Commons Digester example source code file (RowInserterRule.java)

This example Commons Digester source code file (RowInserterRule.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Commons Digester tags/keywords

row, row, rowinserterrule, string, string, stringbuffer, stringbuffer, table, table, util

The Commons Digester RowInserterRule.java source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */ 

import java.util.Map;
import java.util.Iterator;

/**
 * See Main.java.
 */
public class RowInserterRule extends org.apache.commons.digester.Rule {

    private java.sql.Connection conn;
    
    public RowInserterRule(java.sql.Connection conn) {
        this.conn = conn;
    }
    
    /**
     * This method is invoked when the start tag for an xml element representing
     * a database row is encountered. It pushes a new Row instance onto the
     * digester stack (rather like an ObjectCreateRule) so that column data
     * can be stored on it.
     */
    public void begin(String namespace, String name, org.xml.sax.Attributes attrs) {
        digester.push(new Row());
    }
    
    /**
     * This method is invoked when the end tag for an xml element representing
     * a database row is encountered. It pops a fully-configured Row instance
     * off the digester stack, accesses the object below it on the stack (a
     * Table object) to get the tablename, then does an SQL insert). Actually,
     * here we just print out text rather than do the sql insert, but the
     * real implementation should be fairly simple.
     * <p>
     * Note that after this rule completes, the row/column information is
     * <i>discarded, ie this rule performs actions as the input is
     * parsed</i>. This contrasts with the more usual way digester is used,
     * which is to build trees of objects for later use. But it's a perfectly
     * valid use of Digester.
     */
    public void end(String namespace, String name) {
        Row row = (Row) digester.pop();
        Table table = (Table) digester.peek();

        // Obviously, all this would be replaced by code like:
        //   stmt = conn.prepareStatement();
        //   stmt.setString(n, value);
        //
        // Many improvements can then be implemented, such as using the 
        // PreparedStatement.getParameterMetaData method to retrieve
        // retrieve parameter types, etc.
        
        StringBuffer colnames = new StringBuffer();
        StringBuffer colvalues = new StringBuffer();
        
        for(Iterator i = row.getColumns().iterator(); i.hasNext();)
        {
            Row.Column column = (Row.Column) i.next();
            
            if (colnames.length() > 0)
            {
                colnames.append(", ");
                colvalues.append(", ");
            }
        
            colnames.append("'");
            colnames.append(column.getName());
            colnames.append("'");
            
            colvalues.append("'");
            colvalues.append(column.getValue());
            colvalues.append("'");
        }

        StringBuffer buf = new StringBuffer();
        buf.append("insert into ");
        buf.append(table.getName());
        buf.append(" (");
        buf.append(colnames.toString());
        buf.append(") values (");
        buf.append(colvalues.toString());
        buf.append(")");
        
        // here the prepared statement would be executed....
        System.out.println(buf.toString());
    }
}