JavaEE学习之jdbc基础认识

Posted 2020-09-02

JDBC的定义：

　　Java Data Base Connectivity,java数据库连接；是一种用于执行SQL语句的Java API;

JDBC的操作步骤：

　　1.注册驱动

Class.forName();

　　2.获取连接

Connection xxx=DriverManager.getConnection();

　　3.编写sql

String sql=“ ”；

　　4.创建预编译的语句执行者

prepareStatement yyy=xxx.prepareStatement(sql,username,password);

　　5.设置参数

yyy.getString ()或者yyy.getInt();

　　6.执行查询

查询操作

yyy.executeQuery();

增删改操作

yyy.executeUpdate();

　　7.释放资源

？？？.close();

 案例：

  1 package cn.it.jdbc;
  2 
  3 import java.sql.Connection;
  4 import java.sql.DriverManager;
  5 import java.sql.PreparedStatement;
  6 import java.sql.ResultSet;
  7 import java.sql.SQLException;
  8 import java.sql.Statement;
  9 
 10 import org.junit.Test;
 11 
 12 import com.jdbc.utlis.jdbcUtils;
 13 import com.jdbc.utlis.jdbcUtilsDemo;
 14 
 15 public class helloDemo {
 16     @Test
 17     public void Myjdbc() throws ClassNotFoundException, SQLException {
 18         // 1.注册驱动
 19         Class.forName("com.mysql.jdbc.Driver");
 20         // 2.获取连接
 21         Connection connection = DriverManager.getConnection(
 22                 "jdbc:mysql://localhost:3306/day01", "root", "root");
 23         // 3.编写sql
 24         String sql = "select * from user";
 25         // 4.创建语句执行者
 26         PreparedStatement statement = connection.prepareStatement(sql);
 27         // 5.设置参数
 28 
 29         // 6.执行sql语句
 30         ResultSet resultSet = statement.executeQuery();
 31         // 7.遍历结果
 32         while (resultSet.next()) {
 33             System.out.println(resultSet.getString("id") + "----"
 34                     + resultSet.getString("username"));
 35 
 36         }
 37         resultSet.close();
 38         statement.close();
 39         connection.close();
 40     }
 41 
 42     // 测试jdbcUtils测试方法
 43     @Test
 44     public void Utils() {
 45         Connection connection = null;
 46         PreparedStatement statement = null;
 47 
 48         // 获取连接
 49         try {
 50             connection = jdbcUtils.getConnection();
 51             // 编写SQL语句
 52             String sql = "INSERT INTO user VALUES(?,?)";
 53             // 语句预编译
 54             statement = connection.prepareStatement(sql);
 55             // 设置参数
 56             statement.setInt(1, 5);
 57             statement.setString(2, "小明");
 58             // 执行SQL
 59             int i = statement.executeUpdate();
 60             // 判断语句是否执行成功
 61             if (i == 1) {
 62                 System.out.println("OK!!!");
 63             } else {
 64                 System.out.println("NO!!!");
 65             }
 66 
 67         } catch (ClassNotFoundException e) {
 68             // TODO Auto-generated catch block
 69             e.printStackTrace();
 70         } catch (SQLException e) {
 71             // TODO Auto-generated catch block
 72             e.printStackTrace();
 73         } finally {
 74             jdbcUtils.closeStatent(statement);
 75             jdbcUtils.closeConn(connection);
 76 
 77         }
 78 
 79     }
 80 
 81     // 更新操作
 82     @Test
 83     public void update() {
 84         Connection connection = null;
 85         PreparedStatement statement = null;
 86         try {
 87             // 注册驱动
 88             Class.forName("com.mysql.jdbc.Driver");
 89             // 获取连接
 90             connection = DriverManager.getConnection(
 91                     "jdbc:mysql://localhost:3306/day01", "root", "root");
 92             // sq1语句
 93             String sql = " UPDATE user SET username=? where id=? ";
 94             // 创建语句执行者
 95             statement = connection.prepareStatement(sql);
 96             // 设置参数
 97             statement.setString(1, "尔康");
 98             statement.setInt(2, 6);
 99             // 执行sql语句
100             statement.executeUpdate();
101         } catch (ClassNotFoundException e) {
102             // TODO Auto-generated catch block
103             e.printStackTrace();
104         } catch (SQLException e) {
105             // TODO Auto-generated catch block
106             e.printStackTrace();
107         }
108         try {
109             statement.close();
110             connection.close();
111         } catch (SQLException e) {
112             // TODO Auto-generated catch block
113             e.printStackTrace();
114         }
115 
116     }
117 
118     // 删除操作
119     @Test
120     public void delete() {
121         Connection connection = null;
122         PreparedStatement prepareStatement = null;
123         try {
124             Class.forName("com.mysql.jdbc.Driver");
125             connection = DriverManager.getConnection(
126                     "jdbc:mysql://localhost:3306/day01", "root", "root");
127             String sql = "delete from user where id=?";
128             prepareStatement = connection.prepareStatement(sql);
129             prepareStatement.setInt(1, 5);
130             int i = prepareStatement.executeUpdate();
131             if (i == 1) {
132                 System.out.println("OK");
133             }
134         } catch (ClassNotFoundException e) {
135             // TODO Auto-generated catch block
136             e.printStackTrace();
137         } catch (SQLException e) {
138             // TODO Auto-generated catch block
139             e.printStackTrace();
140         }
141 
142         try {
143             prepareStatement.close();
144             connection.close();
145         } catch (SQLException e) {
146             // TODO Auto-generated catch block
147             e.printStackTrace();
148         }
149 
150     }
151 }

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