jfreechart_jdbc_demo

package jfreechart_database; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.ResultSetMetaData; import java.sql.SQLException; import java.sql.Statement; public class DBUtils { // private static String driver= "com.mysql.jdbc.Driver"; // private String url= "jdbc:mysql://127.0.0.1:3306/test"; // private static String username="root"; // private static String pwd="root"; private static String[] props = {"com.mysql.jdbc.Driver", "jdbc:mysql://127.0.0.1:3306/test", "root", "root"}; // 1、加载驱动 static { try { Class.forName(props[0]); } catch (Exception e) { e.printStackTrace(); } } // 2、获取连接 public static Connection getConnection() { Connection con = null; try { con = DriverManager.getConnection(props[1], props[2], props[3]); } catch (Exception e) { e.printStackTrace(); } return con; } // 3、释放资源 public static void release(Object o) { try { if (o instanceof ResultSet) { ((ResultSet) o).close(); } else if (o instanceof Statement) { ((Statement) o).close(); } else if (o instanceof Connection) { ((Connection) o).close(); } } catch (Exception e) { e.printStackTrace(); } } public static void release(ResultSet rs, Statement stmt, Connection con) { if (rs != null) { try { rs.close(); } catch (Exception e) { e.printStackTrace(); } } if (stmt != null) { try { stmt.close(); } catch (Exception e) { e.printStackTrace(); } } if (con != null) { try { con.close(); } catch (Exception e) { e.printStackTrace(); } } } public static void printRs(ResultSet rs) { if (rs == null) return; try { ResultSetMetaData md = rs.getMetaData(); int num = md.getColumnCount(); StringBuffer sb = new StringBuffer(); for (int i = 1; i <= num; i++) { int size = md.getColumnDisplaySize(i); if (size != 0) { String cname = md.getColumnName(i); int blank = (size - cname.length()) / 2; for (int j = 0; j < blank; j++) sb.append(" "); sb.append(cname); if ((size - cname.length()) % 2 != 0) blank++; for (int j = 0; j < blank; j++) sb.append(" "); } } sb.append("\n"); while (rs.next()) { for (int i = 1; i <= num; i++) { int size = md.getColumnDisplaySize(i); if (size != 0) { String value = rs.getString(i); int blank = (size - value.length()) / 2; for (int j = 0; j < blank; j++) sb.append(" "); sb.append(value); if ((size - value.length()) % 2 != 0) blank++; for (int j = 0; j < blank; j++) sb.append(" "); } } sb.append("\n"); } System.out.println(sb.toString()); } catch (Exception e) { e.printStackTrace(); } } }