jdbcjson/src/com/binarythought/jdbcjson/JDBCJSON.java

package com.binarythought.jdbcjson;

import java.io.FileInputStream;
import java.io.FileWriter;
import java.sql.Connection;
import java.sql.DriverManager; 
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
import java.sql.Types;
import java.text.DateFormat;
import java.util.HashSet;
import java.util.Properties;
import java.util.Set;

import com.google.gson.stream.JsonWriter;


public class JDBCJSON
{
	private static final DateFormat dateformat = DateFormat.getDateInstance(DateFormat.SHORT);
	private static final DateFormat timeformat = DateFormat.getTimeInstance(DateFormat.SHORT);
	private static final DateFormat datetimeformat = DateFormat.getDateTimeInstance(DateFormat.SHORT, DateFormat.SHORT);

	private boolean debug;
	private Properties properties;
	private Set<String> warnings;


	public JDBCJSON(boolean debug)
	{
		this.properties = new Properties();
		this.debug = debug;
		this.warnings = new HashSet<String>();
	}


	public void load(String path) throws Exception
	{
		FileInputStream stream = new FileInputStream(path);
		properties.load(stream);
		stream.close();
	}


	public String[] list()
	{
		HashSet<String> jobs = new HashSet<String>();
		for(String name : properties.stringPropertyNames()){
			int dot = name.lastIndexOf('.');
			if(dot > 0){ jobs.add(name.substring(0, dot)); }
		}

		return jobs.toArray(new String[0]);
	}


	public Set<String> getWarnings()
	{
		return warnings;
	}


	public void run(String job) throws Exception
	{
		String url = properties.getProperty(job + ".url");

		String sql = properties.getProperty(job + ".sql");
		if(sql == null){ sql = "SELECT * FROM " + job; }

		String out = properties.getProperty(job + ".out");
		if(out == null){ out = job + ".json"; }

		String driver = properties.getProperty(job + ".driver");
		if(driver != null){ Class.forName(driver); }

		Connection conn = null;
		JsonWriter writer = null;
		try {
			conn = DriverManager.getConnection(url);

			Statement st = conn.createStatement(
				ResultSet.TYPE_FORWARD_ONLY,
				ResultSet.CONCUR_READ_ONLY
			);

			ResultSet rs = st.executeQuery(sql);
			writer = new JsonWriter(new FileWriter(out, false));

			process(rs, writer, null);

		} finally {
			try { writer.close(); }
			catch(Exception ex){ }

			try { conn.close(); }
			catch(Exception ex){ }
		}
	}


	private void process(ResultSet rs, JsonWriter writer, String column) throws Exception
	{
		ResultSetMetaData rsmd = rs.getMetaData();
		int count = rsmd.getColumnCount();

		writer.beginArray();
		while(rs.next()){
			if(column == null){ writer.beginObject(); }
			for(int i = (column == null ? 1 : 2); i <= count; i++){
				switch(rsmd.getColumnType(i)){
					case Types.CHAR:
					case Types.LONGVARCHAR:
					case Types.LONGNVARCHAR:
					case Types.NCHAR:
					case Types.NVARCHAR:
					case Types.VARCHAR:
						if(column == null){ writer.name(rsmd.getColumnName(i)); }
						writer.value(rs.getString(i));
					break;

					case Types.NULL:
						if(column == null){ writer.name(rsmd.getColumnName(i)); }
						writer.nullValue();
					break;

					case Types.BIT:
					case Types.BOOLEAN:
						if(column == null){ writer.name(rsmd.getColumnName(i)); }
						writer.value(rs.getBoolean(i));
					break;

					case Types.BIGINT:
					case Types.INTEGER:
					case Types.SMALLINT:
					case Types.TINYINT:
						if(column == null){ writer.name(rsmd.getColumnName(i)); }
						writer.value(rs.getLong(i));
					break;

					case Types.REAL:
						if(column == null){ writer.name(rsmd.getColumnName(i)); }
						writer.value(rs.getFloat(i));
					break;

					case Types.DOUBLE:
					case Types.FLOAT:
						if(column == null){ writer.name(rsmd.getColumnName(i)); }
						writer.value(rs.getDouble(i));
					break;

					case Types.DECIMAL:
					case Types.NUMERIC:
						if(column == null){ writer.name(rsmd.getColumnName(i)); }
						writer.value(rs.getBigDecimal(i));
					break;

					case Types.DATE:
						if(column == null){ writer.name(rsmd.getColumnName(i)); }
						if(rs.getDate(i) == null){
							writer.nullValue();
						} else {
							writer.value(dateformat.format(rs.getDate(i)));
						}
					break;

					case Types.TIME:
						if(column == null){ writer.name(rsmd.getColumnName(i)); }
						if(rs.getTime(i) == null){
							writer.nullValue();
						} else {
							writer.value(timeformat.format(rs.getTime(i)));
						}
					break;

					case Types.TIMESTAMP:
						if(column == null){ writer.name(rsmd.getColumnName(i)); }
						if(rs.getTimestamp(i) == null){
							writer.nullValue();
						} else {
							writer.value(datetimeformat.format(rs.getTimestamp(i)));
						}
					break;

					case Types.ARRAY:
						if(column == null){ writer.name(rsmd.getColumnName(i)); }
						if(rs.getArray(i) == null){
							writer.nullValue();
						} else {
							process(
								rs.getArray(i).getResultSet(),
								writer,
								(column == null ? rsmd.getColumnName(i) : column)
							);
						}
					break;

					default:
						if(debug){
							warnings.add(
								"Unsupported column, " +
								(column == null ? rsmd.getColumnName(i) : column) + 
								", type " + rsmd.getColumnTypeName(i)
							);
						}
					break;
				}
			}
			if(column == null){ writer.endObject(); }
		}
		writer.endArray();
	}


	public static void main(String[] args)
	{
		boolean debug = false;
		String properties_path = null;

		for(int i = 0; i < args.length; i++){
			if("-d".equals(args[i])){
				debug = true;
			} else if(i == (args.length - 1)){
				properties_path = args[i];
			} else {
				System.out.println("Unrecognized option: " + args[i]);
				break;
			}
		}

		if(properties_path == null){
			System.out.println("Usage:");
			System.out.println("\tjava -jar jdbcjson.jar [-d] myfile.properties");
			System.out.println("Options:");
			System.out.println("\t-d\tDebug mode. Prints warnings and more error detail.");
			System.exit(1);
		}

		JDBCJSON jdbcjson = new JDBCJSON(debug);

		try {
			jdbcjson.load(properties_path);
		} catch(Exception ex){
			System.out.print("Error while loading " + args[0] + ": ");
			System.out.println(ex.getMessage());
			if(debug){ ex.printStackTrace(); }
			System.exit(1);
		}

		String[] jobs = jdbcjson.list();
		for(String job : jobs){
			try { jdbcjson.run(job); }
			catch(Exception ex){
				System.out.print("Error while running job " + job + ": ");
				System.out.println(ex.getMessage());
				if(debug){ ex.printStackTrace(); }
				System.exit(1);
			}

			for(String warning : jdbcjson.getWarnings()){
				System.out.println("Warning in " + job + ": " + warning);
			}
		}

		System.exit(0);
	}
}