JDBC的使用

工具类

package cn.itcast.jdbc;

import java.sql.*;

/**
 * Created by sherry on 000019/5/19 22:54.
 */
public final class JdbcUtils {
    private static String url = "jdbc:mysql://localhost:3306/ssi";
    private static String username = "root";
    private static String password = "123456";

    private JdbcUtils() {
    }

    static {
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
            throw new ExceptionInInitializerError(e);
        }
    }

    public static Connection getCollection() throws SQLException {
        return DriverManager.getConnection(url, username, password);
    }

    public static void close(Connection connection,Statement statement,ResultSet resultSet){
        if (resultSet!=null){
            try {
                resultSet.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }finally {
                if (statement!=null){
                    try {
                        statement.close();
                    } catch (SQLException e) {
                        e.printStackTrace();
                    }finally {
                        if (connection!=null){
                            try {
                                connection.close();
                            } catch (SQLException e) {
                                e.printStackTrace();
                            }
                        }
                    }
                }
            }
        }
    }
}

CRUD

package cn.itcast.jdbc;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

/**
 * Created by sherry on 000019/5/19 23:06.
 */
public class CRUD {
    public static void main(String[] args) {
    }

    static void create(){
        Connection connection = null;
        Statement statement = null;
        ResultSet resultSet = null;

        try {
            connection = JdbcUtils.getCollection();
            statement = connection.createStatement();
            String sql = "INSERT into user(username,password,birthday) VALUES" +
                    "('name1','password1','1990-01-01')";
            int i = statement.executeUpdate(sql);
            System.out.println(i+"条记录被插入");
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.close(connection,statement,resultSet);
        }

    }
    static void read(){
        Connection connection = null;
        Statement statement = null;
        ResultSet resultSet = null;

        try {
            connection = JdbcUtils.getCollection();
            statement = connection.createStatement();
            resultSet = statement.executeQuery("SELECT id,username,password,birthday FROM user");
            while (resultSet.next()){
                int id = resultSet.getInt("id");
                String name = resultSet.getString("username");
                String pass = resultSet.getString("password");
                String birth = resultSet.getString("birthday");
                System.out.println(id+"	"+
                        name+"	"+
                        pass+"	"+
                        birth);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.close(connection,statement,resultSet);
        }

    }

    static void update(){
        Connection connection = null;
        Statement statement = null;
        ResultSet resultSet = null;

        try {
            connection = JdbcUtils.getCollection();
            statement = connection.createStatement();
            String sql = "UPDATE user set username = 'name2' WHERE id = 21";
            int i = statement.executeUpdate(sql);
            System.out.println(i+"条记录被修改");
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.close(connection,statement,resultSet);
        }

    }

    static void delete(){
        Connection connection = null;
        Statement statement = null;
        ResultSet resultSet = null;

        try {
            connection = JdbcUtils.getCollection();
            statement = connection.createStatement();
            String sql = "DELETE FROM user WHERE id < 10";
            int i = statement.executeUpdate(sql);
            System.out.println(i+"条记录被删除");
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.close(connection,statement,resultSet);
        }

    }
}

SQL注入问题

package cn.itcast.jdbc;

import java.sql.*;

/**
 * Created by sherry on 000020/5/20 18:02.
 */
public class SQLInject {
    public static void main(String[] args) {
        read("name2");
    }

    static void read(String name){
        Connection connection = null;
        //解决SQL注入问题
        PreparedStatement preparedStatement = null;
        ResultSet resulSet = null;

        try {
            connection = JdbcUtils.getCollection();

            String sql = "SELECT id,usernme,password,birthday FROM user WHERE username = ?";
            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setString(1,name);

            resultSet = preparedStatement.executeQuery();
            while (resultSet.next()){
                System.out.println(resultSet.getInt("id")+"	"+
                        resultSet.getString("username")+"	"+
                        resultSet.getString("password")+"	"+
                        resultSet.getString("birthday"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.close(connection,preparedStatement,resultSet);
        }

