObject);
+        }
+        else if (dbObject instanceof ForeignKey)
+        {
+            transformForeignKey((ForeignKey) dbObject);
+        }
+        else if (dbObject instanceof Index)
+        {
+            transformIndex((Index) dbObject);
+        }
+        else if (dbObject instanceof PrimaryKey)
+        {
+            transformPrimaryKey((PrimaryKey) dbObject);
+        }
+    }
+    
+    
+
+    private void transformSchema(Schema schema) throws SAXException
+    {
+        simpleStartTag("objects");
+        for (DbObject dbo : schema)
+        {
+            output(dbo);
+        }
+        simpleEndTag("objects");
+    }
+    
+    private void transformTable(Table table) throws SAXException
+    {
+        // Output columns
+        simpleStartTag("columns");
+        for (Column column : table.getColumns())
+        {
+            output(column);
+        }
+        simpleEndTag("columns");
+        
+        // Output primary key
+        output(table.getPrimaryKey());
+        
+        // Output foreign keys
+        simpleStartTag("foreignkeys");
+        for (ForeignKey fk : table.getForeignKeys())
+        {
+            output(fk);
+        }
+        simpleEndTag("foreignkeys");
+
+        // Output indexes
+        simpleStartTag("indexes");
+        for (Index index : table.getIndexes())
+        {
+            output(index);
+        }
+        simpleEndTag("indexes");
+    }
+    
+    private void transformColumn(Column column) throws SAXException
+    {
+        simpleElement("type", column.getType());
+        simpleElement("nullable", Boolean.toString(column.isNullable()));
+    }
+
+    private void transformForeignKey(ForeignKey fk) throws SAXException
+    {
+        simpleElement("localcolumn", fk.getLocalColumn());
+        simpleElement("targettable", fk.getTargetTable());
+        simpleElement("targetcolumn", fk.getTargetColumn()); 
+    }
+
+    private void transformIndex(Index index) throws SAXException
+    {
+        columnNameList(index.getColumnNames());
+    }
+    
+    private void transformPrimaryKey(PrimaryKey pk) throws SAXException
+    {
+        columnNameList(pk.getColumnNames());
+    }
+    
+    
+    /**
+     * Create a simple element of the form:
+     * <pre>
+     *    &lt;tag&gt;content&lt;/tag&gt;
+     * </pre>
+     * 
+     * @param tag
+     * @param content
+     * @throws SAXException
+     */
+    private void simpleElement(String tag, String content) throws SAXException
+    {
+        simpleStartTag(tag);
+        char[] chars = content.toCharArray();
+        xmlOut.characters(chars, 0, chars.length);
+        simpleEndTag(tag);
+    }
+    
+    private void simpleStartTag(String tag) throws SAXException
+    {
+        xmlOut.startElement("", "", tag, DbObjectXMLTransformer.EMPTY_ATTRIBUTES);
+    }
+    
+    private void simpleEndTag(String tag) throws SAXException
+    {
+        xmlOut.endElement("", "", tag);        
+    }
+    
+    private void columnNameList(Collection<String> columnNames) throws SAXException
+    {
+        simpleStartTag("columnnames");
+        for (String columnName : columnNames)
+        {
+            simpleElement("columnname", columnName);
+        }
+        simpleEndTag("columnnames");
+    }
+}