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Package testJDBC

Import java.sql.*

/ * *

@ Author Piglet @ Email zhuhuaikuan@gmail.com@Data 2019-8-28 14:27@Version V1.0

@ description JDBC query database example

, /

Public class JDBCdemo1 {

Public static void main (String [] args) {

Connection conn = null

Statement statement = null

ResultSet resultSet = null

/ / 1. Register the database driver

Try {

Class.forName ("com.mysql.jdbc.Driver"); / / load a class into memory, in which there is a static code block with registered driver code / / static code block pseudo code as follows: DriverManager.registerDriver (new Driver ()) / / 2. Get database connection String url = "jdbc:mysql://localhost:3306/" + "jt_db" + "? characterEncoding=utf-8"; / * jdbc:mysql: protocol name * localhost:3306 host address and port * jt_db database name *? characterEncoding=utf-8? + Parameter * / String user = "root"; / / database connection user name String passWord = "123456"; / / database connection password conn = DriverManager.getConnection (url, user, passWord); / / 3. Get transporter statement = conn.createStatement (); / * Statement s = con.createStatement (); * PreparedStatement p = con.preparedStatement (); * * PreparedStatement is a subclass of Statement * placeholder can be used and is precompiled, and batch processing is more efficient than Statement * * example: * String sql = "update user set password=?" Where username=? "; * preparedStatement = conn.prepareStatement (sql); * / / preparedStatement.setString (the nth question mark, the variable represented); * preparedStatement.setString (1); * preparedStatement.setString (2) username; * preparedStatement.executeUpdate (); * * / 4. Execute the sql statement and return the execution result String sql = "select * from account"; / * executeQuery (); the statement used to produce a single result set, which is used to execute the SELECT statement, and the return value is an ResultSet result set object, including the result of the sql query * executeUpdate () Used to execute INSERT, UPDATE or DELETE statements and SQL DDL (data definition language) statements, return an int value and record the number of affected record rows * / resultSet = statement.executeQuery (sql); / / 5. Processing result / * ResultSet result set object * ResultSet is the result set object returned after executing the sql statement of the query class, including the result of the sql query * a. The method to traverse the data row * next ()-moves the index pointing to the data row down one row * b. Method of obtaining data * getInt (int columnIndex) * getInt (String columnLable) * getString (int columnIndex) * getString (String columnLable) * getDouble (int columnIndex) * getDouble (String columnLable) * getObject (int columnIndex) * getObject (String columnLable) * / while (resultSet.next ()) {int id = resultSet.getInt ("id") String name = resultSet.getString ("name"); double money = resultSet.getDouble ("money"); System.out.println (id + ":" + name + ":" + money);} catch (Exception e) {e.printStackTrace ();} finally {/ / 6. Release resources / / the later you get, the first you release! / / it is best to put the release resource code in finally: if (resultSettings null) {try {resultSet.close ();} catch (SQLException e) {e.printStackTrace ();} finally {resultSet = null;}} if (statementsetting null) {try {statement.close ();} catch (SQLException e) {e.printStackTrace () } finally {statement = null;}} if {try {conn.close ();} catch (SQLException e) {e.printStackTrace ();} finally {conn = null;}

}

}

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