    }
}

复杂数据类型的处理

package cn.itcast.jdbc;

import java.io.*;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

/**
 * Created by sherry on 000020/5/20 19:13.
 */
public class BlobTest {
    public static void main(String[] args) {

    }

    static void create(){
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;

        try {
            connection = JdbcUtils.getCollection();

            String sql = "INSERT into blob_test(big_bin) VALUES (?)";
            preparedStatement = connection.prepareStatement(sql);
            File file = new File("需要读取的二进制文件的路径");
            InputStream inputStream = new BufferedInputStream(new FileInputStream(file));
            preparedStatement.setBlob(1,inputStream);
            int i = preparedStatement.executeUpdate();

            System.out.println(i+"条记录被插入");
            inputStream.close();
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.close(connection,preparedStatement,resultSet);
        }

    }

    static void read(){
        Connection connection = null;
        PreparedStatement statement = null;
        ResultSet resultSet = null;

        try {
            connection = JdbcUtils.getCollection();
            String sql = "SELECT big_bin FROM blob_test";
            statement = connection.prepareStatement(sql);
            resultSet = statement.executeQuery();

            while (resultSet.next()){
                File file =  new File("文件写入路径");
                InputStream inputStream = resultSet.getBinaryStream("big_bin");
                OutputStream outputStream =  new BufferedOutputStream(new FileOutputStream(file));
                byte[] bytes = new byte[1024];
                for (int i; (i = inputStream.read(bytes))>0;) {
                    outputStream.write(bytes,0,i);
                }
                outputStream.close();
                inputStream.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.close(connection,statement,resultSet);
        }

    }
}

package cn.itcast.jdbc;

import java.io.*;
import java.sql.*;

/**
 * Created by sherry on 000020/5/20 18:53.
 */
public class ClobTest {
    public static void main(String[] args) {

    }

    static void create(){
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;

        try {
            connection = JdbcUtils.getCollection();

            String sql = "INSERT into clob_test(big_text) VALUES (?)";
            preparedStatement = connection.prepareStatement(sql);
            File file = new File("需要读取的文件的路径");
            Reader reader = new BufferedReader(new FileReader(file));
            preparedStatement.setCharacterStream(1,reader,file.length());
            int i = preparedStatement.executeUpdate();

            System.out.println(i+"条记录被插入");
            reader.close();
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.close(connection,preparedStatement,resultSet);
        }

    }

    static void read(){
        Connection connection = null;
        PreparedStatement statement = null;
        ResultSet resultSet = null;

        try {
            connection = JdbcUtils.getCollection();
            String sql = "SELECT big_text FROM clob_test";
            statement = connection.prepareStatement(sql);
            resultSet = statement.executeQuery();

            while (resultSet.next()){
                File file =  new File("文件写入路径");
                Reader reader = resultSet.getCharacterStream("big_text");
                Writer writer = new BufferedWriter(new FileWriter(file));
                char[] buff = new char[1024];
                for (int i;(i = reader.read(buff))>0;){
                    writer.write(buff,0,i);
                }
                writer.close();
                reader.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.close(connection,statement,resultSet);
        }

    }
}

package cn.itcast.jdbc;

import java.sql.*;
import java.util.Date;

/**
 * Created by sherry on 000020/5/20 18:39.
 */
public class DateTest {
    public static void main(String[] args) {
        create("zln","123","2022-22-22",new Date());
    }


    static void create(String username,String password,String birthday,Date startDate){
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;

        try {
            connection = JdbcUtils.getCollection();
            String sql = " INSERT into user(username,password,birthday,startday) VALUES (?,?,?,?) ";
            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setString(1,username);
            preparedStatement.setString(2,password);
            preparedStatement.setString(3,birthday);
            //util包中的Date转型到sql包中的Date
            preparedStatement.setDate(4, new java.sql.Date(startDate.getTime()));
            int i = preparedStatement.executeUpdate();
            System.out.println(i+"条记录被插入");
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.close(connection,preparedStatement,resultSet);
        }

    }
}