jdbc操作参数元数据

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ParameterMetaData;
import java.sql.PreparedStatement;

public class Main {
  public static void main(String[] args) throws Exception {
    Connection conn = null;
    PreparedStatement pstmt = null;
    ParameterMetaData paramMetaData = null;
    conn = getMySqlConnection();
    pstmt = conn.prepareStatement("select * from survey where id = ?");

  /**

   * 重点：获取参数个数，可以通过传入数据，迭代替换占位符的方法

   */   

 paramMetaData  pmd = pstmt.getParameterMetaData();
    if (paramMetaData == null) {
      System.out.println("db vendor does NOT support ParameterMetaData");
    } else {
      System.out.println("db vendor supports ParameterMetaData");
      // find out the number of dynamic parameters
      int paramCount = pmd.getParameterCount();

     for(int i=0;i<=paramCount;i++)

{

pmd.getParameterClassName( index ) //获得JAVA中的类型名，如打印出java.lang.String

pmd.getParameterType( index ) //获得类型号，比如打印出 12 ，代表VARCHAR类型

pmd.getParameterTypeName( index ) //获得数据库中的类型名，如打印出VARCHAR

//这些方法需要依赖于数据库的JDBC是否支持，如MYSQL就不支持，都只会打印出VARCHAR类型的值

}

      System.out.println("paramCount=" + paramCount);
    }
    pstmt.close();
    conn.close();
  }

  private static Connection getHSQLConnection() throws Exception {
    Class.forName("org.hsqldb.jdbcDriver");
    System.out.println("Driver Loaded.");
    String url = "jdbc:hsqldb:data/tutorial";
    return DriverManager.getConnection(url, "sa", "");
  }

  public static Connection getMySqlConnection() throws Exception {
    String driver = "org.gjt.mm.mysql.Driver";
    String url = "jdbc:mysql://localhost/demo2s";
    String username = "oost";
    String password = "oost";

    Class.forName(driver);
    Connection conn = DriverManager.getConnection(url, username, password);
    return conn;
  }

  public static Connection getOracleConnection() throws Exception {
    String driver = "oracle.jdbc.driver.OracleDriver";
    String url = "jdbc:oracle:thin:@localhost:1521:caspian";
    String username = "mp";
    String password = "mp2";

    Class.forName(driver); // load Oracle driver
    Connection conn = DriverManager.getConnection(url, username, password);
    return conn;
  }
}