java jdbc连接和使用详细介绍

 java jdbc连接和使用

jdbc

导入驱动

//jar是已经打包好的class文件集，可以引用到其他工程中
//Build Path中add external jars导入

连接JDBC

1. 加载驱动

  Class.from("com.mysql.jdbc.Driver");

创建连接

//导包使用 java.sql.*；
String jdbc="jdbc:mysql://localhost:3306/student?user=root&password=&characterEncoding=utf-8";//student是表名
Connection conn = DriverManager.getConnection(jdbc);

2. 注意 数据库打开之后一定要记得关。

 conn.close();

1. 执行SQL语句 （创建表，插入，删除，更新）

使用Statemant

Statemant st = conn.createStatemant();
 int row = st.executeUpdate(sql语句);//不能做查询操作。

使用PrepareStatement

可以使用？占位符来代替你需要传递的参数

String sql = "insert into " + TABLENAME
+ "(name,subject,score) values(?,?,?)";
PrepareStatement pt = conn.prepareStatement(sql);
 //给每一位占位符设置值,下标从1开始
 pt.setString(1,score.getName());
 pt.setString(2.score.getSubject());
pt.setDouble(3,score.getScore());
 //使用无参的方法
pt.executeUpdate();

1.查询操作

static List<Score> queryScore(Connection pconn,Score pScore)
      throws SQLException {
    ArrayList<Score> mlist = new ArrayList<>();
    String sql = "select * from " + TABLENAME + " where name = ?";
    PreparedStatement ps = pconn.prepareStatement(sql);
    ps.setString(1,pScore.getName());
    ResultSet rs = ps.executeQuery();

    while (rs.next()) {
      // 这里可以通过rs获取所有结果
      String subject = rs.getString("subject");
      int id = rs.getInt("id");
      double score = rs.getDouble("score");
      mlist.add(new Score(id,pScore.getName(),score));
    }
    return mlist;
  }

下面是一个小程序

//建立数据库连接类
public class DAO {

  // 放问数据库的链接地址
  static String jdbc = "jdbc:mysql://localhost:3306/student?user=root&password=&characterEncoding=utf-8";

  // 打开链接
  public static Connection connection() {
    // 使用JDBC的步骤
    // 1. 加载JDBC驱动
    try {
      // 类的全名 包名+类名
      Class.forName("com.mysql.jdbc.Driver");
      // 2. 连接数据库
      Connection conn = DriverManager.getConnection(jdbc);
      return conn;
    } catch (Exception e) {
      System.out.println("驱动加载失败");
      return null;
    }
  }



}


//分数类
public class Score {

  String name;
  String id;
  String subject;
  double score;



  public Score(String name,String subject,double score) {
    super();
    this.name = name;
    this.subject = subject;
    this.score = score;
  }



  @Override
  public String toString() {
    return "Score [name=" + name + ",id=" + id + ",subject=" + subject
        + ",score=" + score + "]";
  }



  public Score(String name,String id,double score) {
    super();
    this.name = name;
    this.id = id;
    this.subject = subject;
    this.score = score;
  }

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }

  public String getId() {
    return id;
  }

  public void setId(String id) {
    this.id = id;
  }

  public String getSubject() {
    return subject;
  }

  public void setSubject(String subject) {
    this.subject = subject;
  }

  public double getScore() {
    return score;
  }

  public void setScore(double score) {
    this.score = score;
  }

}


//实现类
public class Test {


  public static String TABLENAME = "score";

  public static void main(String[] args) {
    try {
      Connection conn = DAO.connection();
      if (conn != null) {
        System.out.println("链接上了");
        // createTable(conn);
        // 插入一条记录
        // Score score = new Score("李四 ","Android",98);
        // System.out.println(addScore2(conn,score));
        // deleteScore(conn,score);
        // updateScore(conn,score);
        List<Score> list = queryScoreByName(conn,"王五"); //queryAllScore(conn);
        for (Score score : list) {
          System.out.println(score);
        }
        conn.close();
      } else {
        System.out.println("链接失败 ");
      }
    } catch (SQLException e) {
      e.printStackTrace();
    }
  }

