JDBC beginner, DAO mode

A, is connected with the eclipse mysql database:

First to add a file: https://www.cnblogs.com/caiwenjing/p/8079227.html

Second, start writing code to connect to the database:

Because the operation of the database connection is generally common, so write in the bag, I called the util

Like entity called the entity class generally written in the package inside

Test classes (JUnit in his explanations how to use) is called in to write a test packet inside

 

Package com.util; 

Import the java.sql *. ; 

public  class ConnectionUtil {
     / ** 
     * Step: Load Driver 
     * Step: Database Link 
     * Step: Be sure to close the flow 
     * Step Four: Test whether the connection success 
     * / 
    Private  static String dRIVER = "com.mysql.cj.jdbc.Driver";          // database-driven 
    Private  static String the URL of = "jdbc: MySQL: // localhost: 3306 / = to true XXXY useUnicode & characterEncoding = UTF-8 & useSSL =? & serverTimezone GMT = false ";     // access the database path
                                                      // XXXY is the name of my database connection 
    Private  staticNAME = String "the root";                             // database username 
    Private  static String = PASSWORD "the root";                         // database password 
 
 
    public  static Connection the getConnection () { 
        Connection Connection = null ;
         the try {
             // load the driver 
            Class.forName (DRIVER);
             // connect to the database 
            connection = the DriverManager.getConnection (the URL, NAME, PASSWORD);
             return connection; 
        } the catch (Exception E) {
             return null;
        }
    }
 
 
    // 关闭流
    public static void closeConnection(Connection connection) {
        try {
            connection.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
 
 
    public static void closeStatement(Statement statement) {
        try {
            statement.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
 
 
    public static void closePreparedStatement(PreparedStatement pStatement) {
        try {
            pStatement.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
 
 
    public static void closeResultSet(ResultSet rs) {
        try {
            rs.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    // 测试数据库是否链接成功
    /*public static void main(String[] args) {
        System.out.println("good"+getConnection());
    }*/
}

Third, deletions written DAO mode change search operation (so that the code written specification more!)

　　DAO mode can be implemented into the operation database table operation of the JAVA class

/* read all data */
    public static List<Users> readDao() {
        String sql = "select * from Journalism";
        Connection connect = null;
        PreparedStatement ptmt = null;
        ResultSet rs = null;
        List<Users> lists = new ArrayList<Users>();
        try {
            connect = ConnectionUtil.getConnection();
            ptmt = connect.prepareStatement(sql);
            rs = ptmt.executeQuery();

            while (rs.next()) {

                Users user = new Users();
                user.setType(rs.getString("type"));
                user.setContent(rs.getString("content"));
                user.setTitle(rs.getString("title"));
                user.setAuthor(rs.getString("author"));
                user.setId(rs.getString("id"));
                user.setImg(rs.getString("img"));
                user.setToday(rs.getTimestamp("today"));

                lists.add(user);
            }
            return lists;

        } catch (Exception e) {
            e.printStackTrace();
            return null;
        } finally {
            ConnectionUtil.closeResultSet(rs);
            ConnectionUtil.closePreparedStatement(ptmt);
            ConnectionUtil.closeConnection(connect);
        }
    }

    
    /* delete the data */
    public static boolean deleteDao(Users user) {
        String sql = "delete from Journalism where id = ?";
        Connection connect = null;
        PreparedStatement ptmt = null;
        try {
            connect = ConnectionUtil.getConnection();
            ptmt = connect.prepareStatement(sql);
            ptmt.setString(1, user.getId());
            int i = ptmt.executeUpdate();
            return i > 0 ? true : false;
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        } finally {
            ConnectionUtil.closePreparedStatement(ptmt);
            ConnectionUtil.closeConnection(connect);
        }
    }