数据库的内容
CATEGORY | VALUE
---------+------
London | 54.3
New York | 43.4
Paris | 17.9
import java.io.IOException;import java.io.OutputStream;import java.sql.Connection;import java.sql.DriverManager;import java.sql.SQLException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.jfree.chart.ChartFactory;import org.jfree.chart.ChartUtilities;import org.jfree.chart.JFreeChart;import org.jfree.data.general.DefaultPieDataset;import org.jfree.data.general.PieDataset;import org.jfree.data.jdbc.JDBCPieDataset;public class PieServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { try { //获得输出流 OutputStream os = response.getOutputStream(); //获得相于的数据对象 DefaultPieDataset dataset = (DefaultPieDataset) this.readData(); JFreeChart chart = ChartFactory.createPieChart("Test", dataset, true, true, false); response.setContentType("image/png"); //写到输出流,并在页面上面显示 ChartUtilities.writeChartAsPNG(os, chart, 800, 600); os.close(); } catch (RuntimeException e) { e.printStackTrace(); } } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doGet(request, response); } /** * 连结JDBC,并创建JDBCPieDataset对象返回 * @return */ private PieDataset readData() { //创建JDBCPieDataset对象 JDBCPieDataset data = null; String url = "jdbc:mysql://127.0.0.1:3306/jfreechartdb"; Connection con = null; try { Class.forName("com.mysql.jdbc.Driver"); } catch (ClassNotFoundException e) { System.err.print("ClassNotFoundException: "); } try { con = DriverManager.getConnection(url, "root", "root"); //把JDBCPieDataset对象和Connection关联 data = new JDBCPieDataset(con); String sql = "select * from piedata;"; //获得数据 data.executeQuery(sql); con.close(); } catch (SQLException e) { System.err.print("SQLException: "); } catch (Exception e) { System.err.print("Exception: "); } return data; }}
同时还有其它对象JDBCCategoryDataset,JDBCXYDataset，对应的是条状和，坐标,用于封装相应的数据
