PreparedStatement对象

Posted 2021-05-16 saxon宋

PreparedStatement对象

• 使用preparedStatement对象，可以有效的防止SQL注入，并且效率更高

• 新增

  import java.sql.Connection;
  import java.sql.PreparedStatement;
  import java.util.Date;
  public class Test01 {
      public static void main(String[] args) {
          Connection conn = null;
          PreparedStatement st = null;
          try {
              conn = jdbcUtils.getConnection();
              String sql = "insert into users(id,`NAME`,`password`,`email`,`birthday`) values(?,?,?,?,?)";
              st = conn.prepareStatement(sql);
              //手动赋值参数
              st.setInt(1,5);
              st.setString(2,"saxon");
              st.setString(3,"123456");
              st.setString(4,"[e-mail]");
              //获得时间戳   new Date().getTime()
              st.setDate(5,new java.sql.Date(new Date().getTime()));
              //执行
              int i = st.executeUpdate();
              if(i>0){
                  System.out.println("插入成功");
              }
          } catch (Exception e) {
              e.printStackTrace();
          }
      }
  }
  

• 删除

  import java.sql.Connection;
  import java.sql.PreparedStatement;
  public class Test01 {
      public static void main(String[] args) {
          Connection conn = null;
          PreparedStatement st = null;
          try {
              conn = jdbcUtils.getConnection();
              String sql = "delete from users where id = ?";
              st = conn.prepareStatement(sql);
              //手动赋值参数
              st.setInt(1,5);
              //执行
              int i = st.executeUpdate();
              if(i>0){
                  System.out.println("删除成功");
              }
          } catch (Exception e) {
              e.printStackTrace();
          }
      }
  }
  

• 修改

  import java.sql.Connection;
  import java.sql.PreparedStatement;
  public class Test01 {
      public static void main(String[] args) {
          Connection conn = null;
          PreparedStatement st = null;
          try {
              conn = jdbcUtils.getConnection();
              String sql = "update users set `name` = ? where id = ?";
              st = conn.prepareStatement(sql);
              //手动赋值参数
              st.setString(1,"xon");
              st.setInt(2,1);
              //执行
              int i = st.executeUpdate();
              if(i>0){
                  System.out.println("修改成功");
              }
          } catch (Exception e) {
              e.printStackTrace();
          }
      }
  }
  

• 查询

  import java.sql.Connection;
  import java.sql.PreparedStatement;
  import java.sql.ResultSet;
  public class Test01 {
      public static void main(String[] args) {
          Connection conn = null;
          PreparedStatement st = null;
          ResultSet rs = null;
          try {
              conn = jdbcUtils.getConnection();
              // PreparedStatement 防止SQL注入的本质，把传递进来的参数当作字符串
              // 假设其中存在转义字符，就直接忽略， 比如说 \' 会被直接转义
              String sql = "select * from users where `id` = ? ";
              st = conn.prepareStatement(sql);
              st.setInt(1, 1);
              rs = st.executeQuery();  // 查询完毕会返回一个结果集
              while (rs.next()) {
                  System.out.println(rs.getString("NAME"));
                  System.out.println("=====================");
              }
          } catch (Exception e) {
              e.printStackTrace();
          }
      }
  }