industry.java

利用多线程从搜索引擎下载网页并提取数据到数据库。

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.Map;

public class Industry {

	public int id;

	public String name;
	static Connection cnn;
	static SQLException e;
	static Map<String, Integer> map;
	static {
		fillBuffer();
	}

	private static void fillBuffer() {
		try {
			cnn = DataAccess.getConnection();
			map = new HashMap<String, Integer>();
			PreparedStatement stmt;
			stmt = cnn.prepareStatement("select * from industries");
			ResultSet rs = stmt.executeQuery();
			while (rs.next()) {
				map.put(rs.getString("name"), new Integer(rs.getInt("id")));
			}
		} catch (SQLException e1) {
			e = e1;
		}
	}

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub

	}

	public Industry(String industry) throws SQLException {
		this.name = industry;
		cnn = DataAccess.getConnection();
		if (e != null)
			throw e;
	}

	private int getIDLocal() {
		if (map.containsKey(this.name))
			return map.get(this.name).intValue();
		else
			return 0;
	}

	public int getID() throws SQLException {
		if (name == null || name == "")
			return 0;
		if (id != 0)
			return id;
		id=getIDLocal();
		if (id != 0)
			return id;
		if (!populateFromDB())
			insert();
		populateFromDB();
		map.put(name, id);
		return id;

	}

	public synchronized static boolean exists(String industry)
			throws SQLException {
		fillBuffer();
		return new Industry(industry).populateFromDB();
	}

	public boolean populateFromDB() throws SQLException {
		PreparedStatement stmt;
		stmt = cnn.prepareStatement("select id from industries where name=?");
		stmt.setString(1, name);
		ResultSet rs = stmt.executeQuery();
		if (rs.next()) {
			this.id = rs.getInt("id");
			return true;
		} else
			return false;
	}

	public void insert() throws SQLException {
		PreparedStatement stmt;
		stmt = cnn.prepareStatement("insert into industries(name) select ?");
		stmt.setString(1, name);
		stmt.execute();
	}

}