  // 创建一张表
  public static boolean createTable(Connection conn) {
    // 开始执行sql语句
    String sql = "create table "
        + TABLENAME
        + "(id integer primary key auto_increment,name varchar(3) not null,subject varchar(20) not null,score double)";
    // 要执行一条语句，需要一个执行的类 Statement
    try {
      Statement st = conn.createStatement();
      int result = st.executeUpdate(sql);
      System.out.println(result);
      if (result != -1)
        return true;
    } catch (SQLException e) {
      e.printStackTrace();
    }
    return false;
  }

  // 添加一条记录
  public static boolean addScore(Connection conn,Score score)
      throws SQLException {
    String sql = "insert into " + TABLENAME
        + "(name,score) values('" + score.getName() + "','"
        + score.getSubject() + "'," + score.getScore() + ")";
    System.out.println(sql);
    Statement st = conn.createStatement();
    int row = st.executeUpdate(sql);
    if (row > 0)
      return true;
    return false;
  }

  // 添加一条记录2
  public static boolean addScore2(Connection conn,Score score)
      throws SQLException {
    // 占位符?来代替需要设置的参数
    String sql = "insert into " + TABLENAME
        + "(name,?)";
    PreparedStatement ps = conn.prepareStatement(sql);
    // 必须给定？所代表的值
    ps.setString(1,score.getName());
    ps.setString(2,score.getSubject());
    ps.setDouble(3,score.getScore());
    // 调用无参的方法
    int row = ps.executeUpdate();
    if (row > 0)
      return true;
    return false;
  }

  public static boolean deleteScore(Connection conn,Score score)
      throws SQLException {
    String sql = "delete from " + TABLENAME + " where name=? and subject=?";
    // 创建PrepareStatement
    PreparedStatement ps = conn.prepareStatement(sql);
    ps.setString(1,score.getSubject());
    // ps.setDouble(3,score.getScore());
    // 执行
    int row = ps.executeUpdate();
    System.out.println(row);
    if (row > 0)
      return true;
    return false;
  }

  public static boolean updateScore(Connection conn,Score score)
      throws SQLException {
    // 修改 score人他的科目的成绩
    String sql = "update " + TABLENAME
        + " set score=? where name=? and subject=?";
    PreparedStatement ps = conn.prepareStatement(sql);
    ps.setDouble(1,score.getScore());
    ps.setString(2,score.getName());
    ps.setString(3,score.getSubject());
    int row = ps.executeUpdate();
    System.out.println(row);
    if (row > 0)
      return true;
    return false;
  }

  public static List<Score> queryAllScore(Connection conn)
      throws SQLException {
    String sql = "select * from " + TABLENAME;
    // 开始查询
    Statement st = conn.createStatement();
    ResultSet rs = st.executeQuery(sql);
    List<Score> list = new ArrayList<Score>();
    while (rs.next()) {
      // 这里可以通过rs获取所有结果
      String id = rs.getString("id");
      String name = rs.getString("name");
      String subject = rs.getString("subject");
      double score = rs.getDouble("score");
      list.add(new Score(name,id,score));
    }
    // 结束
    return list;
  }

  public static List<Score> queryScoreByName(Connection conn,String name)
      throws SQLException {
    String sql = "select * from " + TABLENAME + " where name=?";
    PreparedStatement pt = conn.prepareStatement(sql);
    pt.setString(1,name);
    ResultSet rs = pt.executeQuery();
    List<Score> list = new ArrayList<>();
    while (rs.next()) {
      String subject = rs.getString("subject");
      String id = rs.getString("id");
      double score = rs.getDouble("score");
      list.add(new Score(name,score));
    }
    return list;
  }

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