JDBC简介
JDBC全称为：Java Data base Connectivity (java数据库连接），可以为多种数据库提供填统一的访问。JDBC是sun开发的一套数据库访问编程接口，是一种SQL级的API。它是由java语言编写完成，所以具有很好的跨平台特性，使用JDBC编写的数据库应用程序可以在任何支持java的平台上运行，而不必在不同的平台上编写不同的应用程序。
JDBC编程步骤
（1）加载驱动程序：
下载驱动包 : http://dev.mysql.com/downloads/connector/j/
解压，得到 jar文件。将该文件复制到Java工程目录Java Resources/Libraries/ 下，→ buildpath 。
（2）获得数据库连接
（3）创建Statement对象：
（4）向数据库发送SQL命令
（5）处理数据库的返回结果(ResultSet类)
package com.baidu.emp.jdbcTest;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import com.mysql.jdbc.Driver;
public class Test001 {
public static void main(String[] args) throws Exception {
// 方法一：
// Driver driver = new Driver();
// DriverManager.registerDriver(driver);
// 方法二：(推荐使用)
Class.forName("com.mysql.jdbc.Driver");
String url = "jdbc:mysql://localhost:3306/testjdbc";
String user = "root";
String password = "root";
Connection connection = DriverManager.getConnection(url, user, password);
// 创建statement对象
Statement statement = connection.createStatement();
String sql = "select * from test01";
ResultSet result = statement.executeQuery(sql);
// 遍历结果集
while (result.next()) {
String name = result.getString("name");
int id = result.getInt("id");
System.out.println(name + "t" + id);
}
result.close();
statement.close();
connection.close();
}
}
防止SQL注入改用prepareStatement
package com.boya.emp.jdbcTest;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
public class Test002 {
public static void main(String[] args) throws Exception {
Class.forName("com.mysql.jdbc.Driver");
String url = "jdbc:mysql://localhost:3306/testjdbc";
String user = "root";
String password = "root";
Connection connection = DriverManager.getConnection(url, user, password);
// 写SQL
String sql = "select * from test01 where id = ?";
//创建statement对象，预编译
PreparedStatement statement = connection.prepareStatement(sql);
//设置参数
statement.setInt(1, 2);
ResultSet result = statement.executeQuery();
// 遍历结果集
while (result.next()) {
String name = result.getString("name");
int id = result.getInt("id");
System.out.println(name + "t" + id);
}
result.close();
statement.close();
connection.close();
}
}
进行代码优化，设置配置文件，工具类，实现增删该查
增加配置文件方便修改数据库，用户登录。。。
jdbc.properties(配置文件名)
driverName=com.mysql.jdbc.Driver url=jdbc:mysql://localhost:3306/testjdbc userName=root password=root
注意写配置文件时中间不可以有空格，引号之类的
工具类：增强了代码的复用性
package com.baidu.emp.utils;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;
import org.junit.Test;
public class JdbcUtils {
static String driverClassName;
static String url;
static String user;
static String password;
static {
// 创建配置文件对象
Properties properties = new Properties();
// 加载配置文件输入流
InputStream inputStream = JdbcUtils.class.getClassLoader().getResourceAsStream("jdbc.properties");
// 重新加载配置文件
try {
properties.load(inputStream);
// 获取配置文件的值
driverClassName = properties.getProperty("driverName");
url = properties.getProperty("url");
user = properties.getProperty("userName");
password = properties.getProperty("password");
Class.forName(driverClassName);
} catch (Exception e) {
// 抛出异常
throw new RuntimeException(e);
}
}
@Test
public void testName() throws Exception {
System.out.println(driverClassName);
}
public static Connection getConnection() {
Connection connection = null;
try {
connection = DriverManager.getConnection(url, user, password);
} catch (SQLException e) {
// 抛出异常
throw new RuntimeException(e);
}
return connection;
}
public static void close(Connection connection, PreparedStatement statement, ResultSet resultSet) {
try {
if (resultSet != null) {
resultSet.close();
}
resultSet = null; // 垃圾及时清除
//注意，不要弄成死循环
close(connection, statement);
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
public static void close(Connection connection, PreparedStatement statement) {
try {
if (connection != null) {
connection.close();
}
connection = null;
if (statement != null) {
statement.close();
}
statement = null;
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
}
测试增删改查：
package com.baidu.emp.jdbcTest;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import com.baidu.emp.utils.JdbcUtils;
public class Test003 {
// 初始化值
Connection connection = null;
PreparedStatement statement = null;
ResultSet result = null;
@Before
public void start() throws Exception {
// 创建链接
connection = JdbcUtils.getConnection();
System.out.println("创建链接");
}
@After
public void end() throws Exception {
// 关闭链接
JdbcUtils.close(connection, statement, result);
System.out.println("关闭链接");
}
@Test
public void add() throws Exception {
String sql = "insert into test01 values(null,?)";
statement = connection.prepareStatement(sql);
statement.setString(1, "李四");
int result = statement.executeUpdate();
if (result!=0) {
System.out.println("添加成功");
}
}
@Test
public void del() throws Exception {
String sql = "delete from test01 where id =?";
statement = connection.prepareStatement(sql);
statement.setInt(1,3);
int result = statement.executeUpdate();
if (result!=0) {
System.out.println("删除成功");
}
}
@Test
public void change() throws Exception {
String sql = "update test01 set name = ? where id = ?";
statement = connection.prepareStatement(sql);
statement.setString(1, "张飞");
statement.setInt(2, 2);
int result = statement.executeUpdate();
if (result!=0) {
System.out.println("修改成功");
}
}
@Test
public void findAll() throws Exception {
String sql = "select id , name from test01";
statement = connection.prepareStatement(sql);
result = statement.executeQuery();
if (result.next()) {
System.out.println("查询成功");
}
}
@Test
public void findOne() throws Exception {
String sql = "select id , name from test01 where id = ?";
statement = connection.prepareStatement(sql);
statement.setInt(1, 2);
result = statement.executeQuery();
if (result.next()) {
System.out.println("查询成功");
}
}
}
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